Hydrographic ManualFourth EditionBy Melvin J. Umbach

Rockville, Md.July 4, 1976

U.S. DEPARTMENT OF COMMERCEElliot L. Richardson, Secretary

National Oceanic and Atmospheric AdministrationRobert M. White, Administrator

National Ocean SurveyAllen L. Powell, Director

Foreword

This edition of the Hydrographic Manual, a revision of Coast and Geodetic SurveyPublication 20-2 (Jeffers 1960), was compiled to meet these demands and todefine the applications of the latest available technology. It describes currentNational Ocean Survey methods of planning, executing, and processing a hydro-graphic survey. No claims are made for originality nor do we propose that thetechniques described become universally adopted.

This new Hydrographic Manual is designed so that revisions, additions, and ex-tractions of the material can be made to maintain currency with the state of theart. Our attitudes, approaches, and applications to meet our Nation's ever-changingneeds are not stagnant; thus, we cannot allow this instruction manual, that definesthe standards and methods through which we meet these needs, to become stagnant.It is incumbent upon the readers and users of this publication to ensure vitality inthe information by constant review, evaluation, and improvement of the contents.

Allen L. PowellRear Admiral, NOAADirectorNational Ocean Survey

(Foreword; July, 1976)

Continual and unrelenting demands and pressures on the National Ocean Surveyfor accurate nautical charts of the coastal waters of the United States and herpossessions have led to the development of new concepts and techniques in sur-veying, innovations in cartography, and the introduction and use of sophisticatedautomated data acquisition and processing methods. Acquisition, analysis, anddissemination of related basic oceanographic, hydrographic, and littoral zone datafor coastal engineering and scientific research are charting by-products nearly equalin importance to our nautical charting mission. Exploitation of the Nation's sub-merged lands and natural resources and man's increased concern for his environ-ment, wetland area, flood plains, and ecosystems have altered many of our tradi-tional priorities and have encouraged the development of new techniques to meetthese new responsibilities.

Preface

This Hydrographic Manual, Fourth Edition, by the National Ocean Survey wasprepared under the able direction of Captain Robert C. Munson, Associate Direc-tor, Office of Marine Surveys and Maps, and represents the culmination of morethan 160 years of experience in nautical surveying and marine charting. These con-temporary instructions for hydrographic and related data surveys that define theapplications of the most modern available technology will allow the second andthird editions to be retired.

In this fourth edition, extensive changes have been introduced in both formatand content; the major changes are, of course, based on the use of modern auto-matic data collection and processing techniques. Few of the basic requirementsof hydrography have been altered. An attempt has been made to identify stringentspecifications for hydrographic surveys and to describe survey methods and tech-niques of accomplishment that result in the most effective utilization of manpowerand equipment. I hope each salty old hydrographer who looks askance at whathe considers to be radical departures from tradition is offset by one of ourdedicated young crusaders from the binary generation who is convinced we aremoving too slowly. If this is the case, then I believe a satisfactory balance hasbeen achieved; thus this edition will retain the tradition of usefulness character-izing the previous editions.

Recent streamlining of procedures between the completion of a hydrographicsurvey and the production of a nautical chart has added responsibility uponboth commanding officers and those engaged in survey verification. In many areas,increased emphasis is placed on quality control, completeness, and cohesivenessof field survey data. Quality of our data is as important as quantity. The shop-worn adage that "miles bring smiles'' can no longer be considered a hydrographiccommandment.

New ideas and information were received and added continually throughout thepreparation period. Ultimately, however, editorial deadlines neared, causing themanuscript to be sent to the presses. Because the technology and state of theart of hydrographic surveying are dynamic, the National Ocean Survey will makea constant effort to keep this manual current by issuing periodic amendmentsand supplements. Readers are urged to make suggestions and advise us on im-provements. Through your written comments, the manual can reflect changes inthe state of the art.

The many improvements in this edition stem directly from the enthusiastic responsereceived from personnel throughout the NOAA fleet and at the Marine Centers andHeadquarters. Space does not permit one to credit each person who contributed in atechnical sense, although their efforts are sincerely appreciated; but special thanksmust go to those who made major outstanding contributions: Betty V. Arozian,Gabriel J. Bren, Raymond H. Carstens, Donald R. Engle,I.Y.Fitzgerald, Walter F.Forster II, Wayne L. Mobley, William J. Monteith, Robert K. Norris, Hugh L.Proffitt, Jack WALLACE, and Dale E. Westbrook.

Melvin J. UmbachCommander, NOAA

iii (JANUARY 1, 1979)

Introduction

The ''Survey of the Coast,'' the earliest forerunner of the National Ocean Survey (a major element of theNational Oceanic and Atmospheric Administration), conducted its first hydrographic surveys in 1834. Inthat year, the U.S. Naval schooners Jersey and Experiment, under the respective commands of LieutenantThomas R. Gedney and Lieutenant George S. Blake, initiated field operations for nautical charting in thevicinity of Long Island, N.Y.

Hydrographic surveying and the cartographic representation thereof in the form of nautical charts were notunknown mysteries in 1807 when President Jefferson appointed Ferdinand Hassler as the first Superintendentof the ''Survey.'' Over 4,000 years ago, Cretan warships and merchantmen plied the Mediterranean. Sea-going junks had spread Chinese trade throughout the Indian Ocean well before the time of Marco Polo's ex-plorations. These early navigators neither relied entirely upon memory in familiar waters nor did they en-trust the safety of their commands to chance in uncharted or strange waters. While the instruments andmethods used by these ancient mariners are considered crude and unreliable by today's standards, waterdepths were measured, shoals and channels delineated, landmarks and aids to navigation established, andhazards identified; all were recorded and charted to the best of their ability. By the 19th century, hydrog-raphy was accepted as a scientifically based surveying element capable of meeting rigorous engineeringstandards. Unrelenting pressures and demands for surveys to make maritime commerce safe resulted in plac-ing responsibility on the newer ''Coast Survey'' for the publication and maintenance of nautical charts of thecoastal waters of the United States and her possessions. Upon the arrival of the 20th century, the achieve-ment of this mission by what was then the Coast and Geodetic Survey required the execution of surveys andthe continual updating of charts that included a water area in excess of 2 million square nautical miles.

Since the end of World War II, the demand for hydrographic surveys to update nautical charts has increasedtremendously because of expanded development in coastal areas, an enormous boom in the popularity ofrecreational boating, and a sustained growth in waterborne commerce. The more than 9,000 hydrographicsurveys filed in the archives of the National Ocean Survey are the basis for an assemblance of about 970nautical charts regularly updated and published. Each survey represents a unique and comprehensive rec-ord of the coastline and adjacent waters. A detailed record of changes brought about by natural and culturalcauses can be compiled from a review of contemporary and prior surveys of the same area. These surveys,conducted primarily for nautical charting, are used extensively for engineering, research, and various legalpurposes. Only selected important details and soundings from the surveys are shown on published nauticalcharts.

The hydrographer is engaged in a unique and unusually complex arena within the field of surveying. Uniquebecause, unlike topographic surveying, hydrographic surveying is essentially inferential and deductive sincethe hydrographer cannot directly view the sea bottom features and so must rely upon discrete samplingmethods to construct a continuum of the bottom configuration. And complex in that hydrographic survey-ing includes consideration of and direct dealing with geodetic control networks, nautical datums based uponan analysis of water level conditions, submarine topography, shoreline delineation, and foreshore detail (e.g.,the precise location of navigational aids and landmarks), the total requiring a legion of surveying methodsand instrumentation to bring about the desired results.

(Introduction; July, 1976)vii

On February 10, 1807, an Act of Congress authorized the President ''. . . to cause a survey to be taken ofthe coasts of the United States. . . . '' As it happened, 27 frustrating years passed before Lieutenant Gedney'sJersey would run that first line of soundings on the south coast of Long Island between Conklins Pointand Green Point. This first hydrographic survey eventually was registered and achieved in 1837 (Wraightand Roberts 1957).

Tools and techniques used in hydrographic surveying have improved continuously at varying rates. In theearly days of hydrography, water depths were measured and bottom characteristics determined solely bylead lines, sounding poles, and wire sounding machines. Positions of the sounding vessel were determinedby three-point sextant fixes or, if the shore was not visible, by astronomic observations or dead reckoning.All data were recorded manually for subsequent manual calculation, reduction, correction, and, eventually,plotting. During the past four decades, considerable advances in the science of hydrography have beenachieved through the development of echo sounders and electronic navigation systems. With these instru-ments, the hydrographer acquired much more information for detailed charting of submarine relief thanever before. Although these instruments enabled a substantial increase in the rate and volumes of data acqui-sition and greatly improved the accuracy and completeness of the hydrographic survey, the volume ofmanual labor in recording, processing, and plotting the data was not reduced.

More recently, computer assisted data acquisition, machine plotting, and information processing systems havematerially increased the speed and efficiency of producing a hydrographic survey. Automated data acquisitionand treatment permits the hydrographer to select the optimum sounding line direction without being con-strained by the geometry of the electronic positioning system. Time, depth, and position are recordedautomatically at a much higher rate than was possible manually and with minimal possibility of recordingerror.Automatically entered data correctors have speeded the development of new instruments and techniques,such as the real-time telemetering tide gage. The shipboard computer has opened new possibilities for thefuture; among these are digital electronic sextants, which may result in more efficient surveys in areas wherevisual control must be used, and heave correctors that compensate for vertical motion of the sounding vessel.

Other technological advances are beginning to tear away the veil of water that obscures the configurationof the sea bed. Photobathymetry-underwater mapping with aerial photography — is showing its operationalusefulness. A family of swath mapping instruments is being developed, refined, and tested operationally toprovide complete sonar records analogous to aerial photography. Remote-sensing measurement devices,such as laser depth scanners and air gap echo sounders, are around the corner. Worldwide high precisionpositioning systems are in sight. All of these, together with computer analysis and processing that is replac-ing the inefficient drudgery of processing data manually, promise to make the hydrographer more efficientand effective.

(JANUARY 1, 1979) viii

ContentsPage

Preface iiivForewordviiIntroduction

PART ONE HYDROGRAPHIC FIELD OPERATIONSChapters 1 through 5

1-3Specifications and general requirements1.1-3Hydrographic surveying1.11-3Definition and purpose1. 1. 1.1-3International accuracy standards for hydrographic surveys1.1.2.1-5Hydrographic sheets1.2.

Field sheet 1-51.2.1.1-5Smooth sheet1.2.2.

Scale of survey 1-51.2.3.1-6Sheet sizes1.2.4.1-6Sheet material1.2.5.

Sheet projections1.2.6. 1-61-7Control1.3.

Horizontal control 1-71.3.1.Photogrammetric surveys 1-71.3.2.Hydrographic positioning control 1-81.3.3.

Visual position control 1-81.3.3.1.Sextant three-point fix 1-81.3.3.1.1.

1-8Theodolite intersection1.3.3.1.2.Electronic positioning 1-81.3.3.2.

1-8Short range systems1.3.3.2.1.Medium range systems1.3.3.2.2. 1-8

1-8Long range systems1.3.3.2.3.Electronics systems calibration1.3.3.2.4. 1-8

Hybrid control systems1.3.3.3. 1-9Plotting control1.3.4. 1-9

1-10Sounding lines1.4.1-10Line spacing1.4.1.1-10Crosslines1.4.2.

1.4.3. 1-11Development of shoals and other hazards1.4.4. 1-11Survey overlap at junctions1.4.5. Positions 1-121.4.5.1. Position frequency 1-12

Position numbering1.4.5.2. 1-121.4.6. Sounding interval 1-121.5. Depths 1-121.5.1. Sounding equipment 1-12

Echo sounder calibrations1.5.2. 1-13Graphic depth records1.5.3. 1-13

1-14Reduction of soundings1.5.4.1-14Datums of reference1.5.4.1.

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Tide or water levels observations1.5.4.2. 1-15Depth units1.5.5. 1-15

1-16Field sheet soundings1.5.6.1-16Depth curves1.5.7.

Other survey requirements1.6. 1-161-16Transfer of topographic and planimetric detail1.6.1.

Verification of alongshore detail1.6.2. 1-171-17Bottom characteristics1.6.3.1-18Dangers to navigation1.6.4.1-18Aids to navigation1.6.5.

1.7. 1-19Reports and records1-191.7.1. Field reports1-19Inspection of field sheets and records1.7.2.1-19Forwarding field sheets1.7.3.

2. 2-1Plans and preparations2.1. 2-1Hydrographic survey planning

2-12.2. Hydrographic projectOffice planning2.3. 2-2

2-2Project instructions2.3.1.2-2General instructions2.3.1.1.2-2Control instructions2.3.1.2.

Photogrammetric instructions 2-22.3.1.3.2-2Hydrographic instructions2.3.1.4.2-2Tides or water levels instructions2.3.1.5.

2.3.1.6. 2-6Oceanographic or limnological instructions2-6Ancilliary tasks2.3.1.7.2-6Reports2.3.1.8.

Miscellaneous instructions 2-62.3.1.9.Data to start surveys 2-62.3.2.Presurvey review 2-62.3.3.

2-72.4. Hydrographic sheet planning2-72.4.1. Sheet layout2-9Subplans and insets2.4.2.2-9Sheet numbers2.4.3.2-9Field numbers2.4.3.1.2-9Registry numbers2.4.3.2.

Dog-ears2.4.4. 2-102-10Operations planning2.5.2-10Project study2.5.1.2-10Plan of operation2.5.2.

Horizontal control and shoreline surveys3. 3-13.1. Horizontal control 3-13.1.1. Basic control 3-1

3-1Spacing of main scheme control stations3.1.1.1.Recovery of existing stations 3-13.1.1.2.

3-2Station marks and descriptions3.1.1.3.Connections to geodetic control established by other3.1.1.4.

organizations 3-2Second-order traverse 3-33.1.1.5.

Second-order traverse distances3.1.1.5.1. 3-3

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Second-order directions and azimuths 3-33.1.1.5.2.Supplemental control 3-33.1.2.

Third-order control specifications 3-43.1.2.1.Station spacing 3-43.1.2.1.1.Monumentation 3-43.1.2.1.2.Instruments 3-43.1.2.1.3.Connections to existing control 3-43.1.2.1.4.Horizontal angles 3-43.1.2.1.5.Azimuths and astronomic observations 3-53.1.2.1.6.Distance measurements 3-53.1.2.1.7.Design of traverse 3-53.1.2.1.8.Third-order control data submission3.1.2.1.9. 3-7

Exceptions 3-73.1.2.2.Hydrographic control stations 3-73.1.3.

Traverse methods 3-73.1.3.1.Photogrammetric methods 3-83.1.3.2.Sextant methods 3-83.1.3.3.Plane table methods3.1.3.4. 3-9

3-9Unconventional methods3.1.3.5.3-10Hydrographic signals3.1.4.

Natural and cultural objects 3-103.1.4.1.3-10Construction of signals3.1.4.2.3-10Signal building materials3.1.4.2.1.

Entrance on private property3.1.4.2.2. 3-113-11Shoreline surveys3.2.3-11Coastal mapping3.2.1.3-12Control identification3.2.2.3-13Photogrammetric support data3.2.3.3-13Field edit3.2.4.

Plane table surveys 3-153.2.5.

Hydrography 4-14.4-1General4.1.4-1Hydrographic field surveys4.1.1.4-1Classification of surveys4.1.2.4-24.1.3. Survey operations4-2Field sheet4.2.4-24.2.1. Definition and use4-2Construction of field sheets4.2.2.4-34.2.3. Duplicate sheets

Calibration sheets4.2.4. 4-3Control stations4.2.5. 4-4

Basic and supplemental control stations4.2.5.1. 4-44-4Hydrographic control stations4.2.5.2.4-4Electronic position control lattices4.2.6.

Transfer of topographic detail 4-64.2.7.Transfer of data from prior surveys 4-74.2.8.

4-7Sounding lines4.3.4-7Sounding4.3.1.4-8Junctions and overlaps4.3.2.

Inshore limits of surveys 4-84.3.3.4-9Spacing sounding lines4.3.4.

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4.3.4.1. Line spacing in harbors and restricted areas 4-104-104.3.4.2. Line spacing on open coasts4-104.3.4.3. Line spacing for offshore surveys4-104.3.5. Systems of sounding lines4-114.3.5.1. Parallel straight lines4-11Locus arcs4.3.5.2.

Radiating lines 4-134.3.5.3.Sounding lines in channels and along pronounced4.3.5.4.

4-13topographic features4-13Crosslines4.3.6.4-14Positioning systems and requirements4.4.4-14General4.4.1.

Visual positioning 4-144.4.2.Three-point sextant fix4.4.2.1. 4-14

4-144.4.2.1.1. Selection of objects4-174.4.2.1.2. Change of fix4-174.4.2.1.3. Special problems in sextant fixes4-17Theodolite intersection4.4.2.2.4-184.4.3. Electronic position control4-20Hyperbolic positioning systems4.4.3.1.4-23Range-range systems4.4.3.2.4-23Phase-matching systems4.4.3.2.1.

Distance-measuring systems 4-244.4.3.2.2.4-25Systems calibration4.4.3.3.4-29Shore station sites4.4.3.4.4-31Hybrid positioning systems4.4.4.4-32Position frequency4.4.5.4-32Position identification4.4.6.4-32Running hydrography4.5.4-32Beginning survey4.5.1.4-33Following proposed sounding lines4.5.2.4-344.5.3. Turns and changes in course4-34Speed of sounding vessel4.5.4.4-34Plotting sounding line4.5.5.4-34aSounding interval4.5.6.4-35Measuring depths4.5.7.4-35Depth units4.5.7.1.4-354.5.7.2. Field sheet soundings4-35Depth curves on field sheets4.5.7.3.4-37Depth curve interval4.5.7.4.4-37Verification of alongshore and offshore detail4.5.8.4-39Shoals and dangers4.5.9.4-39Indications of shoals and dangers4.5.9.1.4-40Development and examination of shoals4.5.9.2.4-40Record of shoal examination4.5.9.3.4-41Detached breakers4.5.10.4-41Wrecks and obstructions4.5.11.4-41Soundings along wharves and in docks4.5.12.4-41Aids to navigation4.5.13.4-41Nonfloating aids and landmarks4.5.13.1.4-42Floating aids4.5.13.2.

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4-42Nonfederal aids to navigation4.5.13.3.4-424.5.14. Bridges and cable crossings4-42Verification of charted features4.5.15.4-43Inspection of field sheet4.5.16.4-43Discrepancies in hydrography4.6.4-43Discrepancies at crossings4.6.1.4-44Discrepancies at junctions and overlaps4.6.2.4-44Other discrepancies and sources of error in hydrography4.6.3.4-444.7. Character of bottom4-444.7.1. General4-464.7.2. Classification of bottom materials4-464.7.3. Description of bottom materials4-47Hydrographic records4.8.4-474.8.1. General4-47Use of abbreviations4.8.2.4-47Manually recorded survey data4.8.3.4-47General4.8.3.1.

Page headings 4-484.8.3.2.4-484.8.3.3. Information at beginning of day's work4-48Electronic control information4.8.3.4.4-51Sounding equipment4.8.3.5.4-534.8.3.6. Comparison of sounding equipment4-544.9.3.7. Weather and sea conditions4-54Column entries4.8.3.8.4-554.8.3.9. Position data4-554.8.3.10. Remarks column4-56Information at end of day's work4.8.3.11.4-57Completion of sounding records4.8.3.12.4-574.8.4. Automated survey records4-584.8.4.1. Data identification

4.8.4.2. Survey Information, Processing/ Statistics, and4-58Personnel /Weather blocks4-584.8.4.3. Other data4-584.8.5. Depth records

4.8.5.1. 4-58Graphic depth records4-62Digital depths4.8.5.2.4-62Analog position data4.8.6.4-654.9. Corrections to soundings4-65General4.9.1.

4.9.1.1. Standard nomenclature 4-654.9.1.2. 4-67Standard practices

4-674.9.2. Correction units4-674.9.3. Tide and water levels reductions4-684.9.4. Dynamic draft correction4-694.9.4.1. Static draft4-694.9.4.2. Settlement and squat4-70Velocity corrections4.9.5.4-714.9.5.1. Direct comparisons

4.9.5.1.1. Bar checks 4-714-72Vertical casts4.9.5.1.2.4-744.9.5.1.3. Corrections to soundings from bar check data4-744.9.5.2. Oceanographic and limnologic determinations

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Selection of layers 4-754.9.5.2.1.Determination of velocities at layer mid-depths 4-754.9.5.2.2.Layer corrections 4-764.9.5.2.3.Corrections versus applicable depths 4-764.9.5.2.4.Velocity correction table 4-764.9.5.2.5.Sample computation of velocity corrections 4-764.9.5.2.6.

Combining oceanographic determinations with direct4.9.5.3.comparisons 4-79

Instrument error corrections 4-804.9.6.Initial errors 4-804.9.6.1.Phase errors 4-834.9.6.2.Stylus arm length errors 4-834.9.6.3.Stylus belt length errors 4-844.9.6.4.Fine arc errors 4-844.9.6.5.Frequency errors 4-844.9.6.6.

Transducer correction 4-844.9.7.Scanning analog depth records 4-844.9.8.

Checking recorded depths 4-844.9.8.1.Interpreting analog depth records 4-864.9.8.2.

4-904.9.9. Final field soundings4-924.10. Special Survey Techniques4-924.10.1 General4-924.11. Navigable Area Surveys4-92General4.11.1.4-924.11.2. Hydrography4-92Inshore limits4.11.2.1.4-924.11.2.2. Shoals and dangers to navigation4-924.11.2.3. Chart topography4-92Landmarks4.11.2.4.4-924.11.2.5. Aids to navigation4-93Miscellaneous4.11.2.6.4-934.11.3. Data processing4-934.12. Chart Evaluation Surveys4-93General4.12.1.

Operations 4-934.12.2.4-934.12.2.1. Deficiency investigations4-94Reconnaissance hydrography4.12.2.2.4-944.12.2.3. Waterfront planimetry verification4-944.12.2.4. Harbor reconnaissance4-944.12.2.5. Landmark verification4-944.12.2.6. Aids to navigation verification4-95Coast Pilot inspection4.12.2.7.4-95Tide/water levels observations4.12.2.8.4-95User evaluation/public relations effort4.12.2.9.4-95Data processing4.12.3.4-96Data distribution4.12.4.4-964.12.5. Descriptive report4-96Cover sheet4.12.5.1.4-96Title sheet4.12.5.2.4-964.12.5.3. Descriptive report text4-103Separates following text4.12.5.4.4-1054.13. Special surveys

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4-105Track line surveys4.13.1.4-107Astronomic observations4.13.1.1.4-109Dead reckoning4.13-1.2.4-110Tag line surveys4.13.2.

5-1Field reports5.5-1Periodic administrative reports5.1.

5.1.1. 5-1Monthly progress sketchSeason's progress sketch 5-25.1.2.

5-4Photogrammetric precompilation field reports5.2.Descriptive report 5-45.3.

5-45.3.1. Cover sheet5-5Title sheet5.3.2.

Index of sheets5.3.3. 5-55-55.3.4. Descriptive report text5-10Separates following text5.3.5.5-15Field edit report5.4.

Report on landmarks and nonfloating aids to navigation 5-185.5.5-18Preparation of reports on landmarks5.5.1.

Supporting chart sections5.5.1.1. 5-185.5.1.2. Standardization of nomenclature 5-18

5-21Report on nonfloating aids to navigation5.5.2.5.6. 5-21Tide and water level station reports and records

5-23Geographic names report5.7.5-245.8. Coast Pilot reports5-245.9. Dangers to navigation report5-245.10. Chart inspection report5-255.11. Report on visit to authorized chart sales agent5-255.12. Special reports and photographs

PART TWO FINAL DATA PROCESSINGChapters 6 through 8

Verification and smooth plotting6. 6-16.1. Definition and purpose 6-1

Verification work schedules6.2. 6-1Verification stages6.3. 6-2

Preverification6.3.1. 6-2Verification of horizontal control6.3.2. 6-2

6.3.3. Position verification 6-36.3.3.1. Checking machine-plotted positions 6-56.3.3.2. Resolving erroneous visual positions 6-5

Resolving erroneous electronic positions6.3.3.3. 6-6Verification of soundings6.3.4. 6-7

Sounding overlays6.3.4.1. 6-7Preliminary sounding overlay6.3.4.1.1. 6-7Excess sounding overlays6.3.4.1.2. 6-8

Data listings and printouts6.3.4.2. 6-8Crosslines6.3.4.3. 6-8Depth curves6.3.4.4. 6-9

6.3.4.5. Least depths 6-96.3.4.6. 6-9Photobathymetry

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Comparison with adjoining surveys 6-106.3.4.7.Verification of shoreline, hydrographic, and topographic6.3.5.

features 6-10Wire-drag comparisons6.3.6. 6-11Prior survey data6.3.7. 6-11

Comparison with prior survey data6.3.7.1. 6-11Evaluating prior data6.3.7.2. 6-11Retention of prior data6.3.7.3. 6-11

Geographic datums6.3.8. 6-12Datum ticks6.3.9. 6-13Chart comparison6.3.10. 6-13

Quality control 6-146.4.6.5. Common deficiencies of verified surveys 6-14

Verification reports6.6. 6-15

Smooth sheet7. 7-1Definition and purpose7.1. 7-1General specifications 7-17.2.

Sheet material7.2.1. 7-1Sheet size and layout7.2.2. 7-1

7.2.3. Sheet margins and extensions 7-2Insets and subplans7.2.4. 7-2

7.2.5. Drafting standards 7-37-37.2.5.1. Character of lettering7-3Lettering orientation7.2.5.2.

Placement of lettering7.2.5.3. 7-47.2.6. 7-4Drafting materials7.2.6.1. 7-4Selection and use of ink

Selection and use of pencils7.2.6.2. 7-57-5Drafting instruments and plotters7.2.7.7-5Cartographic specifications and conventions7.3.

Projection7.3.1. 7-57-6Electronic positioning lattices7.3.2.

Control stations7.3.3. 7-6Basic control stations7.3.3.1. 7-6

7-67.3.3.2. Supplemental control stations7-67.3.3.3. Hydrographic control stations

7.3.4. 7-6Shoreline and topographic details7-77.3.5. Low water lines7-8Limit lines7.3.6.7-8Hydrographic features7.3.7.7-8Ledges and reefs7.3.7.1.7-8Coral7.3.7.2.

7.3.7.3. 7-8Bare rocks7-9Rocks awash7.3.7.4.7-9Rock elevations7.3.7.5.7-9Submerged rocks7.3.7.6.7-9Submerged obstructions7.3.7.7.7-9Visible obstructions7.3.7.8.7-10Wrecks7.3.7.9.7-107.3.7.10. Marine growth7-107.3.7.11. Breakers, tide rips, and eddies

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7-10Wire-drag hangs, groundings, and clearances7.3.7.12.7-10Soundings7.3.8.7-11Sounding units and rounding7.3.8.1.7-11Spacing of plotted soundings7.3.8.2.7-11Selection of soundings and excessing7.3.8.3.7-13Depth curves7.3.9.

7.3.9.1. 7-13Standard depth curves7-14Selection of curves7.3.9.2.7-14Bottom characteristics7.3.10.7-147.3.11. Aids to navigation7-14Landmarks and nonfloating aids to navigation7.3.11.1.7-197.3.11.2. Floating aids to navigation7-197.3.12. Miscellaneous detail7-197.3.12.1. Cables and bridges7-19Tide and current stations7.3.12.2.7-197.3.12.3. Geographic names7-20Descriptive notes7.3.12.4.7-20Junctions and adjoining surveys7.3.12.5.7-20Smooth sheet identification block7.3.12.6.7-20Title block7.3.12.7.7-227.4. Special projects and field examinations

Final inspection and approval8. 8-18-1Final inspection8.1.

Administrative approval8.2. 8-18.3. 8-1Shipment of records

PART THREE. APPENDIXESAppendixes A through E

Equipment and instrumentsA. A-1A.1. Introduction A-1

AA-1AA. Hydrographic survey vesselsAA-1A.A.1. Major survey vesselsAA-1AA.2. Coastal survey vesselsAA-1AA.3. Auxiliary and minor survey vesselsAB-1AB. Long range navigation systemsAB-1AB.1. Omega navigation systemAB-1AB.1.1. EquipmentAB-1OperationAB.1.2.AB-3AB.2. LORAN navigation systemAB-4AB.2.1. Equipment

AB.2.2. Operation AB-4AC-1AC. Medium range position-fixing systemsAC-1AC.1. Decca Hi-Fix and Sea-Fix systems

Hi-Fix and Sea-Fix chainsAC.1.1. AC-2AC-4AC.1.2. System characteristicsAC-4AC.1.3. Lane integration and identificationAC-4AC.2. Raydist systemAC-5AC.2.1. System characteristicsAC-5AC.2.2. System componentsAC-7AC.2.3. Checkout procedures

xvii (JUNE 1, 1981)

Page

AC-8AC.3. Hydrotrac SystemAC-9AC.3.1. System CharacteristicsAC-9AC.3.2. System ComponentsAC-10AC.3.3. InstallationAC-11Receiver OperationAC.3.4.AC-11AC.4. ARGO SystemAC-11Principles of OperationAC.4.1.AC-12Description of EquipmentAC.4.2.AC-13System CharacteristicsAC.4.3.AC-13AC.4.4. Operational FeaturesAC-13AC.4.4.1. Multiple rangesAC-13AC.4.4.2. Range Quality IndicationsAC-13AC.4.4.3. Data SmoothingAC-14Lane IdentificationAC.4.4.4.AC-14AC.4.4.5. Hyperbolic OperationsAC-14Aircraft OperationsAC.4.4.6.AC-14Built-In TestAC.4.4.7.AC-14AC.4.4.8. Remote Antenna TuningAC-14AC.4.4.9. Selectable FrequenciesAC-14AC.4.4.10. Transmitter ProtectionAC-14Data Outputs and FormatsAC.4.4.11.AC-15AC.4.5. Installation and OperationsAD-1AD. Short range position-fixing systemsAD-1AD.l. Del Norte Trisponder systemAD-1AD.1.1. Description of equipmentAD-2AD.1.2. System characteristicsAD-2AD.1.3. Installation and operationAD-4AD.2. Motorola Mini-Ranger III SystemAD-4Description of equipmentAD.2.1.AD-5AD.2.2. System characteristicsAD-5Installation and operationAD.2.3.AE-1AE. SextantsAE-1AE.1. Navigating sextantAE-1Adjustment of sextantAE.1.1.AE-1AE.1.2. Index error of sextantAE-2AE.1.3. Use of sextantAE-2Angles to faint objectsAE.1.4.AE-4Inclined anglesAE.1.5.AE-4AE.2. Electronic digital sextantAE-5Adjustment and calibrationAE.2.1.AE-6OperationAE.2.2.AF-1AF. Sounding equipmentAF-1AF.1. Manual depth-measuring devicesAF-1AF.1.1. Lead lineAF-1AF.1.1.1. Marking lead linesAF-2Verification of lead linesAF.1.1.2.AF-2AF.1.1.3. Sounding leadsAF-3Sounding poleAF.1.2.AF-3Bar check apparatusAF.1.3.AF-3Modified trawl sweepAF.1.4.AF-5Pipe dragAF.1.5.AF-5Launch wire dragAF.1.6.

xviii(JUNE 1, 1981)

Page

AG-1AG. Echo-sounding equipmentAG-1IntroductionAG.1.AG-1General principlesAG.1.1.AG-1Echo-sounding transducersAG.1.2.AG-1Echo pulse frequencyAG.1.3.AG-2AG.1.4. Pulse duration and shapeAG-3Transducer beam widthsAG.1.5.AG-4AG.1.6. Attenuation of acoustical signalsAG-4AG.1.7. Frequency, pulse length and shape, and beam widthAH-1AH. Echo soundersAH-1AH.1. IntroductionAH-1Raytheon analog and digital depth soundersAH.1.1.AH-1DE-723 depth recordersAH.1.1.1.AH-2AH.1.1.2. Electronics cabinet unitAH-2Digital depth monitorAH.1.1.3.AH-2AH.1.1.4. Digital phase checkersAH-3AH.1.2. Ross depth-sounding systemAH-3AH.1.2.1. Ross depth recorderAH-4Ross transceiverAH.1.2.2.AH-5AH.1.2.3. Ross digitizerAH-5Raytheon portable echo sounderAH.1.3.AI-1Side Scan Sonar EquipmentAI.AI-1AI.1. IntroductionAI-1AI.2.1. General PrinciplesAI-1AI.2.2. Side Scan Sonar ApplicationsAI-1AI.2.3. System DescriptionAI-2AI.3. Side Scan SonarAI-2AI.3.1. Klein Associates, Inc. Side Scan Sonar SystemAI-2Side Scan RecorderAI.3.1.1.AI-2AI.3.1.2. Side Scan TransducersAI-3Tow Cable AssembliesAI.3.1.3.AI-3Operations ConsiderationsAI.3.1.4.AJ-1AJ. NOS HYDROPLOT systemAK-1Tide and water level gagesAK.AK-1Automatic gagesAK.1.AK-1AK.1.1. Standard gages

AK.1.2. Fischer and Porter analog to digital recordingAK-1(ADR) gageAK-3Gas-purged pressure gageAK.1.3.AK-5AK.1.4. Stevens water level recorderAK-5AK.2. Nonrecording gagesAK-5AK.2.1. Tide staffAK-7AK.2.2. Tape gagesAK-7AK.3. Comparative observationsAK-8AK.4. Bench marks and levelingAL-1AL. Miscellaneous equipmentAL-1AL.1. ProtractorsAL-1AL.1.1. Plastic three-arm protractorsAL-1Odessey protractorsAL.1.2.AL-2AL.1.3. Drafting machineAL-2AL.2. Oceanographic equipmentAL-2AL.2.1. Nansen bottle

xix (JUNE 1, 1981)

Page

AL-4AL.2.2. Reversing thermometersAL-4AL.2.2.1. Care of reversing thermometersAL-5AL.2.2.2. Corrections to observed temperaturesAL-5AL.2.3. SalinometersAL-5AL.2.4. HydrometersAL-8AL.2.5. Temperature, depth, conductivity (TDC) sensorsAL-8AL.2.6. Salinity, temperature, depth (STD) sensorsAL-8AL.2.7. Bottom samplersAL-10AL.3. Hydrographic clock

Cartographic codes and symbolsB. B-1

Miscellaneous conversions, tables, and graphsC. C-1

BibliographyD . D-1

E. Glossary of abbreviations and acronyms E-1

1-1INDEX

FIGURESNOAA ship Fairweather1-1 1-2

Geographic designations for project numbering for the Atlantic2-1and Gulf of Mexico Coasts and the Great Lakes 2-4

2-2 Geographic designations for project numbering for the2-5Pacific Coast, Alaska, and the Pacific Islands

Layout of hydrographic survey sheets 2-82-3

Traverse with checked spur point 3-63-13-6Short base method for checking traverse spur point3-2

3-3 3-6Offset method for checking traverse spur pointWing point method for checking traverse spur point3-4 3-6

3-103-5 Construction of large tripod signal

4-3Stamp 1, hydrographic field sheet title block4-14-54-2 Control station plotted by dm's and dp's on distorted sheet

4-3 4-6Drawing distance-arcs when station off sheet4-64-4 Drawing arcs with three-arm protractor4-124-5 Systems of sounding lines4-154-6 Strong and weak three-point fixes4-16Error contours for various configurations of three-point fix4-74-19Hyperbolic lattice for hydrographic survey4-84-20Hyperbolic lattice lane expansion4-9

4-10 Hyperbolic positioning system relative error contours for4-21standard deviation of 0.01 lanes

4-11 Hyperbolic positioning system error contours for4-22assymetrical base station configurations4-22Root mean square error at electronically determined position4-124-23Range-range lattice for hydrographic survey4-134-24Error contours for range-range system4-144-24Line of sight over horizon4-15

(JUNE 1, 1981) xx

Page

4-16 Manual record of electronic positioning calibration and4-27computation of corrections4-274-17 Comparison of electronic positioning calibrations4-284-18 Position by range-angle method4-28Determination of lane count by buoy circling4-19

4-20 Hybrid positioning system 4-314-21 Range-azimuth positioning system 4-314-21a 4-34bSounding interval vs speed4-22 Manually recorded survey (NOAA Form 77-44, ''Soundings'')

Record of hydrography controlled by sextant fixes and Raydist4-234-24 4-51Recorded hyperbolic-visual controlled hydrography4-25 Record of positions observed by theodolite intersection method4-26

of day 4-534-27 4-53Stamp 3, electronic control information4-28 4-53Stamp 4, record of sounding equipment4-29 4-53Stamp 5, record of bar check4-30 Stamp 5A, record of simultaneous comparison of echo sounder--

4-544-31 Stamp 6, record of weather throughout day4-32 4-56Stamp 7, position of line beginning4-33 4-57Stamp 8, verification of sextants and sounding clock

4-574-34 Stamp 9, statistics for day's work4-35 4-57Stamp 10, processing checklist4-36 4-59Data identification block and tape identification stamp4-37 Survey information, processing/ statistics, and

personnel/ weather blocks 4-604-38 Lead-line comparison and bar check machine listings 4-614-39 4-61Stamp 11, graphic record for identifying bottom profiles4-40 4-63Automated record of hydrography4-41 4-64Sawtooth or analog record of vessel position4-42 4-65Corrections to echo soundings4-43 4-68Construction of predicted tide curve4-44 4-73Direct Comparison Log for echo-sounding corrections4-45 4-78Velocity correction curve from data in table 4-114-46 Velocity versus depth curve 4-814-47 Velocity correction curve with combined observations 4-824-48 4-83Echo sounder stylus arm-lenth error

4-84Echo sounder fine-arc error4-494-50 4-87Bottom profile (fathograms)

4-894-51 Problems of bottom profile interpretation4-52 4-90Deepwater side echoes4-53 4-97Descriptive Report Cover4-54 Hydrographic Title Sheet 4-984-55 Deficiency Item Report 4-1004-56 4-101Deficiency Item Report4-57 4-106Stamp 30, oceanographic survey sheet data stamp

4-1064-58 Ocean Survey Sheets (OSS) and letter identifications4-59 Position of ship from astronomic observations 4-1094-60 Layout of tag line survey 4-111

5-1 Symbols used drawing progress sketches 5-25-2 Monthly Progress Sketch 5-3

xxi (JUNE 1, 1981)

4-54

4-52

4-494-50

Stamps 2A and 213, personnel stamps used at beginning

AD-3 Del Norte Trisponder vessel installation

Page

Descriptive Report cover sheet5-3 5-5Hydrographic Title Sheet5-4 5-6Field Tide Note5-5 5-11List of Geographic Names5-6 5-12

5-145-7 Sounding Correction AbstractElectronic (position) Corrector Abstract5-8 5-15Station List5-9 5-16

5-10 5-17Abstract of Positions5-11 Side I of NOAA Form 76-40, ''Nonfloating Aids or

5-19Landmarks for Charts''5-20Side 2 of NOAA Form 76-405-12

6-1 Change of datum on hydrographic sheet 6-136-16NOAA Form 77-27, ''Hydrographic Survey Statistics''6-2

Verification approval sheet 6-176-3

7-27-1 Smooth sheet, dog ear or temporary extensionSubplan of small cove7-2 7-3Three- and four-digit soundings plotted at angle 7-47-3

7-7Correct and incorrect shoreline delineations7-4Use of 0.5-ft soundings and dashed depth curves 7-127-5

7-15Example one of completed hydrographic smooth sheet7-67-177-7 Example two of completed hydrographic smooth sheet7-20Stamp IA, smooth sheet identification block7-8

Title block non-automated Hydrographic Sheet 7-217-97-227-10 Title block automated Hydrographic Sheet

AA-1AA-1 NOAA ship DavidsonAA-2AA-2 NOAA launch 1257AA-2AA-3 NOAA 29-ft. hydrographic launchAA-2AA-4 Skiff outfitted for shoal water surveyingAB-2AB-1 LORAN-C navigation coverage diagramAB-3AB-2 Omega shipboard navigation unit

AB-3 LORAN-C shipboard navigation unit AB-4AC-1AC-1 Decca Sea-Fix positioning system shipboard installationAC-2AC-2 Decca Hi-Fix shore stationAC-5AC-3 Raydist positioning system vessel componentsAC-6AC-4 Raydist shore station installationAC-12AC-5 Typical 4 Range Transmission Sequence (ARGO)

AC-6 Standard ARGO Fixed Station InterconnectingAC-13Cabling Diagram

AC-7 Standard ARGO Mobile Station InterconnectingAC-13Cabling DiagramAC-15AC-8 ARGO Control and Display Unit and Range Processing UnitAD-1AD-1 Del Norte Trisponder positioning system componentsAD-2AD-2 Del Norte Triponder shore station installationAD-3AD-5AD-4 Mini-Ranger III SystemAD-5AD-5 MRS III schematic diagramAD-7AD-6 Transponder antenna and radiation patternsAE-1AE-1 Hydrographic sextant with telescopeAE-3AE-2 Corrections to inclined sextant angles

xxii(JUNE 1, 1981)

Page

AE-4AE-3 Electronic digital sextantAF-4AF-1 Trawl board constructionAF-4AF-2 Modified trawl sweep

AF-3 AF-4Technique for launch wire dragAG-2AG-1 Short acoustical pulse

AG-2 AG-2Long acoustical pulseAG-3AG-3 Shape of echo sounder acoustical beamAH-1AH-1 Raytheon DE-723 echo sounder recorderAH-2AH-2 Raytheon DE-723 echo sounder electronics cabinetAH-3AH-3 Raytheon DE-723D digital depth monitorAH-3AH-4 Ross depth sounding system components

AH-5 AH-5Raytheon Echo Sounder Model DE-719AH-6 Raytheon Echo Sounder Model DE-719 housing with

AH-6storage areaAI-1 AI-2Klein Hydroscan Dual Channel Side Scan Sonar Recorder

AI-3AI-2 Klein Side Scan Sonar TowfishAJ-1AJ-1 HYDROPLOT system block diagram

AJ-2 AJ-1HYDROPLOT installation aboard shipAJ-2AJ-3 HYDROPLOT system launch installationAJ-3AJ-4 Hydrographic data logger aboard shipAK-1AK-1 Standard tide gageAK-2AK-2 Standard tide gage installationAK-2AK-3 Front view of Fischer and Porter water level recorder

AK-4 AK-2Side view of Fischer and Porter water level recorderAK-5 AK-3Fischer and Porter punched tape record

AK-3AK-6 Gas-purged pressure (bubbler) gage componentsAK-7 Bubbler gage strip chart recorder AK-4AK-8 AK-8Bubbler gage gas flow system components

AK-6AK-9 Stevens water level recorder and digital recorderAK-6AK-10 Tide or water level staff installation

AK-11 AK-8Tide or water level electric tape gageAL-1AL-1 Plastic three-arm protractorsAL-1AL-2 Calibration of three-arm protractor

AL-3 AL-2Odessey protractorAL-2AL-4 Engineer's drafting machineAL-3AL-5 Nansen bottle

AL-6 AL-4Reversing thermometersAL-7 AL-6Induction-type salinometer

AL-6AL-8 NOS hydrometer setAL-9 AL-7Conversion of apparent specific gravity to salinityAL-10 Temperature, depth, and conductivity (TDC) metering system

Expendable salinity, temperature, and depth (XSTD) system AL-11AL-12 AL-9Bottom sediment samplerAL-13 AL-9Clamshell snappers for bottom samplingAL-14 AL-10Hydrographic clock

Rock symbols and elevation references for Atlantic andB-1Gulf Coasts B-8

B-2 Rock symbols and elevation references for Pacific Coast B-9B-10Rock symbols and elevation references for Great LakesB-3B-11Symbols and elevation references for reefs and ledgesB-4

Line-of-sight nomographC-1 C-6

xxiii (JUNE 1, 1981)

AL-8AL-9

PageTABLES

Position numbering of hydrographic survey1-1 1-121-191-2 Field reports

2-1 Area limit designations for project numbering 2-3

4-1 Projection line intervals for various scales 4-34-204-2 Hyperbolic versus range-range system considerations

4-3 Empirically determined velocities of propagation for4-29medium range frequencies4-364-4 Depth units for scaling soundings and applying corrections4-374-5 Standard depth curves

4-6 Supplemental depth curves 4-384-45Hydrographic survey horizontal positioning errors4-74-454-8 Hydrographic survey sounding errors4-464-9 Bottom sediments classified by size

4-10 4-59Definitions of terms used in figure 4-374-774-11 Velocity correction computations, STD cast4-794-12 Velocity Correction Table4-80Velocity correction computations, Nansen cast4-134-854-14 Time tolerances for scaling peaks and deeps4-914-15 Conversion of reduced soundings

4-16 4-106Ocean Survey Sheets (OSS) series numbers and limits

5-235-1 Landmark classifications, definitions, and rules

AC-3AC-1 Characteristics of Hi-Fix and Sea-Fix Positioning SystemsAC-2 Characteristics of Raydist DR-S Electronic

AC-5Positioning SystemAC-9AC-3 General Characteristics of the Hydrotrac System

AC-4 General Characteristics of the ARGO ElectronicAC-13Positioning SystemAC-14AC-5 ARGO Smoothing CodesAD-2AD-1 Del Norte Trisponder system characteristicsAD-3AD-2 Trisponder time-sharing constraintsAD-6AD-3 MRS III package operating characteristicsAF-2AF-1 Markings for lead lines graduated in fathomsAF-2AF-2 Markings for lead lines graduated in feetAH-2AH-1 Characteristics of Raytheon soundersAK-9AK-1 Maximum allowable leveling error between bench marks

B-1 through B-9 are cartographic codes and symbols.Control stations B-1B-1

B-1Low water line and associated featuresB-2B-2Dangers to navigationB-3

Soundings B-4B-4B-5Shoreline and alongshore featuresB-5

B-6 Buoys B-6B-7 Bottom characteristics B-6

Nonfloating aids to navigation and landmarks B-7B-8B-7Miscellaneous featuresB-9

(JUNE 1, 1981) xxiv

Page

C-1C-1 Conversion factors (U.S. Survey Foot)C-2Linear distance conversion (fathoms, meters, feet, and yards)C-2

Linear distance conversion (nautical miles, statute miles,C-3C-3and kilometers)

Temperature conversion (Celsius to Fahrenheit andC-4C-3Fahrenheit to Celsius)

Microwave horizon distance, range versus antenna heightC-5C-4(kilometers)

Microwave horizon distance, range versus antenna heightC-6C-4(nautical miles and statute miles)

Velocity correction factors for calibration velocity ofC-7C-5800 fm/s

E-2Abbreviations and acronymsE-1

xxv (JUNE 1, 1981)

INDEX

A 4-109bisectrics in4-108, 4-109errors in

E-1Abbreviations, glossary of 4-109probable position, and the4-35Abnormal depth curves and inaccuracies 4-110sun, on the

Abstract of corrections to 4-108time of, important4-96, 5-7, 5-13, 6-7echo-soundings 4-108—4-106track line surveys, on

4-96, 5-7Descriptive Report, in the Astronomic position fixes and the6-7Accuracy of analog depth records AB-1 AB-3Omega navigation system

4-107Accuracy of astronomic observations Astronomical azimuth stations 3-4,3-5Accuracy Standards for Atlantic Ocean, the

Hydrographic Surveys, International 1-3, 4-85 1-15depth unit forAG-4, AH-1Acoustical signals, attenuation of 1-15hydrographic reference datum for

Acronyms, glossary of E-1 Atmospheric conditions, unusual,Adjectives for bottom listed in Descriptive Report 5-8

B-6characteristics, symbols for Atmospheric noise and electronicAerial photography 4-30positioning systems

advance use of 3-13 Automated data processing,1-10tide-coordinated 5-10Descriptive Report, a section of the

Aerotriangulation stations selected Automated hydrographic survey3-12, 3-13prior to aerial photography systems 1-6, AJ-1—AJ-4

Agencies, contact with other, prior Automated techniques in verification 6-13-2, 4-43, 4-95to survey Automatic digital recording

Aids to navigation 1-15, AK-1—AK-3(ADR) gages5-9Descriptive Report, listed in Azimuth

7-19floating, smooth sheet, on beacon ranges, of 4-421-4, 1-18, 4-1, 4-41,locating 1-18determination, responsibility for

4-84, 7-14, 7-19Azimuth and astronomic observations 3-5

7-4names and designations of, smooth sheet, on 4-18Azimuth array sheets, preconstructed4-42nonfederal, Descriptive Report, listed in Azimuths in use with electronic

7-14, 7-19nonfloating, smooth sheet, on positioning systems 4-311-4, 1-18, 4-1, 4-41,surveys and Azimuth marks at control stations 3-27-14, 7-14

Azimuth orientation in theodoliteAlongshore detail intersection method of positioning 4-18

1-17-1-18bottom characteristics 4-31Azimuth, polaris or solar observations for1-17verification of Azimuth stations, selection of 3-44-94"Altitude and Azimuth, Tables of Computed''

AG-4—AH-6Analog depth recorders BAnalog depth records

4-86 Bar check(s) 1-13, 4-71, 4-72interpretingAF-3apparatus for4-84—4-90scanning

4-62 4-74data, corrections to soundings fromAnalog position data4-80errors and the velocity correction curveAnalog records, supplementary 4-62

AK-1, AK-3 Bare rocksAnalog to digital recording (ADR) gage(see Rocks, bare)Anchorage holding characteristics, bottom

1-18 4-4Basic control stations on field sheetsdescriptions showing4-44 Basic hydrographic survey, theAnchorages, bottom characteristics and 1-5, 4-1

4-105Bathymetric mapping surveysAngulation instruments 3-5AC-6 Beaches and soundings 4-9Antenna couplers, note on

Beacon ranges, azimuths of 4-42Antenna height versus range,Beam compass used for plottingC-4microwave horizon distance, table of

control stations 4-58-1Approval of surveys, final6-18 Bench marksApproval sheet and verification

AK-9maximum allowable leveling error betweenArcsAK-9line-of-position plane of flotation, and the1-12,4-4, 4-5, 4-11

4-28, 4-31 AK-9principal qualities ofBench marks and tide and waterlocus 4-11—4-13

AK-8, AK-9level gages, leveling between4-5plotting ofBibliography D-1ARGO, a long-rangeBottomposition-fixing system

4-54, 7-13configuration of, sounding selection, and(see also Position-fixing systems)AC-11—AC-15 consideration of nature of 1-11ARGO Survey Systems

4-11contours and sounding line systemsAstronomic observations4-108 materials classificationaccuracy of, factors affecting 4-46

I-1

HYDROGRAPHIC MANUAL

charts available for 4-47 Calibration procedure for electronic positioningdescription of 4-46—4-47 equipment and stations 1-8, 1-9, 4-25—4-29

4-3—4-4profiles of Calibration sheets1-13importance of 4-1 Calibration standard for echo sounders1-17interpreting kelp and 4-86, 4-87, 4-88 Caribbean Sea, shoreline detail

sounding lines, and 4-7 B-1Cartographic codes and symbolssample spacing, guidance on 2-2 Cartographic standards for smooth sheet 1-5, 7-1

AL-8—AL-10 C-band positioning equipmentsamplers 4-28samples Celestial bodies and astronomic observations 4-109

5-13Descriptive Report, listed in Channelsfield survey, in dredged, maintenance of4-1 4-13storage of 4-44 shoal indications in 1-11

sampling 1-4 sounding lines in 4-131-17, 1-18, 4-45, 4-93frequency of 5-9, 6-13—6-14Chart comparison and verification

4-45 Chart Evaluation Surveyssediment samples to Smithsonian Institution 2-1, 2-7, 4-1, 4-93—4-105Chart depths, term definedslopes 4-65

1-19, 5-24—5-25Chart inspection reportabrupt changes in 7-11sand and mud, in 4-9 Chart(s), nautical

accuracy of 4-44 1-3surface layer sampling 1-10 data for compilation of 1-3topography of

Bottom characteristics 1-17, 1-18, 4-44, 4-46, 7-14, B-6 Omega navigation system, forabbreviations used on smooth sheet 7-14, B-6

Chief of Partyadjectives and symbols for B-61-17—1-18 changes in operation plans by 2-7along shore detail, and

7-22 to be named on smooth sheetdescriptions of 5-221-18 Chimney as a landmarklimits for

1-18 4-90Choppy seas and irregular profilesuses ofCircles, drawing, on hydrographic sheets 4-6nouns and symbols for B-6

7-14 Circular pattern generation ofsmooth sheet, and the AC-1, AC-2 position fixing systemssurvey scales, and 1-5

Clamshell bottom snappers in bottom sampling 4-44symbols, cartographic B-6Classification of bottom materials 4-46Breakers

4-1—4-24-41 Classification of surveysdetached, seen during soundings4-46Clay, definition ofsymbol for B-3

4-54, AL-10Clocks used on hydrographic surveysBreakwaters on the smooth sheet 7-9Cloth in the construction ofBridges

3-11—3-12hydrographic signals4-42cable crossings in surveys, and1-19, 4-93—4-95, 5-24Coast Pilot reports4-42field sheets, shown on

3-11—3-13Coastal mapping in shoreline surveys5-22Building as a landmark4-35Coastal shelves, depth curves onAF-1—AF-2Bunting used with lead lines

1-3Coastal zone managementBuoys3-11Coastal zone maps to support nautical charting(see also Aids to navigation)

B-1Codes and symbols, cartographic4-28radar reflectors andB-6Codes, bottom characteristics, for4-70settlement and squat, used in measuring

Colors and symbols, bottom characteristics, for B-64-28U.S. Coast Guard to be informed of use of4-37, 4-38Colors of depth curves4-27—4-28used in phase comparison systems6-15, 6-18Comparison with prior surveys

Comparisons, direct, for determiningCvelocity corrections 4-71

Cable(s) Compass4-42 4-5cable crossings and bridges in surveys beam, used for plotting control stations4-42 4-55field sheets, shown on type to be part of records

3-14sensor conductor, marking of 4-75 Compilation photography in shoreline surveysCalibrating positioning systems, Computer programs for use with

AJ-1, AJ-24-27,4-28 HYDROPLOT systembuoys used inAL-6, AL-84-1Calibration data in field survey Conductivity sensors

4-2—4-3Calibration of electronic Construction of field sheets4-25—4-29 Contemporary nautical chart andpositioning stations

8-2Calibration of instruments 1-8, 4-25—4-29, AB-1 field survey records4-46Continental Shelf, bottom materials of theCalibration phase checks on Ross4-29AH-4analog depth recorders Control chain's geometric strength

I-2

LORAN navigation system, for use with AB-2, AB-4AB-1, AB-3

1-10, 1-11

INDEX

Current measurement methods3-12, 3-13Control identification in shoreline surveys1-7, 2-2 defined on Progress Sketch 5-2Control instructions

Currents instructions 2-65-8Control listings with Descriptive Report1-4Currents, observations ofControl station(s),

1-16Curve lines, supplemental, on field sheetshydrographic 1-9, 3-7—3-10, 4-4—4-62-6 Curve(s), depthbeyond limits of sheet

(see Depth curve(s))5-7Descriptive Report, listed in4-4field sheets, on7-6horizontal, smooth sheet, on D3-2newly established, recording of

Daily journal during survey 5-44-4numbering of

1-18Dangers to navigation1-9—1-10photogrammetrically located

B-2cartographic codes and symbols for, tabulated4-4plotting on field sheetsDescriptive Report, in the 5-9recoverable, and the Season'sfield survey, in 4-15-4Progress Report

4-1importance of discovery ofsmooth sheet, and the 7-2, 7-6indications of 4-393-1spacing

1-19, 5-24report on7-6supplemental, smooth sheet, onshoals and 4-39—4-41weak signals of, discussed in

7-8—7-10smooth sheet, shown on5-8Descriptive Reportsubmerged, awareness of 4-403-4Control, supplementaltransfer to field sheet 4-74-33Control, visual

DataConversion tablesdata-acquisition programs,

C-1area measurementsHYDROPLOT AJ-3, AJ-4C-3Celsius to Fahrenheit

data listings and printouts,C-3Fahrenheit to Celsiusverification of 6-8C-1length measurements

data sheets, forwardingC-2linear distance1-14requirementsC-1mass measurements

defective, causes of 4-86C-1mathematics1-14faulty, correction ofmicrowave horizon distance, range

historical oceanographic, toC-4versus antenna heightcorrect echo soundings 2-6C-2speed measurements

hydrographictemperature measurements C-2, C-3

4-3field sheet, and theC-5velocity correction factors1-14problems during processing ofAL-5Copenhagen Standard Sea Water

4-32, 4-57identification, Julian dates andCoral3-14photobathymetric, described7-8description of

photogrammetric support, in7-8smooth sheet, and the3-14shoreline surveys, list ofCorrections

4-7prior survey, transfer to field sheet of4-1data in field survey, in4-2, 4-93, 4-95processing of, and the field sheet4-68—4-70dynamic draft

7-10wire-drag, on smooth sheet overlay4-67echo sounding, standard practices concerning

1-15, 4-6, 7-8, AK-8Datum lines, low water4-27in calibration of positioning equipment4-67Datum reduction, definition of1-14, 4-65, 4-74in sounding records6-13Datum ticksAB-1Omega

Datum, United States Standard 6-12, 6-134-67units ofDead reckoningversus applicable depths in

4-110corrections for known factors in4-76velocity Correction procedurescurrent drift allowances and 4-1104-55Course changes to be noted in records

4-109definition ofCoxswain's duties in tag line survey 4-1114-109—4-110vessel engine speeds inB-3Crib, symbol for

4-88Debris, echoes fromCrosslinesDecca Hi-Fix Manuals 4-184-13—4-14bottom profiles, andDecca Hi-Fix, a medium-range1-11,4-43discrepancies, and

1-10—1-11 position-fixing system

(see Position-fixing systems)framework of

1-10—1-11soundings by4-18, AC-1, AC-2Decca survey systems6-8—6-9verification of

5-22 Deep water echo sounders 1-13Cupola as a landmark4-35Current drift allowances in dead Deep waters and depth curves6-144-109—4-110 Deficiencies of verified surveys, list ofreckoning procedures

I-3

HYDROGRAPHIC MANUAL

4-93 5-24Deficiency investigations dangers to navigation report in4-18Del Norte Operations Manual Descriptive Report text 5-54-18Del Norte Technology 4-32detached positions in

Del Norte Trisponder, a short-range 5-7echo sounding corrections listed inAD-1—AD-4 5-10position-fixing system electronic control parameters, detailed in

(see also Position-fixing systems) electronic position control detailed in1-17 5-13abstract of corrections toDelimiting of alngshore areas1-16 entries inDepth curves 5-4, 5-5

5-10abnormal 4-35 field tide or water level note in4-35 5-13, 5-24coastal shelves, on geographic names in

4-37, 4-38colors of hydrographic position control listed in 5-87-14congestion on steep slopes hydrographic sheets in 5-74-13 index of sheets ofdisplacement on steep slopes 5-5

4-35—4-37 6-10field sheets, on inspection for verification purposes4-37 7-20group numbers, and junctions and adjoining surveys, and

4-35, 4-37intermediate junctions detailed in 5-84-37intervals of landmarks for charts filed with 5-151-16nonstandard list of stations in 5-13

7-13, 7-14smooth sheet, and the miscellaneous information to be5-104-37standard, list of included with5-104-37, 4-38, 7-14supplemental order of inserts with

4-37topographic experience and 5-8photogrammetric problems listed in3-15verification plane table surveys, and6-9

Depth measurements in hydrographic position verification, and 6-31-5 2-6Presurvey Review, and thesurveying, allowable errors in

4-7—4-8Depth-measuring 6-2preverification, andAF-1—AF-5Depth-measuring devices, manual prior survey comparisons in 5-8

Depth recorders project number included in 5-7AH-I recommendations for additionalanalog

5-104-67calibration of work to be riled with5-104-45errors listed referral list of separate reports in

4-52 5-10Precision sheet projection, and the4-48 shoreline details in 5-8Depth records

1-14,4-86 54,7-1smooth sheet, and theanalog, interpreting1-13, 4-57 5-7graphic sounding equipment listed in

AL-6, AL-8 5-7Depth sensors sounding vessel(s) listed in5-4, 7-22Depth-sounding equipment

(see Equipment, sounding)special project, for a

7-22survey details5-91-15—1-16, 4-35Depth units statistics summary to be included in

3-10Depth(s) subjects for inclusion in4-75 title sheet forchecking measurements of 5-5, 7-221-14 5-7digital and graphic, differences between unconventional survey methods listed in4-84 verification review ofrecorded, checking of 6-84-74 4-53Deviations from standard value, notation ofstandard observation, oceanographic7-20 AB-1Descriptive notes on smooth sheets Differential Omega

1-19, 5-4—5-15 4-62Descriptive Report Digital depth readings4-66abstract of corrections to echo Digital depths, note on4-88soundings to be filed with Digital echo sounders, side echoes and5-7, 5-13, 6-7

5-13abstract of positions reported in Digital electronic sextant(see Sextants)adequacy of survey reported in 5-9

4-42, 5-9 8-2aids to navigation in Digital records on magnetic tapes1-13anomalies in the control adjustment listed in Digital sounding(s)5-74-845-15approval sheet to be filed with considered primary data

area surveyed entry in 5-7 4-34equipment and sounding intervals5-10 4-86automated data processing reported in spurious5-13bottom samples reported in Direct comparison log for recording4-27 bar check data 4-72calibration of equipment differences, and

5-9, 6-13, 6-14comparison with area chart and the Direct comparisons combined with4-79control stations shown in, 5-7 oceanographic determinations

"Directions for Using a Transit Magnetometer''cover sheet for 5-4 2-64-43—4-44crosslines detailed in 5-8 Discrepancies, hydrography, in

I-4

INDEX

4-43 4-70crossings, at salinity and temperature observations and4-43 4-69,4-70settlement and squat, andDescriptive Report, and the4-44 side echoes injunctions and overlaps, at 4-8

4-44, 4-45, 6-7sources of error, and standard nomenclature in 4-65—4-676-20unresolved verification and stray echoes, and 4-863-14 4-83Discrepancy prints in shoreline surveys stylus arm length errors in

4-841-7Disks, National Ocean Survey stylus belt length errors in3-2 transducer correction inDisks, reference, uses of 4-84

4-14 velocity correction computations,Distance, estimated, and vessel positioning4-56 4-76—4-79examples ofDistance estimates to be noted in records

Distance-measuring instruments 4-71,4-76velocity corrections, and, table of3-5Distance-measuring systems, electronic 4-24 Echoes

4-4 side 4-88Distortion between meridians and parallels4-104-4Dividers, the use of desirability of

hyperbolically-shapedDocks and piers' soundings shown 4-887-2on smooth sheet subplans or insets 4-90slant distance to shoal, and

4-864-110 Docks and tag line surveys stray4-41 1-13Docks and wharves, soundings along Echogram

Dog-ears Eddies7-10instructions on smooth sheet, shown on2-10

symbol for7-1smooth sheets, avoidance on B-3use on smooth sheets Editor, field, and alongshore detail7-2

verificationB-2Dolphin, symbol for 1-175-22Dome as a landmark EDM equipment 3-3, 3-5

Draft copies of Project for measuring distances 3-8Instructions 2-2 periodical testing of 3-3

4-66 Edmonston Beam HolderDraft, dynamic 4-54-66, 4-69Draft, static 5-10, AK-7Electric tape gage

Drafting instruments and the smooth sheet 7-5 Electronic control systems aboardAL-2Drafting machine nonautomated vessels 4-32

4-5—4-6Drawing circles, methods of Electronic dataDuck blinds processing in verification procedures 6-1

4-55smooth sheets, on the 7-9 recorded in recordssymbol for Electronic depth digitizersB-3 1-14

Duplicate field sheets 4-3 Electronic digital sextant(see Sextants)4-68Dynamic draft correction

4-66Dynamic draft, term defined Electronic lattices indicated on arcs 4-4,4-54-18—4-31Electronic position control

E corrections in the Descriptive Report 5-8 5-134-20-4-23hyperbolic positioning systems

Echo sounding(s) Electronic positioning lattices on(see also Soundings)abstract of corrections to,

smooth sheets 7-6Electronic positioning systems

5-13, 6-7Descriptive Report, and the (see Position-fixing systems)Electronic positions, erroneous,comparisons with depths measured by lead line 1-13

5-7corrections shown in Descriptive Report 6-6—6-7resolution ofdirect comparison method for 4-74—4-75Electronic sensors, precision of

4-71determining velocity corrections AG-1—Al-3Equipment, soundingequipment 4-53comparison of

(see Equipment, sounding) echo soundingfish echoes and 4-88

acoustical signal attenuation, and AG-4historical oceanographic data, and 2-6 4-66adjustment of

4-80, 4-83initial errors inAF-3bar check apparatus

instrumental errors in velocityAG-3beam width, and

4-80correction procedures 4-56changes in types of, to be noted in records4-72lead-line depth comparisons, and 4-52, AG-4deep-water

oceanographic and limnologic AG-1description of4-74—4-79determinations, and faulty operation of 1-11

4-83phase errors in fix marker on 4-614-34records produced by AG-1frequencies of pulses of

reduction of field soundings 4-90 frequencies used with AG-4

I-5

HYDROGRAPHIC MANUAL

4-55 1-14lead-lines, interspersed with erroneously scaled values in soundings4-66maintenance of 4-7 heave, correction of

4-62, AH-1National Ocean Survey, used by human and sextant errors 6-6AG-1 4-80principles of initial, in setting echo sounding pulseAG-2 AH-4pulse duration and shape instrumentalAG-4pulse length and shape in velocity correction procedures 4-80-4-84AG-1pulses of phase, explained 4-83AH-1Raytheon analog and digital depth sounders 4-21propagation contours, illustrated

4-51—4-53record-keeping, and sources of 4-44,4-454-52, AG-2shoal water 4-11survey, in, vessel speed variations and

1-16smooth plotting, and update, of the Del NorteAG-4 AD-3stabilizing system, and trisponder position-fixing system

4-134-111tag line survey, in Estuaries, sounding line system forAG-3transducer beam widths Exceptions to third-order control procedures 3-8AG-1transducers of

FAG-2undamped transmission pulse, illustratedAJ-1HYDROPLOT system

False color photographs 3-11(see also HYDROPLOT system)lead line(s) Fathogram 1-13

FathomsAF-1description ofas depth units 1-15AF-1marking of

AF-1lead lines marked inAF-1purposes of4-56Feature investigations to be noted in recordsAF-2sounding leads of

Federal Geodetic Control Committee 1974 3-1AF-3sounding pole alternative toFeetAF-1—AF-2units of measurement, and

1-15as depth unitsAF-2verification ofAF-2lead lines marked in4-80—4 84malfunction of

Field and calibration sheets from Marine Centers 1-9AF-1manual depth-measuring devicesField editAF-3modified trawl sweep

1-19, 3-13, 5-15reportAF-5pipe drag3-13—3-15shoreline survey manuscripts inAF-5construction of

surveys 4-38AF-5use ofField editor, responsibilities of 3-13, 4-37Raytheon analog and digital depthField investigations, surveys classified as 4-2AH-1soundersField numbers, instructions on 2-6AH-2accuracy ofField reports 5-1AH-2characteristics ofField operation of survey party 2-1AH-2digital depth monitor ofField sheet(s)AH-2digital logic output of

4-3—4-4calibration sheetsAH-2digital phase checkers of4-2compilation ofAH-1electronics cabinet unit of

4-2—4-3construction ofAH-2environmental specifications of4-4—4-6control lattices constructed onAH-2error, phase position shift

control stations on 4-4,4-5AH-2operating frequency of4-7dangers to navigation transferred toAH-2transmitted pulse length of

data processing, and 4-2AH-1use ofdefinition 4-2, 4-37AH-5Raytheon portable echo sounder

4-35, 4-37depth contours onAH-3—AH-5Ross depth sounding systemdog ears on 2-6AH-4calibration phase checks onduplicate sheets 4-3AH-5digitizer

1-19examination for clarityAH-4initial error, and4-2explanatory notes required onAH-4instrumental errors subject to

features of the 4-2AH-4phase error, and1-19—1-20forwarding ofAH-4stylus belt length error, and

importance of 1-5,4-2AH-4transceiverinspection by Chief of Party 1-19,4-43Error(s)labeling of 4-34-108astronomic observations, in

AK-9 1-6, 2-7, 4-3margin requirements ofbench markmaterial 1-6erroneous electronic positions,

6-6—6-7 method of making duplicates 4-3resolution ofnumbers 2-9erroneous positions recognized at verification 6-3

6-5—6-6erroneous visual positions, resolution of overlays, transparent, and 4-7

I-6

INDEX

4-85projection line intervals for 4-3 secondary, uses ofuses of1-6projections 1-13

signal descriptions on 4-4 Graphs, miscellaneous C-1size of Grass (kelp) a problem in1-6, 4-2

4-86, 4-87—4-881-16, 4-35soundings interpreting bottom profiles4-6—4-7transfer of topographic detail to Great Lakes, the

4-90—4-91 1-15Field soundings, reduced depth unit for4-1 hydrography reference datum for 1-15Field survey(s), hydrographic6-1data, verification of 3-13photogrammetry used in shoreline surveys of

1-16Final inspection and approval of survey 8-1 shoreline detail on field sheets ofFinal inspection team 8-1 surveys of, low water datum line not shown on 4-6

4-84 AK-5water level recorder in use inFine arc errors in echo soundingAK-1Fischer and Porter water level gage 1-15Greenwich Mean Time (GMT)

4-54(see also Tide and water level gages) used in records4-88Fish, echoes from 7-9Groins on the smooth sheet

7-9Fish houses on the smooth sheets Growth, marineFishing areas, bottom descriptions showing 1-18 (see also Kelp; Grass)

7-10Fix marker on echo sounder 4-61 smooth sheet, on5-22 1-15Flagpole as a landmark Gulf of Mexico, the depth unit for5-22 4-75Flagstaff as a landmark Gulf Stream, temperature variations and the5-22 4-28Flagtower as a landmark Gyroscope repeater and pelorus

Floating aids to navigation1-4, 1-18hydrographic surveys, in H

recommendation procedures regarding 1-18Harbors1-18reporting procedures when off station

4-10line spacing inFoot, U.S. Survey, conversion factors based on C-1shoal indications in 1-113-12Form letter to property owners

Hastings-Raydist, Inc 4-291-17, 7-8Foul areas in shoreline plottingHazards to navigation

(see Dangers to navigation)Foul, symbol for B-3Frequencies of positions along

Heave correction, term defined 4-664-32sounding lines, factors influencing1-14Heave error in soundings4-84Frequency errors in echo sounding

Horizontal control 1-6—1-7angulation instruments 3-5Gazimuths and astronomic observations 3-5

Gages basic control 3-1—3-44-67monitoring of connections to existing control 3-5

tide and water levels connections to geodetic control1-15, 5-10, AK-1, AK-7observations established by other organizations 3-2

5-22Gas or oil tank as a landmark control station spacing in 3-1AK-3—AK-5Gas-purged water level gage density of main scheme control, and 3-1

(see also Tide and water level gages)General instructions for

design of traverse in 3-6distance measurements in 3-5

hydrographic survey 2-2 geodetic control reference system 3-1Geodetic control diagrams 2-2, AK-8 horizontal angles in 3-5Geodetic control established by instruments, distance-measuring 3-5

other organizations, connections to 3-2 main scheme control station spacing 3-11-19, 5-25Geodetic report monumentation 3-4

Geodetic triangulation manual National Ocean Survey instructions1-7, 5-4Geodimeters on location of photo-hydro stations 3-9

models of position checks on spur points 3-63-3, 3-53-6readings with recovery of existing stations 3-1—3-2

6-12 second-order directions and azimuthsGeographic datums and verification procedures 3-31-19, 5-13, 5-23Geographic Names Report second-order traverse in 3-2—3-3

7-19Geographic names on smooth sheets 3-1—3-16shoreline surveys4-47Geophysical Instruments and Supply Co. slope correction procedures 3-6

Glossary of abbreviations and acronyms E-1 station marks and descriptions 3-21-13, 1-14, 4-57, 4-62Graphic depth record station spacing 3-4

Graphic depth recording equipment, stations1-14compensation for errors in (see also Control stations, horizontal)1-13Graphic record of sounding profiles 3-4, 3-14supplemental control

I-7

HYDROGRAPHIC MANUAL

third-order control data submission 3-7—3-8 basic 1-5, 2-1, 4-13-4 bottom characteristicsthird-order control specifications

1-17—1-18third-order measurements with alongshoremicrowave instruments 3-5 14sampling in

3-6—3-7 cartographic standards intraverse design procedure 1-52-1, 2-7, 4-1, 4-93—4-105verification of 6-2 Chart Evaluation Surveys

1-19Horizontal positioning errors in a Chief of Party's inspection responsibilities4-1—4-24-45hydrographic survey, list of classification of surveys

Horizontal traverse angles, control instructions in 2-21-10—1-11observation methods crosslines in3-3—3-4

5-22House as a landmark current observations in 1-4AJ-3data-acquisition programs andHumidity

3-3electro-optical measurements, effects on data to start surveys 2-61-14—1-15datums of reference inmicrowave measurements, effects on 3-3

4-31 definitionHybrid positioning systems 1-3Hydrographer delimiting of alongshore areas 1-17

1-164-38cooperation with field editor depth curves in1-14 1-15—1-16depth units forjudgment exercised by3-14 1-14electronic depth digitizers inresponsibilities of

Hydrographer-field editor coordination, electronic positioning system in 1-7, 1-8, 1-103-14essentiality of equipment used in 1-12, 1-13

AL-10 field edit surveys inHydrographic clock 1-171-19—1-20field reports inHydrographic control stations

(see Control stations, hydrographic) field sheet in 4-24-1Hydrographic field survey, list of requirements for (see also Field sheet)

4-2Hydrographic records(see Records, hydrographic)

importance of1-16soundings on

Hydrographic sheet(s) 1-4floating aids in1-5, 1-6field sheet Gulf Coast Low Water Datum (GCLWD), a1-5, 4-2, 4-3

1-15, 1-172-7 reference datum inlayoutgeneral instructions formaterial 2-11-6, 7-1

1-3—1-4numbers general standards2-9, 2-101-6rubber stamping of 3-1geodetic control inadequate for

scale of survey 1-5—1-6 1-11hazards to navigation in, discovery ofsheet projections horizontal control 14—1-5, 1-71-6,4-3sizes of sheets 1-6, 7-1, 7-2 shoreline surveys 3-1—3-16smooth sheet 1-9hybrid control systems in1-5, 7-1

2-7—2-101-4, 3-10—3-12Hydrographic signals hydrographic sheet planning4-4brief descriptions of, helpful on field sheet hydrographic sheets in 1-5

3-11—3-12 importance of region of survey to navigation 1-11building materials forinclement weather, andcalibration of electronic 4-2

4-28,4-29 inshore surveys inpositioning system using 1-53-10—3-11construction of inspection team 8-1

3-10 1-16junctions, adequacy ofdefinition ofline-of-sight measurements in3-11 1-8entrance on private property, and

3-10 AJ-3logger electronics, andexamples of acceptable4-4field sheet, on the Low Water Datum (LWD), a

1-153-11 reference datum inform letter to property owners regardinghorizontal control, in 3-9 Mean Low Water (MLW), a

3-10—3-11 1-15reference datum innatural and cultural objects as3-11publicly-owned areas, in Mean Lower Low Water (MLLW),3-13 1-15a reference datum inratio prints in location of3-12selection of meteorological data in 3-33-10spacing of microwave instruments in 3-3

Hydrographic Survey Inspection Team(HIT) 8-1 modern definition of 1-3Hydrographic stations, location by sextant angles 3-9 Navigable Area Surveys 1-5, 2-1, 4-1, 4-92, 4-93

1-18Hydrographic surveying(see also Running hydrography)

navigation aids in1-18navigation dangers in1-121-3 numbering of positions inaccuracy, degrees of

aids to navigation in 1-4 ocean surveys 1-62-2—2-10automated systems in 1-6, AJ-1—AJ-4 office planning

I-8

INDEX

AJ-3 AL-5off-line plotting programs in Hydrometersoffshore installations and 1-4—1-5 HYDROPLOT

2-10 AJ-2adjunct equipment selection andoperations planningAJ-1operations relative to computer4-2AJ-21-11—1-12overlap at junctions computer programs for use withAJ-21-7 controllerphotogrammetric surveys

2-10plan of operation 4-32, 4-34data acquisition and processing systemplane table in 4-57, 4-58, 4-59, 4-62, 6-4, AJ-2

Del Norte Trisponder position-fixing3-9—3-15

planning for, note on 1-3AD-22-1—2-10plans and preparations for system, and the

1-9—1-10 AJ-2plotting control echo sounders andAE-4polyconic projection in 1-6 electronic digital sextant, and the

1-4position fixes in manual 4-75—4-76, B-1AJ-2position fixes spacing in 1-4 multiplexerAJ-1position frequency intervals 1-12 plotter

1-12position numbering example Raydist DR-S positioning systempositioning control 1-7—1-8 integrates with AC-4

1-12positions Raytheon analog and digital depthAH-1Presurvey Review in 2-6 sounders, and

priorities for 2-1 Hydrotrac, a medium-range positionproject numbers 2-1—2-5 system

(see also Position-fixing systems)purpose of 1-3, 4-1AC-8—AC-11reconnaissance 4-1 Hydrotrac Survey Systems

1-14—1-15reduction of soundings Hyperbolic lattices should be machine drafted 4-31-19—1-20 AC- 1report and records Hyperbolic mode of position-fixing systems1-19—1-20report evaluation by Marine Center Hyperbolic positioning systems

4-201-17rocks in shoreline plotting in considerations for, tabulated1-14salinity measurements in 4-20description of

scale of survey 1-3—1-6 error propagation contours in 4-21scale selection in 1-5 lane expansion factor, and the 4-21

4-211-8sextant angles in measurement of fractional lane reading insextant-controlled hydrography in 4-20range-range systems, versus1-7, 1-8sextant three-point fix in restriction of use of1-7, 1-8 4-23shore stations in 4-211-8 shore station configurations inshoreline surveys in 3-11—3-15 4-20slave and master stations insmooth sheet in, the 1-5 4-21whole lane value, and thesounding lines in 1-4,1-10—1-12 Hypervisual positioning method 4-30

1-14sounding records correctionssoundings, plotted, and 1-4 Ispecial 4-1

7-20Identification block on smooth sheetspecial reports in 1-19Information sought from those usingspecific standards in 1-4—1-5

1-14 local waters 4-40spurious traces reconciliation in3-121-14 Infrared photography, tide-coordinatedtemperature measurements in4-80Initial errors in echo soundingtide and water levels observations in 1-15

Insets to sheetstransfer of topographic and 2-9, 7-21-16—1-19 Inshore preliminary positionplanimetric detail in

overlays and verification 6-4ultimate purpose of 4-2Inshore surveysvertical control in 1-51-5

electronic positioning systems invertical datum and reference of sounding 1-91-51-19vessels in Inspection procedures relative to field sheets

Inspection report(see Vessels, survey) 8-1Inspection team, hydrographic survey 8-1visual position control in 1-7—1-8Instruction manual for obtainingwire sweeps in 1-10, 1-11

wrecks, obstructions, and shoals in oceanographic data 2-61-5Instructions in hydrographic surveysHydrographic title sheet 5-5

4-1—4-111 control instructionsHydrography 2-2AB-1 currents instructionsinstruments and equipment for 2-4

general instructionsrunning 2-2(see Running hydrography) hydrographic instructions 2-2

visually-controlled 3-8 magnetics instructions 2-6

I-9

HYDROGRAPHIC MANUAL

method for making2-6 2-7—2-9miscellaneous instructions2-6oceanographic or limnological instructions tracing to be sent to NOS headquarters 2-7

1-13photogrammetric instructions Lead line and echo soundings comparisons1-7, 2-21-13Project Instructions Lead lines2-1—2-6,2-10

tides or water levels instructions 2-2 (see also Equipment, sounding)Instrument errors correction and echo sounders, used with 4-55

AF-14-79,4-80velocity correction procedures purposes ofAA-1 recording soundings of 4-53Instruments and equipment

4-72International Accuracy Standards for vertical cast procedures, and1-10Least depths over pinnacles, determination of1-3Hydrographic Surveys

International Association of Physical Ledges and reefs, smooth sheet, on the 7-84-74 Lettering on smooth sheets 7-3Oceanography, standard observation depths of

AK-8International Great Lakes Datum Leveling instrument placed ashore 4-70AK-8International Hydrographic Bureau Leveling, state maps for1-3, 4-105

1-3, 4-85 Light List, the (U.S. Coastaccuracy standards of4-41, 5-9, 5-21, 7-194-74,4-75International Standard Depths, use of Guard)

4-17—4-18 Limit lines and the smooth sheetIntersection, theodolite 7-81-12, 1-13Intervals, sounding, Limitations in using third-order

4-34 traverse methods 3-8guidelines regardingB-2Islet, symbol for Limnological instructions 2-6

Line-of-sight measurements inhydrographic surveyingJ 1-8

4-10Line spacing in harbors and restricted areas4-32Julian dates and data identification Lines4-48in records closely-spaced 1-11

Junctions 1-12consecutive numbered positions on7-20adjoining surveys smooth sheet, and the 1-11split

4-8and overlap soundings Location of photo-hydro stations1-12between survey sheets pricked on to photographs 3-9

4-11—4-13Locus arcsK 4-5field sheets, on

4-74Log sheet-AKelpLong-range hyperbolic navigation system

(see LORAN navigation system)4-86, 4-87, 4-88echo sounding, and

7-10smooth sheet, on5-22Lookout tower as a landmarkB-3symbol for

LORAN long-range navigation system(see Navigation systems)

AI-2Klein Side Scan Sonar

Low Water Datum 1-15, 4-6LLow water lines on smooth sheet 7-7, 7-8

7-14, 7-19, 4-92, 4-94Landmarks5-22—5-23classifications of, listed M

5-15for charts, Descriptive Report, listed in4-7Magic marker pen used on field sheet3-11importance of4-2Magnetic observations5-18, 5-21nomenclature standardization, and2-6Magnetics instructions5-18preparation of reports on

1-19Magnetics report5-25reports on4-41 Maintenance of echo soundingrunning hydrography, in

4-7equipment, importance of5-18supporting chart sections onMangrove and swamps and unconventionalLandmarks and nonfloating aids to

survey methods 3-91-19navigation reportManually plotted surveys, duplicate4-23Lane counters in range-range systems

field sheets for 4-34-62, 4-65Lane gains and losses in records1-20Marine Center evaluation of reports4-56Latitudes and longitudes, recording of

Marine Center processing divisions,Lattice labels on smooth sheets 7-6smooth plotting by 7-14-5Lattices, usefulness of

1-10 Marine Centers' requirements 1-9Launch hydrography6-12MEADES RANCH stationsextant-controlled 3-8

4-34 Meridianssoundings in4-76 4-4adjacentLayer corrections and velocity readings4-75 7-6labels for, on smooth sheetsLayer selection for velocity determination

3-3Meteorological data and distance measurementsLayout, sheet

I-10

INDEX

5-21AB-1 report on nonfloating aids toMicro OmegaNavigation systemsMicrowave horizon distance, range

AC- 1Decca Hi-Fix systemC-4versus antenna height, tables ofAB-1long-rangeMicrowave instrumentsAB-33-5 LORAN navigation systemthird-order measurements withAB-4charts for use with3-3used to measure survey lineAB-43-3 equipment forMicrowave measurements, humidity affectingAB-4LORAN C data correctionsMicrowave line-of-sight distanceAB-44-25 operation ofcomputation formulaAB-3Mini-Ranger position-fixing system phasing out of LORAN AAB-4position fixes for use in(Motorola)AB-3range of(see Position-fixing systems)

4-55-4-56 AB-3Miscellaneous entries in record of survey range-range positioning, andskywave correction values, and AB-44-1Miscellaneous operations in field survey

1-19 AB-4tables forMonthly Activities ReportAB-3transmitters of1-19, 5-1, 5-3Monthly progress sketch

1-19 medium-range position-fixingMonthly Ship Accomplishment Report1-19 AC-1 AC-15systemsMonthly Survey Status Report5-22 Omega long-range navigationMonument as a landmark

AB-1Motorola Mini-Ranger III short-range systemAD-4—AD-7 AB-1position-fixing system cesium beam frequency

AB-1(see also Position-fixing systems) charts to be used with4-9Mud and sand in bottom slopes determining systematic bias of AB-37-5Mylar smooth sheets, pencils used on AB-1equipment for

AB-1integration of components ofN AB-3lane counters values

AB-1operation of5-13, 5-23Names, geographicAB-1AL-2 range-range operation of theNansen bottlesAB-1AL-3 skywaves corrections, anddescription ofAB-1AL-3 stations formessengers, and

AL-4 AB-1tables forreversing thermometers, and4-75 AA- 1spacing of NOAA ship Davidson4-74water sampling, for NOAA ship Fairweather 1-2, AA-1AL-3winch used, and the Nomenclature

Nansen cast data in velocity 5-18, 5-21regarding landmarks4-77correction procedures 4-65-4-67standard, in echo sounding

4-29, 4-107National Bureau of Standards "North American Datum of 1927"' 6-12, 6-13National Geodetic Survey 3-1, 3-4 3-13"Notes to the Hydrographer"

data to be submitted to 3-7, 3-8 Nouns for bottom characteristics, symbols for B-63-2disks 4-4Numbering of control stations

3-7—3-8third-order control data submission toNumbering of projects 2-1—2-5

National Horizontal Control Network 3-2, 3-4Numbering of survey positions 1-12

National Ocean Survey 1-3, 1-5, 1-13, 1-14, 1-15,1-17, 1-18, 1-20, 2-1, 2-2, 2-6, 2-9, 3-1, 3-5, 3-8,

3-12, 3-14, 3-15, 4-1, 4-2, 4-7, 4-9, 4-18, 4-26,4-38, 4-41, 4-46, 4-57, 4-62, 4-66, 4-67, 4-70,

0

Objects4-74, 4-105, 5-1, 5-4, 5-15, 5-21, 5-23, 5-24, natural and cultural, as

7-3, AB-4, AH-1, AK-I 3-10—3-11hydrographic signals1-19nautical charting program of

verification of survey control 3-2AK-8State Map for Control Leveling 4-65Observed depths, term defined4-68Tide Tables of Obstructions

1-5Nautical chart construction 1-11finding ofNautical Chart Symbols and Abbreviations 4-46 7-9submerged, on the smooth sheetNavigable Area Surveys 1-5, 2-1, 4-1, 4-91, 4-92 Ocean Survey SheetsNavigation series numbers and limits 4-105, 4-107

aids to 4-105track line surveys plotted on(see Aids to navigation) Ocean surveys and the Continental Shelf 1-6

dangers to Oceanographic and limnologicdeterminations, velocity(see Dangers to navigation)

1-18 4-74---4-79navigational ranges of sound, and the

I-11

HYDROGRAPHIC MANUAL

3-12Oceanographic determinations Photogrammetry, aerial4-79 Photo-identification ofcombined with direct comparisons

AL-2—AL-10 3-14Oceanographic equipment aerotriangulation control5-252-6Oceanographic instructions Photographs and special reports1-19''Oceanographic Log Sheet-M, Photographs report3-13Bottom Sediment Data'' 4-44 Photography, infrared

Oceanographic stations Photo-hydro stations 3-82-2shown on Project Instructions charts location by radial intersection 3-9

4-6, AL-1, AL-2 location by transferOdessey protractors 3-91-104-10—4-11Offshore surveys, line spacing in positions

B-2 2-9Piers and docks, showing on sheetsOil or gas well, symbol forOmega long-range navigation system

(see Navigation systems)7-9Piles on the smooth sheet

Pilots' notes 4-21-10, 1-11, 4-40, AF-5Pipe drags4-46Ooze, definition of

4-10 Pipe, symbol for B-3Open coasts, line spacing along2-102-10 Plan of operationOperations planning

Plane table2-10Operations plans subject to changeDescriptive Reports 3-93-12Orthophoto mosaics

3-0,3-15use of4-44Overlapping survey areas, discrepancies in4-4Plane table control stationsOverlaps

Plane table methods and the7-20extensive, and the smooth sheet3-15Descriptive Report

1-11, 4-8junctions, soundings in, andPlanimetric detail in

7-1Overlays to smooth sheets1-16—1-19hydrographic surveys

3-12Planimetry, interior, in shoreline surveysP 2-1Planning, hydrographic survey

Platforms, symbols for B-3Pacific Ocean, thePlessey Environmental Systems Model 9090,

an expendable salinity, temperaturedepth units for 1-15

1-15hydrographic reference datum forAL-8and depth measurement system

Parallel straight sounding linesPlotters and the smooth sheet 7-5

4-11advantages ofPlotting

4-11disadvantages of 4-3automaticParallels 1-9—1-10control in hydrographic surveying

4-4adjacent 4-45errors listed4-85Peaks and deeps, time tolerances for scaling 7-2hand4-46Pelagic sediment 7-1smooth sheet

4-345-1Periodic reports required, list of sounding line4-24Phase comparison systems Polaris observations 3-3, 3-44-27 4-31buoy use in azimuth by

AF-34-29 Pole, soundingsignal must be uninterrupted in4-52 Polyconic projectionPhase corrections and frequency checks

7-5smooth sheets, used forPhase errors in graphic depth1-14 use of 1-6recording equipment

3-9Polyester drafting film for plane table surveysPhotobathymetric compilations,Position fixes4-8junctional soundings from

1-12additional, occurrences requiring3-13Photobathymetry1-4in hydrographic surveying3-13advantages of

4-14on sounding lines7-13smooth sheet, and thespacing in hydrographic surveying 1-46-9—6-10verification of

Position-fixing systemsPhotogrammetric

AC-2accuracy of3-13bathymetry ARGO System

control stations 1-7,44 AC-11principles of operationinstructions 1-7, 2-2 AC-12description of equipment

6-10locations of shoreline, verification of AC-13characteristics of3-8—3-9methods of locating control stations AC- 1circular pattern generation, and1-19,5-4 AC- 1precompilation field report Decca Hi-Fix and Sea Fix systems

3-13—3-15support data in shoreline surveys Del Norte Trisponder short-rangeposition-fixing systemPhotogrammetrists, experienced,

3-15 AD-1in shoreline survey basic unit

I-12

INDEX

AD-2 AC-5radiated power ofcharacteristics ofAC-5AD-3 range ofdata recording for

AD-3 AC-4range-range mode advantages ofdistance measurements, note onAC-5AD-2electronic drift, and readout resolution of

AD-1 AC-6shielding methods necessary withequipmentAD-4 AC-7error, update, for shore station checkout proceduresAD-3 AC-6fail-safe operation of slave or relay stations ofAD-2 AC-5system components offeatures ofAD-1 AC-4system manuals forfrequencies ofAD-2 AC-5wave transmission ofHYDROPLOT controller, and theAD-2 AC- 1Sea-Fix positioning systeminstallation ofAD-1 characteristics of AC-4microwave frequency energy of

AC-3AD-2 mode of operation ofmode of operation ofAD-1 AC-3operating range ofoperation of

AC-3AD-4 pattern transmission frequency ofposition-error possibility, andAD-1 AC-3round trip time of signal of power supply forAD-3 AC-3radiated power ofsignal overlap and interference prevented inAD-1 AC-3readout accuracy ofsignal time ofAD-1 AC-3stations of. receiver speed ofAD-2 AC-1time-sharing option of shipboard installation ofAD-3 AC-3Hi-Fix and Sca-Fix chains transmission, type of

AC-2Hi-Fix positioning system slave and master stations inAC-3 AC-2accuracy of, claimed stations used inAC-4 1-12,4-32characteristics of Position frequencyAC-3 1-12mode of operation of Position numberingAC-3 4-32Position numbers, assigning ofoperating range ofAC-3pattern transmission frequency of 6-3Position overlay, verification of data and theAC-3 Positional data in recordspower supply for 4-55AC-3 1-7—1-8Positioning control, hydrographicreadout accuracy ofAC- 1hyperbolic pattern generation, and Positioning, electronic control systems 4-18—4-30AC-2increased accuracy requirement, and 4-14—4 18Positioning, visualAC-4 three-point sextant fixlane count in 4-14AC-1lattice patterns of Positioning lattices, electronic, on smooth sheets 7-6AC-3locking signals used in Positioning systems and requirements 4-14—4-31

Motorola MRS III system Positioning systems, electronic,AD-5 4-55characteristics of and data recording

Positioning systems, hyperbolicAD-4coding system of 4-20—4-23description of operating characteristics of Positioning vessel, theodoliteAD-6

intersection method forAD-4equipment of 1-8,4-47—4-18AD-4pulse radar system, a Precompilation field reports 5-4AD-6 4-68radiation patterns of Predictions, tidalAD-4 Preliminary sounding overlayrange of 6-7AD-5transponders for Presurvey Review 2-6—2-7,4-7AC-1operating principle of approval of 2-6AC-2range-range mode, and the examination of entries in 4-56AC-4Raydist DR-S system 1-4Primary shore stations in hydrographic surveying

all-weather system, an AC-4 Prior records furnished as presurvey data 2-6AC-6 4-7antenna coupler for Prior survey data transfer to field sheetAC-6 4-1—4-2antenna height, and Prior survey information in field surveyAC-6batteries use, and Priorities for hydrographic survey 2-1, 2-10AC-5 7-19characteristics of Private markers shown on smooth sheetAC-7checkout procedures 4-57Processing/Statistics block in survey records

high frequency band operation of AC-4 Progress Sketchcontents ofHYDROPLOT system integrated with AC-4 5-1

AC-7mobile station checkout procedures current measurement methods on 5-2AC-5mode of operation of 5-1registry numbers, andAC-4NAVIGATOR, and the scales to be shown on 5-1AC-5operating frequencies of sheet limits to be shown on 5-1

operating principle of AC-4 survey details to be shown on 5-1AC-5positional accuracy of 5-2symbols to be used onAC-5 2-1—2-6,2-10power supply for Project Instructions

I-13

HYDROGRAPHIC MANUAL

amendments to column entries in 4-542-2charts furnished with compass type used to be noted in2-2 4-55

4-55draft copies of course changes in2-2Project preparation 2-6—2-7 data identification in 4-57

4-56Projection intersection, plotted, day's work statistics indeletion of nonessentialand control station plotting 4-6

4-57Projection line intervals for various sheet scales 4-3 information from certain blocks4-48,4-57Pronounced topographic features, depth records

4-544-13sounding lines alongside deviations from standard value inAL-1Protractors digital depth readings in 4-62AL-1 distances, estimated, in 4-56OdesseyAL-1plastic three-arm 4-48electronic control information, and

4-56used in manual plotting equipment operation to be noted in4-66-4Pseudofixes, verification and feature investigations to be noted in 4-56

4-95Public relations-user evaluation 4-47field records, essentialGreenwich Mean Time used in 4-54Pulse radar position-fixing system AD-4

1-19inspection ofJulian dates in 4-48Qlane gains and losses in 4-62

6-14Quality control procedures 4-56latitudes and longitudes inQuestionable features and

4-48legibility requirements in1-17alongshore detail verification

4-47manually recorded data4-56notations on passing features inR4-48page headings in

Radar position-fixing system AD-4 4-55positional data in4-55—4-56remarks column in theRadar reflectors as an aid in finding buoys 4-28

5-22 4-56rock heights to be noted inRadar tower as a landmark4-48rubber stamps inRadial intersection location4-47of photo-hydro stations sheet registry number, and the3-8

Radiating sounding lines shipment of4-13 8-14-56shoal examinations inRadio in theodolite intersection

4-25 shore station information to be noted in 4-56positioning method5-22Radio mast as a landmark 4-57simultaneous comparison in5-22Radome as a landmark 4-55simultaneous soundings, of

4-514-5 sounding equipment, andRange arcs on field sheets4-31Range-azimuth positioning system 4-54,4-57soundings

4-23—4-25,AC-2Range-range positioning systems 4-47NOAA form 77-444-24distance-measuring 4-56speed of vessel in

AB-3 4-55supplemental angles inLORAN C navigation system, and the4-62supplemented by analog records4-24phase comparison systems

4-23—4-24 4-57phase-matching systems survey information blocks in the4-20 4-57tape number entries inversus hyperbolic system, table

4-59Range-visual system terms used in4-314-55theodolite intersection data inRapids, symbol for B-3

AC-4 4-56tidal anomalies to be noted inRaydist DR-S positioning system(see also Position-fixing systems) time of occurrence in 4-48

AH-1 visual control and 4-48Raytheon analog and digital depth soundersAH-5 4-48watches on ship, andRaytheon DE-719 depth recorderAH-5 4-54weather conditions, andRaytheon portable echo sounder

(see also Equipment, sounding) 4-91Reduced soundings, conversion of1-14,4-90Reconnaissance surveys Reduction of soundings4-1,4-94

1-144-47 datums of reference inRecords, hydrographic4-674-47 Reductions, tide and water levelsabbreviations used in

4-86analog depth, interpreting Reference datums in hydrographic1-14, 1-15, AK-8surveys4-56analog depth recorder phase to be noted in

3-2Reference mark disks4-62analog position data2-9—2-10Registry numbers, instructions on4-47automated data recording and

4-55—4-56Remarks column in records of survey4-57—4-58automated survey records1-19bar check in 4-57 Reports5-244-47 Chart Inspectionchronological recording method for5-244-54, AL-10 Dangers to navigationclocks used in hydrography, and

I-14

INDEX

4-39,5-4—5-13 4-41soundings along wharves and docksDescriptive1-20 4-34asounding intervalevaluation by Marine Center

1-19,5-1—5-25 4-34, 4-34bsounding speedfieldverification of charted features 4-42—4-435-18landmarks, on

4-34vessel speed, factors influencing5-1periodic, list of4-545-25 weather conditionsspecial reports and photographs4-415-21 wrecks and obstructionstide and water level station, on

6-15verification reportsS6-1Responsibilities of verifier of survey data

Restricted areas1-10Safety of personnel and equipment4-10line spacing in

Salinity4-110, 4-111tag line surveys, and4-74—4-75checks ofReversing thermometers

(see Thermometers, reversing) determinations 2-61-14, AL-5measurement of2-6—2-7Review, Presurvey

4-70temperature observations and4-56examination of entries inAL-5Salinometers

RocksAL-8Samplers, bottomawash4-44Samples, bottom, storage of7-9smooth sheet, on the

1-18,4-47Sampling of bottom7-9symbol for4-9Sand and mud, bottom slopes inbare

4-46Sand, definition of7-8description of4-62Sawtooth record described7-8elevations of4-83Scale errors and stylus arm length7-8photogrammetric manuscripts, on

Scale selection in hydrographic surveying 1-5, 1-67-8smooth sheet, and the4-84—4-90Scanning analog depth recordscartographic codes and symbols

Schedules for hydrographic surveys 2-1illustrated B-8, B-9, B-10Sea conditions and running hydrography 4-547-9dangerous, elevations ofSea-Fix medium-range position-fixing system

4-39Descriptive Report requirements, and(see Position-fixing systems)4-39determination of heights of

Seamountelevations on the smooth sheet 7-9definition of 4-1074-56heights to be noted in records

4-107track line surveys, insubmerged, on the smooth sheet 7-91-19Season's Progress Report

B-2symbol for5-4control stations and the4-9Rocky bottoms, and, soundings

Season's progress sketch 1-19, 5-24-9Rocky coasts, and, soundingsSecond-order, Class II surveys,Root mean square error in uncertainty

requirements for 3-14-22exampleSecond-order directions and azimuths 3-3AH-3—AH-5Ross depth-sounding systemSecond-order traverse 3-2—3-3(see also Equipment, sounding)

directions in 3-34-66Rough seas and heave correctiondistances in 3-3Ruins, symbol for B-2, B-3

Sedimentology 4-454-32—4-43Running hydrographySensors4-41aids to navigation

precision of 4-754-57—4-58automated survey recordsAL-8salinity, temperature, and depth4-32beginning the surveyAL-8temperature, depth, and conductivity4-44—4-47bottom, characteristic of, and

Settlement and squat4-42bridges and cable crossingsbuoy used to measure 4-704-42cable crossings and bridgesinstruments for measuring 4-704-33course change limitations

1-14soundings, in4-39dangers and shoalstransducer displacements, and 4-694-35depth units

Sextant angle observations and4-43field sheet inspectionhybrid positioning systems 4-314-35field sheet soundings

Sextant angles to locate hydrographic4-42floating aids to navigationstations 3-94-33, 4-34following proposed sounding lines

Sextant control stations 4-44-35measuring depthsSextant-controlled hydrography 1-74-42nonfederal aids to navigation

4-41 changes of fix required in 4-11nonfloating aids and landmarksSextant-controlled launch hydrography4-34, 4-35 3-11plotting sounding line

4-54 Sextant cuts to locate hydrographic stationsrecords in 3-9

I-15

HYDROGRAPHIC MANUAL

Sextant fixes height values, note on 4-254-31position control, and information to be noted in records 4-56

special problems in 4-17 site selectionvessel position from 4-17 factors in 4-29

Sextant positions, erroneous, local topography and 4-304-14verification procedures and 6-5 used in vessel positioning

Sextant surveys and the numbering 4-107Shore ties in track line surveysof control stations 4-4 Shoreline

1-17Sextant three-point fix 1-7 actual and apparentSextants 7-6, 7-7delineation on smooth sheets

AE-1 detailadjustment ofAE-2 1-17star in, use of changes inAE-2angles to faint objects, and on field sheets 1-16, 1-17, 4-6AE-4electronic digital type features verification 6-10AE-5 1-10adjustment and calibration of manuscriptAE-4 1-17description of and approximate shoal and channel limitsAE-5 3-13direct readings from drum, and prints as support data

encoder scale of 7-7AE-4 not to be smoothed or generalizedAE-4error-free digitizing of 7-7revisedAE-4HYDROPLOT system, and the surveys ofAE-1index mirror of 3-13aerial photogrammetry inAE-5 3-12observer safety, and Atlantic Ocean, methods forAE-6 3-12operation of Caribbean Sea, methods for

sturdiness of AE-4 3-11—3-15Coastal mappingAE-5 3-13telescope attachment use, and compilation photography inAE-1horizon mirror of control identification 3-12—3-13AE-4 3-14—3-15inclined angles, and discrepancy examples inAE-1 3-14index error of discrepancy prints inAE-1 3-14micrometer drum sextants field edit of manuscripts inAE-1 3-12mirrors, position of Great Lakes, methods forAE-1 3-12Gulf of Mexico, methods fornavigating sextant, description ofAE-2 3-1—3-15horizontal control, andscaling angles from field sheets, andAE-1screw clamp type, use of hydrographer and field editor in,

3-144-111tag line survey, in coordination essential betweenAE-2three-point fixes using 3-11importance of topographic features inAE-2 3-14use of Marine Center Director's role in

2-7—2-9 3-11Sheet layout orthophoto mosaics in3-12Sheet limits on progress sketches photobathymetry in5-13-15plane table methodsSheet planning3-152-7—2-10hydrographic plane table surveys in

2-9 3-11subplans and insets planimetry, interior, and3-14Sheets, field relief displacement errors in

3-13—3-14(see Field sheets) support data, photogrammetric, inSheets, hydrographic 3-11topographic survey methods in

Side echoes(see Hydrographic sheets)Sheets, smooth (see Echoes, side)

Side Scan Sonar(see Smooth sheets)AI-14-40,4-56Shoal examination to be entered in records General principlesAI-1B-3 applicationsShoal, symbol for

1-12 AI-3Shoal water digital echo sounders operations, considerations of1-12-1-13preference for Signals, hydrographic

(see Hydrographic signals)1-12, 4-52Shoal water echo sounders4-46Silt, definition of4-88Shoalest depths and side echoes

4-110, 4-1111-11Shoaling, investigation of Skiff, tag line survey, used inShoals Skywave correction values,

AB-44-39—4-41,4-92and dangers inaccuracies of predicted1-11,4-40 Skywave corrections and thedevelopment of

AB-14-39indications of Omega navigation system4-40—4-41record of examination of Slant distance to shoal and side echo 4-90

1-10Small-boat hydrographyShore stationSmithsonian Institution,4-21configurations, accuracy of

I-16

INDEX

4-45 8-2nautical chart and the, contemporarybottom sediment samples to7-11 numbersSmooth bottom soundings, plotting 2-9, 2-10

6-1—6-20 7-9Smooth plotting obstructions, submerged, shown on7-9obstructions, visible, shown onSmooth sheet

annotation of control stations on 7-2 7-3orientation of lettering onarrows used on 7-4 7-1overlays, material for

7-13, 7-14bottom configuration shown on 7-5pencils used on7-10 7-1permanent record of survey, is thebreakers shown on7-19buoy symbol on 7-13photobathymetry and the

7-4cartographic specifications and conventions 7-5 placement of lettering on7-5cartographic standards for polyconic projection used for7-1

7-19characters, standard, used on private markers shown on7-57-22 7-1chief of party to be named in protection o

composite, may be a registry numbers2-9 2-9, 2-107-3control stations beyond sheet limits, and retention in government archives7-2

control stations to be described on rocks shown on7-6, 7-20 7-8, 7-9scale ofdanger areas shown on 7-8 1-5, 7-1

7-14definition and purpose of 7-1 selection of depth contours, and7-13, 7-14 8-1depth curves and the shipment of

7-20 7-13depth curves in overlap areas shoaler soundings plotted on7-20descriptive notes on 7-6, 7-7shoreline details on

7-1Descriptive Report and 7-1 size and layout7-1dog ears and smooth position overlay, with2-10, 7-1

drafting aids for delineating depth sounding numerals on 7-3, 7-107-13 7-10, 7-11, 7-13curves on soundings, and the

7-1 7-13drafting film used for soundings overlap, and7-4drafting materials for soundings, selection of 7-11, 7-13

7-22drafting standards for special projects and7-3electronic position lattices, and 7-1specifications, general7-1, 7-6

7-10erasures on tide rips and eddies shown on7-57-20, 7-22extension of survey coverage on 7-2 title block on

7-6final approval of 8-1 topographic details on7-10fixative used on 7-5 wire-drag hangs, and7-14formula for determining area of coverage 2-9 zero-depth curve and the

7-19geographic names on 7-8zero soundings, and7-10grass shown on B-3Snag, symbol for7-10 4-109groundings and clearances, and Solar observations

AI-1-AI-3hand plotting of 7-2 Sonar, Side Scan1-13hydrographic features on 7-8 Sounder, echo, calibrations for

7-20identification block on 1-12, 1-13Sounders, types ofink for 7-4, 7-5 5-13Sounding correction abstract

1-10, 1-127-2insets and subplans Sounding line(s)4-146-20, 7-1inspection and approval of abnormal tides and

2-7instructions for layout of beach observation advantage, and the 4-13instruments, drafting, used on 7-5 beaches, and 4-8

7-20 4-7junctional notes lettering on bottom profile, and the7-20junctions and adjoining surveys and changes and turns in course, and 4-337-10kelp on the channels, in 4-13

labels for meridians on 7-6 control, visual, and 4-33labels for parallels on 7-6 4-33course change limitations, and

7-14, 7-19 crosslineslandmarks symbols on 4-13—4-14lattice labels on 7-6 4-39dangers and shoals, and

2-7—2-9 4-11layout deep ridges and valleys, inledges and reefs on 7-8 4-11,4-35depth curves, andlettering on 4-9Descriptive Reports, and7-3, 7-4limit lines and the 7-8 echo sounders, and 4-7, 4-52low water lines on 7-7 estuaries, system for 4-13margin areas, note on 7-2 following of proposed 4-32—4-33margins and extensions frequencies of positions along7-2 4-31

7-10marine growth on the harbors, spacing in 4-104-8—4-9material used for 7-1 inshore limits of surveys, and

I-17

HYDROGRAPHIC MANUAL

junctions and overlaps1-4intervals and spacing 4-8lead-line, note on4-11—4-13locus arcs 4-53, 4-55

marine vegetation, and 4-7 NOAA form 77-44 to be used to record 4-47,4-654-35measuring depths, and numerals on the smooth sheet 7-3

4-10—4-11offshore surveys, in plotted, uniformity of 4-35parallel straight preliminary, overlay4-11 6-7

1-12recording, between fixes4-10parallel system of4-34 1-14—1-15parallel to shoreline reduction of

4-33—4-34plotting of 4-9rocky bottoms, and1-15—1-164-32position identification, and rules for recording of7-11, 7-134-31 selection ofpositions along, factors influencing

pronounced topographic features, along 4-13 settlement and squat, and 4-69,4-704-13radiating 4-55simultaneous, by two instruments4-39rock heights, and small docks and piers, in,

4-9rocky coasts, and smooth sheet, and the 7-2recording of numbered 4-47Sounding Volumes

4-31—4-32positions along 4-52sources must be shown in recordsspacing of plotted4-10 7-11restricted areas, spacing in

shallow water, in 4-14 symbols, cartographic, tabulated B-4, B-54-10 4-32taken at highest speedside echoes' desirability, and4-34 transfer to field sheet 4-7sounding intervals, and4-32 7-11soundings taken at highest speed units and rounding

4-541-10, 4-9—4-10, 4-33spacing of units, changes to be noted in records4-70—4-804-32steering arcs, and velocity corrections, and

streams, and verification of 6-74-84-10—4-11systems of 4-39visible evidence of dangers during

4-8 Spacing of sounding lines 1-10, 4-9, 4-10tidal areas, in7-224-14vessel positioning, and Special projects and smooth sheets

4-13 1-19vessel steered along arc, from Special report (field report)4-1, 4-2, 4-105visual control 4-33 Special surveys

with S indicatorwind and current difficulties, and 4-13, 4-33 2-1—2-21-13, AF-3 Speed of sounding vesselSounding pole

4-33factors influencingSounding record, conversion of4-91reduced soundings on 4-11survey errors, causing

to be noted in records 4-56Sounding(s)5-22(see also Echo sounding(s); Sounding line(s)) Spire as a landmark

4-54 4-13accuracy and units used in Splits and sounding line spacing reduction4-8 1-11beaches, and Split lines, use of

1-12 B-3Spoil area, symbol forchange in vessel speed, and4-53 3-6comparison of equipment for Spur points, check on geomeric position of4-57completion of records of Squat and settlement, combined

4-69—4-704-74 effects ofcorrections, incremental, scaling of4-691-13, 1-14, 4-65—4-91 Squat, definition ofcorrections to5-224-41detached breakers, and Stack as a landmark

1-13digital B-2Stake, symbol forAK-74-65discrepancies dsovered in Standard tape gage

4-54 Standard conversion table C-1entry in recordsAF-1 Standardizations recorded in aequipment4-51records, entered in 4-53Sounding Volume1-13 1-3—1-4erroneous, reconciliation of Standards, general, hydrographic survey

5-22Standpipe as a landmark4-45errors, lists of4-35fathom as depth unit in Static draft

4-7 measurement of 4-69first operation, a4-1, 7-10 4-69variations inimportance of

Station control errors listed 4-45in hydrographic surveying, verticaldatum reference and 1-5 Stations

established by other organizations, use of4-40 3-2information sought from local persons5-134-34,4-85 list of, in Descriptive Reportintermediate

3-24-34, 4-34a, 4-34b marks and descriptionsinterval(s)4-34, 4-34a, 4-34b monumentedguidelines regarding 3-2

AC-2used in position-fixing systems4-34hydrographer responsible for determining

I-18

INDEX

AL-8 4-18radio use inSTD sensorsSteep slopes, displacement of depth 4-18third direction observations, and

4-13curves on 4-74, AL-4Thermometers, reversing

AK-5 AL-4care ofStevens water level recorderdescription of operation of(see also Tide and water level gages) AL-4

AL-44-8Stray echoes Nansen bottles, andAL-5Streams seasoned, with stable calibration histories

Third-order control data submissionsoundings, and 3-7—3-84-84-18theodolite directions and stadia in Third-order control specifications 3-4

Three-point sextant fix(es)B-2Stump, symbol for4-154-83Stylus arm length errors in echo sounding accuracy of

4-84Stylus belt length errors in echo sounding 4-15beginners using

4-52Stylus revolutions, check of 4-17change of fix in4-174-1 creation of aSubmarine topography, changes in

Subplans 4-15delineation of strong

in sheet planning 2-9 4-15relative strength of, estimation of4-17on smooth sheets 7-2 revolvers to be avoided in

4-109 4-14Sun, observations on selection of objects in

3-10 4-15Sunlight, hydrographic signals, reflected by small angles to be avoided in4-17special problems inSupplemental control stations

(see Control stations, supplemental) 4-17split fix, and the

4-75Surface check values, water 4-17swingers to be avoided inThree-station hyperbolic positioning system

(see Hyperbolic positioning systems)Surveys, hydrographic

(see Hydrographic surveys)Swamps and mangrove and 4-45Tidal and water level observations, errors listed

3-10unconventional survey methods 4-8Tidal areas and soundings

AF-3 Tidal or water level reducers, verification, andSweep, modified trawl 6-7

4-90Swell, sea, and irregular profiles Tidal waters' shoreline detail1-16, 1-17Swingers and verification 6-5 on field sheets

B-6Symbols, cartographic, bottom characteristics, for Tidal zoning, preliminary 4-68AK-14-11Systems, sounding line Tide and water level gagesAK-1analog to digital recording (ADR) gageAK-1T automatic gagesAK-8bench marks and leveling

Tables AK-1bubbler gagemiscellaneous C-1 AK-7comparative observations

4-75oceanographicAK-1, AK-7electric gage

Tag line survey 4-110 Fischer and Porter gage,4-111equipment used in AK-1description of

method exemplified 4-110 AK-1gas-purged water level gage5-23Tank as a landmark

AK-5accuracy of5-10, AK-7Tape gages AK-3operating principles of

(see also Tide and water level gages) AK-1nonrecording gagesTapes, master data 1-11

AK-1spring-driven gageTDC sensors AL-6

AK-7standard tape gage5-23Television tower as a landmark AK-5Stevens water level recorder

Tellurometer, models of 3-3, 3-5 AK-5description of4-70Temperature and salinity observations AK-5importance of

Temperature measurements, periodic,AK-7tape gages

1-14in hydrographic surveys AK-5tide staffTemperature observations 2-6 AK-7installation of

AL-6Temperature sensorsAK-7location of

Temperature, water, checks of 4-74, 4-75 AK-5National Ocean Survey, scales onTemplates for drawing circles on sheets 4-6 AK-7protection ofTheodolite cuts and position control 4-31 AK-1uses ofTheodolite intersection stations 1-8, 3-1 AK-1weight-driven gageTheodolite intersection method 1-8, 4-17 Tide and water level reductions 4-67

accuracy requirements 4-18 5-21Tide and water level station reports4-17advantages of 1-15Tide observations, manual of4-18azimuth orientation in Tide or water level observations 1-15,4-954-18drafting machines in field survey, in 4-1

I-19

HYDROGRAPHIC MANUAL

6-12,6-13United States Standard DatumTide rips7-10smooth sheet, shown on U.S. Army Corps of Engineers 4-13, 4-43, 5-9, 4-93B-3 surveys by 4-8symbol for

AK-5 U.S. Coast GuardTide staff 4-41, 4-43, 4-934-42(see also Tide and water level gages) beacons maintained by

4-67Tide stages, predicted values for U.S. Naval Oceanographic Office AB-IU.S. Navy Bathymetric Charts,4-68Tide tables, NOS

Tide-coordinated infrared photography track line surveys plotted on 4-1053-134-14Tides, abnormal, and crosslines C-1U.S. Survey Foot, conversion factors based on

Tides and water level station report1-19 Vand records

Tides or water levels instructions 2-2, 2-4Vegetation, marine, and soundings 4-7Time synchronization,Velocity corrections 4-70AB-1Omega shipboard receiver, and the

4-71bar checks, and4-54Times used in records4-75layer selection in7-21, 7-22Title block on smooth sheet

4-76, 4-77, 4-80sample computation4-85Tolerances, time, for scaling peaks and deepsstandard methods for determining 4-71Topographic and planimetric detailtables of 4-76, 4-77, 4-78, 4-79, C-51-16—1-19hydrographic surveys, intemperature variations and 4-754-6—4-7transfer of, to field sheettransducer and 6-76-10Topographic features, verification ofvertical casts, and 4-72Topographic maps of area furnished

Velocity of propagationa factor in use of electronic

2-6at start of surveyTopography

positioning systems 4-29,4-307-6smooth sheets, onmedium-range frequencies of

4-1submarine, changes in4-29,4-30electronic positioning equipment, and5-23Tower as a landmark

of electromagnetic wave, uncertainy of 4-304-105—4-111Track line surveys1-14Velocity of sound through water, soundings and4-107—4-109astronomic observations in

Verification4-105charts forapproval sheet in 6-204-105position change recording inautomated techniques in 6-14-107seamounts in

6-13, 6-20chart comparison, and4-107shore ties incharted features, of, during survey 4-42—4 434-106, 4-107soundings logging in

6-4checking of detached positions atuncharted features found in 4-1076-14common deficiencies of verified surveysAH-4Transceiver, Ross6-10comparison with adjoining surveys, andTransducer6-20compliance with instructions, andAG-3beam widths and echo sounders

6-8—6-9crosslines, of4-84correction in echo soundingdata listings and printouts, of 6-81-14draft in soundings

6-13datum ticks, and4-45errors, list ofdepth curves, of 6-94-69settlement displacements, andDescriptive Reports, of 6-84-7Transparent overlays on field sheetserroneous position recognition and 6-34-4Traverse control stationsexcess sounding overlays, and 6-8Traverse, design of, in third-order

6-12geographic datums, and3-6measurementshorizontal control, of 6-2Traverse methods, third-order,human judgment in 6-13-8limitations to be observed in usinginshore surveys, and 6-83-9Traverses used to locate photo-hydro stations

6-9least depths variations, andAF-3Trawl sweep, modifiedmachine-plotted positions and 6-55-23Tree as a landmarkparallel sounding lines and 6-36-12Triangulation networks established in US

6-9 — 6-10photobathymetry, andTrisponder position-fixing systemposition verification 6-3(see Position-fixing systems;preverification in 6-2Del Norte Trisponder system)prior data evaluation and 6-114-11Troughs and parallel sounding lines

4-88Turbulence, echoes from prior survey data, and 6-116-14quality control procedures, and

U 6-15reports of6-5 — 6-6resolving erroneous visual positions4-4Unconventional control stations

61rocks and4-1Underwater features in field survey

I-20

INDEX

AK-1Water level recorders6-10shoreline, of6-1 — 6-20 5-23smooth plotting, and Water tower as a landmark

sounding overlays, of 6-7 Waterfall, symbol for B-3soundings, of 6-7 6-4Weak positions and verification

6-2stages ofWeather and sea conditions and

6-1survey, of4-54running hydrography6-7tidal or water level reducers, of

Weather conditions and distance6-20unresolved discrepancies and4-28 — 4-29verifier's responsibilities in measurements variation6-1

weak positions and 6-4 Wharves and docks, sounding along 4-41wire-drag comparisons, and 6-11 Wilson's Equation 4-70, 4-75, D-5

6-20wire-drag surveys, and Wind and current difficulties,work schedules in 6-1

sounding line systems, and 4-13Verification. report furnished toWinding sloughs, theodolite8-1survey officers

4-18directions inVertical angle observations 3-3Vertical cast comparisons Wire-drag comparisons and verification 6-11

4-72in velocity corrections 7-10Wire-drag hangs and the smooth sheetswith echo soundings 1-13 6-20Wire-drag surveys and verification reports

Vessel positioning3-10Wire, floating

electronic, errors listed 4-451-10, 1-11, 4-40Wire sweepsvisual, errors listed 4-45

WrecksVessel positioning and shore station4-41description4-25height values

Vessel positioning systems and 4-86echo-sounding discrepancy, and4-1 — 4-31requirements obstructions, and 4-41

Vessel speed smooth sheet, on 7-9, 7-104-33factors influencing

symbol for B-2variations, alertness of4-11hydrographers, and

Vessels, nonautomated electronic X4-32control systems on

X-band positioning equipment 4-28Vessel(s), surveyAL-8AA-1 XSTD systemsauxiliary and minor

coastal AA- 1major AA- 1 YNOAA ship Fairweather,

description of AA- 1AA-1 ZNOAA ship Davidson

1-19Visit to authorized chart sales agent reportZero depth curve4-39Visual control and three-point fixes

7-14a legal seaward boundaryW smooth sheet, on 7-8

5-10, AK-7Zero electric tape gage (ZETG)AK-1Water level and tide gages(See also Electric Tape Gage (ETG))Water level or tide observations 1-15

I-21

PART ONE

Hydrographic Field Operations

(JUNE 1, 1981) 1-2

• FIGURE 1.1. — NOAA ship fairweather a class-II hydrographic survey vessel •

SPECIFICATIONS AND GENERAL REQUIREMENTS1.

change of views by correspondence between the Bu-reau and Member States. This group was made up ofthe following experts:

1. 1. HYDROGRAPHIC SURVEYING

1.1.1. Definition and Purpose

Chairman:

Mr. M.R. ULLOM (U.S.A.: NAVOCEANO)Members:

Rear Admiral D.A. JONES, USESSA(U.S.A.: C.&G.S.), Commander F. MENDONCA DACOSTA FREITAS (Brazil); Mr. H. TUORI (Finland)

In preparation of these accuracy standards,hydrographic surveys were classified as those con-ducted for the purpose of compiling nautical chartsgenerally used by ships. Special surveys for engineer-ing and research projects were not considered. Thestudy confined itself to determining the density andprecision of measurements necessary to portray the seabottom and other features sufficiently accurate fornavigational purposes.

Most mariners rarely attempt to evaluate anautical chart. They have unquestioning faith in itsaccuracy; and where no dangers are shown, they be-lieve that none exist. The accuracy and adequacy ofa nautical chart depend on the quality of the hydro-graphic surveys from which it is compiled.

1.1.2. International Accuracy Standards forHydrographic Surveys

Certain degrees of accuracy are, nevertheless,commonly acceptable for hydrographic operations, andit is reasonable that such standards should be statedin order that they may serve as a guide for planningan adequate hydrographic survey.

PART A. —GENERAL STANDARDS

Section I.—Scale of survey

1. The scale adopted for a survey of a particulararea should not be smaller than the scale of the exist-ing or proposed chart of the area and preferablyshould be at least twice as large as that of the largestscale of the published or proposed chart of the area.

The following are pertinent extracts fromSpecial Publication 44.

"The standards were drawn up in April-May1967 by a working group that met at the IHB beforeand after the 9th I.H. Conference to complete a studywhich had previously been the subject of a long ex-

2. Ports, harbours, channels and pilotage watersshould be surveyed on a scale of 1/10 000 or larger.

(JULY 4, 1976)1-3

Hydrography is that branch of physicaloceanography dealing with the measurement anddefinition of the configuration of the bottoms andadjacent land areas of oceans, lakes, rivers, harbors,and other water forms on Earth. Hydrographic sur-veying in the strict sense is defined merely as thesurveying of a water area; however, in modern usageit may include a wide variety of other objectivessuch as measurements of tides, currents, gravity,Earth magnetism, and determinations of the physicaland chemical properties of water.

The principal objective of most hydro-graphic surveys conducted by the National OceanSurvey is to obtain basic data for the compilation ofnautical charts with emphasis on the features thatmay affect safe navigation. Other objectives includeacquiring the information necessary for related ma-rine navigational products and for coastal zone man-agement, engineering, and science.

Accuracies attained for all hydrographicsurveys conducted by the National Ocean Surveyshall equal or exceed the specifications stated in In-ternational Hydrographic Bureau (1968) Special Pub-lication 44, ''Accuracy Standards Recommended forHydrographic Surveys.'' Significant deviations fromthese standards, other than those defined in thismanual, must be expressly approved by the Director,National Ocean Survey.

The planning for each hydrographic surveyand the preparation of appropriate specifications is aunique task, and it is not possible to prepare a treatiseon accuracy standards for hydrographic surveys whichwould be applicable for any area to be surveyed. Thedensity of sounding and the precision of measure-ments depend on several factors; the depth of water,the composition and configuration of the bottom, andthe type of ships which will navigate in the area allneed to be considered.

HYDROGRAPHIC MANUAL

Section VI.—Current observations

When velocity is expected to exceed 0.2 knot,both velocity and direction of currents shall be ob-served at entrances to harbours or channels, at anychange in direction of channels, in anchorages, andadjacent to a pier or wharf area. It is also desirable tomeasure coastal and offshore currents when they areof sufficient strength to affect shipping.5. Offshore hydrographic surveys in depths greater

than 20 m (11 fm) may be plotted on a scale smallerthan 1/50000 dependent on the importance of thearea covered, the depth, and bottom configuration.The scale of the offshore plotting sheet should not besmaller than is necessary to provide a sheet of conve-nient size that will extend a short distance beyond theoffshore limit of the survey and will, where feasible,include the stations necessary for control of the survey.

PART B.-SPECIFIC STANDARDSSection I.—Horizontal control

1. Primary shore stations

Section II.—Interval of sounding lines at the scale ofthe survey

1. Spacing of principal sounding lines:

2. Spacing of cross-check lines:2. Hydrographic signals7.5 cm (3.0 in) or less.

Section III.—Interval of plotted soundings

Frequency along sounding lines:

Spacing should be less than the interval be-tween lines, preferably one-half of the interval withpeak and deep soundings shown, but this interval maybe increased in areas of even bottom, and where thesoundings are recorded on an echogram.

3. Position fixes and floating aids

Section IV.—Sampling of bottom characteristics

(b) Ocean surveys for nautical charts (shoalsearches, investigation of doubtful soundings, etc.):acceptable error when fixing a reference beacon byastronomic or electronic means: 1 km (0.5 M).

In waters that may be used for anchoring,samples should be taken at regular intervals not toexceed 5 cm (2 in) at the scale of the survey. In otherareas, shoaler or deeper, a spacing of 8 cm (3 in) issufficient depending on the regularity of the bottom.Deep-water bottom samples, over 100 m (55 fm), are classed as oceanographic observations requiring specialequipment and samples will be taken as required.

4. Aids to navigation

(a) Fixed aids to navigation shall be locatedwithin the same limits of accuracy as primary shorestations stated in para 1.

Section V.—Spacing of position fixes

5. Offshore installations dangerous to navigationLocation of offshore installations dangerous

The spacing of position fixes on the surveysheets shall be from 2- 4 cm (1-1.5 in).

(JULY 4, 1976) 1-4

4. Surveys of coastal and harbour approach areas toa depth of at least 20 m (11 fm) should be conductedon a scale of 1/50 000 or larger.

1.0 cm (0.4 in) or less, as may be needed tothoroughly develop the area at the scale of the survey,except where depth and character of the bottom willpermit wider spacing.

In general, sufficient sampling should bedone to demarcate the limits where one general typeof bottom changes to another.

The location of primary shore control stationsand electronic positioning stations shall be within thelimits of accuracy for third-order control when thegeodetic survey extends no more than 50 km (27 M)from the point of origin or from stations of a geodeticnet of higher order used as the origin. When the ex-tent of the geodetic survey is in excess of 50 km theuse of second-order control methods is desirable, andif the stations of an electronic positioning system areseparated by distances in excess of 200 km (110 M)ties shall be made to basic first-order control wheneverpossible.

The error in location of hydrographic signalsused for visual fixing, with relation to the primaryshore control should not exceed 1 mm (0.03 in) at thescale of the survey.

(a) The indicated repeatability of a fix (ac-curacy of location referred to shore control) in theoperating area, whether observed by visual or elec-tronic methods, combined with the plotting error, shallseldom exceed 1.5 mm (0.05 in) at the scale of thesurvey.

(b) Floating aids to navigation shall be lo-cated within the same limits of accuracy as positionfixes stated in para 3.

3. Other waters used by shipping with possible shoalsor other dangers to navigation should be sounded on ascale of 1/20 000 or larger.

SPECIFICATION AND GENERAL REQUIREMENTS

to navigation should, when feasible, meet the require-ments for third-order control.Section II.— Vertical control

1. Measurements of depthAllowable errors:

(a) 0 - 20 m (0 - 11 fm): 0.3 m (1.0 ft)

(b) 20 - 100 m (11 - 55 fm): 1.0 m (0.5 fm)

(c) Deeper than 100 m (55 fm): 1% of depth.

The smooth sheet is ultimately archived asthe official permanent record of the survey and isthe principal source and authority for charted hy-drographic data.

1.2.3. Scale of Survey

2. Sweeping over wrecks, obstructions, and shoals

3. Reference of sounding to vertical datum

Inshore surveys, defined as those conductedadjacent to the shoreline and in general depths of 20fm or less, shall be plotted at scales of 1:20,000 orlarger, unless smaller scales are authorized specifi-cally in the project instructions. In contrast, offshoresurveys are those conducted in waters of generaldepths between 20 and 110 fm not adjacent to theshoreline. As the survey progresses in an offshoredirection and the depths and required sounding linespacing intervals increase, smaller scales are appli-cable (usually decreasing to 1:40,000 and 1:80,000).

1.2 HYDROGRAPHIC SHEETS1.2.1. Field Sheet

The field sheet (formerly called the boatsheet) is a worksheet that graphically displays thehydrographer's most accurate representation of allrequired surface and subsurface features in the areabeing surveyed. (See 4.2.) The sheet is an indis-pensable aid to the hydrographer for visualizingthe progress and adequacy of the work accom-plished and for planning future operations. Fieldsheets may be the composite product of severalplotter sheets, overlays, insets, or rough prelimi-nary launch or skiff worksheets on which most ofthe errors have been detected, corrected, and elimi-nated by replotting the data. Under ideal condi-tions, the field sheet may be the direct product ofan on-line real-time machine or manual plot of hy-drographic data.

Basic hydrographic and navigable area sur-veys of all important harbors, anchorages, restrictednavigable waterways, and areas where dangers tonavigation are numerous shall be plotted at scales of1-10,000 or larger. Larger scales shall be even multi-ples of 1-10,000, with each scale double that of thepreceding scale (e.g., 1:5,000 and 1:2,500). Scales

1.2.2. Smooth Sheet

1-5 (JUNE 1, 1981)

Normally, a disagreement of cross check lineswith principle sounding lines of three times or morethe allowable error stated above indicates error in ei-ther position, depth, or both, and should be further in-vestigated.

The same accuracy as that specified for themeasurement of depths (Section II, paragraph 1) to adepth of 30 m (16 fm). In depths greater than 30 m(16 fm) the same accuracies as for measurement ofdepth (Section II, para 1) where the depth and equip-ment available permit these accuracies.

Location and duration of tidal observations tobe such that each sounding can be referred to thesounding datum with an error no greater than one-half that specified in Section II, para 1 above. Tidalreductions are not usually applied to oceanic sound-ings over 200 m (110 fm)."

The smooth sheet is the final carefully madeplot of a hydrographic survey. In contrast to the

field sheet, which is plotted from preliminaryunverified field data, the smooth sheet is plottedfrom checked and corrected data and conformswith rigid cartographic standards of the highestquality. (See chapters 6 and 7.)

The basic scale for hydrographic surveysperformed by the National Ocean Survey is1:20,000; almost all other survey scales used willhave a simple ratio relationship. The criteria forscale selection are based on the area to be coveredand the amount of hydrographic detail necessary todepict adequately the bottom topography and por-tray the least depths over critical features. (See4.10 and 7.2.2.) A cardinal rule of nautical chartconstruction is data from a hydrographic surveyshould always be plotted at a scale ratio largerthan that of the chart to be compiled. The surveyscale is generally at least twice as large as that ofthe largest scale chart published or proposed forthe area. For example, the scale of a survey shouldbe 1:20,000 or larger for a chart that will bepublished at a scale of 1:40,000.

Surveys at scales of 1:30,000 and 1:50,000may be authorized if their use would result in amore efficient sheet layout (2.4) or would permit aclearer portrayal of the bottom configuration.

HYDROGRAPHIC MANUAL

larger than 1:2,500 may be in even multiples of1,000. Scales for chart evaluation, reconnaissance,and special project surveys will be specified in theproject instructions.

1.2.5. Sheet Material

Ocean surveys are conducted in watersdeeper than 110 fm in areas that generally lie sea-ward of the Continental Shelf. (See F.4.1.) The small scales at which ocean surveys are plotted de-pend on the purpose of the survey and will be speci-fied in the project instructions.

1.2.6. Sheet Projections1.2.4. Sheet Size

Field parties equipped with fully automatedsystems normally plot hydrographic data on the mod-ified transverse Mercator projection because of thesimpler calculations involved. Subsequent computerplotting at the Marine Centers during the survey veri-fication phases and for the smooth sheet shall be on thepolyconic projection.

Regardless of the sheet size, a minimummargin of 7 cm is required on all edges of a smoothsheet. The latitude-longitude annotations and gridlines normally will extend to within 4 cm of the edgeof the sheet, but should be no closer than 2 cm to theedge of the sheet. The hydrographic data should sel-dom, if ever, extend into the 7-cm margin area.

Rubber stamp 1, ''Hydrographic Survey,''shall be impressed or machine drafted near the lowerright corner of each sheet and on each overlay used.(See figure 4-1 in section 4.2.2.) Appropriate entriesshall be made in all applicable spaces of the titleblock stamp. Projection lettering and numerals shall

(JUNE 1, 1981) 1-6

The standard size for hydrographic surveysheets, whether plotted manually or machine plot-ted, is 91 by 137 cm, with the hydrography limitedto an area 76 by 122 cm. The Chief of Party may in-clude a request with the sheet layout when it is sub-mitted for approval (see 2.4) to increase the sheetsize to a maximum of 91 by 152 cm, with hydrogra-phy limited to an area of 76 by 137 cm. Such re-quests should be submitted only in cases wherefailure to extend the survey area from 122 to 137 cmwould necessitate an additional, undersized, sheet toprovide complete coverage of the project area.

Sheets larger than 106 by 152 cm, with hy-drography limited to an area of 91 by 137 cm, shallnot be used under any circumstances. Should a situa-tion arise where data already acquired will not plotwithin the maximum 76- by 122-cm area, Hydro-graphic Surveys Division (OA/C35) shall be ad-vised. These data may be reformatted into twoseparate surveys and an additional registry numberassigned upon approval of Hydrographic SurveysDivision (OA/C35).

Sheets should be the standard size exceptwhen larger size sheets have been approved as aboveor when the standard size would result in a marginin excess of 20 cm. (The margin is defined as thatarea between the limits of hydrographic data and theedge of the sheet.) When an excessive margin exists,the sheet shall be trimmed during Marine Centerprocessing so that the margin is reduced to no morethan 20 cm or less than 7 cm. However, the sheetshall not be trimmed any smaller than 76 by 76 cm.

Field sheets shall be prepared on grained oremulsion coated transparent polyester base draftingfilm, on transparent paper designed specifically forautomatic plotter use, or on suitable material easilyreproduced and convenient for making comparisonswith other plotted data. Material on which hydro-graphic data will be plotted must be relatively dis-tortion free. (See 7.2.1 for smooth sheetrequirements.)

Hydrographic survey data shall be plotted ei-ther on the modified transverse Mercator or on apolyconic projection. At the relatively large scales re-quired for hydrographic surveys, the two projectionsare essentially equivalent and may be used inter-changeably for comparisons and transfer of hydro-graphic data.

Hydrographic parties not equipped with anautomated system shall request field sheets and elec-tronic control calibration sheets from the MarineCenters. Extra base sheets with ruled projectionsand electronic control arcs should be requested asnecessary for display and comparison of junctionalsoundings, presurvey review items, bottom sampledata, and other pertinent hydrographic information.

The polyconic projection should generallybe used if machine-drafted projections are not avail-able. The manual construction of a polyconic pro-jection is a relatively simple task although extremeaccuracy and care are required. All necessary in-structions and data for the manual construction arecontained in the U.S. Coast and Geodetic Survey(1935) Special Publication No. 5, ''Tables for aPolyconic Projection of Maps and Lengths of Ter-restrial Arcs of Meridians and Parallels, Based UponClarke's Reference Spheroid of 1866.'' (See 4.2.2.)

SPECIFICATIONS AND GENERAL REQUIREMENTS

be oriented to read from the south. Refer to 2.4.1 forinstructions on the orientation of the projection withrespect to the edges of the field sheet. Projection lineintervals between meridians and parallels depend onthe scale of the sheet and are specified in 4.2.2.

Electronic positioning system antenna sitesand calibration stations may be located photogram- nlmetrically, provided that the stations have beenmarked with targets prior to aerial photography, thepositions have been determined by analytic aerotrian-gulation, and the method is approved in the projectinstructions.

1.3 CONTROL1.3.1 Horizontal Control

A thorough search shall be made for allpreviously established horizontal control stations,reference marks, and azimuth marks in the general vi-cinity of the shoreline throughout the project area.Recovery notes shall be prepared and submitted inaccordance with Input Formats and Specifications forthe National Geodetic Survey Data Base.

1.3.2. Photogrammetric Surveys

Mapping of planimetric features such asshoreline, buildings, and landmarks for most inshorehydrographic surveys is accomplished through theuse of modern photogrammetric techniques. Theprincipal products supplied the hydrographer arecopies of appropriate shoreline maps and other relat-ed support data. Signals for visual control of hydrog-raphy may be located by photogrammetricprocedures utilizing the support data. (See 3.2.4.) Al-though photogrammetry has largely replaced theplane table for planimetric mapping, there occasion-ally are limited areas where use of the latter is farmore practical because of cost, time available, orneed to supplement or verify the photogrammetricdata.

Pending publication of a revised topograph-ic manual, a series of Photogrammetric Instructionshas been issued to provide specifications for stan-dard field and office procedures for photogrammet-ric surveys. [For a current list, consult chapter 76,section 27, of NOS Manual No. 1, ''Operations Man-

The photo-hydro support data have been pre-pared and provided to the field party. (See 1.3.2 and3.2.)

1-7 (JUNE 1, 1981)

For National Ocean Survey hydrographicsurveys, horizontal control shall be based on triangu-lation, traverse, or trilateration of Third-order, Class1, or higher accuracy. (See 3.1.1, Federal GeodeticControl Committee (1974) Classification, Standards ofAccuracy, and General Specifications of Geodetic Con-trol Surveys, and ( 1 975) Specifications to Support Classi-fication, Standards of Accuracy, and GeneralSpecifications of Geodetic Control Surveys.) The proj-ect instructions may require control surveys that meetthe standards for Second-order, Class II accuracy ifadditional main-scheme stations are needed to supple-ment the National Horizontal Control Network or ahiatus exceeding 20 km exists between establishedgeodetic control stations along the coastline.

Third-order, Class I accuracy is generallythe minimum acceptable criteria for the location ofelectronic positioning system antenna sites and cali-bration signals, theodolite intersection instrument(cutoff) stations, and supplemental control schemesfrom which hydrographic signals will be located byconventional survey methods. (See 3.1.2.) Third-or-der control stations when established for the hydro-graphic survey shall be described, monumented, andmarked with standard National Ocean Survey disksat intervals of 4 to 8 km along the coastline for futuresurvey use. (See 3.1.2.1.2.)

Hydrographic signals for sextant-controlledhydrography may be located by sextant fixes or bysextant cuts. Less than third-order traverse methodsmay be used if the distance from a basic or supple-mental control station does not exceed 4 km for hy-drographic surveys at scales of 1: 10,000 or smaller or2 km for larger scale surveys. (See 3.1.3.)

Photogrammetric methods may be used toposition hydrographic stations for visually controlledsurveys (photo-hydro stations) if these two condi-tions are met:

The compilation scale of the shorelinemanuscript is larger than or equal to the scale of thehydrographic survey sheet.

Photogrammetric and hydrographic surveysare conducted jointly as a part of combined opera-tions in areas where land transportation systems andother facilities are inadequate for shore-basedparties. Photogrammetric field work may consist ofany or all of the following operations in addition tothose required to directly support hydrography: re-covering or establishing horizontal control, placingtargets on control stations prior to aerial photogra-phy, observing tides in support of tide-coordinatedinfrared photography, and field editing. Experiencedphotogrammetrists are generally assigned to per-form these operations and to give advice, assistance,and training in their execution.

HYDROGRAPHIC MANUAL

1.3.3. Hydrographic Positioning Control1.3.3.1. VISUAL POSITION CONTROL

Long range, effective over distances rang-ing from a few kilometers to over 8000 km.

1.3.3.2.1. Short range systems. Short rangeelectronic positioning systems operate in the two-sta-tion range-range mode either in the ultrahigh fre-quencies (300 to 3000 MHz) or in the superhighfrequencies (3000 to 30,000 MHz). At these frequen-cies, the systems are limited to line-of-sight measure-ments (4.4.3.2.2 and A.4.1) and shall never be usedwhere intervening objects obstruct the line of sightbetween the survey vessel and either shore station orwhere the distance from the sounding vessel antennato either shore station antenna exceeds the line-of-sight condition. Refer to section 4.4.3 for detailed dis-cussions of line-of-sight limitations and requirementsfor siting shore stations, pattern geometry, and sys-tem calibration.

A check angle shall be observed on each vi-sually determined detached position to verify the fix.A detached position is a recorded fix taken to posi-tion an object that does not lie on a continuoussounding line (e.g., a bottom sample, least depth overa shoal, and floating aid to navigation).

If a computer system is not available for areal-time automated plot of the sounding line, thevessel positions are plotted using a standard draftingmachine. The angle of intersection at the vessel shallbe such that a directional error of 1 min from a theod-olite station will not cause the position of the vessel

1-8(JUNE 1, 1981)

ual'' (National Ocean Survey 1971)a).] The applicableinstruction is cited herein as appropriate.

1.3.3.1.1. Sextant three-point fix. The posi-tions of a sounding vessel when conducting an in-shore survey may be determined by three-pointsextant fixes if precise electronic positioning controlsystems are not available or are inadequate for thesurvey. (See 4.4.2.) Hydrographic sextants are usedto measure two angles between three points ofknown geographic position. The middle point of thethree should be common to both angles. The visualthree-point fix shall be plotted using a three-arm pro-tractor if the field party is not equipped with an auto-mated system for computing and plotting the fixlocation. (See A.7.)

Sextant angles shall be observed simulta-neously and recorded to the nearest minute of arc.Hydrographic sextants must be checked for adjust-ment before the start of each day's work, and the in-dex error determined and recorded in the surveyrecords. (See A. 5.3.) The adjustments are verified pe-riodically throughout the day and on completion ofeach day's work. (See 4.8.3.3.)

1.3.3.1.2. Theodolite intersection. Positions ofthe sounding vessel may be determined by the theod-olite intersection method (also called transit cutoff).This method of visual control may be advantageousin harbors, rivers, and other restrictive areas whereelectronic positioning or sextant fixing is impractical.(See 4.4.2.2.)

Directions to the vessel are observed from atleast two and preferably three shore-based theodolitestations of Third-order, Class I, or better accuracy.Directions shall be observed and recorded to thenearest minute of arc. True azimuths accurate towithin + 30 s of arc are required for absolute orienta-tion of the observed directions.

to be in error by more than 1.0 mm at the scale of thesurvey.

1.3.3.2. ELECTRONIC POSITIONING. Elec-tronic positioning systems currently used by the Na-tional Ocean Survey for hydrographic surveys maybe grouped into the following categories:

Short range, effective over distances rang-ing from a few meters to about 80 km.

Medium range, effective over distancesranging from a few hundred meters to about 250 km.

1.3.3.2.2. Medium range systems. Mediumrange electronic positioning systems operate in thetwo-station range-range mode or in a three-or four-station hyperbolic mode. These systems operate ei-ther in the ranges of medium frequency (300 to 3000kHz) or high frequency (3 to 30 MHz) and, therefore,are not limited to line-of-sight restrictions.

Caution must be exercised when using medi-um range positioning systems to control inshore hy-drography because of the potential adverse effects ofland mass-induced signal attenuation. The presence ofsevere attenuation is usually manifested by relativelylarge and unexplainable variations in the series of cal-ibrations within a survey area. Refer to section 4.4.3for detailed discussions on shore station require-ments, calibration procedures, system geometry, andthe effects of signal attenuation.

1.3.3.2.3. Long range systems. Currentlyavailable long range systems that are acceptable forcontrolling ocean surveys operate in both the three-station hyperbolic mode and in the range-range mode(See 4.4.3 and A.4.) These systems operate in eitherthe very low frequency (less than 30 kHz) or

SPECIFICATIONS AND GENERAL REQUIREMENTS

the low frequency (30- to 300-kHz) ranges. Longrange systems shall be used to control surveys onlyin those areas that fall beyond the effective ranges ofshort or medium range systems unless otherwise au-thorized in the project instructions.

1.3.3.2.4. Electronics systems calibration. Foruse in this manual, ''calibration'' is defined as thecomparison of one or more positions determined byan electronic positioning system with correspondingknown positions. Corrections to be applied to ob-served electronic values are computed from thesecomparisons. Recommended minimum system cali-bration requirements follow. Chiefs of party shallmake additional calibrations when necessary. (See4.4.3.3.)

1.3.4. Plotting Control

Electronic control lattices shall be plotted inink on the hydrographic sheets using a distinctive col-or for each family of arcs. Lattices are not necessaryon the final field sheet. (See 4.2.6.) Plotted arcs shouldbe spaced approximately 8 to 10 cm apart on thesheets. Each arc shall be identified in an appropriatematching color by its distance or lane value and itscontrol station number or numbers of origin. Thename, identification number, and year of establish-ment shall be indicated on at least one arc for each sta-tion.

Hydrographic parties not equipped withautomatic plotters should request field and calibra-tion sheets from their Marine Center to avoid manualplotting. Control stations and electronic control arcswill be plotted on the sheets if the necessary data arefurnished. Geographic positions of these stationsmust be logged, tabulated, and submitted in accor-dance with the individual Marine Center require-ments. The class or type of each station has to be

Long range navigation systems used to con-trol small-scale offshore surveys shall be calibratedas frequently as practical by the most accuratemeans available. (See 4. 10. 1)

1-9 (JUNE 1, 1981)

Short range navigation systems used to con-trol inshore surveys shall, at the minimum, be cali-brated at the beginning and at the end of each workdayand at such times when the hydrographer is uncertainof the validity of the previous calibration. When usedfor smaller scale offshore surveys, calibrations shouldbe made at least once each day. Two or more three-point sextant fixes with check angles or positions ofequivalent accuracy shall be observed simultaneouslywith the electronic position value. Corrections to theobserved electronic values are then determined foreach fix, and the mean correction is computed. (See4.4.3.3.) Corrections that differ from the mean value bymore than 0.5 mm at the scale of the survey shall be re-jected and redetermined. Calibrations shall be made inor as close as possible to the area being surveyed.

Medium range positioning systems used tocontrol inshore surveys shall be calibrated using thesame criteria as prescribed for the short range sys-tems. Calibration corrections for medium range sys-tems occasionally have a tendency to varysignificantly in different areas of the survey, particu-larly close inshore. (See 4.4.3.4.) The hydrographermust be continually alert for this phenomenon andshall make additional calibrations at his discretion.When used for smaller scale offshore surveys, medi-um range systems shall, at a minimum, be calibratedat the beginning and at the end of each cruise. Medi-um range systems may also be calibrated using shortrange systems that have been properly calibrated.

Refer to section 4.4.3.3 for a detailed discus-sion on calibration procedures and requirements.

1.3.3.3. HYBRID CONTROL SYSTEMS. Thesesystems combine line-of-position data from two ormore different types of positioning systems. Themost commonly used hybrid systems include combi-nations of electronic positioning data with visual ob-servations. (See 4.4.4.) During sounding operationscontrolled by hybrid methods, the vessel is generallymaneuvered along electronic line-of-position arcs.

Visual observations may be sextant anglesbetween hydrographic signals observed from thevessel or may be theodolite azimuths observed froma shore station. The objects used for sextant observa-tions must straddle the electronic line of position.Calibration requirements for short and medium rangepositioning systems also apply to hybrid systems.

Each control station used during the surveythat lies within the hydrographic sheet limits shall beshown in ink by the appropriate symbol (appendixB) and shall be identified by a three-digit number.(See 4.2.5.) Identification numbers begin with 001,are consecutive, and must not be repeated on anyone hydrographic sheet. Recoverable control sta-tions shall, in addition, be identified on the sheets byname and year of establishment. (Refer to 4.2.5 formanual plotting of control.) Station names and num-bers are entered in ink using vertical numerals andupper case letters approximately 3 mm high in colorsmatching the symbol. Names and numbers shouldnot be placed in areas where they may be confusedwith soundings or other hydrographic data.

HYDROGRAPHIC MANUAL

any circumstances. Sounding lines are not requiredover extensive tidal flats or in other areas shown bythe survey to uncover at low water.Photogrammetrically located hydrographic

control stations may be transferred directly from sta-ble base copies of the shoreline manuscripts (at com-pilation scale) to hydrographic sheets of equal scale.If the scales vary or if photo-hydro station positionsare needed for computer input, geographic coordi-nates must be carefully scaled from the manuscriptcopy. All control computations, scaled distances andconversions, plots, and direct transfers shall bechecked carefully as the work progresses.

1.4.1. Line Spacing

1.4 SOUNDING LINES

1.4.2. Crosslines

Shoreline manuscripts at the required scaleare the source of the charted low water or other da-tum line provided that the line has been compiled us-ing tide-coordinated aerial photography taken afteran accurate datum of reference has been established.The low water line shall be determined hydrographi-cally only when so directed by the project instruc-tions. (See 1.6.) The safety of the personnel andequipment, however, shall not be jeopardized under

3. Crosslines shall be run at angles of 45to 90º with the regular system.

Crosslines are generally of little value forchecking in areas of very irregular submarine relief.

1-10(JUNE 1, 1981)

clearly indicated to assure that the correct color andsymbolization are shown on the plotted sheet.

Hydrography is begun by sounding along apredetermined system of lines that will delineate thesubmarine relief in the most thorough and economicmanner. (See 4.3.5.) A series of evenly spaced paral-lel sounding lines is usually the best method to ac-complish this objective. In general, the soundinglines should be run normal to the depth contours, butfrequently it is more advantageous to adopt anothersystem. For the development of steep features, suchas ridges or submarine valleys, the system of linesshould cross the depth contours at an angle of ap-proximately 45º. A restricted channel may be devel-oped by a series of lines parallel to the axis of thechannel if the sounding vessel cannot safely and ef-fectively maneuver on lines that cross the depth con-tours at a sharper angle. (See 4.3.5.4.)

When hydrography is controlled by anelectronic positioning system and positions are plot-ted by hand, sounding lines may be run along equi-distant or hyperbolic line-of-position arcs to gainpositive control of the vessel on the sounding line.Vessels equipped with modern computers and auto-matic plotters have the flexibility of running arcs orstraight lines with equal positive control. Straightlines are generally used because of greater flexibilityin the selection of direction. Regardless of the systemselected for a hydrographic project, the lines or arcsfollowed shall permit the most effective develop-ment of the bottom topography.

The spacing of sounding lines required to de-velop an area properly depends upon the depth of thewater, the topographic configuration of the bottom,the general nature of the area, and the purpose of thesurvey. (See 4.3.4.) The bottoms of harbors, channels,anchorages, and shoal areas that may present dangersto navigation should be developed by a system ofclosely spaced lines (e.g., lines spaced from 50 to 100m apart on a 1:10,000 scale survey). As depths increaseand survey scales decrease, the line spacing increases(up to 8 km for ocean surveys in depths over 1,000 fm).Project instructions specify the maximum allowablesounding line spacing for the various survey depthsanticipated. (See 2.3. 1.) It may be necessary, however,for the hydrographer to reduce the line spacing andincrease the survey scale to delineate the bottom con-figuration adequately.

Least depths over pinnacles or other signif-icant sharp features usually cannot be determinedadequately merely by decreasing line spacing. Sup-plemental observations such as direct depth mea-surements by divers or drift soundings supple-mented with lead-line depths over these featuresshall be obtained. (See 4.5.9.) Frequently, these fea-tures can be located by wire sweeps or pipe drags.

The regular system of sounding lines shallbe supplemented by a series of crosslines (4.3.6) forverifying and evaluating the accuracy and reliabili-ty of surveyed depths and plotted locations. Thefollowing procedures are used:

1. All launch and small boat hydrogra-phy shall be verified by crosslines to the extent of 8to 10% of the principal system of sounding lines(exclusive of development).

2. All ship hydrography in areas of fairlyregular bottom shall be verified by crosslines to theextent of 5 to 6% of the regular system of lines (ex-clusive of development). In areas where the princi-pal system of sounding lines is generally parallel tothe depth contours, the crosslines shall be 8 to 10%of the regular system.

SPECIFICATIONS AND GENERAL REQUIREMENTS

ber of examinations may be reduced; however, theleast depth over detached features surrounded bynavigable waters shall be determined regardless ofthe importance of the area.

After the feature has been developed byclosely spaced lines, each critical area thereon mustbe thoroughly examined to determine the leastdepth. Pinnacles, rocky shoals, and other sharplyrising features hazardous to navigation should bedetected by wire sweeping or pipe dragging; theirdepths should be measured by a diver. (See 1.4.1.)As an alternative, extensive drift soundings shouldbe taken over the feature using both depth recorderand lead line.

The development of a shoal and search forthe least depth frequently result in the running oflines that cannot be smooth plotted at the plannedscale of the survey. Lines not adding to the data al-ready recorded should be marked ''not to be smoothplotted'' in the sounding records. Excess data of thisnature should be deleted from the master data tapestransmitted for processing at the Marine Centers.Raw field data tapes must not be altered or de-stroyed.

1.4.4. Survey Overlap at Junctions

An overlap of at least one sounding line orequivalent distance shall be made with each adjacentsurvey, except as specified below. If the depths atthe junction do not agree, sounding lines of the newsurvey should be extended into the older survey un-til a satisfactory agreement has been reached. (See4.3.2.) If a reasonable extension into the other sur-vey fails to reach agreement, an investigation shouldbe made, conclusions and recommendation devel-oped, and a report submitted to the appropriate Ma-rine Center with a request for further instructions.

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(See 4.3.6.) The hydrographer should exercise judg-ment and seek areas of regular relief where meaning-ful Crosslines can be run.

In areas of regular bottom, a framework ofCrosslines should be run first as an aid in planningthe regular system of lines and to provide a runningcheck on the soundings and their positions. TheCrosslines should be very accurately controlled, andthe sounding equipment should be in excellent oper-ating condition. The lines should be run near thetimes of predicted low water if practical. The sound-ings should be reduced to the actual reference datumif possible. Soundings observed on the regular sys-tem of lines shall be checked with crossline sound-ings on a daily basis. Serious discrepancies are evi-dence of errors in control, vessel positioning, faultyoperation of the echo sounder, or use of incorrectvalues for the reduction of soundings. (See 4.6.1.)

1.4.3. Development of Shoals and OtherHazards

A basic hydrographic survey is not completeand adequate until there is reasonable assurance thatall obstructions, shoals, and other dangers to naviga-tion in the survey area have been found and theleast depths over them determined. Every soundingslightly less than the general, surrounding depthsmust be regarded as an indication of a possibleshoal or potential hazard to navigation. (See 4.5.9through 4.5.11.) In many localities where the bottomis extremely irregular, however, it is not practical toexamine every shoal indication. When selectingsoundings to be further exmined, the importance ofthe locality and the types of shoals or dangers to beexpected must be carefully evaluated. Hydrographers,should be guided by the following considerations:

1. In general depths of 20 fm or less ina navigable area, all indications of shoaling shouldbe investigated.

2. At any depth in excess of 20 fm, allshoal indications rising more than 10% above thegeneral surrounding depths should be investigated.

3. The nature of the bottom must beconsidered. If it is rocky, there is more likelihood ofdangerous pinnacles being present. If the bottom iscomposed of sand or mud, there is less chance thata natural danger exists.

4. The importance of the region shouldbe considered from the point of view of navigation.All shoal indications in channels and harbors mustbe examined. In areas of lesser importance, the num-

The development of shoal indications re-vealed by the general system of fines is the most im-portant part of hydrography, and frequently themost extensive. The line spacing shall be reduced byrunning intermediate ''split'' lines to develop theseindications. (See 4.5.9.) A second pattern of closelyspaced lines, usually parallel to the axis of the fea-ture, should be run to provide greater detail in criti-cal areas. In some instances, radiating lines crossingat the center of a small shoal may better develop thefeature. (See 4.3.5.)

HYDROGRAPHIC MANUAL

The overlap specified herein shall apply tothe following classes of surveys:

1. All noncontemporary surveys (4.3.2).

On automated electronically controlled sur-veys where a position fix is obtained for each re-corded sounding, occurrences 2 and 3 may be omit-ted, provided the event and time of occurrence arenoted in the hydrographic records.

1.4.5.2. POSITION NUMBERING. Hydrogra-phic survey positions are numbered consecutivelyover the range I through 9999. When more than onevessel is used on the same survey, this range orblock of numbers should be proportioned to corre-spond to the amount of hydrography expected to beaccomplished by each vessel. Table 1-1 is an exam-ple.

If the hydrographic survey is continuous inthe same year, by the same method, and by thesame survey vessel, junctions between adjacentsheets may be made by spacing the sounding lines asthey would have been spaced had the two surveysbeen combined on one sheet.

1.4.5. Positions1.4.6. Sounding Interval

1.4.5.1. POSITION FREQUENCY. The positionof the vessel shall be determined and recorded atintervals that permit an accurate plot of the sound-ing line. (See 4.4.5.) The length of time interval be-tween successive fixes along a line is dependent onthe scale of the survey, speed of the vessel, and typeof positional control. All information necessary toplot the position accurately, such as time, course,speed, and fix data, must be included in the hydro-graphic records.

I-

The maximum distance between consecu-tively numbered positions along a line shall not ex-ceed 5 cm at the scale of the survey provided that aposition is determined and recorded for each sound-ing. Otherwise, the maximum distance shall not ex-ceed 4 cm on the hydrographic sheet regardless ofthe type of position control or the scale of the sur-vey. If the survey is controlled visually and the ves-sel is not steered along electronic line-of-positionarcs, the interval between plotted positions shall notexceed 3.5 cm. If the vessel is steered on an arc ofsmall radius, the interval shall be reduced as neces-sary to permit accurate plotting of the soundingsbetween recorded fixes.

1.5.1. Sounding Equipment

Shoal water echo sounders (A.6.3) shall beused to the limit of their capability to record depthsaccurately. Shoal water digital echo sounders are

TABLE 1-1,-Position numbering of Hydrographic SurveyMI 20-3-74

AssignedVessel position nos.

1. At the beginning and end of eachsounding line.

Mt. Mitchell 1-40004001-6000Launch 16001-9000Launch 3

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2. Contemporary surveys conducted bya different survey party.

3. Contemporary surveys conducted by the same field party in different years, by differentmethods, or by different vessels.

4. Surveys conducted by other organiza-tions.

Additional position fixes should be takenand recorded for each of the following occurrences:

2. At each change of course greaterthan 10º.

3. At each appreciable change in thespeed of the sounding vessel.

4. At each detached position for asounding, bottom sample, aid to navigation, or othersimilar purpose.

Soundings shall be recorded and plotted atregular intervals close enough to provide a realisticrepresentation of the bottom configuration. (See4.5.6.) Regular spacing intervals should neither beless than 4 mm nor exceed 6 mm at the scale of thesurvey. Maximum depths over depressions and mini-mum depths over shoals or dangers to navigationshall be recorded as they occur or be inserted in therecords when the hydrographic data are fieldchecked. Recording excessive soundings, however,results in wasted effort when the data are processedand shall be avoided. The time that each soundingwas taken shall be noted. When echo soundings aresupplemented with depths measured by lead line, bysounding pole, or by a diver, the records shall indi-cate clearly the method used.

1.5 DEPTHS

SPECIFICATIONS AND GENERAL REQUIREMENTS

ters to be surveyed shall be determined, computed,applied, and reported in accordance with section 4.9.

1.5.3. Graphic Depth Records

Echo sounders used by the National OceanSurvey for hydrographic surveying produce a perma-nent graphic or analog record of the bottom profile.The graphic record, also known as an echogram orfathogram, shall be used for:

Scanning and checking soundings recordedmanually or digitally.

A sounding pole or lead line (A.6.1) shall beused to measure depths that are too shoal for echosounders, to supplement and verify echo soundingsin areas containing kelp or grass, to verify leastdepths over shoals, obstructions, and other dangersto navigation, and as a calibration standard for echosounders. (See A.6 for a discussion of depth-measur-ing equipment.)

1.5.2. Echo Sounder Calibrations

Pertinent information shall be annotated ac-curately and neatly on the graphic records during thecourse of the survey for use by the hydrographer andothers in the later verification and use of the surveydata. (See 4.8.) This information shall include:

2. Sounding apparatus.3. Weather and sea conditions.4. Calibrations and operational checks.

5. Position marks and numbers.

Every record shall be thoroughly, carefully,and conscientiously scanned and checked by experi-enced field personnel to ensure completeness and ac-curacy of all field data. A mere cursory inspectionActual velocities of sound through the wa-

1-13 (JANUARY 1, 1980)

preferred over sounding instruments limited to ana-log output. Graphic records of the sounding profiles,however, must be obtained in conjunction with digi-tal records as supporting information for the hydrog-rapher and for survey verification.

The project instructions may authorize theuse of deep water echo sounders for surveys in wa-ters deeper than 150 fm to preclude frequent switch-ing between shoal water and deep water instruments.

Digital and analog echo sounders used bythe National Ocean Survey (A.6.2) for hydrographicsurveys are normally calibrated at 800 fm/s for theassumed velocity of sound in water. Periodic fieldcalibrations of the sounding equipment shall be madeto determine the corrections to observed soundingscaused by variations in the velocity and for other in-strumental errors. When the summation of calibra-tion and datum corrections to an echo sounding isless than half of 1% of the depth, the correctionsmay be disregarded; the corrections shall be appliedin all other cases.

On small vessels, bar checks shall be madetwice daily and at other times when necessary, suchas when equipment is changed or adjusted. Routinebar checks should be made only when sea conditionspermit accurate observations. (See 4.9.) On larger ves-sels where bar checks cannot be taken, echo sound-ings are compared with depths observed by lead line(vertical cast) at selected intervals. The simultaneouscomparisons are recorded for use in compiling instru-ment corrections. All vertical cast comparisonsshould be made in shoal water when the sea condi-tions are calm and the bottom is relatively smoothand hard. Lead-line comparisons should be made inthe areas where junctions are effected with launch hy-drography or where soundings were taken by anothervessel. If digital soundings are used for the survey,bar check or lead-line values are compared with boththe digital readings and the graphic record.

Scaling the depths over peaks, deeps, andother significant hydrographic features found be-tween regularly spaced interval soundings. (See sec-tion 1.4.3.)

Adjusting digital soundings for the effectsof wave action on the vessel (heave) or, if un-compensated wave action is excessive, serving as theprimary record.

Reconciling erroneous soundings causedby kelp beds, fish, or unaccountable strays.

1. Dates, times, vessel, and survey andsheet numbers.

6. Brief notes defining the beginningsand endings of lines, turns of the vessel, and changesin speed while sounding.

7. Other descriptive information relatingto or confirming more detailed notes in the surveyrecord that pertain to detached positions for aids tonavigation, obstructions, and for references to othersignificant features passed on sounding lines.

8. A definitive statement as to whetherundulations on the graphic record were caused bywave action on the vessel.

HYDROGRAPHIC MANUAL

Many of the problems experienced duringthe processing of hydrographic data can be traced toimproper calibration and operation of the soundingequipment or to incorrect interpretation of thegraphic depth record. Knowledgeable interpretationof indications on the graphic records can lead to thedetection and correction of faulty data. During thescanning process, the hydrographer should be able tointerpret and reconcile most spurious traces causedby stray returns, side echoes, fish, and grass. (See4.9.8.2.) The actual bottom trace on the graphic re-cord shall be scanned and interpreted to the best ofthe hydrographer's capability. The graphic record isthe key source for indications of the presence ofshoals that may have been missed by the regularsounding line system. Variations in initial or otherapplicable corrections shall be applied as necessaryto correct the observed soundings to true waterdepths.

1.5.4. Reduction of Soundings

Required corrections to soundings includeany or all of the following:

Compensation for the following errors, ifpresent, in the graphic depth recording equipment:

Rigid specifications cannot be defined foracceptable differences between digital depths anddepths scaled from a graphic record. Close agree-ment, however, is essential as depths are scaled fromthe graphic record to supplement the digital data.The hydrographer must continually exercise soundjudgment as acceptable differences vary with thedepth of the water, the relative importance of thearea, and the irregularity of the bottom. (See4.9.8.1.)

Where size permits, graphic depth recordsand raw sounding data printouts shall be folded in10-in (25-cm) lengths and forwarded to the appropri-ate Marine Center in letter size accordian folderswith the other survey records. Data for each sound-ing day shall be filed in a separate section and la-beled, using tabs to show the first and last position

1.5.4.1. DATUMS OF REFERENCE. The da-turns of reference adopted for the reduction ofsoundings on hydrographic surveys and for depthson charts published by the National Ocean Survey

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of peaks and deeps is not sufficient. (See 4.8.5 and4.9.8.)

Under favorable sounding conditions, thegraphic depth record should agree with digital ormanually recorded depths to within ± 0.5 ft or ± 0.2fm (except on steep slopes). Because electronic depthdigitizers; are programed to record soundings at fixedintervals only and cannot distinguish wave actionfrom undulations in the bottom, adjustments mustfrequently be made to the recorded digital soundings.Additional soundings must be scaled from the analogdepth record to depict the bottom configuration ade-quately. (See 4.9.8.1.)

numbers, Julian date, and the name and identifica-tion number of the sounding vessel.

Recorded soundings on hydrographic surveysshall be corrected for any departure from true depths at-tributable to the method of sounding or to a fault in themeasuring apparatus and for the elevation of the tide orwater level above or below the chart datum (tidal or stagecorrection). Corrections shall be applied in the same unitin which the soundings have been recorded. Fractions ofcorrection units are entered in the records as decimals.

Corrections for erroneously scaled values.Heave error (wave effects).Transducer draft.Settlement and squat (or lift).Velocity of sound through water.Reduction to datums of reference.

Variation of the initial from theadopted index, speed, and radius of rotation of therecording stylus arm.

Corrections for phase errors betweenscale settings, misalignment of recording paper, andother instrumental errors caused by variations in sig-nal strength and time lags in the circuitry.

Periodic measurements of temperature andsalinity shall be made to compute velocity correc-tions to echo soundings (4.9.5) except in areas wheresatisfactory bar checks can be obtained down to atleast 75% of the range of depths sounded. If oceano-graphic data are used to determine velocity correc-tions for soundings, at least one temperature and sa-linity cast should be taken each month in an arearepresentative of the deepest waters surveyed. Thespecific frequency for observing velocity data is amatter of judgment and is dependent upon the com-plexity of variations in the area. Special instructionsfor velocity corrections will be issued for surveys inareas requiring unusual methods, such as those con-ducted in the Gulf Stream.

SPECIFICATIONS AND GENERAL REQUIREMENT'S

are:

1. For the Atlantic Ocean and Caribbeanareas, mean low water (MLW). See figure B- 1.

2. For the Gulf of Mexico, Gulf CoastLow Water Datum (GCLWD). See figure B-1. (Fordatum limits see chart 11462.)

3. For the Pacific Ocean, mean lower lowwater (MLLW). See figure B-2.

4. For the Great Lakes and connectingchannels, low water datum (LWD). See figure B-3.

5. For most other larger navigable riversand lakes, special datums. In such cases, the project

1.5.5. Depth Unitsinstructions will specify the datum of reference.

1.5.4.2. TIDE OR WATER LEVELS OBSERVA-

TIONS. If there is no tide or water level gage located inor near the project area that can serve as a control sta-tion, an automatic tide or water level recording gageshall be installed at a central point and operated dur-ing the entire period of the survey. Secondary tide andwater level stations may also be required at other sitesthroughout the survey area. Sites for the gages to beused for the datum determination. and corrections tosoundings will be designated in the project instruc-tions. The number and distribution of stations dependon the character of the area and the anticipated chang-es in the times and ranges of tides and water level fluc-tuations.

If it is impractical or impossible to installtide or water level gages at the designated sites, thechief of party shall initiate a proposal for alternatelocations. Major changes in gage locations must beapproved at National Ocean Survey Headquartersunless stated otherwise in the project instructions.

Instructions for installation, maintenance,and removal of tide and water level gages are con-tained in appendix A and in U.S. Coast and Geodet-ic Survey (1965a) Publication 30-1, ''Manual of TideObservations.'' Unless stated otherwise in the projectinstructions, continuous observations at each second-ary station shall be continued for a minimum periodof 30 days to permit a datum determination of suffi-cient accuracy. If necessary, the hourly heights of thetide or water levels required for reduction of sound-ings shall be tabulated prior to sending the recordsto Headquarters. (See 4.9.3.) However, tide andwater level records from automatic digital recording(ADR) gages generally are not tabulated in the fieldunless the data are required for resolving discrepan-cies. Knowledge of the binary code and for-

Regardless of the methods used for deter-mining depths during a survey, soundings shall berecorded in whole numbers or to the nearest decimalpart (4.5.7.1) and in accordance with the followingrules:

1-15 (JANUARY 1, 1979)

mat of the ADR gage punched paper tapes (A.8.1.2)is necessary to extract these data. Verified hourlyheights [Greenwich Mean Time (GMT)] for controland secondary stations will be furnished by Head-quarters on request.

The time meridian used shall be clearlymarked on each tide or water level record. When theobservations at any station are terminated, a nota-tion of the hour and date of discontinuance shall beentered on the last record removed from the gage.The location of each gage shall be shown on the hy-drographic sheets. (See 4.9.3.)

The depth unit for hydrographic surveys inthe Great Lakes, the Atlantic Ocean, the Gulf ofMexico, and bodies of water tributary thereto is inte-gral feet. Offshore areas that lie entirely beyond thelimits of charts where the depth unit is feet are sur-veyed and charted in fathoms. In certain areas suchas the coast of New England where echo soundersare operated on the fathom scale for most of the sur-vey, the field sheets may be plotted in fathoms, butthe smooth sheet shall be plotted in feet unless otherunits are designated in the project instructions.

The depth unit of hydrographic surveys inthe Pacific Ocean and bodies of water tributarythereto shall be fathoms; but when the major part ofthe survey is within the limits of a chart with depthsin feet, the smooth sheet shall be plotted in feet.

Although the recorded depths may changefrom one unit to another within the area of a survey,all measurements shall be corrected and reduced tothe unit to be plotted on the smooth sheet. Only oneunit of depth shall be used on any hydrographic sheet.

1. Echo soundings for a hydrographic sur-vey that will be plotted in feet shall be recorded infeet and decimals unless the methods in rules 2 and 3are employed.

2. When depth recorders are used that canreadily be switched to record feet or fathoms in areasof irregular bottom, the first phase in feet shall beused to its maximum depth limit. Where numerouschanges in phase would be required on the footscale, fathoms shall be used for greater depths.

HYDROGRAPHIC MANUAL

been properly controlled and soundings have beenplotted correctly.

No single requirement for the spacing ofdepth contours can be prescribed that will apply to alltypes of terrain. (See 4.5.7.3 and 4.5.7.4.) The contourlines must be spaced at an interval to depict the sub-marine relief as completely and accurately as possibleand to permit the hydrographer to visually inspectevery sounding shown on the sheet. A good generalrule is that the depth contour on field sheets should bedrawn, if practical, at the following intervals:

1.5.6. Field Sheet Soundings4. At 25-fm intervals in depths greater

than 100 fm.

In those areas where the bottom is relativelyflat and featureless, nonstandard depth contours areshown at a spacing of 3 to 4 cm at the scale of thesurvey.

Copies of the field sheet are often used torevise and update nautical charts before smoothsheets of the survey are completed. It is critical,therefore, that soundings and other hydrographicdata on the field sheets be clearly shown and easilyinterpreted.

1.6.1. Transfer of Topographic andPlanimetric Detail

1.5.7. Depth Contours

Shoreline shall be shown on hydrographicsurvey sheets in accordance with the following:

Whether or not the survey in an area has

1-16(JANUARY 1, 1979)

4. All depths measured by echo soundersfor a hydrographic survey that will be smooth plot-ted in fathoms shall be recorded in fathoms and deci-mals except for rule 5.

5. The project instructions may specifythat shoal water soundings be obtained in feet andtenths for surveys that will be smooth plotted infathoms.

6. Lead-line soundings that are inter-spersed with echo soundings shall be recorded in thesame unit as the echo soundings.

Soundings should be plotted on the fieldsheet in black ink as the survey progresses. Soundingnumerals shall be of uniform size and clearly legible.(See 4.5.7.2.) Position and sounding numbers shall beplotted at a density and intensity to permit adequatephotographic reproduction of the field sheet. Leastdepths over shoals are inked in slightly larger andheavier numerals. A note and leader may be used toemphasize an important feature. Rock symbols mustnot be obliterated by soundings or other symbols.

These shall be drawn by the hydrographeron the field sheet in pencil as the work progresses. Acareful study of both the soundings and closelyspaced contours will disclose:

Areas where additional hydrographic de-velopment is needed to delineate the bottom configu-ration adequately.

Where errors have been made or wherethere are discrepancies that require further investiga-tion.

The adequacy of junctions with adjacentsurveys or between those areas of a survey controlledor sounded by different methods.

3. At 10-fm intervals between 50 and 100fm.

1. At l-fm intervals to 20 fm.

2. At 5-fm intervals between 20 and 50

fm.

Standard depth contours required on smoothsheets are drawn on the field sheet in the colors pre-scribed for smooth sheets prior to submitting thesurvey for smooth sheet processing. (See 4.5.7.4.)Supplemental contour lines shall be shown to empha-size relief as necessary.

1.6. OTHER SURVEY REQUIREMENTS

The shoreline and alongshore detail shall becarefully transferred from the shoreline manuscriptsto the field sheets. If shown on the manuscripts, thelow water line will also be transferred to the sheets(except for surveys in the Great Lakes).

Great Lakes, the line formed by the inter-section of the land with the water surface at the timeof the survey.

Tidal waters, the line formed by the inter-section of the land with the water surface at meanhigh water (MHW).

3. Depth recorders that cannot beswitched quickly from feet to fathoms shall be op-erated on the foot scale to the maximum extentpractical in those areas which will be charted infeet. In areas where depths exceed the limit of thefoot scale or if the submarine features are very ir-regular, the instrument may be operated on thefathom scale.

SPECIFICATIONS AND GENERAL REQUIREMENTS

The low water line shall be shown as follows:

After the transfer has been field verified, theshoreline and other details are inked in black with an un-broken line 0.4 mm wide. (See 1.6.2.)

1.6.2. Verification of Alongshore Detail

Close coordination of the activities of the hy-drographer and field editor is essential throughout allphases of the survey. The chief of party shall reviewand evaluate all such data to ensure that errors ofomission were not made and all discrepancies wereresolved satisfactorily.

Symbols inked in blue on the field sheet arere-inked in black when field verified. If the positionof an offshore rock is changed by the hydrographeror if there is no rock at the position shown,

1.6.3. Bottom Characteristics

1-17 (JANUARY 1, 1979)

Changes to shoreline delineation, rock loca-tions, or other details shown on photogrammetricmanuscripts are made in red ink on the hydrographicfield sheet with explanatory notes and references torevisory location data. Both hydrographer and fieldeditor must be kept informed of all such changes toavoid discrepancies between the manuscripts and hy-drographic sheets. (See ''Provisional PhotogrammetryInstructions for Field Edit Surveys.'' ) A dashed redline is used to show an approximate or estimatedshoreline on the field sheet. (See appendix B.)

appropriate notes must be made in the hydrographicrecords, on the field sheets, and on the field editsheet. Failure to reconcile and explain differences be-tween a shoreline manuscript and a hydrographicsurvey may cause errors, result in unnecessary delaysand difficulties during verification, and in some casesrequire a field unit to return to the area to resolve amajor discrepancy.

Each isolated bare rock, rock awash, orother hazard seaward of the shoreline must be locat-ed by hydrographic or photogrammetric methods.Each such feature shall be described definitively onthe field sheet. The height or depth of the featurewith respect to the water surface and the date andtime of the observation shall be recorded for subse-quent reduction to the chart datum. Rocks of agroup or of a rocky area that are important from anavigational standpoint also shall be located andtheir elevations determined. If predicted tides wereused by the field editor for the determination of ele-vations, the hydrographer shall verify the elevationwhen observed tides are available.

Areas in which sounding operations cannotbe conducted safely or in which individual featuresare too numerous to be located economically shouldbe delimited by a surveyed line and appropriate de-scriptive notes entered on the field sheet and in thehydrographic records.

All other waters, as defined in the projectinstructions.

If the actual shoreline is obscured from themariner by vegetation such as in marsh and swamp, theapparent shoreline is shown. The apparent shoreline isthe intersection of the shoreline datum with the outeredge of vegetation.

Tidal waters of the Atlantic Ocean and Ca-ribbean Sea, the line formed by the intersection of theland with the water surface at mean low water.

Tidal waters of the Gulf of Mexico, the lineformed by the intersection of the land with the watersurface at Gulf Coast Low Water Datum.

Tidal waters of the Pacific Ocean includingAlaska, the line formed by the intersection of the landwith the water surface at mean lower low water.

Great Lakes, the line formed by the intersec-tion of the land with the water surface at the elevation ofthe low water datum. This line is generally not shown onsurveys of the Great Lakes.

Rocks, limits of marine growth or foul areas,and similar detail lying seaward of the shoreline areshown in blue except that offshore islets and rocks withpositions definitely established are shown in black ink.Shoreline manuscripts often delineate the approximatelimits of shoals and channels. These limits are trans-ferred to the field sheet and indicated by fine dashedblue lines. (See 4.2.7.)

The hydrographer and field editor share the re-sponsibility of verifying features seaward of the shore-line that are shown on photogrammetric manuscripts.[See ''Provisional Photogrammetry Instructions forField Edit Surveys'' (National Ocean Survey 1974).]These details may include the existence, positions, andheights or depths of rocks, ledges and reefs, limits of foulareas, wrecks, and other similar objects. (See 4.5.8.)Questionable features below the water surface such asreef limits, rocks, pilings, and similar objects must be in-vestigated thoroughly by the hydrographer.

The character of the bottom shall be deter-mined by sampling with corers, clamshell bottomgrabbers, or similar grab samplers that produce a

HYDROGRAPHIC MANUAL

and to ensure proper dissemination of information tothe public. (See 5.9.)

1.6.5. Aids to Navigation

The hydrographer is responsible for locatingnonfloating aids and determining the azimuths ofnavigational ranges on projects conducted withoutphotogrammetric support. In such cases, positionsand azimuths shall be determined by conventionalground survey methods that meet the accuracy stan-dards prescribed for Third-order, Class I horizontalcontrol.

All bottom samples shall be classified, prop-erly recorded, labeled, stored, and transmitted. (See4.7.2.) The abbreviations shown in table B-7 in ap-pendix B are used to record bottom character-istics.

Extensive bottom sampling is not required ifthe project area has been surveyed previously andthe characteristics have been determined adequately.Sufficient samples, however, must be taken to verifythat changes have not occurred or to indicate areasof change where additional sampling is necessary todescribe the present characteristics adequately.Where the general trend of the newly surveyeddepths has changed significantly since the prior sur-vey, one should assume that the charted bottomcharacteristics are no longer accurate. In such areas,sampling should be conducted at the prescribed in-tervals.

When a floating aid to navigation is off sta-tion, as shown on the largest scale chart of the area,the facts should be reported promptly to thecommander of the nearest U.S. Coast Guard Dis-trict. If the aid is off station to an extent that it con-stitutes a danger to navigation, the facts shall be re-ported immediately. Recommendations based on newhydrographic surveys for additional aids or for moredesirable locations of existing aids are submitted tothe U.S. Coast Guard in writing through the appro-priate Marine Center as soon as practical; a

1.6.4. Dangers to Navigation

All shoals, rocks, wrecks, and other dangersto navigation discovered during the course of a sur-vey shall be reported immediately by radio, tele-graph, or telephone to the commander of the nearestU.S. Coast Guard District and to the appropriateMarine Center. A copy of the message and a tracingfrom the field sheet or from a large-scale chart show-ing the exact location of the danger shall be sent toNational Ocean Survey Headquarters for disposition

1-18(JANUARY 1, 1979)

recognizable sample. Bottom descriptions are shownon nautical-charts for the mariner as a guide to theholding characteristics of a potential anchorage. Thedescriptions are also useful for fishermen in locatinggood fishing areas and in avoiding foul or rockyareas where equipment may be damaged or lost.

In anchorages, the distance between bottomsamples should not exceed 5 cm at the scale of thesurvey. The distance between samples in other areason inshore surveys should not exceed 6 cm. Indepths less than 100 fm in offshore survey areas, thedistance should not exceed 12 cm. For ocean surveysconducted between the 100- and 1,000-fm depth con-tours, the character of the bottom is determined atintervals of about 8 to 16 km. In greater depths, bot-tom samples are obtained at all oceanographic sta-tions and at such other places as the project instruc-tions may specify. In harbors and anchorages,enough information should be obtained to permit thedelineation of the approximate limits of each type ofbottom. (See 4.7.1.)

Locations of all floating and nonfloating aidsto navigation shall be provided to the chart compilerto enable him to produce accurate nautical charts forsafe navigation. The azimuths of all navigationalranges must also be accurately determined.

Responsibility for the determination of thepositions of nonfloating aids to navigation and ofthe azimuths of navigational ranges is generallyassigned to the field editor for inshore hydrographicsurveys that include photogrammetric support. Posi-tions of aids and range azimuths are normally deter-mined as part of the photogrammetric mapping op-erations. [See Photogrammetry Instructions No. 64and ''Provisional Photogrammetry Instructions forField Edit Surveys" (National Ocean Survey 1971band 1974).]

The hydrographer has the responsibility fordescribing the salient features of each floating aidand for determining its position and the depth ofwater in which it is located. (See 4.5.13.) The mostaccurate means of positional control available shouldbe employed for this purpose, and check observa-tions should be taken if practical. On visually con-trolled surveys, floating aids are located by three-point sextant fixes with one or more check angles orby theodolite intersection with a check cut. Sextantcuts alone shall not be used.

SPECIFICATIONS AND GENERAL REQUIREMENTS

copy or tracing of the field sheet shall accompanythe report.

1.7. REPORTS AND RECORDS

1.7.1. Field Reports

After the survey is completed and prior todeparture from the project area, the chief of partyshall make a final inspection of all sheets. All ques-tions of adequacy or completeness of the survey mustbe resolved before leaving the area. The field sheetshould also be thoroughly examined for clarity.

In addition to the reports listed in table 1-2,special reports shall be prepared on items or matters ofunique interest or historical documentation. Topics forspecial reports include but are not limited to innova-tive operational procedures, trial equipment evalua-tion, and additional observations not generally associ-ated with hydrographic surveying. (See section 5.12.)

1.7.3. Forwarding Field Sheets

Within 6 weeks of the termination of fieldoperations, field sheets and data for surveys shall beforwarded to the appropriate Marine Center for pro-cessing. Surveys are then forwarded to NOS Head-quarters for quality control evaluation and final ac-ceptance. Ordinarily, field sheets need not besubmitted to headquarters following a satisfactoryevaluation; however, commanding officers and Ma-rine Centers have an inherent responsibility to en-

Schedule AddresseeSectionReport title

Routine during Monthly Ship Accomplishment ReportMonthly Progress SketchMonthly Survey Status ReportMonthly Activities Report

operations

As required Dangers to NavigationPhotogrammetric Precompilation Field Reportduring operations

As appropriate duringor immediatelyfollowing operations

Routine and as appro-priate immediatelyfollowing operations

Immediately afterclose of field season

1-19 (JANUARY 1, 1980)

Copies of reports listed in table 1-2 shall besubmitted to the indicated addressee, through the ap-propriate Marine Center, as supporting documenta-tion for hydrographic surveys and to meet other re-quirements of the National Ocean Survey NauticalCharting Program. The original of each report willbe sent by the Marine Center to National Ocean Sur-vey Headquarters for official archiving. (See chapter5 for details on the required content and preparationof these reports.)

1.7.2. Inspection of Field Sheets andRecords

TABLE 1.2 — Field reports

The chief of party shall inspect the fieldsheets, shoreline manuscripts, and records at regularintervals, daily if possible, to assure himself that alloperations are in accordance with the requirementscontained in applicable manuals and project instruc-

tions. When making his examinations, particular at-tention must be given to the adequacy and complete-ness of the survey with special emphasis on indica-tions of shoals and dangers; determination of leastdepths over submerged rocks, shoals, bars, andwrecks; verification of charted features; and the de-velopment of navigable channels. He should ascertainthat junctions with adjacent surveys are satisfactoryand no unsurveyed gaps (holidays) remain in thearea. (See 4.3.2.) Following this review, the chief ofparty shall indicate to the hydrographer and field ed-itor where additional work is required and ensurethat satisfactory methods and procedures are used.

Chart InspectionVisit to Authorized Chart Sales AgentCoast PilotLandmarks and Nonfloating Aids to NavigationTide and Water Level Station Report and RecordsPhotographsGeodeticMagneticsspecial

Descriptive ReportGeographic NamesField Edit

Season's ReportSeason's Progress Sketch

5.1.5.1.2

5.35.75.4

5.105.115.85.55.65.125.125.125.12

OA/C322OA/C44OA/C324OA/C322OA/C23OA/C5131OA/Cl8x2OA/D62OA/C5131

5.95.2

OA/C322OA/C34

5.15.1.15.15.1

OA/C7OA/C351OA/C35x1OA/C3

OA/C5131OA/C5131

OA/C353OA/C3x5OA/C3415

HYDROGRAPHIC MANUAL

sure timely publication of unreported survey datathat could affect the safety of marine navigation. If aMarine Center evaluation reveals such critical infor-mation, the survey or pertinent portion thereof shall

be sent immediately to National Ocean Survey Head-quarters with specific recommendations for chart ap-plication.

1-20(JANUARY 1, 1980)

2. PLANS AND PREPARATIONS

The following code designations have beenselected for the major survey or project tasks gener-ally performed:

TaskTask Code

At least once each year, schedules for hydro-graphic survey projects are prepared. Among the fac-tors that influence project scheduling are the relativepriorities, the resources available including time, andthe predominant climatic conditions in the subjectareas. After project schedules are approved, detailedproject instructions are issued to field units throughthe appropriate Marine Center.

Each set of project instructions written will beassigned two digits beginning with ''00'' which shallidentify the sequence of issue of those instructions.Once begun, this numbering system will be appliedcontinuously through the digits ''99'' after which thesequence will revert to ''00'' and begin again. The issuenumbers for a given project shall remain unchanged forthe duration of a designated project within a given area.

2.2 HYDROGRAPHIC PROJECT

Project designations include a four-characteralphanumeric identification number which sequential-ly defines:

Examples of project designations are:

The four-character code consists of a letter to identifythe project area, a single digit number to identify thetype of survey or task performed, and two digits to iden-tify the order of issue (sequence) of the instructions. Special projects are field examinations or

surveys of very limited extent or scope and frequent-ly require unique survey or data collection pro-

The code letters for the specific geographicareas of National Ocean Survey operations are listed

2-1 (JANUARY 1, 1979)

2.1 HYDROGRAPHIC SURVEY PLANNING

Requirements for hydrographic surveys ariseas the result of policy decisions, product user reportsor requests, national defense needs, and other de-mands. The inception of a specific hydrographic sur-vey project follows an evaluation of all known re-quirements and the establishment of priorities.Among the many objective and subjective factorsthat influence the establishment of priorities are na-tional and agency goals, quantitative and qualitativemeasures of shipping and boating in an area, the ade-quacy of existing surveys in the area, and the rate ofchange of the submarine topography in the area.

Priorities are under constant review and aresubject to change as a result of the dynamic charac-teristics of some of these factors.

The field operation of a survey party in aspecified geographic area is defined as a project andis assigned a unique project designation.

1. The general project area,2. The type of survey or project task

performed, and3. The issue number of the project in-

structions.

in table 2- 1, with these areas geographically definedin figures 2- 1 and 2-2.

1 Basic Hydrographic Sur-vey - Ship

2 Basic Hydrographic Sur-vey - Field Party

3 Navigable Area Survey(NAS)

4 Chart Evaluation Survey(CES)

5 Ocean Dumping Opera-tions (ODO)

6 Wire-Drag Survey (WDS)7 Track Line Survey (TLS)8 Tides and Currents

Project (T&C)9 Other

OPR-X 115-PE-78, a basic hydrographicsurvey project assigned by National Ocean SurveyHeadquarters for a ship survey in Lake Huron to beconducted by the NOAA Ship Peirce, the project tobe performed during calendar year 1978.

OPR-P820-AR-77, a tides and currentssurvey project assigned by Headquarters for a surveyin Prince William Sound, Alaska, to be conducted bythe NOAA Ship McArthur, the project to beperformed during calendar year 1977.

HYDROGRAPHIC MANUAL

2.3.1.1. GENERAL INSTRUCTIONS. The gener-al part of the instructions shall clearly and specifical-ly state the classification and the purpose of the sur-vey to provide the chief of party with all pertinentbackground information. Limits of the area to besurveyed shall be specified. General instructions willinclude a plan indicating the priorities of survey op-erations by areas, sheets, or activities, and the de-sired or required direction of progress. When two ormore chiefs of party are assigned to operate in thesame area on the same project, their respective areasof operation and authority shall be defined.

Examples of special projects designations are:

2.3.1.2. CONTROL INSTRUCTIONS. Copies ofthe latest geodetic control diagrams, lists of geograph-ic positions, and descriptions of control stations willbe furnished for the project area. A horizontal controlindex will also be included with the data. The projectinstructions will state whether new control surveys arenecessary and, if so, will also specify junction require-ments and the order of accuracy.

All correspondence, reports, and messagesrelating to the project shall be referenced to the proj-ect designation.

Areas where field edit is necessary.

Charted features that will require specialinvestigation. (See 2.3.3.)

Copies of charts of the project area will befurnished with the project instructions. Project limits,limits of prior surveys, and proposed current, magnet-ic, and oceanographic stations will be shown on thesecharts.

2.3.1.5. TIDES OR WATER LEVELS INSTRUC-TIONS. This section of the instructions shall specifywhich tide or water level gages are to be used as ref-erence control stations for the project. An inspectionof an existing station and a report on the in-

(JANUARY 1, 1979) 2-2

cedures. They characteristically are recognized andconducted with much less preparation time than isprovided for general projects. Special projects aredesignated similarly to general projects with the ex-ception of an initial ''S'' indicator added whichprecedes the normal four-character code. The issuenumbers for special projects revert to ''01'' at the be-ginning of each calendar year.

S-L906-RA-77, a special project requiringLORAN-C comparisons assigned by the Marine Cen-ter or by Headquarters for a project off the Californiacoast to be conducted by the NOAA Ship Rainier, theproject to be performed during calendar year 1977.

S-C524-MI-78, a special project requiringoperations at Deepwater Dumpsite 106 assigned bythe Marine Center or by Headquarters for a projectoff the New Jersey coast to be conducted by theNOAA ship Mt. Mitchell, the project to beperformed during calendar year 1978.

These instructions to supplement the generalinstructions in this and other manuals are prepared atNational Ocean Survey Headquarters for each project.The details of the project instructions vary from spe-cific to general depending on the nature, the locality,and the unique requirements of the survey. Draft cop-ies. of project instructions shall be prepared at least 4mo prior to sailing to permit revision comments by theappropriate Marine Center, the chief of party, andother interested organizational elements. Final in-structions are usually issued 3 mo prior to the start ofthe project. Amendments or supplements shall berecommended in the interest of safety of personnel orproperty, for reasons of real economy, or for valid en-gineering reasons. Ordinarily, the project instructionsfor hydrographic surveys will be divided into discus-sions of some or all of the following subjects: general,control, photogrammetry or topography, hydrogra-phy, tides or water levels, currents, magnetics, ocean-ography or limnology, and miscellaneous.

Maximum spacing of sounding lines thatare referenced to certain areas or depths.

Guidance on bottom sample spacing.Project limits and junctions to be made

with other surveys.Wire drag or sweeping investigations re-

quired.

Scales to be used for the survey. (The chiefof party is authorized to use larger scales in smallharbors as necessary.)

2.3.1.4. HYDROGRAPHIC INSTRUCTIONS. Theinstructions for hydrography will ordinarily specify:

The tentative schedule for the delivery ofcopies of the shoreline map manuscripts.

Areas where photo-hydro support datawill be available.

Requirements for horizontal and verticalcontrol identification.

2.3.1.3. PHOTOGRAMMETRIC INSTRUCTIONS.

The photogrammetric portion of the project instruc-tions indicate:

2.3 OFFICE PLANNING

2.3.1. Project Instructions

PLANS AND PREPARATIONS

TABLE 2-1. — Area limit designations for project numbering

GEOGRAPHIC AREAPROJECTAREA

SPECIFICGENERALCODE

-Canadian Border to Cape CodAtlantic CoastA

-Cape Cod to Sandy Hook (includes Long Island Sound, New York Harbor, andthe Hudson River below Troy)

B

-Sandy Hook to Cape May (includes south shore of Long Island)

-Cape May to Cape Hatteras (Includes Delaware Bay)

-Chesapeake Bay (includes all charted tributary waters)

C

D

E

-Cape Hatteras to Cape FearF

-Cape Fear to Cape Canaveral (Including St. Johns River)

-Cape Canaveral to Fort Meyers

-Puerto Rico and Virgin Islands

-Fort Myers to Mississippi River

-Mississippi River to Mexican Border

-Mexican Border to Point Reyes

-Point Reyes to Yaquina Head

-Yaquina Head to Canadian Border

-Canadian Border to Point Manby

-Point Manby to Unimak Pass

G

H

I

Gulf of MexicoJ

K

Pacific CoastL

M

N

Alaska0

P

-Aleutian IslandsQ

-Unimak Pass to Seward PeninsulaR

-Seward Peninsula to Canadian BorderS

-Pacific Islands (Hawaii, Samoa, Guam, Marianas, etc.)

-Lake Champlain & New York State Barge Canal System

Pacific OceanT

Inland WatersU

-St. Lawrence River, Lake Ontario, & Lower Niagara RiverV

-Upper Niagara River, Lake Erie, Detroit River, Lake St. Clair, & St. Clair RiverW

-Lake Huron & St. Marys RiverX

-Lake Michigan, Lower Fox River, & Lake WinnebagoY

-Lake Superior, Lake of the Woods, Rainy Lake, & Minnesota-Ontario BorderzLakes

2-3 (JUNE 1, 1981)

HYDROGRAPHIC MANUAL

established in accordance with instructions con-tained in U.S. Coast and Geodetic Survey (1965a)Publication No. 30-1, ''Manual of Tide Observa-tions,'' except as amended by project instructions.

spection may be required. Supplemental tide or wa-ter level gages are often required, and the instruc-tions will specify the desired locations. (See1.5.4.2.) All tide or water level stations shall be

Fic;URE 2-1-Geographic designations for project numbering for the Atlantic and Gulf of Mexico Coasts and the Great Lakes.

2-4(JUNE 1, 1981)

FIGURE 2-2 — Geographic designations for project numbering for the Pacific Coast, Alaska, and the Pacific Islands.

2-5

PLANS AND PREPARATIONS

JUNE, 1 1981

HYDROGRAPHIC MANUAL

2.3.1.7. ANCILLARY TASKS. Hydrographicproject instructions may require any or all of the fol-lowing ancillary tasks: 1. bottom samples, 2. currentobservations, 3. water characteristics, 4. verificationof floating aids, 5. call attention to special or unique re-quirements for Coast Pilot notes (5.8) and chart in-spection reports (5. 10), and 6. magnetics for anomalydetection, in which case the project instructions willspecify locations where magnetic observations are re-quired. Magnetic observations shall be made in accor-dance with Office of Marine Surveys and Maps (1959)letter instructions File DO-T-3 (revised), ''Directions

2.3.3. Presurvey Review

for Using a Transit Magnetometer.''

A brief report is placed as an inset on thefirst chart of a series. Accompanying charts contain,as insets, pertinent portions of the report. The reportshall include a general statement on the extent of thereview and the character of the area. Either a state-ment or legend shall be included to explain chartmarkings. Charted items requiring complete investi-gation shall be encircled and designated by a number

2.3.2. Data To Start Surveys

2-6(JUNE 1, 1981)

2.3.1.6. OCEANOGRAPHIC OR LIMNO-LOGICAL INSTRUCTIONS. When oceanographic orlimnological observations are to be made in additionto the standard temperature and salinity determina-tions required for correction of echo soundings, theproject instructions will specify:

Station locations.Types of observations to be made.Frequency of observations.Instruments to be used, sample analysis

and preservation requirements, and disposition ofthe sample.

Observations shall be made in accordancewith instructions contained in U.S. Naval Oceano-graphic Office (1968) Publication No. 607, "Instruc-tion Manual for Obtaining Oceanographic Data,''except as modified by the project instructions.

2.3.1.8. REPORTS. 1. Reports shall be submit-ted in accordance with chapter 5 of this manual, 2.project instructions will specify the scale of the chartto be used for the progress sketch to be submitted eachmonth (5.11), 3. the instructions will state the require-ment for submission of the monthly Activities Report.

2.3.1.9. MISCELLANEOUS. The miscellaneoussection of the project instructions will cover any re-quirements for 1. public affairs, 2. dump sites, 3. drillrig location, 4. Loran-C chart verification, 5. clear-ance for research in foreign waters, 6. notification ofproject operations to U.S. Coast Guard for inclusionin Notice to Mariners, and 7. support data which mayinclude copies of prior surveys, presurvey review,chart blowups, and fixed and floating aids listing.

The Chief of Party shall acknowledge re-ceipt of project instructions and amendments theretoin writing.

Copies of all prior survey data and othersupporting information considered necessary to ac-

complish the survey project will be furnished tothe hydrographic field party or vessel with theproject instructions. These data will include:

Descriptions and geographic positions ofrecoverable horizontal control stations in the proj-ect area.

Copies of prior hydrographic and topo-graphic surveys for comparison and junction pur-poses.

Reports on tide or water level stationspreviously established in the area, together withthe descriptions and elevations of bench marks andthe names and addresses of contract observers atprimary stations.

Information on reported dangers to navi-gation.

Prints of the most recent aerial photogra-phy and copies of the shoreline manuscripts.

U.S. Geological Survey (U.S. Depart-ment of Interior, Washington, D.C.) topographicmaps of the area.

Historical oceanographic data, if needed,to correct echo soundings.

A presurvey review shall be conducted atNational Ocean Survey Headquarters in advance ofeach hydrographic survey project. Although the hy-drographer will have copies of the latest large-scalecharts and will be furnished copies of pertinent priorsurveys, an office review of all survey records andchart information received from other sources is in-valuable during all phases of hydrographic surveyoperations. The presurvey review is updated eachyear for continuing projects to provide the hydrog-rapher with the most recent information.

Prior records, surveys, and the largest scalecharts of the project area are carefully examinedfor critical soundings and unverified or question-able charted data. Specific items selected for exam-ination during the survey are described and markedon nautical charts covering the project area. Cop-ies of these charts are furnished to the hydrograph-ic field party.

PLANS AND PREPARATIONS

Charted items and depths that have not beenadequately developed during the prior survey may beenclosed by dashed circles. Such items are not num-bered or lettered and do not require specific disposalor discussion in the Descriptive Report; they provideadditional guidance to the hydrographer on featuresthat require special attention during the field survey.

Information contained in the presurvey re-view is provided to ensure a more complete, defini-tive hydrographic survey. The review is neither in-tended to relieve the hydrographer of the respon-sibility to compare the results of the new survey withthe features shown on the largest scale charts of thearea or with prior surveys nor does it preclude therequired development of shoals and indications ofshoals discovered during the progress of the survey.

Hydrographic field sheets may be laid out inany convenient manner to suit the area being sur-veyed and the plotting equipment available. A finalsmooth sheet may be the composite of a group offield sheets, overlays, and insets. (See 1.2.2 and4.2.1.) To maintain orderly survey records and sim-plify the data-processing tasks, the hydrography con-tained on any one field sheet or overlay should lieentirely within the limits of a single smooth sheet. Itis usually convenient to adopt identical field sheetand smooth sheet layouts if the survey is to be man-ually plotted in the field.

Field parties engaged in Chart EvaluationSurveys shall be furnished copies of nautical chartsof the project area on which specific items selectedfor examination are marked. Copies of the sourcedocument(s) from which each item originated arealso furnished. Each numbered item on a Chart Eval-uation Survey is of critical importance and must bespecifically investigated and disposed of by definitestatements in the reports that accompany the survey.

A convenient method for making the sheetlayouts is to construct, on tracing cloth or clear plas-tic, one or more models of each standard size sheet(1.2.4) according to the scale of the chart on whichthe layout is to be made. The models may then beshifted on the chart, giving major consideration torequired overlap, until the best position for eachsheet is determined. If the area is complex, it is fre-quently necessary to try various layouts of sheets be-fore the most practical layout is found.

2.4 HYDROGRAPHIC SHEET PLANNING

2.4.1. Sheet Layout

For complete coverage of the survey area, asmooth sheet layout shall be prepared prior to begin-

2-7 (JANUARY 1, 1980)

or letter. The feature shall be described under thesame number or letter in the report, unless a briefnotation beside the circle can furnish adequate in-formation. The description of the item should in-clude all available information that may be of inter-est or assistance to the hydrographer. Each pre-survey review shall be dated, inspected by theChief, Requirements Branch, and approved by theChief, Hydrographic Surveys Division. The originalpresurvey review is filed for use during the reviewof the new survey.

All fully circled items identified for investi-gation in the presurvey review shall, unless notedotherwise, be thoroughly examined during the fieldsurvey to prove or disprove their existence. Eachitem shall be mentioned specifically in the Descrip-tive Report that accompanies the survey. [See5.3.4(K).] The hydrographer shall make a definiterecommendation as to the disposition or existence ofeach item for charting.

ning the project. The number of sheets required andtheir orientation and coverage shall be delineated ona chart of appropriate scale — preferably on the larg-est scale chart covering the entire project area. Atracing of the layout at chart scale shall be sent tothe Requirements Branch (C351) in NOS Head-quarters for approval. Figure 2-3 is an example of asheet layout.

Each smooth sheet should be laid out so itincludes as large a water area as practical, allows theproper overlap with adjacent sheets and space for thesheet title, and provides room for plotting all neces-sary control stations. Handling and aging causesmooth sheets to crack or crumple along the edges;soundings or other data plotted too near the edgemay become illegible. For this reason, the sheetsshould be laid out so that no data will be plottedcloser than 8 cm (about 3 in) from the edge of anysheet. Smooth sheets containing small or detachedareas of hydrography shall be avoided if possible.This can generally be accomplished by usingsubplans or insets. (See 2.4.2.)

Smooth sheets should be laid out so that theprojection lines are approximately parallel to theedges of the sheet, with north toward the top.Skewed projections may be used when a nonskewedlayout is extremely uneconomical or impractical. Theuse of skewed projections, however, will be the ex-ception rather than the rule.

HYDROGRAPHIC MANUAL

FIGURE 2.3 — Typical layout of hydrographic survey sheets showing reference letters, scales, and dimensions

(JANUARY 1,1980) 2-8

PLANS AND PREPARATIONS

2.4.3. Sheet Numbers

2.4.3.1. FIELD NUMBERS. For a convenientreference while a survey is in progress, each hydro-graphic field sheet shall be assigned a field number. Apermanent field number shall not be assigned to anysheet until hydrography is started on the sheet; thenumber shall not thereafter be changed although thesurvey is completed by another unit. Unused fieldsheets constructed by or for one survey unit and sub-sequently transferred to another unit prior to the startof survey operations shall be assigned a field numberby the latter when the survey is started. The final twodigits of the field number that represent the calendaryear in which the survey was initiated are notchanged if the survey extends into the following cal-endar year.

D = (d) × (sheet scale) -¹ × Cwhere

D = dimension of sheet (nmi),d = dimension of sheet (cm),

andC = 1/185,200, conversion factor (cm to

nmi).

D = 90 × 20,000 × (1/185,200) = 9.7 nmiand

D = 135 × 20,000 × (1/185,200) = 14.6nmi. Field numbers shall be a dashed combination

of letters (identifying the vessel or field party startingthe survey) and numerals (defining the scale, the se-quence, and the calendar year in which the surveywas started). Sequence numbers assigned shall beconsecutive for a specific scale throughout the calen-dar year regardless of changing project numbers.Composite overlays that will eventually make up anentire smooth sheet are assigned letter designationsfollowing the sequence number.

Although a 1:20,000 scale sheet 90 × 135cm in size would cover an approximate area of9.7 x 14.6 nmi, the hydrographer should be awarethat, because of overlay constraints, hydrographymust be limited to an area approximately 8.1 ×13.0 nmi.

2.4.2. Subplans and Insets

Examples are:

Intensive development of certain featuresof limited extent is often better depicted by usingoverlays showing successive series of soundinglines. Where specific features have been surveyedin greater detail than can be shown satisfactorily Atthe scale of the survey, the soundings should beplotted on a subplan at a larger scale.

(JUNE 1, 1981)2-9

The area of coverage on a sheet of givendimensions may be readily determined by

For example, to compute the area of cover-age for a sheet with the dimensions of 90 by 135cm at a survey scale of 1:20,000, use

Hydrographic sheets containing small de-tached areas of a survey shall be avoided when-ever possible. This problem can often be resolvedby placing an inset on an unused portion of asheet near the area. Insets should always be in-cluded on the sheet of comparable scale closest tothe area. (See 7.2.4.)

Where a small harbor, anchorage, or otherarea will be surveyed at a larger scale than the re-mainder of the inshore coastal waters, it may fre-quently be included as a subplan on the sheet thatincludes the area. (See figure 7-7.) Soundings takenin small docks and along the sides and ends ofsmall piers, which are located by reference dis-tances to or along the piers, are most convenientlydisplayed by a subplan. Such plans need not con-tain a scale, but shall be adequately referenced tothe proper area of the hydrographic sheet. Princi-pal dimensions of piers and docks shall be shown.

WH 2.5-IA-75 NOAA ship Whiting(WH) — scale 1:2,500 (2.5) — first sheet (1) in the se-ries of that scale; first overlay or first in the sequenceof plotter sheets (A) that will be grouped into a com-posite smooth sheet — survey started in 1975 (75).

DA 25 - 4B - 74 NOAA ship Davidson(DA) — scale 1:25,000 (25) — fourth sheet (4) at thatscale; second overlay or plotter sheet (B) of a com-posite smooth sheet — 1974 (74).

HFP 10 - 6 -75 Hydrographic Field Party(HFP) — scale 1:10,000 (10) — sixth sheet at thatscale (6) — 1975 (75).

2.4.3.2. REGISTRY NUMBERS. When fieldwork has begun on a hydrographic survey, the Chief ofParty shall promptly request the assignment of a regis-try number from the Hydrographic Surveys Division(OA/C353), through the Director of the appropriateMarine Center. The project number, the field number,and the locality of the survey must be included in the re-quest. Requested registry numbers will be forwardedfrom the Hydrographic Surveys Division to the fieldunit through the Marine Center. All field survey

HYDROGRAPHIC MANUAL

records, reports, and correspondence associatedwith that sheet shall be referenced by the registrynumber.

2.5 OPERATIONS PLANNING

2.5.1. Project Study

The chief of party shall make a carefulstudy of the project instructions and accompany-ing data to assure himself that all necessary datahave been received. If omissions are discovered orthe data forwarded are considered insufficient, heshould request additional data that may be re-quired from the appropriate Marine Center. Heshould also report immediately his recommenda-tions for revisions to the instructions, request clari-fication on any parts of the instructions that arenot clearly understood, and ask for more completeinformation which he believes necessary on anysubject relative to the project.

Requests for field examination registry num-bers will be submitted to the Hydrographic SurveysDivision, OA/C353, by the Marine Center at thetime the Marine Center processing begins. (See 4.1.2and 7.4)

2.5.2. Plan of Operation

2.4.4. Dog-Ears

The preferred method for showing such sta-tions is to plot them on a separate overlay that willaccompany the hydrographic survey sheet. A lessdesirable but acceptable method is to add a small sec-tion of stable base drafting film to the field sheet andplot the station thereon. This addition is called a''dog-ear.'' (See 7.2.3.) If a dog-ear is needed on afield sheet, the sheet layout should be re-examined;and revisions should be made to eliminate the dog-ear from the smooth sheet.

Any general plan of operations is subjectto change as field work progresses. The Chief ofParty shall alter the original plan as necessary andnotify the Marine Center of significant deviations.

2-10(JUNE 1, 1981)

Sheets for field examinations shall be givenregistry numbers. The registration for a field exami-nation shall be changed to an alpha-numeric format(e.g., FE-219 WD) from the previously used format(e.g., F.E. No. 2 1979 W.D.). Accordingly all futurefield examinations will be assigned a sequential regis-tration number similar to the present practice for ba-sic hydrographic (''H'') surveys. The letters ''WD''are added when applicable to indicate that the fieldinvestigation is a wire drag investigation. When re-ferring to a field investigation, the year of the fieldwork is usually added to the registry number and isshown in the format FE-xxx (19xx) WD.

The exact limits of a hydrographic sheetcannot always be planned accurately. Unexpecteddevelopments occasionally arise during the progressof a visually controlled manually plotted survey thatmake it desirable or necessary to use a control stationwhich falls beyond the original limits of the sheet.

The project instructions may call for workpriorities in certain phases of the operations; ac-complishment of this work must be planned in theorder of precedence established. In the absence ofpriorities, the work should be planned to provideuniform and parallel progress of the various opera-tions. To plan and carry out extensive combinedoperations effectively and systematically, one gen-erally must plot on a chart of suitable scale theproject limits, the limits of previously surveyedareas with which junctions must be made, all geo-detic control stations in the area, and all other datathat can be used in developing the plan. Operationsshall be divided between the various units of thefield party to attain maximum progress consistentwith economy, safety, and maximum use of allavailable resources.

3. HORIZONTAL CONTROL AND SHORELINE SURVEYS

3.1 HORIZONTAL CONTROL

3.1.1. Basic Control

Hydrographic surveys shall be based on areference system of geodetic control upon which thecoordinates of the survey can be established in asystematic manner. Hydrographic surveys conductedby the National Ocean Survey are controlled by acoordinate system referenced to the National Geo-detic Datum — currently the 1927 North AmericanDatum (NAD— 1927) — unless specified otherwise inthe project instructions. Surveys conducted in theCaribbean Sea, South Pacific, and in the waters ofAlaska may be referenced to local datums. NOSgeodetic control surveys are classified by order ofaccuracy for definition purposes. Classification,Standards of Accuracy, and General Specifications ofGeodetic Control Surveys (Federal Geodetic ControlCommittee 1974) and Specifications to Support Clas-sification, Standards of Accuracy, and General Speci-fications of Geodetic Control Surveys (FGCC 1975)specify the details and criteria for the different or-ders.

When supplemental control surveys are con-nected to the national network, field techniques spec-ified for Second-order, Class 11 surveys should beused although Third-order, Class I positional accura-cy may be acceptable.

3.1.1.1. SPACING OF MAIN SCHEME CON-

TROL STATIONS. These stations must be spaced at in-tervals sufficiently close to provide basic control forthe project at hand. The use of photogrammetric andelectronic methods for controlling hydrographic sur-veys has reduced the required density for main-scheme control; however, a certain minimum spacingshould be established and maintained for future use.The required density of control depends on the scaleof the survey, the configuration of the coastal area,and the requirements for photogrammetric mapping.Control stations are used in survey work by otherengineers, public and private, so their density shouldbe adequate to meet anticipated needs for control inthe area. Generally, main-scheme stations should beestablished at intervals of 5 to 10 km along thecoastline. See section 3.1.2 for supplemental controlspacing requirements.

3.1.1.2. RECOVERY OF EXISTING STATIONS.

A thorough search shall be conducted for allpreviously established horizontal control stations,reference marks, and azimuth marks in the vicinity ofthe shoreline throughout the project area. A reportshall be made on NOAA form 75-82 (5-76) or75-82A (4-78) to conform with the Input Formatsand Specifications for the National Geodetic SurveyData Base for each station searched for, includinglost and destroyed stations. A station shall not be re-ported as lost unless there is conclusive evidence toestablish the fact beyond a reasonable doubt. Old de-scriptions must be verified in detail or corrected asnecessary to conform with circumstances at the timeof recovery. Damaged stations or reference marksshould be repaired. All control stations shall be

First- or second-order control surveys areusually not required for hydrography. Second-orderaccuracy surveys, however, may be assigned to hy-drographic field units where additional main-schemestations are urgently needed to supplement the Na-tional Geodetic Network or if a hiatus of 20 km ex-ists between established geodetic control stationsalong the coastline. In this case, NGS shall assist inthe preparation of the control survey specificationsand instructions. Thus, unless second-order control isspecified in the project instructions, Third-order,

3-1 (JANUARY 1, 1980)

Where existing geodetic control is inade-quate for a hydrographic survey, the field partymay be required to establish supplemental controlas necessary. If needed, supplemental control shallbe established with an accuracy not less than thatprescribed for Third-order, Class I control. (See1.3.1 and 3.1.2.) Basically, first- or second-ordercontrol surveys are the responsibility of the NOSNational Geodetic Survey (NGS); hydrographicfield parties are generally responsible for third-ordersurveys to establish needed supplemental control.

Class I surveys are generally acceptable to controlhydrographic and shoreline surveys and to positionaids to navigation, landmarks, theodolite intersectionstations, and electronic control system antenna sites.(See 3.1.2 and 3.1.3.)

HYDROGRAPHIC MANUAL

marked or re-marked and the disks stamped in ac-cordance with ESSA Technical MemorandumC&GSTM-4, ''Specifications for Horizontal ControlMarks'' (Baker 1968).

and ESSA Technical Memorandum C&GSTM—4(Baker 1968).

Each newly established control station shallbe described on NOAA form 75-82 (5-76) or 75-82A (4 -78) and conform to the Input Formats andSpecifications for the National Geodetic Survey DataBase. Descriptions must be clear, concise, and com-plete narratives. They should enable a person to pro-ceed with certainty to the immediate vicinity of themark and, by measured distances to permanent refer-ence points, inform the searcher of the exact locationof the station. Monumented stations of other organi-zations included in the control scheme should also bedescribed on one of these NOAA forms.

When new control surveys are connected topreviously established control stations, positive re-covery of the old stations must be verified by check-ing distances and directions to existing referencemarks to ensure that none of the monuments havebeen moved. This check will ordinarily be consideredadequate proof of recovery of a third-order station.Reference marks are required at all NOS-monu-mented third-order stations. More rigorous checkingprocedures are required when connecting higher or-der surveys to established control stations (e.g.,reobserving original angles, remeasuring old lines,and connecting to more than one existing station). Alisting of previous observations at anticipated controlstations should be requested from the National Geo-detic Survey prior to beginning the survey. If specificmethods for connecting required first- or second-order control surveys are not included in the projectinstructions, refer to U.S. Coast and Geodetic SurveySpecial Publication No. 247 (Gossett 1959) for guid-ance.

Spires, tanks, and similar objects located byintersection are also described on either NOAA form75-82 or 75-82A, following the same procedure asoutlined above. An observer shall visit such stationsand identify the objects by a descriptive name, thename of the property owner, the year of construc-tion, and the type of construction. Lighthouses andother fixed aids are identified by the name as shownin the most recent edition of the U.S. Coast Guard(1976) Light List. If possible, the appropriate U.S.Coast Guard District, Aids to Navigation Branch,should be consulted for outdated entries in the LightList.

Objects (e.g., flagpoles, chimneys, smoke-stacks, beacons, and signal towers) with previouslydetermined positions shall not be used for controluntil they have been positively identified and theirpositions verified by an onsite inspection and localinquiry. A recovery note is required for these sta-tions.

3.1.1.3. STATION MARKS AND DESCRIPTIONS.

Each new main-scheme station shall be marked witha standard National Geodetic Survey disk and twostandard reference mark disks — except that well-de-fined natural or cultural objects of substantial con-struction (e.g., lighthouses and water tanks) are gen-erally located by intersection methods and are notmarked with disks. Subsurface marks, set below thefrostline or in bedrock, shall be established at first-and second-order main scheme stations where practi-cal. Azimuth marks set at least 400 meters from thestation are established at all control stations unlessanother station or at least two other objects such aslighthouses, tanks, church spires, or similar featuresare visible from the ground at the station. Instruc-tions for naming and marking stations and for stamp-ing the disks are contained in U.S. Coast and GeodeticSurvey Special Publication No. 247 (Gossett 1959)

If practical, positions of stations establishedby other organizations should be determined insteadof establishing new stations nearby, provided the sta-tion marks are in good condition and suitably locat-ed. Two standard reference marks should be estab-lished if none exist. Under no circumstances shallsurvey station monuments or disks established by

3-2(JANUARY 1, 1980)

3.1.1.4. CONNECTIONS TO GEODETIC CON-

TROL ESTABLISHED BY OTHER ORGANIZATIONS. In-dependent schemes of horizontal control establishedin the project area by other organizations shall, whenfeasible, be connected to the National HorizontalControl Network so their positions may be reliablyand accurately computed and adjusted on the appro-priate datum (NAD-1927 in the contiguous UnitedStates and Alaska). Before establishing new controlfrom independent schemes, two stations at the con-nection should be reobserved as a check. (See3.1.1.2.) Federal, State, and local agencies should becontacted by the field party to ascertain what controlexists in the project area and to obtain copies of de-scriptions and positions of marks and diagrams ofthe control schemes.

HORIZONTAL CONTROL AND SHORELINE SURVEYS

Angles differing by more than 5 s from themean of the set shall be reobserved before leaving thestation. When method 2 is used, the sum of themeans of the traverse angle and its explement mustagree to within ± 5 s of 360º 00' 00''.

other organizations be altered or amended. Thesemarks must not be moved, replaced, or reset unlessspecified in the project instructions. When needed,such marks should be reinforced to prolong their ex-istence but must not be disturbed or moved. Theestablishing agency must be notified prior to takingany action.

Recording and computing procedures speci-fied in US. Coast and Geodetic Survey Special Publi-cation No. 247 (Gossett 1959), pages 111-112 and131-137, are to be followed.

3.1.1.5.1. Second-order traverse distances. Re-quirements for Electronic Distance Measurements(EDM) are given in Classification, Standards of Accu-racy, and General Specifications of Geodetic ControlSurveys (FGCC 1974); Specifications to Support Clas-sification, Standards of Accuracy, and General Specifi-cations of Geodetic Control Surveys (FGCC 1975);and the Technical Monograph CS-2, Electronic Dis-tance Measuring Instruments (American Congress onSurveying and Mapping—ACSM 1971).

Horizontal traverse angles may be observedby either one of these methods:

3.1.2. Supplemental Control

3-3 (JANUARY 1, 1980)

3.1.1.5. SECOND-ORDER TRAVERSE. Whenadditional main scheme control stations are neededalong the coastline, traverse methods are generallyrecommended over triangulation and trilateration.The ready availability of modem electronic distancemeasuring (EDM) equipment, the ease and speedwith which distance observations can be made, andthe use of digital computers for reducing data in thefield greatly simplify the work. Requirements forSecond-order, Class II traverse described in 3.1.1.5.1and 3.1.1.5.2 are to be used as guidance to ensurethat field survey data will meet specified accuracies.The information is intended to augment existing geo-detic manuals.

3.1.1.5.2. Second-order directions and azi-muths. Direction and azimuth observations for sec-ond-order traverses shall be made using theodolitescapable of measuring horizontal angles to the nearestsecond of arc. Each observation shall be recorded tothe nearest second.

1. Measure the traverse angle not lessthan eight times using different positions of the hor-izontal circle. See Specifications to Support Classifica-tion, Standards of Accuracy, and General Specifica-tions of Geodetic Control Surveys for proper circlesettings.

2. Measure the traverse angle four times,and the explement of the traverse angle four timesusing different horizontal circle positions when thereis only one object for a foresight and one object fora backsight.

Astronomical azimuth stations are selectedin accordance with various factors such as the lengthof the traverse and the availability of existing azi-muth control in the vicinity of the initial and termi-nal stations. The use of azimuth marks and intersec-tion stations at starting and ending stations forazimuth control is not adequate for second ordercontrol surveys. We therefore recommend that Polar-is observations be made at these stations if an ac-ceptable azimuth check cannot be obtained. Thenumber of intermediate stations between azimuth sta-tions should rarely exceed 15 and should never ex-ceed 20. Observational procedures and checks shallconform to the specifications for first-order azimuths(outlined in chapter 4 of Special Publication No.247) except that only 12 positions and 1 night's ob-servations are required. If Polaris observations areneeded for azimuth control, at least two main-schemestations shall be observed. Stride levels must be usedon theodolites when observing Polaris for azimuthbecause of the increased sensitivity of their bubbles.

All second-order field data shall be submit-ted to the National Geodetic Survey for processing,verification, adjustment, and inclusion in the Nation-al Horizontal Control Network. Data shall be assem-bled and submitted in accordance with the InputFormats and Specifications for the National GeodeticSurvey Data Base.

Third-order, Class I accuracies are generallythe minimum acceptable criteria for the location ofelectronic position control antenna sites, calibrationsignals (1.3.1), and theodolite intersection stations(1.3.3.1.2), and for supplemental traverses or controlschemes from which hydrographic signals will besubsequently located using ground survey methods.Since it is frequently impractical to include every hy-drographic signal in a third-order traverse or controlscheme, less accurate traverses may be run to locatethe signals. (See 3.1.3.) The principles discussedthroughout 3.1.1 for basic control are also generally

HYDROGRAPHIC MANUAL

Traverse methods are generally recommend-ed over triangulation and trilateration; however,depending on the nature of the terrain, availableexisting control, and number of new stations re-quired, other methods may prove advantageous (e.g.,a theodolite three-point fix with a check angle or atwo-point fix from both ends of a measured baseline). Regardless of the method used, there must be ageometric check on the positions of new stations. Sidecheck and closure criteria are listed in Classification,Standards of Accuracy, and General Specifications ofGeodetic Control Surveys (Federal Geodetic ControlCommittee 1974).

3.1.2.1.3. Instruments. Distance-measuring in-struments include light wave, infrared, or microwave(e.g., Geodimeter, Model 76; Hewlitt-Packard, Model3800; and Tellurometer, Model MRA- 101).

Angulation instruments include a 1-s or bet-ter theodolite (e.g., Wild T-2 and Kern DKM-2).

3.1.2.1. THIRD-ORDER CONTROL SPECIFI-

CATIONS. Procedures and instrumentation discussedin the following sections should produce control sur-veys with an anticipated minimum accuracy of onepart in 10,000 (Third-order, Class I).

Leveling instruments include geodetic levelsand rods (e.g., Zeiss Ni2 Level and a Kern Rod). Agood quality Philadelphia or Chicago Rod may beused if a geodetic rod is not available.

Check-angle observations and distance mea-surements shall be made to existing reference and azi-muth marks to provide assurance that the stationshave not been disturbed.For use during future surveys, supplemental

control stations of third-order accuracy establishedfor the current survey shall be monumented (3.1.2.1.2)and described at intervals of 4 to 8 km along the tra-verse line. Stations located for electronic control an-tenna sites and calibration purposes and for theodoliteintersection instrument stations shall also be monu-mented and described if practical and if there is rea-sonable assurance of permanence for future recovery.

Observed angles between azimuth marks, in-tersection stations, and other established geodeticcontrol at the starting and ending stations of the tra-verse are acceptable for azimuth control, provided theobserved angle checks with the angle previously ob-served or computed from published data to within 10s of arc. If the observed angle does not check within10 s, two sets of Polaris azimuths (3.1.2.1.6) shall beobserved for azimuth control.3.1.2.1.2. Monumentation. Marks of the type

described in US. Coast and Geodetic Survey SpecialPublication No. 247, ''Manual of Geodetic Triangula-tion'' (Gossett 1959) are considered the most suitablefor monumenting recoverable stations; but rod orpipe marks with a disk attached on occasion may beutilized where there is reasonable assurance of perma-nency. The primary consideration is to establish a de-scribed monument that surveyors can find and use inthe future. National Ocean Survey disks shall be usedon all third-order stations.

3.1.2.1.5. Horizontal angles. A minimum offour positions of the circle must be observed with a1-s theodolite on 1 day. Angles at any position of thecircle that differ by more than 5 s from the mean ofthe set shall be reobserved before leaving the station.The procedures and circle settings are given on pages111-112, 131-137, and 141-144 of U.S. Coast andGeodetic Survey Special Publication No. 247 (Gossett1959) and in Technical Monograph No. CS-1 (Dra-cup 1973).

3-4(JANUARY 1, 1980)

applicable to third-order horizontal control surveys.Exceptions to these principles are outlined in 3.1.2.2.

3.1.2.1.1. Station spacing. Traverse stationsshould be spaced at 2- to 5-km intervals, but closerspacing is permitted where the terrain limits the lineof sight. The minimum length of line should seldombe less than 200 m for lines measured by electro-opti-cal instruments and 500 m for lines measured by mi-crowave instruments. ''Wing'' or ''spur" stations notincluded in the regular traverse must have a positioncheck. One of the methods described in 3.1.2.1.8should be used.

Station names, if used, are assigned as de-scribed in the Input Formats and Specifications for theNational Geodetic Survey Data Base; however, tra-verse parties may use different designations such asTRAV-1, PT1, and Al. In any case, the year of es-tablishment of the mark must be indicated on thedisk. Mark designators must be selected carefully toavoid duplicate names. (This can be accomplished bythe yearly sequential numbering of traverse points.)

3.1.2.1.4. Connections to existing control.Third-order traverses for hydrographic survey controlshall begin and end at existing first- or second-orderstations. If excessive traverse distances over difficultterrain would be required to tie into a control surveyof higher accuracy, connections to existing third-orderstations are acceptable as a less desirable alternative.

HORIZONTAL CONTROL AND SHORELINE SURVEYS

If the traverse forms a closed loop, the posi-tion closure will generally be at least 1:20,000 betweencontrol stations. Angle closures should not exceed 3 sper angle station or 10 √ N, whichever is smaller.

Third-order measurements with microwaveinstruments consist of a full set of coarse and finereadings, as recommended by the manufacturer,taken at both the master and remote units. Measure-ments should be completed at one end of the line be-fore beginning observations at the other. The differ-ence between the two measurements should seldombe greater than 10 cm and never exceed 15 cm beforeapplying the meteorological corrections. (AB) sin A(BB' ) =

sin B',

A complete set of measurements using anelectro-optical device that does not have a direct and compared with the measured distance.

3-5 (JANUARY 1, 1980)

3.1.2.1.6. Azimuths and astronomic observa-tions. Astronomic azimuth stations are selected in ac-cordance with various factors such as the availabilityof existing azimuth control in the vicinity of the ini-tial and terminal stations and the length of the tra-verse. In addition to the requirements in 3.1.2.1.4,the number of intermediate traverse stations betweenazimuth stations should rarely exceed 20 and neverexceed 25. Polaris, when necessary, shall be observedaccording to the procedures for Third-order, Class Iazimuths as specified in Classification, Standards ofAccuracy, and General Specifications of Geodetic Con-trol Surveys (Federal Geodetic Control Committee1974). Two main-scheme stations are observed inconjunction with the Polaris observations. Most 1-stheodolites require a stride level on the telescopewhen performing these observations because of theincreased bubble sensitivity.

n

n

Azimuth closures between astronomic azi-muths should not exceed 3.0 s per angle station or10 √ N, whichever is smaller (N = number of anglepoints), following the most direct route of the tra-verse. For example, if there are nine angle stations be-tween azimuths, the closure should not exceed 27 s.

3.1.2.1.7. Distance measurements. Accuracyfor distance measurement shall conform with the stan-dards cited in Classification, Standards of Accuracy,and General Specifications of Geodetic Control Surveys(Federal Geodetic Control Committee 1974). EDMprocedures for Third-order, Class I surveys are givenin Specifications to Support Classification, Standards ofAccuracy, and General Specifications of Geodetic Con-trol Surveys (FGCC 1975). Meteorological observa- tions required for determining atmospheric correc- tions are identical to those specified for second-orderdistance measurements. (See 3.1.1-5. 1 -)

readout consists of observations for internal calibra-tion for each of the three operating frequencies. Thespread between the measurements as determined foreach of the three frequencies should not exceed 6 cm.When two complete measurements are made, thespread between the two should seldom exceed 3 cm.When using EDM instruments that have direct read-out, one measurement from each end of the line ismade, or two readings are taken from one end of theline with the prism or instrument offset on the secondreading. Measurements with a Ranger 11, III, or AGAModel 76 Geodimeter should consist of five measure-ments read in meters and five read in feet. The meansof each set should agree to within 15 mm.

Slope correction procedures and reduction ofdistances to sea level are as specified for second-ordermeasurements in 3.1 1.5. 1.

3.1.2.1.8. Design of traverse. This is deter-mined by the terrain and the purpose for which thework is being performed. In general, it is designed asshown in figure 3-1 and follows the surveyor's line ofleast resistance.

To reduce the number of angle stationsthrough which the azimuth is carried, observe direc-tions directly between points A and C, A and A or Band D when possible. Also, distance measurementsover these lines provide internal checks on the obser-vational data.

Third order control stations not included inthe main traverse scheme, or ''spur points,'' that maybe established for a variety of purposes must include ageometric check on the position of the point to avoidblunders. Depending upon the terrain and conditionsof point intervisibilities, several methods or variationsthereof are suggested to provide a position check.

1. (See figure 3-1.) ABCD is the main tra-verse route. Spur point B' is to be located. In additionto measuring the main traverse distances and angles:

a. Locate point B' by observing theangle ABB' and measuring the distance BB'.

b. Observe the angle B'AB at traversepoint A.

c. The angle at B' is concluded bysubtracting the sum of the angles at points A and Bfrom 180*.

d. Distance BB' is computed using thelaw of sines,

HYDROGRAPHIC MANUAL

a. Locate spur point by observing an-gle ABB' and measuring distance BB'.

c. Observe angles B'' AB and AB" B'.

d. Measure the distance BB'' usingEDM equipment or standardized steel tape.

e. Compute distance AB" using thelaw of sines. In this computation,FIGURE 3-1. — Traverse with a checked spur point.

angle BB" A = 180º — angle AB'' B'.

4. (See figure 3-4.) In this method:

FIGURE 3-2. — Short base method for checking a traverse spurpoint.

c. Measure distance B'B''.

FIGURE 3-3. — Offset method for checking a traverse spur point

FIGURE 3-4. — Wing point method for checking a traverse spurpoint

3-6(JANUARY 1, 1980)

f. The position of spur point B' ascomputed by distance and azimuth from traversepoint B is checked by the independent traverse routeA to B" to B'. Distance B"B' is determined bysubtracting BB" from BB'.

a. Locate spur point B' by azimuthand distance from traverse station B.

b. Wing point B'' is established with-in easy taping distance from B' and is intervisiblewith both B and B'.

The check observation could have beenmade from traverse point C or from other pointsalong the traverse as well.

2. (See figure 3–2.) As before, ABCD isthe main traverse route; spur point B' is to be locat-ed. The following method will provide a check onthe location of point B' that is determined initiallyby azimuth and distance from traverse point B;

a. Establish auxiliary point B'' online with B and C. Distance BB'' should be aboutone-tenth of distance BB' but not less than one-twentieth.

b. Distance BB'' is measured usingEDM equipment or a steel tape.

c. Angle BB" B' is observed at auxil-iary point B''.

d. The angle at B' is concluded bysubtracting the sum of the angles at points B and B"from 180º.

e. Distance BB' is computed usingthe law of sines and compared with the measureddistance as a check.

3. (See figure 3—3.) The following meth-od is useful where spur point B' can be seen onlyfrom traverse station B:

b. Establish auxiliary point B'' online with B and B'.

HORIZONTAL CONTROL AND SHORELINE SURVEYS

e. Observe angle B"B'B. When horizontal directions are observed,only one position of the circle, consisting of one di-rect pointing and one reverse pointing of the tele-scope, is required; the explement of the angle is alsoobserved, and the sum of the two shall check towithin 20 s of 360º 00' 00".

Distances may be taped or measured usingEDM equipment. If taped, the distance is to be mea-sured in both directions. Tape corrections may be ig-nored except for the slope correction. If measuredwith EDM equipment, an on-line offset may be usedto check the original measurement.

There are many acceptable variations of thefour methods described that can be used to provideadequate geometric checks on spur point positions.

3.1.2.1.9. Third-order control data submission.Data shall be assembled in the following groups forsubmission to the National Geodetic Survey:

3.1.3. Hydrographic Control Stations

3.1.3.1. TRAVERSE METHODS. Stations forsignals to be used for visually controlled hydrogra-phy may be located by less than third-order traversemethods from existing basic or supplemental controlstations provided that the following limitations andprocedures are observed:

4. Initial azimuths may be determined byany method accurate to within 1 min of arc.

Beginning azimuths may be determined bysolar observations, using a Roelofs or equivalent so-lar prism on the theodolite for increased pointing ac-curacy. See ''Photogrammetric Instruction No. 19,Sun Azimuths — Observations and Computations,''Revision 2, June 15, 1973, for detailed instructionson observing and computing solar azimuths (Nation-

8. Hydrographic stations used for visualcontrol need not be permanently monumented.

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d. While occupying traverse station B,observe all four angles as shown.

f. Compute distance BB" using thelaw of sines. Angle BB"B' is concluded for use inthe computation.

g. The position of spur point B' ischecked through the independent traverse route B toB" to B'.

1. Data submitted to the National Geo-detic Survey shall be assembled and transmitted inaccordance with the procedures outlined in InputFormats and Specifications for the National GeodeticSurvey Data Base.

2. A progress sketch showing the workaccomplished is prepared for the project. This sketchshould be similar to the example shown on page 192of U.S. Coast and Geodetic Survey Special PublicationNo. 247 (Gossett 1959). Also refer to NGS ActionMemo 77-03.

3. A project report describing the workperformed is also prepared (page 190 of Special Pub-lication No. 247).

4. Data shall be forwarded to the Direc-tor, National Geodetic Survey (Attention: OA/C13x4). All records are to be submitted in at least twomailings so surveys can be reconstructed from the re-cords that would be available if a package were lost.Record books should be forwarded separately fromcomputer-readable data.

3.1.2.2. EXCEPTIONS. If locations of electron-ic positioning system antenna sites, calibration sig-nals, or theodolite intersection stations require onlyone- or two-leg traverses over distances of less than 2km, the following exceptions to third-order proce-dures are permitted:

al Ocean Survey 1971 a). Solar azimuth errors shouldrarely exceed 1 min of arc.

1. Lengths of open or closed traverseswhere less than third-order methods are used shallnot exceed 2 km in total length.

2. Traverses containing more than twolines shall be closed to within one part in 2,500.

3. These traverses should start from sta-tions of Third-order, Class II accuracy or better(3.1.3.2).

5. Traverse angles and their explementsmay be measured by one pointing of the instrumentand shall ''close the horizon" to within 1 min of arc.

6. Traverse distances may be measuredusing a nonstandardized steel tape. Stadia distancesshould not be used except as a last resort when ter-rain conditions prevent the use of a steel tape; dis-tances should be kept short (less than 500 m). If sta-dia distances are used, readings on each of the threewires shall be observed and recorded.

7. Slope corrections to taped distancesneed not be applied unless the slope exceeds 2º

9. Position computations and field notesfor work of less than third-order accuracy shall beretained by the field party for inclusion with thetransmitted hydrographic records upon completion

HYDROGRAPHIC MANUAL

the hydrographic survey. If photogrammetrically lo-rated points are used for azimuth control on thesetraverses, at least two points must be sighted on toprovide a check.

of the survey. They are not to be transmitted to theNational Geodetic Survey.

3.1.3.2. PHOTOGRAMMETRIC METHODS. Hy-drographic control stations for visual fixes may belocated by photogrammetric techniques (photo-hydrostations) when traverse or other ground survey meth-ods are impractical or uneconomical. Two basicmethods of field photogrammetric locations are ap-proved:

Three sextant cuts from points located onthe photogrammetric plot may be observed to locatehydrographic stations. Such cuts must intersect atgeometrically strong angles. Azimuth orientation sta-tions used for these cuts should be as distant as pos-sible. Identification of photogrammetric points mustbe positive.

Identifiable points (such as images of smallrocks, corners of buildings or piers, and forks ofstreams) may be selected as hydrographic signals.When using forks of streams or other similar ob-jects subject to change, extreme caution must be ex-ercised because of the time difference in the currentfield work and date of photography. Supplementalstations may be located by reference measurementsto such details if the objects themselves are not con-venient for use as signals or as sites for the erectionof signals. (See Photogrammetric Instruction No.22.)

3.1.3.3. SEXTANT METHODS. Hydrographicstations are occasionally located by sextant angles tosupplement existing control. Such stations may be lo-cated by observing strong three-point fixes at the sta-tions. (See 4.4.2.) Check angles to a fourth stationshould always be measured. Navigation sextantsshould be used and, wherever possible, angles ob-served to control stations of third-order accuracy orbetter and read to the nearest 0.5 min. New stationpositions may be computed and machine plotted orbe plotted on the field sheet using a three-arm pro-tractor.

Stations may also be located by fixing theposition of the survey vessel by strong three-pointsextant fixes with sextant cuts to the station simulta-neously observed. At least three well-intersected cutsare required. The vessel should be stationary whencuts are observed. Accurate results cannot be ob-tained from vessels making way.

Hydrographic stations may also be locatedby sextant cuts observed from three or more existingcontrol stations. Angles are measured from othercontrol stations to the new stations. The cuts shouldbe observed from stations as close as possible to thenew station and provide strong geometric intersec-tions. Stations located by sextant angles shall not beused for locating other stations.

Traverses starting and closing on photo-grammetrically located points may be used to deter-mine positions of photo-hydro stations — providedthat the traverse length is less than 2 km and theclosure does not exceed 0.25 mm at the scale of

3-8(JANUARY 1, 1980)

1. Location by transfer. Field identifiedphoto-hydro stations can be transferred directly froma photograph to a transparent stable-base copy of ashoreline manuscript by holding to adjacent shore-line pass points shown on the photographs and onthe manuscript.

2. Location by radial intersection. Sta-tions can be positioned graphically on shorelinemanuscripts using classical radial intersection tech-niques for points with images on at least twooverlapping photographs.

Once points have been plotted on shorelinemanuscripts, coordinates may be scaled (to the near-est 0.25 mm) for use as input for machine drafting ofhorizontal control and automated hydrographic oper-ations. For manually plotted field surveys, pointsmay be transferred directly to field sheets providedthe field sheets and the shoreline manuscripts are ofequal scale. Photo-hydro stations shall be establishedin accordance with ''Photogrammetric InstructionNo. 22, Field Recovery and Identification of Hori-zontal and Vertical Control,'' Revision 2, September30, 1965, and ''Photogrammetric Instruction No. 45,Photogrammetric Location of Hydrographic Controlin the Field,'' Revision 1, March 15, 1954 (NationalOcean Survey 1971a).

Locations of photo-hydro stations should bepricked on the photographs as accurately as possible.Prick marks shall be within 0.2 mm of the correctpositions of the points. Errors in the final geographicpositions of photo-hydro stations should not exceed0.5 mm at the scale of the shoreline manuscript.Field photogrammetric methods shall not be used tolocate stations for hydrographic surveys conducted atscales larger than those of the shoreline manuscriptswithout the prior approval of the Director, NOS.

HORIZONTAL CONTROL AND SHORELINE SURVEYS

3.1.3.4. PLANE TABLE METHODS. Althoughlargely replaced by photogrammetric techniques, theplane table remains a useful instrument in hydro-graphic surveying. Graphic triangulation or traverseoccasionally provides the most economically effectivemeans for locating hydrographic control stations.

When hydrographic surveys of small but im-portant areas are required at scales larger than thoseof available shoreline manuscripts, plane table meth-ods may be used to locate additional control. Ifpoints located by analytical aerotriangulation are notavailable to control the graphic survey, stationsmeeting Third-order, Class II accuracy should beused.

Methods and instruments used shall be suchthat 90% of the control stations located will be with-in 0.5 mm of their correct geographic position at thescale of the plane table sheet. No stations shall be inerror by more than 0.8 mm. Closing errors of planetable traverses prior to adjustment shall not exceed0.25 mm/km at the scale of the sheet; and in no caseshall the total closing error (which shall be adjusted)exceed 2.0 mm.

3.1.3.5. UNCONVENTIONAL METHODS. Wa-terways with sufficient depth of water and consideredimportant enough to be useful for navigation requireaccurate detailed surveys. Control in such waterwaysmust be established by conventional methods. Insloughs through swamps and mangrove, in minortributaries, or in extensive shallow and featurelessareas, less accurate methods can be tolerated. Hydro-graphic control for these areas may be established bysextant triangulation.

Traverses may be run using sextant angles tocarry azimuths; distances may be measured by stadiaor by sextant angles using a subtense bar or itsequivalent. Hydrographers should exercise ingenuityand devise methods appropriate to the instrumentsavailable — such as range finders, floating wiremarked at intervals, or other fast convenient meth-ods. Traverse angles measured by sextant are read tothe nearest 0.5 min. Traverses and graphic triangula-tion should be plotted on a low-distortion polyesterbase drafting film, preferably at a scale at least twiceas large as that of the hydrographic sheet. Such tra-verses should seldom be more than 2 km in length,and the end of the traverse should be firmly posi-tioned by connecting to established control of ahigher order (if possible without undue expense).

Graphic control surveys are retained through-out the processes of hydrographic verification, finalinspection, and final quality control analysis, afterwhich they may be destroyed if there is no furtheruse for them. Registry numbers are never assigned tothese sheets.

A separate Descriptive Report shall be writ-ten to accompany each plane table sheet. DescriptiveReports supplement the plane table surveys with in-formation that cannot be conveniently shown on thesheets. Reports must be written concisely and ar-ranged in a systematic manner with each class of in-formation shown under separate paragraphs with un-

On certain Chart Evaluation, reconnaissance,or some special project surveys, the project instruc-tions may specify that landmarks and other detailsshown on the nautical chart of the area may be

3-9 (JANUARY 1, 1980)

Suitably grained, dimensionally stable poly-ester drafting film is preferred for plotting plane ta-ble surveys. Each graphic control sheet is designatedby a capital letter assigned in alphabetical order dur-ing the season. A new series, beginning with the let-ter ''A," shall be started each season. The complete designation is composed of the first two letters of thename of the survey vessel, or other assigned designa-tor, followed by the capital letter, followed by thelast two digits of the calendar year. For example, SU-C-75 is the third plane table sheet started by theNOAA ship Surveyor in 1975. The location of eachsheet shall be shown on the sheet layout sketch forthe project.

derlined headings. Reports shall not be prepared inthe form of a letter or a journal of the field work.Headings shall be ''Descriptive Report to Accompa-ny Sheet ____.'' Dates of project instructions underwhich the work was done must be stated.

Particular attention must be given in De-scriptive Reports to the following subjects:

General description of the area, reason(s)for making a plane table survey, field and registrynumbers of hydrographic survey sheets affected, anddates when the work was done.

Horizontal control used.

Closing errors of traverses and method of

adjustment.

Descriptions of any work that is incom-plete, unreliable, or requires further examination.

Inadequate junctions with adjacent sur-veys (include recommendations for adjusting discrep-ancies).

HYDROGRAPHIC MANUAL

used to control sounding lines. In such cases, theidentity and position of each object shall be positive-ly verified before use.

signal every kilometer may be sufficient. Where thebeach is irregular and signals must be built close tothe shoreline, spacings of 300 to 400 m are usuallynecessary.3.1.4. Hydrographic Signals

3.1.4.2.1. Signal building materials. Wherenatural objects are not available, the most satisfacto-ry and economical signals are constructed usingwhite cloth or a highly reflective, plasticized cloth.

3.1.4. 1. NATURAL AND CULTURAL OBJECTS.

The term ''signal'' designates any type of object, ei-ther natural or cultural, observed when measuringangles to locate the positions of a survey vessel en-gaged in sounding. Signals may be of any size orshape although very large signals should not be usedwhen the observer is close. The measurement of an-gles is simplified when the objects at the control sta-tion are sufficiently conspicuous to be seen easily.For this reason and for economy and durability, nat-ural objects such as prominent boulders, pinnaclerocks, waterfalls, and lone trees, and cultural objects(such as beacons, lighthouses, tanks, spires, andbuilding gables) are used wherever available.

(See figure 3-5.)

The nature of the project and the availabilityof electronic positioning equipment for offshore hy-drography are the determining factors that influencethe siting of large signals. There should be enoughlarge signals to provide control for calibration ofelectronic positioning systems at maximum distances.For inshore launch work signals constructed ofwhite, red, or orange cloth in various shapes shouldbe used. Cross banners, flags on stumps, or clothwrapped on trees or poles are generally adequate.Black cloth may show well if the signal is skylined.Most signals made of cloth show best if they reflectsunlight and will reflect most efficiently if set at anangle of about 30* from the vertical. While plain redor orange cloth can be seen only from relatively

Care must be taken to vary the sizes, shapes,heights, and colors of the signals to prevent confu-sion. The largest and most conspicuous signalsshould be sited where they can be readily seen fromthe offshore areas and where strong fixes will result.Smaller signals should be appropriately spaced forinshore work. If the signals can be built well backfrom the shoreline, a spacing of approximately one Construction of a large tripod signalFIGURE 3 - 5.

3-10(JANUARY 1, 1980)

3.1.4.2. CONSTRUCTION OF SIGNALS. Thoseappropriately located and erected are a critical pre-lude to successful sextant-con trolled launch hydrog-raphy. The ease and smoothness with which a hydro-graphic team operates depends to a large extent onthe competency of the signal building party. Whenstations are located and spaced so that strong fixesare available at any point in the area and they arevaried in size, shape, or color for quick and unmis-takable identification, the control will be adequatefor hydrographic surveying.

Stations established along sandy beaches orlow flat areas should, if possible, be placed well backfrom the beach to provide strong sextant fixes withfewer signals (4.4.2.1.3). In all cases, signals must beset far enough back from the beach to avoid destruc-tion by wave action during storms.

Where signals are built along an irregularcoast, one signal should always be located at thehead of each inlet or small cove. Stations high abovethe water on cliffs or bluffs are generally unsatis-factory for fixes close inshore. (See 4.4.2. L) Signalsmust be designed to remain intact until the hydro-graphic survey is completed,

HORIZONTAL CONTROL AND SHORELINE SURVEYS

When cloth is used to construct a signal, itshould be securely fastened with a stapling gun orlacks. U-shaped slits should be cut in the material torelieve wind pressure and discourage vandalism.

3.1.4.2.2. Entrance on private property. If sta-tions and signals are to be established on privateproperty, permission must be obtained from theowner. Property shall not be damaged or defacedunder any circumstances without the owner's priorwritten consent. When surveys are made along theshores of publicly owned areas (such as parks, na-tional or state forests, or reservations), the superin-tendent or other official in charge should be contact-ed. This requirement is particularly important ifvegetation must be cleared.

Shoreline maps portray complete interiorplanimetry in an area approximately parallel to theshoreline and generally not more than 1 km wide;these areas include both shoreline and alongshorefeatures. Modern photogrammetric techniques andconventional cartographic practices are used to pro-duce these maps. They are not published and areusually compiled at the scale of the hydrographicsurvey. Under certain conditions, specially preparedphotographs and copies of the map manuscripts onstable base plastic material are furnished for locatingsignals for visually controlled hydrography. If photo-grammetric positioning of hydrographic stations isanticipated, photograph centers and shoreline passpoints are shown on the manuscript copies sent tothe field.

Nothing arouses the ire of a property ownerso much as unauthorized entrance on his property.When the nature of the work is explained, there willseldom be any difficulty in obtaining permission toestablish a station. Use of NOAA Form 76-163,''Form Letter to Property Owners,'' is often helpfulin gaining access to private property. If crops,shrubs, or trees must be damaged, a written agree-ment must be secured beforehand that states theamount of damages, if any, to be paid. When thesurvey has been completed, all signals shall be re-moved and the site restored to its original conditionunless other arrangements have been made with theowners or officials. Coastal zone maps are prepared to support

nautical charting and to provide data for the deter-mination of coastal boundaries and other informa-tion essential for coastal zone management. Ortho-photo mosaics made from black-and-white rectifiedprints of natural color or from false color photo-graphs are used for these maps in flat terrain, usual-ly at 1:10,000 scale. The shoreline, low water line(1.6. 1), alongshore features, nonfloating aids to navi-gation, and landmarks for charts are compiled.There is no representation of relief. Photographicimages of objects on these maps are in true horizon-tal position in relation to each other and to the ref-erence datum. Objects therefore may be selected foruse as hydrographic signals their images identifiedon aerial photographs, transferred to stable basecopies of the manuscript, and the positions of theobjects scaled. Good judgment must be exercised inselecting objects and identifying their images toavoid introduction of errors because of relief dis-placement.

Topographic surveys made to support hy-drography include determinations of the positions ofnatural and cultural features in a locality and theirdelineation on a plane surface. These surveys weremade solely by plane table methods until about1930. Aerial photogrammetry is now used almost ex-clusively to supply topography and related data in

3-11 (JANUARY 1, 1980)

short distances, it can provide the break in a series ofwhite signals necessary to reduce confusion.

3.2 SHORELINE SURVEYS

3.2.1. Coastal Mapping

Topographic features shown on nauticalcharts are of nearly equal importance to the waterdepths. The mariner operating in sight of land isguided primarily by aids to navigation and promi-nent landmarks on shore. An adequate nautical chartmust include some planimetric detail along the adja-cent coast, especially salient landmarks visible from aship at sea and features identifiable on radar. (See1.6.5 and 4.5.13.)

support of hydrography and nautical charting. Planetable and topographic survey methods are still usedoccasionally to locate control for hydrography andto map changes in shoreline and alongshore featuresthat do not warrant supplemental photography. (See3.1.3.4 and 3.2.5.)

The basic coastal mapping products areshoreline maps, coastal zone maps, and photogram-metric bathymetry. Related data, consisting of land-marks for nautical charts, nonfloating aids to naviga-tion, rocks, ledges, reefs, and other obstructions anddangers to navigation, are included on these maps.The shoreline (1.6.1) is shown to within 0.5 mm ofits true position at the scale of the survey.

HYDROGRAPHIC MANUAL

state additional requirements for field verification ifthere is any doubt as to the validity of the compiledline.

Photogrammetric operations are scheduled aspriorities permit to provide support data that con-form with planned operating schedules of theassigned hydrographic unit. In general, aerial pho-tography must be obtained at least 1 and preferably2 yr before hydrographic operations are scheduled inareas such as Alaska, Hawaii, or other locationswhere transportation facilities and accessibility arelimited or difficult. Field support is essential in mostof these areas, starting with the recovery or the es-tablishment of horizontal control and the placementof targets on stations required for aerotriangulationin advance of photography. Hydrographic survey in-structions may provide for one or more tide observ-ers for tide-coordinated infrared photography. Fieldoperations for areas in the Great Lakes, along theAtlantic Ocean and Gulf of Mexico Coasts, and inthe Caribbean Sea will normally be performed byphotogrammetric field parties, usually with 12-moleadtime.

Photogrammetric office procedures are des-cribed in U.S. Coast and Geodetic Survey SpecialPublication No. 249, ''Topographic Manual, Part II''(Swanson 1949). The series of Photogrammetric In-structions (National Ocean Survey 1971a) are contin-ually being revised, modernized, and expanded tocomplement the outdated manual (now out of printbut being revised). Complete instructions and specifi-cations for topographic surveying by plane tablemethods are contained in U.S. Coast and GeodeticSurvey Special Publication No. 144, ''TopographicManual'' (Swainson 1928). Special Publication No.144, an earlier version of 249, is also out of print butwill be replaced by one or more of the series of Pho-togrammetric Instructions. Except as modified inproject instructions, the requirements stated in thePhotogrammetric Instructions shall be adhered to byhydrographic parties engaged in topographic surveys.

3.2.2. Control Identification

Shoreline and mean low water (MLW) ormean lower low water (MLLW) lines (1.6.1) oncoastal zone maps are generally compiled using tide-coordinated black-and-white infrared aerial photogra-phy. These maps are prepared only for areas whereadequate tidal datums are available on the date ofphotography. The same technique is used to deline-ate these lines on shoreline maps when planningleadtime is sufficient. The primary objective is toprovide data for nautical charting and marine bound-ary determination; a secondary benefit is the elimina-tion of the need for the hydrographer to develop thelow water line. Complete and accurate location ofthe low water line is desirable because it may be usedas the base line from which offshore boundaries aredetermined. Hydrographic survey instructions shall

3-12(JANUARY 1, 1980)

Photogrammetric bathymetry (photobathym-etry), consisting of depth contours and discretedepths, may be compiled from color aerial photogra-phy in selected waters wherever turbidity and bottomreflectance characteristics permit sufficient penetra-tion. These operations are restricted to areas of rela-tively shallow water where the bottom is light col-ored and the water is nearly free of suspendedparticulates. Photobathymetry can often relieve thehydrographer of the need to sound in hazardous surfzones. Unfortunately, water in the surf zone may car-ry a heavy load of suspended sediments makingphotobathymetry impractical. Bathymetry is usuallycompiled and furnished at the scale of the contempo-rary hydrographic survey. Field edit and field com-pletion of the compiled sheets are assigned to the hy-drographic unit by the project instructions.

Horizontal control requirements for aerotri-angulation are furnished to field units on a speciallyprepared copy of the large-scale diagram for themapping job involved. ''Photogrammetric InstructionNo. 22, Field Recovery and Identification of Hori-zontal and Vertical Control,'' Revision 2, dated Sep-tember 30, 1965 (National Ocean Survey 1971a) con-tains specifications and procedures for markingcontrol for aerotriangulation prior to aerial photogra-phy (premarking) and for photo-identification of thecontrol after photography is available. Analog andanalytical aerotriangulation techniques developed bythe National Ocean Survey have replaced the graphicmethods previously in use. The new techniques per-mit increased production, require less basic control,and yield more accurate results; however, control foraerotriangulation by either technique, particularly bythe latter method, must be identified with greater ac-curacy and reliability. Current practice is to placetargets, prior to aerial photography, on all horizontalcontrol stations for aerotriangulation. Photo-identifi-cation of aerotriangulation control in the field afterphotography using the substitute station method hasconsistently proven to be less than satisfactory withsmall-scale photographs and has largely been discon-tinued for coastal mapping operations. The substitutestation method may still be used occasionally

HORIZONTAL CONTROL AND SHORELINE SURVEYS

to identify a station where the target image is notidentifiable.

3.2.3. Photogrammetric Support Data

When needed, photogrammetric support datawill be furnished for all hydrographic surveys exceptfor surveys of areas completely offshore and for sur-veys not classified as basic. These data include printsof aerial photographs, copies of photogrammetricmap manuscripts, flight line photo center index, andother related support data.

Manuscript copies (support data 3) are madeafter the manuscript is complete except for field edit.One copy is for use with the ratio prints to locatehydrographic signals; the other is for use when trans-ferring shoreline and alongshore detail to the hydro-graphic field sheet.

If necessary, the hydrographer is furnishedcontact color prints of compilation photography,usually at 1:30,000 scale for 1:10,000 scale mappingand at 1:40,000 or 1:60,000 scale for 1:20,000 scalemapping. Color ratio prints of selected exposures willbe supplied when special circumstances make theiruse desirable. Prints of tide-coordinated infrared pho-tographs are not furnished routinely because specialexperience and knowledge of the spectral response ofthe emulsion and filter combination are needed foraccurate interpretation. Supplemental horizontal control for hydrog-

raphy that will be controlled electronically may beestablished using analytical aerotriangulation proce-dures. In this case, suitable objects are selected andtheir images photo-identified, or targets are placedand marked semipermanently in advance of aerialphotography. This procedure requires sufficient lead-time to permit proper planning, scheduling, andcompletion of supporting field operations.

Specially prepared support data will be fur-nished for all assignments where photogrammetriclocations of hydrographic stations are anticipated. Insome selected areas, specially prepared support datawill be provided to establish the positions of elec-tronic positioning system antenna sites. The datanormally will consist of:

Photobathymetric data consist of copies ofthe compilation on both paper and on a dimensional-ly stable medium, a copy of all pertinent reports, andthe field edit requirements. Copies provided will beat the scale of the contemporary hydrographic fieldsheets.

3.2.4. Field Edit

This must be completed on every shorelinemanuscript prepared to support hydrography beforephotogrammetric data for smooth sheet processingcan be furnished. Consequently, it is essential thatfield edit be planned and scheduled as an integralpart of combined operations. Photogrammetrists ex-perienced in this operation normally will be assignedfrom a photogrammetric field party for all projectsin the Great Lakes, along the Atlantic Ocean andGulf of Mexico Coasts, and in the Caribbean Seaareas. Experienced photogrammetrists may not beavailable for most mapping projects on the PacificOcean Coast, in Alaska, or in the Hawaiian Islands.Commanding officers of all vessels conducting hy-

Shoreline pass points and photo centers arelocated and shown on the manuscripts, then trans-ferred and inked on specially prepared prints by thecompiler to aid in the location of hydrographic sta-tions and signals in the field. [See ''PhotogrammetricInstruction No. 45, Revision 1, Photogrammetric Lo-cation of Hydrographic Control in the Field,'' datedMarch 15, 1954 (National Ocean Survey 1971a).]

3-13 (JANUARY 1, 1980)

1. Contact prints of compilation photog-raphy (1 set).

2. Specially prepared ratio prints at specif-ic ratios to the shoreline manuscript scale (1 set).

3. Positive copies of each shoreline manu-script on a dimensionally stable plastic base (2 each).

4. Diazo (ozalid) prints of each shorelinemanuscript, to be used as specified in the project in-structions (2 each).

5. ''Notes to the Hydrographer,'' whichare similar to the field edit questions prepared by thecompiler to provide information to supplement theaccompanying manuscript (1 set).

Such prints are normally made on dimensionally sta-ble plastic base film either in black and white or incolor; they are costly to prepare and should never besubjected to rough handling or exposed to excessivedampness.

The specially prepared ratio prints shall bereturned to the compilation activity that originallyfurnished them immediately after their usefulness inthe field has ended. Prompt application of field editcorrections to the shoreline manuscripts prior to fur-nishing smooth sheet data is facilitated by availabili-ty of these prints. Other data are to be included withthe hydrographic records and are forwarded by thehydrographer.

HYDROGRAPHIC MANUAL

drographic surveys in those areas shall assign an ex-perienced field editor to this duty. Training and as-sistance shall be requested from the appropriate Ma-rine Center if an experienced editor is not available.

tended only for hydrographic processing should notbe duplicated on shoreline manuscripts or on photo-graphs that will be returned for photogrammetricprocessing. Duplicated efforts of this nature in thefield result in duplicated efforts when processing thesurvey and may cause discrepancies during compila-tion; however, all features for which location data areentered in the field edit notes or in the hydrographicrecords must be plotted on the appropriate sheet.

All field edit work shall conform with thespecifications and requirements stated in ''ProvisionalPhotogrammetry Instructions for Field Edit Surveys''(National Ocean Survey 1974). The Director of eachMarine Center shall establish procedures to ensurethat field edit is completed on a satisfactory sched-ule, that completed data conform with specifications,and that data are forwarded promptly upon comple-tion.

Several hypothetical cases and examples ofitems frequently left incomplete (the most trouble-some discrepancies) are:

A positive unequivocal division of responsi-bilities between the hydrographer and the field editorcannot easily be made. In general, the hydrographeris responsible for features below the sounding datumwhile the field editor is responsible for features abovethat datum. (This may vary in the Great Lakes be-cause of the charting datums used. See 1.6.1.) Inmany cases, their combined efforts are needed for thecomplete determination of features that uncover;however, duplication is unnecessary and must beavoided. The unique character of the zone betweenthe sounding datum and high water datum (1.6.1) cre-ates a gray area of overlapping responsibilities that re-quires careful consideration to ensure that all vitalcharting data are acquired. Data plotted on hydro-graphic field sheets or in hydrographic records in-

3-14(JANUARY 1, 1980)

Close cooperation and coordination betweenhydrographers and field editors are necessary to re-solve all discrepancies in the field. Each query shownon the ozalid discrepancy prints shall be investigatedand answered. Annotated snapshots should be sub-mitted to supplement and clarify field data where theeditor cannot adequately describe a feature in a fieldblock or on a discrepancy print. The chief of partymust ensure that the necessary coordination iseffected. Many discrepancies created by the failure tocoordinate activities properly may not be discovereduntil the later stages of hydrographic verification andinspection when the problem cannot be resolvedproperly. The hydrographer shall inform the field ed-itor promptly of any changes or corrections that heconsiders necessary or desirable. Submerged or sunk-en objects discovered by the hydrographer, which donot appear on the appropriate manuscript(s), neednot be reported to the field editor as items to be add-ed to the manuscript(s). Items such as these are with-in the province of the hydrographic survey and re-main the responsibility of the hydrographer.

1. A field sheet shows an uncharted rockin the vicinity of a rock shown on the contemporaryshoreline manuscript of the area. A comparison of thetwo sheets during hydrographic verification showsclearly that the positions differ. The hydrographer didnot delete the rock symbol that was transferred to thefield sheet from the shoreline manuscript; and thefield editor failed to verify or delete the rock asmapped. The verifier and photogrammetric reviewernow must decide how to resolve the difference. Themost logical solution, in the interest of safety, is toshow a rock at each of the two positions althoughlarge-scale color photography with good water pene-tration qualities does not show any image that mightbe the second rock. It seems clear that there is onlyone rock; however, a satisfactory solution would re-quire a field investigation. This situation would nothave occurred if the activities of the hydrographerand field editor had been coordinated properly.

2. A rock shown on a photogrammetricmanuscript does not appear on the appropriate fieldsheet. What happened? Was the rock inadvertentlyomitted from the sheet by the hydrographer or didthe hydrographer find that the rock does not existand then fail to note the fact? The photogrammetricreviewer examines the compilation photography andconfirms the existence of this rock. The discrepancyjust discovered now becomes the problem of the of-fice verifier and of the reviewer. In all likelihood, therock will be added to the chart from the shorelinemanuscript only because the reliability of the combi-nation of color aerial photography and the judgmentof experienced photogrammetrists justifies this action.Proper execution of field edit or adequate coordina-tion of field edit and hydrographic operation wouldhave prevented the occurrence of this discrepancy.

3. Images of two of a group of six chartedpiers were not visible on the aerial photography usedfor compilation and were not shown on the manu-

HORIZONTAL CONTROL AND SHORELINE SURVEYS

scripts. Requirements of this kind normally arisewhen hydrographic surveys at a larger scale are nec-essary to develop a specific area (3.2.1) and photo-grammetric mapping is not feasible or cannot becompleted in a reasonable period of time.

Horizontal control meeting Third-order,Class-I accuracy standards, if available, should beused to control plane table surveys. Otherwise,photogrammetrically determined positions are ac-ceptable; however, stations located photogrammetri-cally using specially prepared data shall not be usedto control plane table surveys at a scale larger thanthat of the shoreline manuscripts.

Materials to be used for plane table sheets,sheet projections, and positional accuracy of featuresand objects located by plane table surveys for map-ping and charting are specified in ''Provisional Pho-togrammetry Instructions for Field Edit Surveys''(National Ocean Survey 1974).

3.2.5. Plane Table Surveys

A Descriptive Report shall be prepared foreach plane table survey made to provide data per-taining to the shoreline and alongshore features aspart of a large-scale hydrographic survey. Headingsare similar to those specified in section 3.1.3.4, butshall include an additional section specifying the tideor water level station used as a reference to identifythe shoreline and to determine the heights of rocks,reefs, and ledges above specified charting datums. Ifa tide or water level station was not used, explainhow the appropriate datums were identified. Thedate of identifying and locating shoreline is essentialand must be stated in this report. Separate reportsare not required for plane table surveys conducted aspart of field edit operations.

Plane table methods should be used whenshoreline delineation is required in small areas atscales larger than that of supporting shoreline manu-

3-15 (JANUARY 1, 1980)

script; but neither the field editor nor the hydrogra-pher made any reference to them. As a result, thesepiers would be shown erroneously as ruins onpublished charts until the next field investigation ismade. Adequate coordination of field edit and hy-drographic operations would have clarified the sta-tus of the missing piers and prevented appearance ofnonexistent piers in ruins on published charts.

4. The offshore end of a pier as it ap-pears on the shoreline manuscript includes a remov-able float. Such objects cannot always be recognizedby the pbotogrammetric compiler. The field editoroverlooked the float, but the hydrographer deleted iton the field sheet and actually plotted a sounding atthe position. He failed, however, to inform the fieldeditor of the float, thus creating another discrepan-cy.

The most frequent use of the plane table isto establish graphic control (3.1.3.4) and to delineatechanges in the shoreline and alongshore features.Plane table methods should be used in field edit op-erations to map sections of the shoreline that wereobscured on the aerial photography. These methodsalso may be used to locate certain nonfloating aidsand obstructions to navigation, alongshore rocks,reefs, and ledges and to revise alongshore naturaland cultural features that reflect changes since thedate of aerial photography. [See ''Provisional Photo-grammetry Instructions for Field Edit Surveys'' (Na-tional Ocean Survey 1974).]

4. HYDROGRAPHY

continuous profile along each line. Enough bottomprofiles must be obtained to permit the determina-tion of bottom slopes in all areas. The possibility ofirregularities and dangers to navigation remainingundiscovered between sounding lines is always pres-ent. The greatest responsibility and most difficulttask of the hydrographer is to assure reasonably thatnone of these remain undetected and that, whenfound, the least depths over shoals and other dangersare determined.

GENERAL4.1.

4.1.1. Hydrographic Field Surveys

The National Ocean Survey conducts hydro-graphic surveys to obtain the basic detailed informa-tion needed to map submarine topography and tocompile and publish nautical charts and related aids tomariners. A basic hydrographic field survey is notcomplete until it meets all of the following require-ments:

4.1.2. Classification of Surveys

5. Calibration and correction data havebeen applied to the observed depths and positions.

Navigable Area Surveys (NAS) are basic hy-drographic surveys with restricted area coverage. (SeeF.2.) The coverage is reduced by omitting require-ments for: (1) development of the 0-foot depth curveand foul, nearshore areas not considered navigable;and (2) complete field edit of the survey area. Navi-gable Area Surveys may also be restricted to themain navigable channel or corridor.

Sounding is perhaps the most important partof the hydrographer's duties. An accurate knowledgeof the depths is essential for safe navigation, particu-larly in harbors and their approaches where the draftof many vessels is often nearly as great as the depthsin which they navigate. It is not practical, however,to measure the depth at every point, although graph-ically recorded echo soundings do provide a nearly

Surveys conducted prior to the developmentof modem electronic positioning and recording echo-sounding equipment are generally considered to beinadequate for modern charting. Submarine topogra-phy in many areas is subject to frequent change bystorms, currents, or engineering developments andthus must be resurveyed periodically. Chart Evalua-tion Surveys (CES) are a rapid means of determining

4-1 (JANUARY 1, 1980)

1. The area has been systematically cov-ered with accurately located depth measurements suf-ficient to reasonably ensure that all dangers tonavigation have been found.

2. The configuration of all underwater fea-tures including channels, shoals, banks, and reefs hasbeen determined; and least depths have been deter-mined over all dangers to navigation.

3. Aids to navigation and landmarks havebeen described and located.

4. Contemporary tidal or water level ob-servations have been made from which soundings maybe reduced to the appropriate chart reference datum.

6. Bottom samples have been obtainedwith sufficient frequency to reveal the general physicalcharacteristics of the bottom.

7. Charted information and prior surveyfindings in disagreement with or not supported bypresent survey data have been thoroughly investigatedand resolved.

8. Other miscellaneous operations havebeen completed. Examples are field editing shorelinemanuscripts, accumulating data to be published in theCoast Pilot and measuring magnetic variations if re-quired (e.g., National Ocean Survey 1976a).

Hydrographic surveys are primarily classifiedas basic, navigable area, chart evaluation, or specialproject. The project instructions will specify the clas-sification required. (See 2.3.1.) A basic survey mustbe so complete that it need not be supplemented byother surveys. It must be adequate to supersede forcharting purposes all prior surveys, and it must satis-fy the requirements set forth in 4.1.1. In addition, abasic survey shall verify or disprove the existence ofall charted or reported features of significance.

Unless specified otherwise by project instruc-tions, a basic survey need not cover channels andother areas that have been surveyed recently with ad-equate detail and on an acceptable scale by otherqualified and authoritative organizations, providedthat the survey by the other agency can be correlatedwith the basic survey and that satisfactory agreementof depths is attained at the junction of the two sur-veys. (See 4.3.2.)

HYDROGRAPHIC MANUAL

The field sheet (formerly called the boatsheet) is the hydrographer's work sheet; it presents agraphic display of all surface and subsurface featuresin the area being surveyed. It is indispensable to thehydrographer for visualizing the progress and ade-quacy of work accomplished and for planning futureinvestigations and operations. The field sheet itselfmay be the composite product of several overlays, in-sets, and rough preliminary launch or skiff worksheets from which gross errors in the raw field datahave been corrected; or it may be a final real-timeplot of hydrographic survey field data.

Hydrographic surveys are classified as spe-cial if the general requirements or specifications donot logically fall into any of the preceding categories.A special survey may cover small areas for limitedpurposes such as to prove or disprove the existenceof reported dangers or obstructions, to provide datafor harbor development, or to supplement prior sur-veys for construction of a large-scale chart. Othersurveys, regardless of size of area, may be classifiedas special if significant deviations from line spacingor degree of coverage requirements are authorized.Project instructions for this type of survey shall ex-plicitly define variations from established field proce-dures and data-processing requirements.

Whether plotted by hand or by automation,the field sheet must portray neatly and legibly all po-sition fixes, preliminary field soundings, inked depthcontours that adequately delineate the bottom con-figuration, bottom characteristics, electronic controllattices, shoreline features where applicable, and allaids and hazards to navigation, particularly rocks,shoals, reefs, ledges, wrecks, piling, dolphins, piers,and breakwaters with their elevations or depths asappropriate. A complete field sheet must also showinformation pertinent to all geographic names recom-mended for charting, landmarks, tide or water levelgage sites, horizontal control stations, uncharted ha-zards, presurvey review items, junctional soundings,piers, floats, berthing facilities, and all other data re-quired for charting. Overlays and insets should befreely utilized to prevent the field sheet from becom-ing cluttered and to present the information in theclearest manner possible. Copious explanatory notesare required on every field sheet and in the hydro-graphic records to clarify any unusual or question-able circumstance that cannot be depicted by routinegraphics and to provide a complete understanding ofthe survey and charted features not otherwise indi-cated in the field records.

Generally, only standard basic surveys willbe assigned registry numbers and be archived. Othersurveys are normally filed as field investigations.

4.1.3. Survey Operations

The field sheet also serves as an invaluableguide and aid during the verification and smooth plot-ting phases of data processing. Frequently, critical in-formation is extracted from the field sheet prior to ver-ification and applied directly to the nautical charts.

A hydrographic survey has not served its ul-timate purpose until the data have been incorporatedin a published nautical chart. The data accumulatedmust be processed as rapidly as possible to keep pacewith the field work accomplished. Periods of inclem-ent weather should be devoted to field processing.When a considerable volume of unprocessed recordshas been accumulated, one should process during pe-riods of marginal weather. (See 4.9.)

4.2.2. Construction of Field Sheets

Hydrographic survey sheets are constructedto cover efficiently the project area as shown on theapproved sheet layout. (See 2.4.2.) The recommendedsheet size is 36 by 54 in (91 by 137 cm); maximumsheet size is 42 by 60 in (107 by 152 cm). Refer to1.2.4 for other constraints on sheet size and

FIELD SHEET4.2.

4.2.1. Definition and Use

4-2(JANUARY 1, 1980)

the adequacy and accuracy of charted data and ofupgrading the general area of the chart through com-plete resolution of all reported or discovered chartdeficiencies. (See F.3.) Chart evaluation projects mayinclude all of the following types of operations: re-connaissance hydrography, Coast Pilot inspection,tide/water level observations, waterfront planimetry,chart deficiency investigation, and user evaluation.

Instructions for a survey project (2.3.1) willbe issued and the necessary data furnished sufficient-ly in advance of field work to permit formulation ofa general plan of operation. (See 2.3.2.) Plans forday-to-day operations must be coordinated with thegeneral plan as circumstances dictate so that surveyoperations can be carried on smoothly and efficient-ly. All survey operations required in an area shouldbe completed as the work progresses. Required mag-netic observations, field edit, compilation of CoastPilot notes, and similar operations must be kept upto date (e.g., National Ocean Survey 1976a ).

HYDROGRAPHY

for sheet margin requirements. For convenience, hy-drographic data are recorded, filed, and referencedon a separate sheet-by-sheet basis. The hydrographyshown on any field sheet or portion thereof shouldnot be extended in a continuous manner beyond thelimits for that sheet as shown on the approved lay-out.

HYDROGRAPHIC SURVEYNo. 1

Field no.

Reg no.Projections shall be machine drafted on sta-

ble-base transparent materials insofar as practical.Procedures for a hydrographic field party notequipped with an automatic plotter to obtain plottedprojections are established by that unit's MarineCenter. Units capable of automatic plotting shall useonly NOS-approved projection plotting programs.

Scale

Datum

Projection

Soundings plotted in

Soundings corrected for

Draft

Tides

Velocity

Instr error

Set-squat

within the limits of a photogrammetric manuscript,a duplicate field sheet can be constructed by simplytransferring the projection and shoreline directlyfrom a stable-base reproduction of the manuscript.Two or more manuscripts shall not be joined forthis purpose.

4.2.4. Calibration Sheets

Projections required for calibrating an elec-tronic positioning system by manual methods shallbe constructed on a stable-base plastic material. Thescale of the projection should be at least twice that

4.2.3. Duplicate Sheets

TABLE 4–1.—Projection line intervals for various scales

Scale of survey Projection line interval

Every 5 s1:2,000 and larger1:2,001 to 1:3,000 Every 10 s1:3,001 to 1:6,000 Every 15 s1:6,001 to 1:12,500 Every 30 s1;12,501 to 1:25,000 Every minute1:25,001 to 1:60,000 Every even minute1:60,001 to 1:125.000 Every 5th min1:125,001 to 1:250,000 Every 10th min

When the area to be surveyed lies entirely

4-3 (JULY 4, 1976)

If one must manually construct a projectionon nonstable material, it should be plotted andchecked for accuracy the same day. Procedures forthe manual construction of a field sheet are detailedin U.S. Coast and Geodetic Survey (1935) SpecialPublication No. 5, ''Tables for a Polyconic Projec-tion of Maps and Lengths of Terrestrial Arcs of Me-ridians and Parallels Based Upon Clarke ReferenceSpheroid of 1866.'' Control stations should also beplotted and checked as soon as possible to reducethe adverse effects of distortion of the material. (See4.2.5.) For the same reason, electronic distance arcsshould be drawn as soon as the base station posi-tions are known. (See 4.2.6.) Accurate hyperboliclattices are not easily plotted by hand and shouldonly be machine drafted.

Table 4–1 specifies projection line intervalsfor various hydrographic sheet scales. The width ofinked projection lines shall be 0.15 mm. Hydro-graphic field sheets shall be labeled on the lowerright-hand corner of the sheet in accordance withfigure 4-1. The label may be impressed with a stampor be machine drafted.

Marine Centers normally provide duplicateor additional field sheets as required by hydro-graphic field units for manually plotted surveys. Ifadditional sheets cannot be made available, duplicatesheets can be constructed by pricking through theprojection intersections with a fine needle. A longsteel straightedge should be placed along each me-ridian line as the points are pricked; care must betaken not to disturb the relation between the twosheets as the straightedge is moved. Field numberswill be assigned in accordance with section 2.4.3.1.

FIGURE 4–1.—Rubber stamp 1. This hydrographic fieldsheet title block is to be stamped or machine draftedon the lower right-hand corner of the sheet.

HYDROGRAPHIC MANUAL

of the survey on which the control system will beused. The principles and methods of projection con-struction and plotting control and line-of-positionarcs are identical to those for other hydrographicsheets; extreme precautions and care are required toensure plotting accuracy. These sheets need not benumbered and may be discarded after the survey haspassed final inspection.

4.2.5. Control Stations

Control stations that will be used for thesurvey which lie within the field sheet limits shouldbe plotted on or transferred to the field sheet usingstandard symbols. (See appendix B.) All basic andsupplemental control stations used for calibration ofelectronic positioning systems or for visual sound-ing control shall be assigned a three-digit number.A numbering system such as the following is recom-mended:

New control stations are plotted by anyconvenient and accurate method. The plotting of allcontrol stations should be verified and noted on thefield sheet before the station symbols are inked.

4.2.5.1. BASIC AND SUPPLEMENTAL CON-

TROL STATIONS. On manually constructed fieldsheets, recoverable control stations of third-order orhigher accuracy shall be plotted from the computedvalues of latitude and longitude. The differencesalong adjacent meridians (dm's) and the differencesalong adjacent parallels (dp's) are plotted from thesouth parallel and east meridian, respectively, usinga beam compass and metric scale. (See figure 4-2.)Dividers can be used to measure short distances, butthey become less accurate when spread appreciably.The dm and dp distances (in meters) shall bemarked by fine prick points adjacent to each set ofprojection lines then connected by fine pencil lines.To check the plotting and to compensate for sheetdistortion, plot the back dm's and back dp's fromthe north parallel and the west meridian. Distortion,if present, shall be proportioned between each set ofdm and dp parallel lines. The position of the stationat the intersection of the final dm and dp lines ismarked by a fine needle hole that may be blackenedby rotating a sharp pencil point in the hole. Neveruse ink to mark the point. The plot of the controlstation shall be checked either by the same methodor with Sylar-Lockerbie latitude and longitude scalesbefore the symbol is drawn in ink.

Signals constructed over basic or supple-mental control stations are identified on the fieldsheet by name and assigned number. The names andnumbers of stations may be lettered by hand pro-vided the lettering is completely legible. These iden-tifiers should not be placed in water areas nor coverup essential detail on the field sheet and must bepositioned so they are clearly associated with thecorrect symbols. Existing names of geodetic controlstations must be shown with their exact spelling. Ifa station such as a beacon or an off-lying rock liesin the water area, the station name should be inkedon a land area nearby; in such cases, an arrow orleader is used to indicate the station to which thename refers. Each control station in the water areashould be described briefly and a notation made on

4.2.5.2. HYDROGRAPHIC CONTROL STA-

TIONS. Additional hydrographic control stations aredesignated as traverse, photogrammetric, sextant,plane table, or unconventional as specified in section3.1.3. Standard cartographic symbols to be used onhydrographic sheets for each type of station areshown in appendix B.

4.2.6. Electronic Position Control Lattices

These shall be constructed on all surveysheets (or on suitable overlays) in those areas where

4-4(JULY 4, 1976)

001-100, basic and supplemental controlstations (3.1.1 and 3.1.2) used for electronic controlantenna sites;

101-200, other control stations (3.1.3 and3.1.4) on the first field sheet or part of a field sheetof the project;

201-250, other control stations on thesecond sheet,....

Although use of such a system is not man-datory, grouping of stations in this manner can sim-plify signal recognition for the observers and the hy-drographer during visual sextant surveys. Signalsmay also be numbered consecutively in the directionof survey progress to further simplify recognitionand identification.

the field sheet as to whether the feature on which itis erected is permanent or temporary.

When sextant control stations are numerous,as on an inshore hydrographic sheet, identificationwill be made easier if brief descriptions of the signalsare noted on the field sheet. The more prominentsignals should be identified as such. Visual controlstations of a permanent or semipermanent natureshall be so described; state whether each is conspicu-ous enough for use as a landmark.

HYDROGRAPHY

Plotteddistances

FIGURE 4–2.—Control station plotted by dm's and dp's on a dis-torted sheet

Whole numbered line-of-position arcs shallbe plotted at intervals spaced approximately 7 to 10cm at the scale of the survey. The lane or distancevalue and control station number(s) for each arcshall be labeled (in distinctive colors) as follows:

Range arcs should be drawn as soon as theprojection and control stations have been plottedand checked. An Edmonston Beam Holder or other

(JUNE 1, 1981)4-5

hydrography is controlled electronically. Latticesare not required on the final field sheet. Latticesserve as a visual check of the geometric strength ofthe intersecting lines of position, as a convenientreference for plotting or locating plotted data onthe sheet, for planning and executing daily work,for positioning the vessel at the desired points, andas an overall aid to the hydrographer for checkinglane count or measured distance when the positionof the vessel is known. If a large number of posi-tion arcs shown on one sheet would result in con-fusion, lattice overlays should be used.

200(126) is a range arc or distance circlewith a lane or distance value of 200 units; thetransmitting station number is 126.

140(103-211) is a hyperbolic arc with alane value of 140; the transmitting station numbersare 103 and 211— the left and right stations, respec-tively, as viewed from the survey area.

If the control station(s) for an electroniclattice do not lie within the sheet limits, the sta-tion(s) name and year(s) of establishment shall beshown on at least one of the arcs.

Automated plotting facilities should be uti-lized for constructing locus arcs on field sheets. Ifone must plot range arcs on the sheet manually, thefollowing methods are recommended:

suitable device should be placed over the stationmark to prevent damage to the sheet as the arcsare drawn. If the arcs are drawn later, the projec-tion must be checked for the presence of distortionand significant distortion amounts distributed assubsequently described.

When control stations lie within or nearthe sheet limits, circular arcs can be drawn using abeam compass and meter bar.

If the control station falls on the sheet,radii for the circles are measured and marked alongthree radial lines drawn from the station. The linesshould be well distributed throughout the surveyarea. Coordinates of three points on the circle oflargest radius are then computed and plotted onthe projection. If the measured radii do not checkwith the corresponding computed and plottedpoints, the radius measured from the point plottedin the central portion of the survey area is held ascorrect; the center of the arc system is adjusted sothe drawn arcs will pass through each of the com-puted positions. If the amount of distortion is small,the distance from the plotted arc to the next arcmay be scaled along each radial; the new arc maybe drawn from the adjusted center. If the distortionis significant, the procedure of computing positionsfor arc points and adjusting centers must be repeat-ed for each arc.

If the control station lies beyond thesheet limits, the sheet is laid flat and secured firmlyat one end of a drafting table. A section of Bristolboard or other suitable material is fastened to thetable at the approximate plotting location of thecontrol station. The coordinates of three or morewell-distributed points on each arc are computedand plotted. The center of the arc system is locatedby using a beam compass to swing radius arcs fromthe plotted points for the nearest circle. The arcsshould intersect at a point. The relative location ofthis point with respect to the points plotted for theother arcs must be checked before the arcs aredrawn in ink. As before, one may have to adjustthe center so the arc passes through each of thecomputed positions.

If the center of the arc system lies beyondthe practical limits of beam compass use, three radiiare drawn through points for which coordinateshave been computed and drawn. (See figure 4-3.) Asheet layout on a small-scale chart on which thecenter has been plotted and the arcs drawn is help-ful for determining approximate radial azimuths

HYDROGRAPHIC MANUAL

FIGURE 4–3.— Principle of drawing distance-arcs when the sta-tion is off the sheet

FIGURE 4–4.—Drawing arcs with a metal three-arm protractor

4.2.7. Transfer of Topographic Detail

Field sheets for all inshore surveys shallshow the shoreline (as defined for the particulararea (1.6)) and all other available information onalongshore and offshore rocks, aids to navigation,channels, approximate limits of shoal areas, and po-sitions of reported dangers to navigation. The twoprincipal sources of such information are thepublished charts and shoreline manuscripts. The hy-drographic party normally will be furnished copiesof the shoreline manuscripts or, if not available,copies of prior topographic surveys. (See 1.6.1 and3.2.)

The shoreline and important details sea-ward of the shoreline are transferred from themanuscript copies to the field sheets after the posi-tions of the necessary control stations have beenplotted. If the low water line as defined for the par-ticular area (1.6) has been delineated on the shore-line manuscripts, it shall also be transferred to thefield sheet. (The low water datum line usually is notshown on Great Lakes surveys.)

If transparent material is used for the fieldsheet, the important details are carefully traced from

4-6(JUNE 1, 1981)

and distances. Scale the coordinates of a point nearthe center of the survey area (B2 ) and compute theinverse between the point and the control station.For convenience, the point may be a plotted pro-jection intersection. From the computed inverseazimuth and distance, a pattern of points on the cir-cles for various radials can be developed. The posi-tions of points A1, B2,..., C3 are computed and plot- ted. Radial lines should pass through the computedpoints along each azimuth; a circle should passthrough the three points at equal distance. Pointson the other circles to be drawn can be located bysubdividing the radial lines and compensating fordistortion in a proportional manner. Points alongadditional arcs and radial lines may be necessary,depending on the orientation of the arcs on thesheet. All computations should be retained and in-cluded with the survey records.

Plastic templates are available commer-cially for drawing circles of large radius. If thetemplates are not long enough to permit drawing acontinuous curve across the entire sheet, the coor-dinates of four or more points should be computedand plotted to permit accurate placement of thetemplate.

Another method of drawing circles isshown in figure 4–4. Two pins are set firmly at po-sitions A and B. The angle D =180º– (X/2). Thisrelationship is true for any point along the arc AB.The angle D is set on a three-arm protractor usingthe movable arm that can be closed to a zero read-ing. A pencil is centered in the protractor, and thearc AB is drawn by moving it across the sheet withthe arms sliding against the pins. The arc BC can bedrawn in a similar manner using the angular differ-ence in azimuths of the lines PB and PC as the angleX. The portion of the arc that falls beyond A or B is

Odessey protractors (A.9.1.3) are gener-ally used to manually plot positions determined byelectronic ranging systems.

plotted with the protractor set at the angle X/2This method is approved for field sheet plottingonly.

HYDROGRAPHY

4.3. SOUNDING LINES

4.3.1. Sounding

After the transfer of shoreline and along-shore details has been verified, the shoreline is inkedin a fine black line about 0.4 mm wide. (See appen-dix B.)

Offshore rocks, limits of marine growth orfoul areas, and other details (including the low waterline transferred from photogrammetric manuscripts)are inked in blue on the field sheet at the time oftransfer and then inked in black after verification ofposition and character by the hydrographic survey.(See 1.6.1.)

4.2.8. Transfer of Data From Prior Surveys

All dangers to navigation, including leastdepths over shoals, shall be transferred to the fieldsheet from copies of prior hydrographic surveys andinked in distinctive colors. Representative soundingsand sections of depth contours should also be trans-ferred to provide a direct comparison with previoussurveys.

Analog and digital echo sounders recordsoundings with a consistency and accuracy directlyrelated to the care with which the instruments arecalibrated, maintained, and operated. Digital sound-ings are usually more accurate than soundings scaledfrom an analog bottom profile because there are nomechanical recorder malfunctions or errors. Differ-ences, however, between digital soundings andsoundings from a well maintained and calibratedgraphic recorder should not exceed 0.5 ft or 0.2 fmexcept on steep slopes. If this tolerance is exceededor if there is doubt as to the accuracy of the sound-ings or of the control, sounding should be discontin-ued and not resumed until all uncertainties havebeen resolved. To continue sounding under such cir-cumstances is usually a waste of time and often in-troduces processing complications. The hydrographershould remember that the recording of a sounding isonly the first operation in a lengthy process of pub-lishing a depth on a nautical chart.

Each locally reported shoal or hazard tonavigation shall be plotted on the field sheet so thatits position may be accurately determined or its exis-tence disproved during the survey.

Depths of water shall be measured with thegreatest accuracy consistent with efficiency. Depth-measuring instruments or methods used to soundover relatively even bottoms or in critical depthsshould measure depths less than 20 fm to within0.5-ft accuracy–greater depths to within 1% accu-racy.

Soundings and other hydrographic datatransferred to the field sheet are liable to be obliter-ated or obscured while surveys are in progress. Asan aid to daily inspection of the survey, a transpar-ent overlay may be used to show the data trans-

4-7 (JULY 4, 1976)

the shoreline manuscript. If opaque material is used,the details are transferred by applying ''dri-rite'' inkor ink from a felt tip marking pen such as ''MagicMarker'' to the reverse side of the manuscript. Theprojections are then matched, and the shoreline istraced with a stylus or hard pencil. Shoreline neednot be shown on field sheets for offshore surveys.

The most recent edition of the largest scalenautical chart covering the area must be examinedcarefully; any additional dangers and significant fea-tures must be transferred to the field sheet.

A presurvey review (2.3.3) is usually fur-nished for each project. Each presurvey review itemmarked on the chart shall be transferred to a fieldsheet or overlay for examination during the survey.Discrepancies and questions that arise during thephotogrammetric compilation of the shoreline manu-script are also indicated to the field unit as part ofthe basic data on a copy of the manuscript. Thoseitems seaward of the shoreline shall also be trans-ferred to the field sheet for investigation. (See 1.6.1.)

ferred to the field sheet from the charts or prior sur-veys.

Equipment and instruments used by the Na-tional Ocean Survey for hydrographic depth mea-surements are described in appendix A. Graphic oranalog records of the bottom profile shall be ob-tained whenever possible. When digital echo sound-ers are used for a hydrographic survey, correspond-ing analog depth records shall accompany the digitaloutput and be treated as part of the original surveyrecords.

When sounding in areas where kelp or othervarieties of marine vegetation partially or totally ob-scure the bottom trace, a lead line or sounding polemust be used to supplement or replace echo sound-ings. Lead-line or pole soundings must be verticalmeasurements. When bottom samples are beingtaken, depths should not be recorded if the pole orlead line is sloping. Such erroneous soundings causeconfusion in later processing unless such discrepan-cies are fully explained in the record.

To ensure continuity in survey coverage anddepths, one must transfer the soundings from thelimits of adjoining surveys to the field sheet or to asuitable overlay prior to beginning a new hydro-graphic survey. (See 1.4.4.) Transferred soundingsare marked on the field sheet in colored ink; use adifferent color for each survey with which a junctionis to be made. Soundings are transferred from priorsurveys, contemporary surveys, and new surveysmade on adjoining sheets of the same or differentscales. In areas where the U.S. Army Corps of Engi-neers maintains dredged channels, soundings fromthe most recent Engineer survey may be transferredto the field sheet; if a satisfactory junction is made,a complete survey of the channel need not be re-peated unless directed otherwise by the project in-structions. (See 4.1.2.) Soundings, however, shall beobtained along mid-channel lines and along othersuch lines marked by navigational ranges.

HYDROGRAPHIC MANUAL

In rapidly changing depths and over irregu-lar bottoms, accuracy requirements may be de-creased to 1 ft in depths less than 20 fm. Althoughecho soundings in submarine valleys or on steepslopes may indicate depths less than the true verticaldepths under the vessel, corrections for bottomslopes are not usually required. 4.3.3. Inshore Limits of Surveys

4.3.2. Junctions and Overlaps

Sources of soundings at junctions are refer-enced on the field sheet by field or registry numberof the survey or by identifying number of the U.S.Army Corps of Engineers survey.

An overlap of at least one sounding line orequivalent distance shall be made with an adjoiningsurvey except that, when the survey is continuous inthe same year, by the same method, and by thesame survey vessel, sounding overlaps are not re-quired.

However desirable it may be to extend ahydrographic survey to the inshore limits stated, thehydrographer shall never subject his boat or person-nel to undue risks and avoidable hazardous situa-tions. Along regular sandy beaches, lines should berun parallel to the shore during periods of high tideand calm weather. Risk can often be reduced byrunning these lines early in the survey to delineate asafe turning zone for terminating sounding lines thatare run toward the beach. In areas of small tidalranges such as the Gulf of Mexico, a wide band ofvery shoal water difficult and uneconomic to developoften extends offshore from the low water line. Insuch areas, inshore lines should be run as close aspossible to the shoreline; the hydrography should besupplemented by a few widely spaced depths ob-

Where depths in junctional area do notagree, the new survey shall be extended into the olduntil agreement is reached. If a reasonable extensionfails to reach agreement, a detailed report shall be

4-8(JULY 4, 1976)

Junctional soundings from photobathymetriccompilations shall be transferred to the field sheet orto a suitable overlay; then a satisfactory junctionmust be made. Sounding lines shall be run in areaswhere accurate depths could not be measured on thephotobathymetric survey or where the photogram-metric compiler or hydrographer has reason to ques-tion measured depths.

submitted to the Marine Center with a request forfurther instructions.

The best evidence of a proper junction ofsurveys is revealed by the continuity of the depthcontours in the overlap area. (See 4.6.)

Hydrographic surveys shall extend as closeto the shoreline as safety and practicality permit,unless the low water line as defined for the area(1.6.1) has been delineated on the shoreline manu-script using tide-coordinated aerial photography. Insuch cases, the survey need not be extended inshoreof the low water line. Otherwise, the low water linemust be developed by soundings or other acceptablehydrographic methods wherever conditions permit.Project instructions may require periodic verifica-tions of the compiled line.

In tidal areas, sounding lines close to shoreshould be run during rising tides (near high) andcalm weather. Complete hydrographic developmentover extensive tidal flats or similar areas is not re-quired, but a few sounding lines spaced at three tofour times the maximum spacing in adjacent areasshould be run inshore of the sounding datum ifpractical without jeopardizing the safety of the ves-sel and personnel. This does not reduce the require-ment to fully develop reefs, ledges, or other hazardsto navigation.

Streams within the project limits shall besurveyed to the head of navigation for small boats;unless the project instructions specify otherwise,tidal sloughs and estuaries shall be surveyed to thesame limit or until the low water line has been de-lineated adequately.

HYDROGRAPHY

If sounding lines are to be run in rocky in-shore areas, the hydrographer should examine thearea at low water (preferably at a low spring tide)and locate all breakers and exposed rocks by sextantfixes or cuts or equivalent methods. Sounding linesmay then be run at high tide with a greater degreeof safety.

When the low water line has not beenphotogrammetrically delineated and a hydrographicdetermination would be overly hazardous, the areasshould be fully described in the descriptive reports;an explanation should be given of the conditionspreventing the extension of the survey close inshore.Copious notes must be entered in the sounding re-cords and on the field sheet to show the limits ofbreakers, kelp, or foul areas that prevented closerapproach to shore.

4.3.4. Spacing Sounding Lines

The spacing of sounding lines on basic hy-drographic surveys must be such that sufficient in-formation will be provided to satisfy the require-ments stated in section 4.1.1. Prominent submarinefeatures and those objects dangerous to navigationmust be detected; least depths must be determinedto an absolute accuracy of less than 1 ft in watershallower than 20 fm. Depths varying by more than2 ft from general surrounding depths must be devel-oped in existing or potentially important navigableareas. (See 4.3.1.) Lines must be spaced sufficientlyclose to permit drawing of accurate depth contours

Bottom slopes in mud or sand are usuallysmall (except in areas of large sand waves); areas ofshoals in these types of bottoms are generally largein proportion to heights. It is unlikely that a shoalinvolving any great change in depth could lie whollybetween two adjacent lines and remain undetected.Conversely, where the bottom is rocky, sharp irregu-larities must be expected and every shoal indicationexamined. Although a shoal is typically indicated bya decrease in depth, abnormally deep soundingsmust be viewed with suspicion since they often markthe scour caused by the currents near a rock or

4-9 (JULY 4, 1976)

tamed by sounding from a skiff or by wading at lowwater.

On rocky coasts, it may be unsafe or im-practical to survey any portion of the low water line.Where a rocky area is considered too dangerous fora launch to enter or where kelp is so thick it pre-vents a sounding boat from passing through, thefacts shall be stated in the survey records and theareas delineated on the field sheet as accurately aspossible using appropriate notes. The area often canbe delineated by estimated distances and bearingsfrom fixed positions observed in safer waters.

throughout the area and to provide reasonable assur-ance that all submerged dangers are detected. Thegeneral spacing must be reduced as necessary to de-velop fully all bottom relief and to obtain leastdepths over shoals, banks, and pinnacles. (See 1.4.3.)

Project instructions will specify the maxi-mum spacing to be used in various depths or areas.The hydrographer or the chief of party shall reducethe line spacing in critical areas as needed for acomplete hydrographic survey; but the general spac-ing specified in the project instructions shall not beincreased or decreased over large areas without priorapproval of the Director, National Ocean Survey. Ifthe chief of party believes that the general spacingshould be changed, a full report to support the re-quest for an amendment to the instructions must besubmitted.

Proper spacing of sounding lines depends onthe purpose of the survey, depth of the water, char-acter of the submarine relief, scale of the survey, andimportance of the area. (See 1.1, 1.4.1, and 4.1.)Equally important is the accuracy and adequacy ofcoverage of prior surveys of the area by modernstandards and the susceptibility of the submarinetopography to change. (See 4.1.2.)

There is a practical limit to the number ofsounding lines that can be plotted at any givenscale. Sounding lines 5 to 6 mm apart can be plottedeasily; the soundings can be inked or machinedrafted without difficulty. With a little care in plot-ting and in selecting soundings to be plotted, theline spacing on the sheet can be reduced to about3.5 mm. Lines plotted in excess of this number sel-dom. contribute significantly to the survey unless alarger scale inset or overlay is used. After the gen-eral bottom configuration has been determined, thehydrographer often finds it necessary to run addi-tional lines to determine least depths over shoals.These additional lines should be plotted on the fieldsheet or an overlay; but unless revealing informationis provided, the data should be marked ''not to besmooth plotted'' and the reasons stated. (See 1.4.3.)Data from such lines are not rejected; the analogdepth records and other data pertinent to these linesshall be forwarded with the records. Bottom profilesof these lines must be carefully studied to ascertainthat least depths were not overlooked.

HYDROGRAPHIC MANUAL

other obstruction rising steeply from the bottom. Inarea where the bottom consists of irregular steepfeatures, it is often desirable to record side echoesscanned from the graphic depth record (4.9.8) asthey may be indications of shoals or hazards not di-rectly beneath the vessel.

400 m in depths of 20 to 30 fm, and800 m in depths of 30 to 110 fm.

In sea lanes or coastal steaming routeswhere deep draft vessels are operating or are ex-pected to operate, sounding line spacing is generallydecreased; such decreases will be specified in theproject instructions.

4.3.4.1. LINE SPACING IN HARBORS AND

RESTRICTED AREAS. Unless specified otherwise byproject instructions, the maximum spacing of sound-ing lines for basic hydrographic surveys in harbors,bays, passages, channels, and rivers shall not exceed: 4.3.4.3. LINE SPACING FOR OFFSHORE SUR-

VEYS. Hydrographic surveys in offshore areas (1.2.3)may be plotted on scales as large as 1:40,000 wherethey join inshore surveys or on a scale as small as1:500,000 in ocean areas of great depth. Regardlessof the type of bottom, the fine spacing shall not ex-ceed:

100 m in depths less than 20 fm,200 m in depths from 20 to 30 fm, and400 m in greater depths.

1600 m in depths of 110 to 500 fm,3200 m in depths of 500 to 1500 fm, and8000 m in greater depths.If the area is of sufficient navigational im-

portance to warrant a survey at a scale of 1:5,000,the sounding lines are spaced at maximum intervalsof 50 m.

In all cases, the sounding line spacing is re-duced as needed to develop shoals, to ascertain leastdepths over them, and to provide enough soundingsto permit an accurate portrayal of the bottom con-figuration.

Such wide spacing may not always be ade-quate to permit detailed contouring of the bottom.The surveyor must study the soundings and analogdepth records to detect indications of submergedfeatures that warrant surveys of greater detail. Pre-scribed line-spacing intervals must be reduced andthe survey scale increased as necessary to determinethe configuration of submerged mountains, valleys,trenches, and canyons and to determine the limits ofescarpments. Smaller features such as mounds, seaknolls, and depressions should also be developed.Breaks in slopes along continental or island shelvesshould be well defined by soundings.

4.3.4.2. LINE SPACING ON OPEN COASTS.

Sounding line intervals along open coasts depend onthe type and draft of maritime traffic, water depths,and bottom characteristics. In areas such as the Gulfof Mexico and parts of the Atlantic Coast wherebottoms are composed mostly of sand or mud anddepths change slowly, sounding lines can often bespaced at twice the interval used in areas of irregularbottom. In areas of smooth bottom along opencoasts, line-spacing intervals shall not exceed:

200 m in depths less than 20 fm,400 m in depths of 20 to 30 fm, and800 m in depths of 30 to 110 fm.

4.3.5. Systems of Sounding Lines

Because one cannot measure the depth overevery point, methodical and systematic examinationof each area shall be made. Usually, this is best ac-complished by running a system of parallel soundinglines. (See 1.4.) The purposes of this regular systemof lines are to (1) provide reconnaissance to the hy-drographer for indications of shoals or submergeddangers that subsequently must be investigated for

In areas of irregular bottom on open coasts,the line-spacing interval shall not exceed:

100 m in depths less than 20 fm aroundrocky points and spits and in entrances to channels,

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In dredged or natural narrow channels, theline spacing shall not exceed 50 m. Soundings shallbe obtained along the faces of all piers and in adja-cent berthing areas. (See 4.5.12.)

At entrances to harbors in areas adjacent tospits or rocky points where major changes in bot-tom contours are expected or found, the fine spacingshall be reduced to half the regular interval.

200 m in all other areas where the depthis less than 20 fm,

Bottom composition, importance of thearea, and survey scales will be considered when line-spacing intervals are determined and project instruc-tions written. In areas of rocky or irregular bottom,closer spacing may be required and different break-points specified. The spacings specified are maxi-mums that must not be exceeded.

HYDROGRAPHY

frequently obtained with a minimum of soundinglines, (2) three-point fixes are more easily obtainedsince fewer changes in objects are required, (3) posi-tions close inshore which cannot be fixed by sextantangles may be determined accurately by course anddistance from the last fixed position, and (4) naturalranges can be used to keep the vessel on course.Disadvantages are that it may be difficult to controlthe lines when close to shore (with sextant fixes) andit may be dangerous heading inshore. Variations inspeed at the inshore ends often cause erroneous plot-ting of soundings, making it necessary to run addi-tional lines.

In the top illustration of figure 4–5, systemsof radiating lines and parallel straight lines are usedto develop depth contours and delineate hydro-graphic features. In the bottom illustration, parallelstraight lines are combined with electronic line-of-position arcs.

Hydrographers must be continually alert forvessel speed variations that can alter the spacing ofsoundings between fixes and introduce errors intothe survey. Speed variations may occur when sound-ing lines cross natural or dredged channels andshoals, where landmasses limit sounding lines to twoor three positions, during approaches and departuresfrom a beach or shoal water, and where drag or bot-tom suction suddenly slows the speed of the sound-ing vessel. If sounding positions are plotted by deadreckoning between fixes (time and course), hydrogra-phers should try to anticipate changes in bottomconditions that affect launch speed and be preparedto take a position on the next sounding interval.(See 4.4.5.) If a speed variation occurred betweenfixes, soundings are plotted at their most probableposition. Straight parallel lines run at an angle of

about 45º to the depth contours are advantageous incertain areas. This system often provides better de-velopment of long, narrow, steep-sided ridges ortroughs.

4.3.5.1. PARALLEL STRAIGHT LINES. Regu-larly spaced parallel sounding lines, approximatelynormal to the depth contours and general trend ofthe shoreline, are generally used for visually con-trolled hydrographic surveys or for those surveyselectronically controlled and conducted by a vesselequipped with real-time computer plotting capabil-ity. Principal advantages of this system are that (1)the best delineation of the depth contours is most

4.3.5.2. LOCUS ARCS. Systems of parallel ornear parallel line-of-position arcs are often used onelectronically controlled surveys by nonautomatedvessels. Line-of-position arcs are either circular orhyperbolic, depending upon the control system or

4-11 (JULY 4, 1976)

least depths (1.4.3) and (2) furnish a realistic repre-sentation of the sea bottom and submarine relief.

Systems of sounding lines normal to thedepth contours generally provide the most conve-nient and economic development of any area; butoften it may be advantageous to use a different sys-tem. The system ideal for an open coast may not besuitable for bays and harbors. Steep features such assubmarine ridges and valleys should be developed bya system of lines that cross the depth contours atangles of approximately 45º. Selection of the mostappropriate systems of lines for a particular surveyoften must be governed by the type of positioningcontrol used and the area configuration and locationwith respect to an anchorage or base of operations.Three systems in general use are parallel straightlines, radiating lines, and concentric circles or hyper-bolic locus arcs.

If parallel straight lines are run, two ormore lines should be run parallel to the shore duringa rising tide when the sea is calm. One line shouldbe run as close to shore as safety and circumstancespermit. The second line should be about 50 m off-shore from the first (or less on large-scale surveyswhere depths increase rapidly); additional linesshould be run as necessary to determine a safe zonefor the launch to turn in when lines are run normalto the shore.

If the coastline has an even trend and agradually sloping bottom, a system of lines parallelto the shore may be used, whereby the line spacingis gradually increased as the depth increases. If sucha system is used, longer lines may be run with lessdanger to the launch since the inshore lines are runwhen sea conditions are best. With sextant-controlled hydrography, however, more frequentchanges of fix are required; thus the development ofdepth contours is less accurate. Systems of lines par-allel to the coast are impractical if the shoreline isirregular. Unless control stations lie a considerabledistance inshore from the shoreline or a dense net-work of signals has been established, inshore sextantfixes are often weak because one angle is generallyvery large, the other small, and both change veryrapidly.

HYDROGRAPHIC MANUALS

Figure 4-5.—Systems of sounding lines. Solid lines represent depth contours; broken lines show sug-gested systems of sounding lines for the different conditions encountered

HYDROGRAPHY

atively short and not used over an extensive area.the mode of the system adopted for the survey.Sounding lines are run at the desired spacing bysteering the vessel along a preselected arc; devia-tions from the arc are continually observed, and im-mediate correctional course changes can be made.The position of the sounding vessel on the arc isfixed by the intersection of another electronic lineof position, sextant angle, or theodolite azimuth ob-served from the beach. (See 4.2.6, 4.4.3, and 4.4.4.) 4.3.5.4. SOUNDING LINES IN CHANNELS

AND ALONG PRONOUNCED TOPOGRAPHIC FEA-

TURES. Limits of narrow channels are first definedby a series of crosslines running normal to or diago-nally across the channel axis. Extreme care is re-quired to avoid displacement of depth contours onsteep slopes. Variations in speed at the beginningand ending of short crosslines can cause errors insounding positions. Errors of this nature are gener-ally indicated by uncharacteristic depth contoursalong the edges of the channel.

After the limits of a channel have beenestablished, the channel must be developed by a sys-tem of closely spaced lines approximately parallel toits axis. If a channel is marked by a range, a line ofsoundings shall be run on the range line.

When this system is used, the hydrographerhas the choice of running lines on either of theparalleling segments of two sets of arcs. He shouldselect the set that provides the most efficient cover-age of the area and affords the best development ofsubmerged features. The system is most suitable forinshore hydrography in wide passages, in areaswhere offshore islands are available for siting shorestations, and in wide bays or estuaries. The systemcan also be used advantageously for line guidanceduring visually controlled surveys in areas wherethe electronic system may not meet survey accuracyrequirements or where severe electronic positionanomalies exist. Electronic shore stations can be sit-ed to satisfy sounding line directional considerationswithout concern for strength of fix or accurate posi-tioning of the station.

Most dredged channels are maintained bythe U.S. Army Corps of Engineers, but some aremaintained privately. Nautical charts contain thelatest available information on project depths andcontrolling depths in dredged channels on a stateddate. Data on primary channels are usually tabulat-ed on the charts — least depths are listed for theright and left quarters and the center half of thechannel (or for each quarter of the channel width).When the hydrographic survey reveals that shoal-ing of a hazardous nature is occurring in a channel,the Chief of Party should notify the nearest office ofthe U.S. Army Corps of Engineers and the U.S.Coast Guard. Copies of all correspondence andsketches shall be forwarded to the HydrographicSurveys Division (OA/C353), through the appro-priate Marine Center. (See 5.9)

If electronic control systems are not avail-able and wind or currents make it particularly diffi-cult to stay on a proposed sounding line, concentriccircles can be run by steering an arc of a constantsextant angle between two hydrographic signals. 4.3.6. Crosslines

4.3.5.3. RADIATING LINES. Radiatingsounding lines often provide the most efficient de-velopment of the bottom in small bays, around smalloff-lying islets, and along shorelines where there is amarked break or change in the trend or where a sig-nificant topographic feature occurs. (See figure 4-5.) Radiating lines are a special application; becausethey diverge on one end, they must be kept compar-

Regular systems of sounding lines shall besupplemented by crosslines to provide a check andto disclose discrepancies in the main system. (See1.4.2.) Major sources of discrepancies, such as thoseindicated by poor comparisons of soundings at thecrossings, include the use of an erroneous datum ofreference, weak or erroneous control, malfunctionof the sounding equipment, or abnormal tides. (See

4-13 (JUNE 1, 1981)

This system has two important advantages.First, the effects of current are apparent immediate-ly, and timely course corrections can be made tomaintain the desired line spacing. Second, soundingline spacing can be reduced by running ''splits'' atany interval. When this system is used properly, theappropriate maximum line spacing for the depthsencountered can be rigorously adhered to becausethe control along the sounding line is so positive.Because lines are generally run where they are pro-posed, few are wasted.

Shoals or sharp submarine features of smallextent can sometimes be best developed by runninga system of radial lines that cross in the vicinity of atemporary marker buoy planted near the center ofthe shoal, provided that the position is already rea-sonably well known.

HYDROGRAPHIC MANUAL

and recorded for detached positions. If controlledelectronically and if practical, a check line of posi-tion should be observed and recorded.

4.6.1.) Crossline bottom profiles should be scannedthoroughly for indications of shoals or hazardsmissed by the regular system of lines.

4.4.2. Visual Positioning

If electronic positioning systems are notavailable or adequate for the survey, hydrographymay be controlled by three-point sextant fixestaken from the vessel or by the intersection of twoor more theodolite directions observed from shorestations. Visual positioning methods are also usedto calibrate electronic positioning systems.

4.4.2.1. THREE -POINT SEXTANT FIX. Thisis a convenient and accurate method for determin-ing the position of a hydrographic survey vessel.Sextants are used to measure two angles betweenthree objects of known geographic position. (SeeAE.l. for use, care, and calibration of a sextant.)The center object is common to both angles. (Seefigure 4-6.) The position of the observers takingthe angles is fixed by the intersection of three cir-cles. Two of the circles are the loci of the anglesobserved from the vessel between the left and cen-ter objects and between the center and right ob-jects. The third circle is the locus of the sum of theleft and right angles. When three-point sextant fixesare used to calibrate an electronic positioning sys-tem, the vessel should be stopped; the angle ob-servers should stand as close together as possible.

If necessary, regular tide or water level ob-servations should be supplemented by a short seriesof observations in the immediate vicinity. Correc-tions can often be deduced with reasonable accura-cy by comparing soundings at crossings. Until dis-crepancies are resolved and necessary correctiveactions taken, further hydrographic operations maybe counterproductive.

4.4 POSITIONING SYSTEMS ANDREQUIREMENTS4.4.1. General In figure 4-6, illustration A represents the

strongest fix possible where the vessel is at the cen-ter of an equilateral triangle; B is the strong fix

where the vessel is closer to the center object thanto the left and right objects, the observed anglesare sufficiently large, and the loci intersect at alarge angle; C is the weaker but adequate fix — fixesof this type should be avoided if stronger fixes are

available; D is the unacceptable weak fix — note thesmall loci intersection angles at the vessel where asmall error in either of the observed angles causesa large positional error; E is the ''swinger,'' an in-determinate fix, where the sum of the angles (A +L + R) = 180º and the vessel and the three objectslie on a common circle.

Hydrographic position fixes on soundinglines are almost always determined by the intersec-tion of two lines of position; dead-reckoning posi-tions based on course and speed provide an addi-tional internal check. (See 4.5.5.) Occasionally, aposition is expressed as an estimated distance andbearing from the vessel or from a known point or asan estimation of the position directly on the fieldsheet.

4.4.2.1.1. Selection of objects. The geometricstrength of a three-point fix is greatest when twoof the loci intersect at right angles; it is weakestwhen the three loci approach coincidence. Figure4-6 shows several configurations of the three-pointfix. The relative strength of each fix can be esti-mated by the intersection angles of the loci.

Detached positions are those usually takenat discrete points such as least depths and bottomsamples. When conducting visually controlled sur-veys, a check angle or azimuth shall be observed

4-14(JUNE 1, 1981)

Crosslines need not be run in areas of ex-tremely irregular submarine relief; they are of littlevalue for checking because large vertical differ-ences occur across small horizontal distances. Insuch cases, the hydrographer should try to find agently sloping bottom where meaningful crosslinescan be run. Regular spacing requirements forcrosslines may be varied for this condition.

Shallow water sounds and bays may besubject to unusual tides or water level fluctuationsresulting from abnormal meteorological conditions.If crosslines are run first at the predicted chart da-turn under normal wind and sea conditions, the oc-currence of abnormal tides will be reflected bypoor crossings.

To chart soundings and related data formariners, one must accurately determine the posi-tion of the vessel at frequent intervals along thesounding line and at other discrete points forwhich the latitude and longitude are needed. If thevessel proceeds at a nearly constant speed along afixed course, soundings between position fixes canbe plotted with reasonable accuracy.

HYDROGRAPHY

FIGURE 4-6—Various configurations of strong and weak three-point fixes

Experienced hydrographers should be able toestimate the relative strength of a fix at a glance andimmediately select a strong fix. Beginners may havedifficulty in visualizing the problem and often selectweak fixes. The following general rules may be help-ful when selecting objects to be used:

4-15 (JANUARY 1 ,1979)

Figure 4-7 shows, for various arrays of thethree points, error contours (in meters) that corre-spond to errors of 1 min in each of the observed sex-tant angles and an accuracy of 1:10,000 for the con-trol stations. The observational errors were combinedin the direction that resulted in the maximum posi-tional error. These figures may be used to estimatepositional errors of varying magnitude because therelationship between the observational errors and theerror contours are approximately linear for an angu-lar error and base line lengths. For example, with er-rors of 2 min in each of the observed angles, themagnitude of the 1-m positional error contourbecomes 2 m.

triangle, the observer is at the center, and the objectsare close to the observer.

2. A fix is strong when the three objectslie in a straight line, the center object lies betweenthe observer and a line joining the other two, andthe center object is nearest to the observer.

3. The sum of the two angles generallyshould not be less than 50º (figure 4-7); better re-sults are usually obtained when neither angle is lessthan 30º.

4. A fix is strong when two objects thatlie a considerable distance apart are alined and theangle to the third is not less than 45º.

5. A fix is strong when at least one of theangles changes rapidly as the survey vessel movesfrom one location to another (i.e., one of the objectsis close to the vessel).

6. Small angles should be avoided since, inmost cases, they result in weak fixes difficult to plotby hand. Strong fixes, however, are obtained whentwo objects are nearly in range and the nearest one isused as the center object.

7. Fixes are always strong if the distancebetween the center object and the left- and right-hand objects is longer than the distance from the ob-server to the center.

8. Nearby signals should generally be fa-vored over distant signals. If only one signal isnearby, it should be used as the center object. Theuse of nearby signals will position the vessel moreaccurately relative to nearby shoreline and inshorefeatures.

Beginners should demonstrate the validity ofthese eight rules by plotting examples of each andtheir opposites. One should note that a fix is strongif a slight movement of the center of a three-armprotractor moves the arms away from one or moreof the stations. Conversely, a fix is weak if suchmovement does not significantly change the relationof the arms to the three points. An appreciation ofthe accuracy required for measuring angles can beobtained by changing one angle about 5 min in eachexample and noting the resulting shift in plotted po-sitions. Most automated processing systems use asimilar test to determine whether a fix is weak. A''weak fix'' message is printed if the addition andsubtraction of 1 min to both the left and right an-gles, respectively, displaces the computed position bymore than 8 m. Maximum errors in positions deter-

1. Strong fixes occur when the observer isinside the triangle formed by the three objects; a fixis strongest when three objects form an equilateral

HYDROGRAPHIC MANUAL

FIGURE 4-7. — Error contours for various configurations of the three-point fix

4-16(JANUARY 1, 1979)

HYDROGRAPHY

mined by a weak fix result from a positive error inone angle and a negative error in the other.

4.4.2.1.3. Special problems in sextant fixes.Sextant fixes at distances approaching the limit ofvisibility of the signals are likely to be weak becausethe angles or changes therein are small. In suchcases, small errors in the angles induce large posi-tional errors. When signals are far away or are diffi-cult to reflect, a telescope must be used on the sex-tant. The sextant must be in perfect adjustment, andthe angles measured and read with extreme accura-cy – to the nearest 30 s of arc if necessary. (SeeA. 5.3.1.4.)

4.4.2.2. THEODOLITE INTERSECTION. Posi-tioning a survey vessel by the theodolite intersectionmethod is advantageous in areas where hydrographymust be controlled visually, when the entire area canbe viewed from several sites, and when a prohibitivenumber of control stations and signals would be nec-essary to support three-point sextant fixes. Two ormore theodolites are sited (depending on the size

When angle observers do not have ready ac-cess to the field sheet, a rough tracing of the shore-line should be made showing the location, number,and a brief description of each signal in the vicinity.This enables trained observers to select strong fixesand positively identify the stations used.

4-17 (JUNE 1, 1981)

Avoid the selection of objects that result ina "revolver'' or "swinger.'' If the vessel ties on orvery near the loci circle described by the three ob-jects observed, the fix is indeterminate and definedas a swinger. The hydrographer should estimate hisposition with respect to the circle passing throughthe three signals when selecting objects. An easyway to predict a swinger is demonstrated in figure 4-6E. If the sum of the angles (A + L + R) is equalto 180%, the fix is a swinger. The automated systemis programmed to reject fixes when the sum of theseangles is between 178º and 182º. One can also seethat, if the angle A is greater than 180º , a swingercannot result.

Because of observational errors, some theo-retically acceptable fixes may prove inadequate if ei-ther of the angles is less than 30º(i.e., where thethree objects lie on a straight line). See figure 4-6.

Insofar as practical, the objects used for sex-tant angles should be approximately equal in eleva-tion with the observer. If an angle must be mea-sured between two objects of considerable dif-ference in elevation, the observed angle must becorrected before plotting. When one of the objectsis at or near sea level and the other is at an elevationsufficient to cause a horizontal angular error in ex-cess of 2 min, the angular elevation of the elevatedobject shall be observed and the inclined angle cor-rected as described in A.5.3.1.5.

4.4.2.1.2. Change of fix. Generally, thestrongest fix available should be used for each posi-tion; but there are other practical limits that maygovern selection of a fix. Poor visibility and fre-quent changes of objects contribute to both observ-ing and recording errors. Signals that can be posi-tively identified often prove to be a better choicethan less distinct signals although a slightly strongerfix would be obtained using the less distinct signals.Some observers, however, lack judgment and tendto use the same object long after a change to astronger fix should have been made.

Strong sextant Fixes often cannot beobtained at the inshore end of each line because thevessel may be nearly on line with shoreline signals.The sum of the two angles frequently approaches180º with one angle often being very large and theother very small. Under these conditions, angleschange rapidly when the vessel is moving; thus, un-usual care must be taken to mark angles simulta-neously. The effects of errors introduced by failureto mark angles simultaneously is minimized whenthe signals used are at short distances from the ob-server.

When one cannot obtain a three-point fix,two angles to four signals may be measured to fixthe position. A fix of this type is called a ''split fix''because there is no common center object. The lo-cus of each angle must be plotted separately – theposition of the vessel is the intersection of the twoloci. If the signal and vessel configuration is suchthat the loci of the observed angles intersect at anangle greater than 45º , the fix is considered strong;however, split fixes are inefficient because of the re-cording procedure and plotting time involved andshould be taken intentionally only when three-pointfixes are unavailable. In addition, split fixes are in-valid input for the automated processing system. If asplit fix is observed, a three-point fix must be ''creat-ed'' by plotting the split fix manually, then scaling aleft and right angle between three objects.

HYDROGRAPHIC MANUAL

of the area, shoreline configuration, and availabilityof existing geodetic control) to provide a pattern ofstrong geometric intersections throughout the sur-vey area. Theodolite stations shall meet the accura-cy requirements for Third-order, Class I horizontalcontrol. (See 3.1.2.) The angle of intersection at thevessel shall be such that a directional error of 1 minfrom a theodolite station will not cause the positionof the vessel to be in error by more than 1.0 mm atthe scale of the survey. Angles greater than 30º andless than 150º will usually ensure meeting this condi-tion.

Although two observed directions from the-odolite stations are adequate for positioning the sur-vey vessel while running routine sounding lines,third directions should be observed as checks on de-tached positions and when intersecting aids to navi-gation, landmarks, and similar features. When thesurvey is progressing rapidly, a third instrumentshould be used in a ''leapfrog'' manner to providecontinuity of sounding operations and ensure geo-metrically strong intersections.

In narrow winding sloughs or streamswhere any form of hydrographic control is difficult,theodolite directions and stadia distances may beused to position the sounding vessel. This method isalso a flexible technique for strengthening fixeswhen directional intersections are weak or if acheck on the position is needed.

4.4.3. Electronic Position Control

Electronic position fixing systems currentlyused by the National Ocean Survey for controllinghydrographic surveys may be classified by their op-erating ranges (1.3.3.2), and further subclassified bythe system mode of operation (i.e., hyperbolic orrange-range). Further classifications such as wavetiming and pulse matching defining the electroniccharacteristics of the system can be made; but theyare beyond the scope of this manual.

Standard drafting machines are portablecompact instruments clamped on drafting boards ortables large enough for the field sheet. Machinesmust be equipped with a full 360º circle; the verniermust be graduated to 1 min of arc. The length ofthe straightedge attached to the machine dependsupon required plotting distances. When plotting po-sitions, the circle of the drafting machine is lockedin the orientation parallel to the line joining the the-odolite stations being used. An orientation line isdrawn and labeled on the field sheet, preferablyclear of the working area. Periodic reference to the

Range-range modes of operation with me-dium range systems are generally preferable to hy-

4-18(JUNE 1, 1981)

Generally, depending on the scale of thesurvey, directions to the vessel are observed and re-corded to the nearest minute of arc. (See 4.8.3.1.)Azimuths accurate to within ±30 s of arc are re-quired for absolute orientation of the observed di-rections. Absolute azimuthal orientation is bestachieved by sighting on at least two points ofknown position. If a geodetic azimuth is not imme-diately available for absolute orientation and thetheodolite stations are intervisible, relative orienta-tion for plotting can still be accomplished (i.e., as-sume an approximate azimuth for an observed line,then by angulation extend that azimuth to the othercontrol stations). Solar or Polaris observations forazimuth may be used for eventual absolute orienta-tion of the survey or for azimuth checks.

Radios are used to coordinate events, assurethat directions are observed simultaneously when afix is needed, and relay fix data to the hydrogra-pher. Positions are usually plotted by automation orby using a standard drafting machine (AL.1.3)aboard the vessel as the positions are observed. Oc-casionally, other means such as preconstructed azi-muth array sheets are used. Plotting may be accom-plished at any convenient location, provided thatradio communications with the sounding vessel andtheodolite stations are maintained.

orientation line with the locked straightedge assurescorrect orientation of the drafting machine whileplotting positions.

Dutton's Navigation and Piloting (Dunlapand Shufeldt 1969) and International HydrographicBureau (1965) Special Publication No. 39, ''RadioAids to Maritime Navigation and Hydrography,''contain a comprehensive discussion of the principlesof electronic positioning. The hydrographer shouldhave all pertinent literature, handbooks, and manu-als prepared by the manufacturer for the specificequipment in use. The Decca Hi-Fix Manuals andthe Del Norte Operations Manual are especiallygood references from which much of the followingmaterial has been extracted (e.g., Decca SurveySystems 1972 and Del Norte Technology 1974).This section (4.4.3) will not deal with any particularbrand name but will outline in general the basicprinciples of each system and how each systemshould be used. Refer to AB through AF for moredetailed discussions of specific equipment.

HYDROGRAPHY

FIGURE 4–8 — Hyperbolic lattice for a hydrographic survey (courtesy of Decca Survey Systems, Inc., Houston, Texas)

(JULY 4, 1976)4-19

HYDROGRAPHIC MANUAL

4.4.3.1. HYPERBOLIC POSITIONING SYS-

TEMS. Arrays of the hyperbolic positioning systemconsist of one ''master'' station and two ''slave'' sta-tions located at known geographic positions (1.3.1),with the receiver aboard the vessels in the workarea. Unlimited numbers of vessels can timeshare thesystem using the same shore stations. (See figure4-8.)

FIGURE 4–9.—Hyperbolic lattice lane expansion (courtesyof Decca Survey Systems, Inc., Houston, Texas)

move away from the base line. On the base line, thedistance between these adjacent hyperbolas (a"lane'') is equal to half the wavelength at the trans-mission frequency; it may be computed by

λ λ = v/ƒ

where λ is the wavelength in meters; v, the velocityof propogation of an electromagnetic wave (NOSusing 299,670 km/s); and ƒ, the system frequency inkilohertz.

Lines between the master stations and eachslave station are called ''base lines.'' Figures 4–8 and4–9 show that adjacent hyperbolas diverge as they The lane width w equals λ/2. As the dis-

TABLE 4–2.—Hyperbolic versus range-range system considerations

Consideration Range-range

Relatively simple

Two shore stationsThree shore stations

Unlimited Some systems limitedto one

4-20(JULY 4, 1976)

perbolic operation because of greater flexibility.Some range-range systems, however, do not permitmultivessel time-sharing operations. In table 4–2 areseveral basic situations that must be considered be-fore the mode of operation is finally selected.

Each pattern of hyperbolas consists of linesof equal phase difference between the signals re-ceived from two transmitting stations. The patternsform lines of position, the intersection of which fixesthe position of the vessel. A hyperbolic chain, there-fore, needs a minimum of two pairs of transmittingstations to provide a position fix. In practice, onestation is common to each pair and is called the"master." The two remaining stations are called''slaves.'' Each family of hyperbolas has the masterstation and a slave as its foci.

Geometric compu-tations, latticeconstruction, andposition plotting

Limited by angleof line-of-positionintersection only

Suitable for anycoastline configu-ration

Required for twostations

Three-stationhyperbolic

Complex if donemanually

Limited by laneexpansion and angleof line-of-positionintersection

Best suited for con-cave coastlines

Required for threestations

Extent of high-accuracy coverage

Shorelineconfiguration

Control surveysfor shorestation sites

Support andlogistics

Number of time-sharing receivers

HYDROGRAPHY

tance from the base line increases, the width of alane expands according to

w1= w (csc µ/2)

Typical error propagation contours for vari-ous base line intersection angles are shown in figure

4-21 (JULY 4,1976)

where w is the lane width on the base line; w1 , thelane width at the point of observation; and µ, theangle subtended by the base line at the point of ob-servation. The position fixing accuracy of a hyper-bolic system is inversely proportional to the term cscµ/2, the ''lane expansion factor.''

In a hyperbolic chain, the master drive unitenergizes the transmitter at the master station (M)with the ''trigger'' and master pulses. Each slave sta-tion (S) receives these pulses; the first pulse triggersthe electronic timer while the master pulse locks thereceiver to the phase and frequency of the mastersignal. Each of the locked slave receivers then con-tains a phase datum continually kept in phase withthe master transmission. Both slave receivers triggerpulses to their transmitters; the resulting signal ispicked up by the vessel's receiver. Vessel receivers"see" two sets of hyperbolas called pattern I andpattern II. Positional values for each pattern are reg-istered (in lanes) on a digital lane counter aboardthe vessel. Lane values are usually shown to thenearest one hundredth of a lane. The position is de-termined by the intersection of the lines of positioncorresponding to the corrected observed lane values.Most manufacturers provide additional lane and po-sitional displays.

Hyperbolic positioning systems measureonly the fractional lane reading (i.e., the relative po-sition of the vessel between two lanes). Whole lanevalues are not resolved by most of the precise hyper-bolic fixing equipment available. Whole lane valuesmust be set manually on the display pattern counter.The observer, therefore, must know the position ofthe vessel, within an accuracy of ± 0.5 lane. Afterthe lane number has been determined and set, theequipment will automatically keep track of thewhole lanes by ''lane integration.'' Losses of signalduring operations can cause faulty integration. If thefaulty integration cannot be resolved, the hydrogra-pher must return to a point of reference to deter-mine and reset the whole lane value. (See 4.4.3.)

It is difficult and time consuming to manu-ally construct hyperbolic lattices on charts to deter-mine where to locate shore stations when planning aproject. The following guidelines and diagrams canbe used to determine the coverage and degree of ac-

curacy for various shore station configurations.Shore stations should generally be located to providea clear water path between the master station andeach slave station. (See 4.4.3.)

FIGURE 4–10.— Hyperbolic positioning system relative errorcontours (meters) for a unit standard deviation of 0.01lanes. The operating frequency used in the computationof the curves is about 1.8 MHz. Illustration A has baselines at 60º; B, 90º; C, 120º; D, 150º; and E, 180º(courtesy of Decca Survey Systems, Inc., Houston,Texas).

HYDROGRAPHIC MANUAL

tions are best described by the classical normal dis-tribution.

4-10. The base lines are shown equal in length forconvenience although this may not be typical inpractice. On each illustration, the sides of thesquares are one-fifth the length of the base lines topermit quick estimation of ranges and areas. Figure4-11 shows the shape of the contours for chains inwhich one base line is twice the length of the other.The most accurate positions are obtained within thetriangle formed by the three stations at the pointwhere the hyperbolas cross at right angles. The mostaccurate point in a chain in which stations areplaced at the corners of an equilateral triangle lies atthe intersection of the perpendicular bisectors of thebase lines. Base line angles of 120º to 150º generallygive the best compromise between accuracy and areaof coverage.

In figure 4–12, the pattern-I coordinate hasa standard deviation of σ1 m, and the pattern-II co-ordinate a standard deviation of σ2 m. Every fix forwhich the pattern errors are less than its standarddeviation will lie within the parallelogram PQRS.The maximum error of such a fix is the diagonal ofthe parallelogram OP, but the actual error distribu-tion is the ellipse inscribed within and tangent toPQRS.

--d rmse

4-22(JULY 4, 1976)

In the following discussion, we assume thetransmitting stations have been located accuratelyand constant displacements or systematic errors inthe electronic position coordinates have been elimi-nated. Random errors result in a variable displace-ment of position lines about their computed posi-tions. Magnitudes of these errors are defined by thestandard deviations of the distribution of such er-rors. Errors encountered here and in survey observa-

A combination of the effects of randommovements in the two position lines results in aspread of position plots about the true geographicalposition of the receiver. To describe the likely degreeof uncertainity of a single fix taken at this or at anyposition covered by the chain, we use the root meansquare error (rmse).

In this situation, the rmse is the radius ofthe symmetrically drawn circle of the fix distributionthat encloses approximately 65% of the plotted fixes(i.e., odds against a computed fix falling outside thiscircle are two to one). This probability level is gen-erally used to estimate hyperbolic system positioningerrors for survey purposes. Note that a circle with aradius of 2 rmse (twice the standard deviation) in-cludes approximately 95% of the plotted positions; acircle with a 3 rmse radius includes 99% of the plot-ted positions.

The rmse of a position can be determinedfrom

FIGURE 4–12.—Root mean square error (rmse) at an elec-tronically determined position (courtesy of Decca Sur-vey Systems, Inc., Houston, Texas)

FIGURE 4–11.—Hyperbolic positioning system error contours(meters) for assymetrical base station configurations.The operating frequency used in the computation ofthe curves is about 1.8 MHz (courtesy of Decca Sur-vey Systems, Inc., Houston, Texas).

√a² + b²

HYDROGRAPHY

where a and b are the semi-axes of the standard er-ror ellipse, or

lar set of parameters, the system should not be usedfor the survey.

4.4.3.2. RANGE-RANGE SYSTEMS--d4.4.3.2.1. Phase-matching systems. When us-

ing phase-matching systems in a range-range mode,the master station is installed aboard the vessel. Thecomplement of required radio equipment is the sameas that used for hyperbolic operation. As the vesselmoves, the base lines vary in length. (See figure4-13.) Pattern values for circular lines of positioncentered at the respective slave stations are displayedon the hydrographer's receiver. Positional data areregistered by lane counters (as with the hyperbolicsystem), but the lane count is arranged to increasewith distance from the slaves. Lane numbers in thehyperbolic mode increase with distance from themaster station.

rmse

In the formula

σ 1 , 2 = σ•w1 , 2 •

Lane widths are constant and may be com-puted by the formulas shown in 4.4.3.1. Without theeffects of lane expansion, measured ranges are al-ways coincident with base lines between the masterand the slave stations; therefore, phase errors origi-nating at the stations or in the vessel receiver resultin distance errors in which magnitudes are indepen-dent of range. This is clearly in contrast to the hy-

Hyperbolic control systems should not beused for surveys in areas where the combined effectsof lane expansion and angle of position line intersec-tion cause the rmse of position to exceed 0.5 mm atthe scale of the survey. A value for unknown un-compensated systematic errors that may be presentmust also be assumed and be added to the standarderror σ for a meaningful computation. The hydrog-rapher must exercise judgment when estimating areasonable value for σ. For survey planning, valuesin lanes of 0.02 to 0.2 should be used depending onequipment make (model, age, and past performance)and anticipated calibration frequency and accuracy.If the equation becomes indeterminate for a particu-

4-23 (JULY 4, 1976)

√σ1² + σ2² csc ß

where ß is the angle of intersection between thelines of position at the vessel; σ1 , the standard devi-ation of the pattern-I coordinate at the vessel, in dis-tance units; and σ2, the standard deviation of thepattern-II coordinate at the vessel in distance units.

csc µ 1,2

2( ),

σ is the standard deviation (in lanes) of the randomerrors (generally in lanes of 0.01 to 0.03 for hyper-bolic chains); w1 the lane width on the pattern-Ibase line; w2 the lane width on the pattern-II baseline; µ 1, the angle subtended by the pattern-I baseline at the point of observation (figure 4–9); and µ 2,the angle subtended by the pattern-II base line atthe point of observation.

Assuming that both patterns have the samestandard deviation (i.e.,σ1 = σw1, and σ2 = σw2),one can express the rmse of a position in the areasof front and back hyperbolic coverage as

The corresponding formula for side coverageis

FIGURE 4–13.—Range-range lattice for a hydrographic sur-

vey (courtesy of Decca Survey Systems, Inc., Houston,

Texas)

HYDROGRAPHIC MANUAL

perbolic configurations whereby small errors at thebase line can propogate substantially (in terms ofdistance) at the outer limits of the system.

Since there is no lane expansion in range-range operations, the rmse from section 4.4.3.1 sim-plifies to

FIGURE 4–15.—Line of sight over the horizon

Light and highly mobile vessel and shorestation equipment.

4.4.3.2.2. Distance-measuring systems. Thosenow in use operate in the ultrahigh frequency range(300 to 3000 MHz) or in the super high frequencyrange (3000 to 30,000 MHz) and are limited to line-of-sight measurements. Typical characteristics ofthese systems include:

Measuring capability of 100 m to 80 km

4-24(JULY 4, 1976)

Figure 4-14 shows typical error propogationcontours for a set of slave stations located approxi-mately 50 km apart, a reasonably representative dis-tance for hydrographic surveys. The contours areshown in meters for an assumed standard deviation(σ) of 0.015 lane (daylight operation) along the baseline. These accuracy contours are circular. The lineconnecting the two slave stations is straight. Highaccuracy regions for range-range systems alongstraight shorelines may be several hundred timeslarger in area than would be the case if the surveywere controlled hyperbolically. The system operatingfrequency is about 1.8 MHz.

where µ is the angle at the vessel subtended by theshore stations (and angle at which lines of positionintersect); σ, the standard deviation of a coordinateat the vessel (in lanes); and w, the lane width.

Figure 4–12 shows graphically the ellipticaldistribution of the rmse about a point.

Phase comparison systems operating in arange-range mode should not be used in areas wherethe rmse, as computed by the preceding formula,exceeds 0.5 mm at the scale of the survey. As in hy-perbolic operation, judgment must be exercisedwhen estimating a value for σ. Values for σ (gener-ally from lanes of 0.025 to 0.25) should include boththe random errors and the unknown uncompensatedsystematic errors present in the system. If the equa-tion becomes indeterminate for a particular set ofparameters, the system should not be used for thesurvey. Regardless of the computed value, the angleof intersection should generally not be less than 30ºor more than 150º.

FIGURE 4–14.—Error contours for a typical range-range sys-

tem (courtesy of Decca Survey Systems, Inc., Houston,

Texas)

Direct distance readout displays at themaster station (usually located aboard the vessel).

Very accurate position fixing at shortranges.

Time-sharing multivessel field operationcapability.

HYDROGRAPHY

provided that line-of-sight conditions between themaster unit and slave stations are maintained.

The effective microwave line-of-sight dis-tances may be computed by drms < < 1.0 mm at the scale of the sur-

vey for 1-10,000 scale surveys.L(km) = 4.04 [ √ h1(m) + √ h2(m) ]1.5 mm at the scale of the surveyfor scales of 1:5,000 and larger.

or

Here, drms = √2σ csc µ; σ, the standard deviationof a distance measurement (meters); and µ, the angleof intersection of the lines of position at the vessel.

where L is the line-of-sight distance and h1 and h2

are the heights of the shore antenna and the vesselantenna. (See figure 4-15.)

For example, if the height of a slave stationantenna is 27 m above sea level and the antennaaboard the survey vessel is 12 m above the watersurface, the effective microwave line-of-sight dis-tance is

The preceding formulas can also beexpressed in terms of the minimum allowable angleof intersection of the lines of position at the vesselfor different survey scales; for example,

L = 4.04 ( √ 27 + √ 12) ≅ 35 km.

(See tables C-5 and C-6 and figure C-1 for an-tenna elevations and related line-of-sight dis-tances.)

Conservative values for the heights ofshore stations must be used in areas where the tidalrange is relatively large and where sea swells maydiminish the effective line-of-sight distance to thehorizon.

where K is 3.54 for scales of 1:20,000 and smaller;7.08 for 1 -10,000; and 10.62 for 1:5,000 and larger.

Super high and ultrahigh frequency sys-tems should not be used where any obstruction,however slight, may penetrate the line of sight be-tween the master station and the slave stations.Obstructing objects cause a complete loss of signalor can result in undetected erroneous distancereadings. Elevated shore stations should be used asnecessary to avoid lower obstructions and attaingreater operating ranges. Caution must be exer-cised when the vessel is working near elevatedshore stations since the system measures slantranges. Slant range measurements shall be correct-ed to horizontal distance if the magnitude of thecorrection exceeds 2 m. Refer to section AD for amore detailed discussion of the distance-measuringsystems now in use.

4.4.3.3. SYSTEMS CALIBRATION. Electronicpositioning systems shall be calibrated in accordancewith the specifications in section 1.3.3.2.4 and the fol-lowing guidelines. The purposes of calibration are:

2. To determine and correct systematicerrors in observed electronic positional data.

4. To serve as a check on the accuracyof the basic chain and the station positions.

Super high frequency direct distance mea-suring systems shall be used for hydrographic posi-tion control only when line-of-sight conditions canbe maintained within the maximum operating rangelimits specified by the manufacturer; they should beused only where the following conditions are met:

The specifications for calibration containedin section 1.3.3.2.4 are the minimum acceptable cri-teria. Under certain conditions for some hydro-graphic surveys, it may be desirable or necessary to

4-25 (JUNE 1, 1981)

L(nmi) = 1.23 [ √ h1(ft) + √ h2(ft) ]

0.5 mm at the scale of the sur-vey for scales of 1:20,000 andsmaller.

As with phase comparison systems, the hy-drographer must use judgment when estimating avalue of σ for his system. Depending on the system,values of σ can be expected to vary from 3 to 10 munder normal operating conditions.

Regardless of the computed value, minimumangles of intersection should not be less than 30º. C-band and X-band positioning systems shall not beused to measure distances less than 100 m becausesevere accuracy degradations may occur within thatrange.

1. To establish a geographic positionalreference (i.e., true lane count or distance).

3. To determine anomalies or variationsin the performance of the system throughout thesurvey area.

HYDROGRAPHIC MANUAL

used. (See 1.3. 1.) When locating the vessel by theod-olite intersection methods, the theodolites are point-ed on the receiving antenna. The automated systemcan adjust for an eccentric observation by comput-ing the position of the vessel antenna by azimuthand distance from the observers.

Requirements for daily or twice daily cali-bralions are, again, minimal and should be presumedto apply only if the positioning equipment is operat-ing smoothly. Calibration frequency for a particularpiece of equipment during a particular survey is amatter of judgment. The hydrographer must main-tain and calibrate this equipment with sufficient ac-curacy to ensure that National Ocean Survey stan-dards will be met.

A complete calibration consists of at leasttwo independent observations to determine correc-tions to be applied to the electronic positional val-ues. The recommended procedure is:

1. The vessel is maneuvered as close aspossible to the area of survey operations.

4-26(JUNE 1, 1981)

use more accurate methods, such as locating the ves-sel by theodolite intersections from known geodeticstations ashore. (See 1.3.3.1.2 and 4.4.2.2.) Whennecessary, the need for greater calibration accura-cies is generally indicated in the project instructions.The hydrographer, however, is not relieved fromthe responsibility to adopt more rigorous standardsif survey conditions warrant.

The importance of calibrating electronicpositioning equipment in or as near to the operatingarea as possible cannot be overemphasized, particu-larly when using medium range systems. (See1.3.3.2.2.) Calibration correction values often varysignificantly over small areas within the survey area.The degree or magnitude of local calibration varia-tions that may be expected during the course of thesurvey should be determined prior to beginning hy-drography. To accomplish this goal, calibrations areobserved throughout the survey area for each shorestation configuration. Frequency and spacing ofthese area calibrations are a matter of judgment, butmust be sufficiently dense to give the hydrographera working perception of the variations. Calibrationstaken during the progress of the survey should becompared frequently with those taken previously atthe same location to determine system variationswith time and under varying meteorological condi-tions.

2. Simultaneously, a fix is taken, and theelectronic line-of-position values are observed andrecorded. Three-point Fixes should be observedfrom a point as near as practical to the receiving an-tenna of the vessel. Check angles shall be taken—only control of third-order accuracy or better thathas been recovered and positively identified may be

3. The fix position is then converted toelectronic positional values graphically or by ma-chine computation. Graphic conversions are madeby plotting the fix on a calibration sheet (4.2.4), thenscaling the electronic positional values for the fix.Most NOS major survey vessels, however, areequipped for automatic computation of calibrationdata. Nonautomated launches operating from a ma-jor survey ship should transmit the data to the shipby radio for the necessary computations. For cali-bration, electronic values computed from observedfixes are considered to be true values.

4. True values are then compared withthe observed electronic values, and corrections to beapplied to the electronic values are computed. (Seefigure 4-16.)

5. A second set of calibration observationsare made as in procedure 2, and a second set of cor-rections are computed as in 3 and 4.

6. Independent calibrations can best becompared by comparing resultants or vector sums ofthe line-of-position correctors for each observation.(See figure 4-17.) For this comparison, the line-of-position intersection angle µ is selected for the areaof weakest geometric strength in the survey areawhere the calibration data will be applied. Selectionof the proper value of µ is important if calibration isnot accomplished in the immediate work area.

7. If the difference in calibrations (i.e., dif-ference in correction vectors) exceeds 10 m or 0.5mm at the scale of the survey, whichever is less, ad-ditional observations shall be made until satisfactoryagreement is reached. Refer to figure 4-17 for thefollowing example:

C1 is the computed negative correction(in meters) to the P1 line-of-position arc from the ob-served position of the vessel, O.

C2 is the computed positive correction(in meters) to the P ² line-of-position arc.

R1 is the sum of the C1 and C2 correc-tions.

R2 is the sum of a second set of similarcalibration observations that has been translated tothe vessel at O.

HYDROGRAPHY

FIGURE 4-17.—Comparison of electronic positioningcalibrations

Although the three-point sextant fix is most

equipment, other methods of equivalent or betteraccuracy are often used. Using the range and anglemethod, the vessel steers along a sensitive range atslow speed until a predetermined sextant angle tothe right or left of the range is closed. Electronicposition data are observed at that instant and com-pared with values that have been computed in ad-

for P1,... P4, have been computed beforehand. A,B, and C are stations of at least third-order accu-racy, and the angles a have been preselected foreach point on the range.

When using phase comparison systems (i.e.,lane counting) in a survey area offshore or relativelydistant from an area where good calibrations may beobtained, it is advisable to moor small buoys thatcan be used to redetermine or check the whole lane

4-27 (JULY 4, 1976)

The distance between T1, and T2, or thedifference in correction vectors should not exceed 10m or 0.5 mm at the scale of the survey, whichever isless.

If the observations fail to agree, calibrationsshall be repeated until satisfactory agreement isreached. Mean values of agreeing calibrations arethen computed and applied to the electronic posi-tioning values observed during hydrographic opera-tions.

If electronic computers are not available forcalculating the calibration data and calibrationsheets are needed to determine the correctors (4.2.4),the correctors determined for each observation mustagree to within 0.5 mm at the scale of the survey.

Calibration corrections within the same areaoccasionally vary with time (e.g., the correctors de-termined in the morning may not agree satisfactorilywith those determined at the end of the day). Thereis no set rule for times between required calibrationobservations. In addition to regular calibrations, thehydrographer should take every opportunity tocheck the system calibration against accurately lo-cated topographic features. Unless a specific eventoccurred that the hydrographer believes to be thecause of a variance, a linear interpolation of the cor-rectors is generally advised. The occurrence andtreatment of relatively large differences in calibration

data over a period of time should be thoroughly dis-cussed in the Descriptive Report. (See 5.3.5.)

Another acceptable and often preferredmethod is to bring a launch or small vessel along-side a piling, dolphin, beacon, or other similar ob-ject for which a position is accurately known. Inpractice, a wide variety of acceptable methods of cal-ibration has been devised. The hydrographer shouldexercise ingenuity in adapting methods for his par-ticular circumstances.

A complete record of all calibrations andcalibration data shall be maintained for the Descrip-tive Report (5.3) and the hydrographic records thataccompany the survey.

FIGURE 4-16.—Manual record of electronic positioning cali-bration and computation of corrections (hyperboliccontrol, three-point fix). Similar formats can be con-structed for computer output or other means of cali-bration and types of control.

HYDROGRAPHIC MANUAL

FIGURE 4-18.—Position by range-angle method

If it is impractical for the survey vessel tocome alongside a buoy for determination of lanecount, one of these two methods may be used:

4-28(JULY 4, 1976)

count if necessary. The method of determining theposition of the vessel by using a buoy shall not beused for calibration — its use is limited to establish-ing or checking only the whole lane count.

The buoys should be anchored securely withminimum scope of mooring gear. The position of theanchor must be determined and proper accountmade for the current direction and scope of the an-chor cable when used to check the lane count.Buoys used for this purpose should be painted inter-national orange and be lit when moored in areas oflikely surface navigation. Radar reflectors are ad-vised in open waters as an aid in finding the buoys.The U.S. Coast Guard must be notified of the pres-ence, position, characteristics, purpose, and antici-pated time these buoys will be in position to ensureinclusion of the information in the Notice to Mari-ners (e.g., Defense Mapping Agency HydrographicCenter et al. 1976).

1. If line-of-position arcs are of largeradius and curve slowly, the whole lane count maybe determined by circling the vessel around the buoyat slow speed. Compute or scale azimuths for thelines of position where the buoy is located. As thevessel circles the buoy, the bearing of the buoy fromthe vessel is continually observed with a pelorus.

When the bearing of the buoy is equal to the azi-muth of a line of position for a particular arc, thelane count for that arc aboard the vessel is equal tothat of the buoy. (See figure 4—19.) The vesselcrosses each arc twice during each full circle. If thevalues shown on the position display device must becorrected, the setting of the new values must bechecked by another circling of the buoy.

2. If the vessel is not equipped with agyroscope repeater and pelorus from which accuratebearings can be observed, whole lane values may bedetermined by estimating the bearing from the vesselto the buoy and by obtaining the distance by rangefinder or depression angle from the horizon. If agraphic solution is necessary, the scale should besufficiently large to discern tenths of lanes. As acheck, at least three comparisons must be made atvarious positions with respect to the buoy.

C-band and X-band positioning equipmentmanufacturers recommend calibrating field systemseither between known ranges within the survey areaor between several points along a measured base line(e.g., at 500, 750, and 1000 m). The range calibra-tion potentiometers are adjusted to make the equip-ment readout distances agree with the known baseline distances. This procedure permits a good initialcalibration of the electronic delay circuits under themeteorological conditions at the time and thestrength of the signal at the calibration range. Be-cause changes in either the meteorological conditionsor the signal strength can cause distance measure-

FIGURE 4-19.—Determination of a lane count by buoy cir-cling. When the observed bearing of the buoy from thevessel is 268°, the whole lane value for the line ofposition P2 is 335 lanes.

HYDROGRAPHY

TABLE 4-3.— Typical empirically determined velocities of propaga-tion for medium range frequencies

Medium Velocity (km/s)

Vacuum 299,792

Over waterSea water 299,350-299,670Great Lakes 299,350Fresh water 299,250

Over landRich farmland 299,400

298,900Dry sandy flatlandRocky mountainous land 298,800

6. Accessibility to the site, station secur-ity, and availability of shore power if needed.

-

Medium range position-fixing systems requireseveral additional considerations when selecting shoresites. Velocity of propagation is a fundamental factorin the formulas for the computation of most mediumrange position-fixing lattices. Any error or variationin the assumed value introduces systematic errorsinto all position plots or computations. Since the val-ue for velocity varies under different physical condi-tions, small errors should always be expectedthroughout large portions of the chain coverage. At-mospheric properties such as temperature, humidity,and pressure have an effect on the velocity of propa-gation. Major variations in velocity values, however,are caused by differences in the conductivity of thesurface over which the wave travels. The effect of sur-face conductivity is analogous to friction - that is, apoor conductor has an effect similar to that of arough surface; it absorbs energy and reduces thespeed of movement. Thus, a poor conductor results ina low velocity or propagation, high attenuation, andreduction of effective signal range. (See table 4-3.)

The HYDROPLOT software uses the rela-tionship v/f to convert lanes to meters. Since the val-ue for v is fixed at 299,670 km/s, the only way toaccomodate a different v is to modify the relationshipv/f by changing the value of f. This may be accom-plished by using

v2- -- -

- pseudo frequency for plottingwith a fixed velocity of299,670 km/s

where: f 2 -

- 299,670 km/s-ν2

--f1

- new velocity of propagation-ν 1

Example: If the true frequency of an electronic posi-tioning system to be used in a hyperbolic mode inthe Great Lakes is 1618.65 kHz, and the known ve-

locity of propagation is 299,350 km/s, what frequen-cy should be entered on the HYDROPLOT signaltape to compensate for an erroneously preprogramedpropagation velocity of 299,670 km/s?

The current software package of theHYDROPLOT system employs an electromagneticpropagation velocity of 299,670 km/s in the conver-sion of lanes to meters and in the computer genera-tion of hyperbolic position lattices, for hydrographicoperations conducted over seawater. This value was

4-29 (JANUARY 1, 1980)

ments to vary considerably, these systems shall alsobe periodically calibrated or checked in the work-ing area by one of the methods describedpreviously.

4.4.3.4. SHORE STATION SITES. Many factorsmust be considered when determining good locationsfor electronic positioning system shore stations. Fac-tors to be carefully weighed include:

1. Size and shape of the area to be sur-veyed.

2. Topography and configuration ofshoreline.

3. Accuracy requirements and lattice ori-entation.

4. Atmospheric noise levels and externalsignal interference.

5. Available and acceptable horizontalcontrol.

7. Willingness of the property owner torent or lease.

determined by empirical methods in the late 1950'sby the National Bureau of Standards in conjunctionwith the Coast and Geodetic Survey and Hastings-Raydist, Inc., Hampton, Virginia. For operationsover freshwater, it is recognized that the propagationvelocity should be less than that derived for opera-tions over seawater. For the Great Lakes, a velocityof 299,350 km/s is recommended.

f1

v1

f2or

v2

v1x

true frequency of the elec-

f2 f1

tronic positioning system

HYDROGRAPIC MANUAL

Ans: masses, base lines in excess of 50 km should beavoided unless knowledge of the area indicates morefavorable conditions.

V2--f2 V 1

299,670- (1618.65) -f2299,350 The effects of external noise must also be

taken into consideration when selecting shore sites.Natural atmospheric noise generally increases from aminimum at Earth's geographic poles to a maximumin the Tropics. Superimposed upon atmospheric noiseis manmade electrical noise reaching its highest levelaround cities, factories, shipyards, and similar areas.Such local interference is generally "unimportant inthe vicinity of the master station but can seriously af-fect conditions if near a slave station by masking aweak master signal.

--f2 1620.38 kHz

Local topography and ground conditions areprincipal field factors to be considered when selectingstation sites. With many systems, a firm connectionto a stable electrical ground is essential if the vessel

is to receive stable pattern values. Every effort mustbe made to attain stable electrical grounding by driv-ing ground rods down to the water table or by mak-ing a connection to a metallic water supply system.Frequently, large ground planes radiating from anantenna must be constructed for a good ground.Moist soil of good conductivity is preferred oversand where the electrical characteristics of the anten-na are subject to variation with rainfall or tidalstage. Variations of this nature cause troublesomepattern shifts.

Medium range stations should be sited wherelocal power is available. Most systems are batterypowered with the batteries floating on a 110- or220-V a.c. power supply through a battery charger.If local power is not available, generators are gener-ally used.

Distances and heights of nearby elevated ob-jects must also be considered. Fixed objects such astrees, cliffs, buildings, cranes, and the like should beat distances at least six times their height away fromthe antenna. The figure should be doubled if the ob-ject is metal and liable to move during station oper-ation. Overhead power cables, telephone wires, andsimilar objects should be at least 50 m away fromthe master station and at least 100 m away from theslaves.

Base lines that lie entirely over water arehighly desirable because of the greater homogeneityof the conducting surface. A homogeneous surfacereduces random fluctuations in the velocity of propa-gation and eliminates excessive signal attenuation.Experience has shown that, under average electronicnoise conditions, base lines for most systems shouldrarely exceed 80 km. When one considers the widelyvarying conductivity characteristics of most land-

Although line-of-sight conditions are not arequirement for medium range position-fixing sys-

4-30(JANUARY 1, 1990)

f1 x

x

From these facts, it is clear that wave pathsover terrain of varying conductivity should beavoided wherever practical. Each shore station siteshould be located either within 100 m of the water'sedge or so that the landmass between the station andthe vessel does not change appreciably throughoutthe survey area. Shore station configurations wherebase lines are subject to varying conductivitiesshould also be avoided wherever possible (e.g., tidalflats that dry at low water).

If a station must be placed inland, thechange of signal instability will be greatly reduced ifthe antenna is at least 1 km inland of the shoreline.In this case, the requirement to calibrate the systemfrequently in the vessel's immediate working areamust be observed rigorously.

Hydrographers must have a basic under-standing of the uncertainties in the velocity of prop-agation of an electromagnetic wave. There is a com-mon tendency when using medium range systems to"stretch" base line lengths to achieve the largestpossible chain of high accuracy coverage. Withphase comparison positioning systems, however, it isvital that an uninterrupted signal be transmittedfrom the master station to each of the slaves. If thesignal is lost, even momentarily, the receiver maylose lane integration. If this occurs, the vessel mustreturn to a known point for calibration or forreestablishment of lane count. Although the geomet-ric strength of a control chain may be increased bylonger base lines, the pattern stability is usually de-creased by random variations in wave propagationconditions.

HYDROGRAPHY

tems, it is desirable to site shore stations on highground sloping toward the survey area to attain thegreatest effective range. (See 1.3.1 for horizontalcontrol accuracy requirements for station location.)

4.4.4. Hybrid Positioning Systems

For hydrographic surveys, hybrid position-ing systems combine positional data of mixed originto provide accurate fixes. Hybrid systems generallyinvolve the intersection of a visual line of positionwith an electronic line of position. (See figure4-20.) Visual data may be sextant angles or azi-muths determined by theodolite measurements.Electronic positional data are normally obtainedfrom a short or medium range system.

Objects sighted on for initial azimuthsshould be at least 500 in from the theodolite. If asecond object is not available for an azimuthcheck, Polaris or solar observations can be taken tocheck the initial azimuth.

For example, a launch conducting an in-shore hydrographic survey may not be in an areawhere positional accuracy criteria would be met ifan established hyperbolic chain were used. For onereason or another, it would be impractical to alterthe existing configuration of the chain. A reason-able alternative under these conditions is to use the''hypervisual'' method (i.e., a hyperbolic line of po-sition intersecting a visual line of position). Hydro-graphic signals along the beach are located andconstructed as necessary. During sounding opera-tions, the vessel is maneuvered along the hyperbol-ic arc; and on the fix, a sextant angle is observed.Objects used for the sextant angles must straddlethe electronic arc along which the vessel is steer-ing. The ''range-visual'' system is similar exceptthat the positioning system operates in a range-range mode.

4-31 (JUNE 1, 1981)

FIGURE 4-20. —Hybrid positioning system. The vessel ismaneuvered along electronic line-of-position arc AB;sextant angle a is observed between signals 178-182.

The ''range-azimuth'' method is a conve-nient system to use in small, restricted, or congest-ed areas where the line-of-sight conditions cannotbe met for two short range system lines of position.(See figure 4-21.) Using this method, the soundingvessel maneuvers along a range or circular line-of-position arc; the vessel is fixed along this line by atheodolite azimuth observed from shore. The idealtheodolite site is directly below the electronic con-trol station antenna. This method produces excep-tionally strong fixes because the lines of position al-ways intersect at right angles.

FIGURE 4-21. —Range-azimuth positioning system. The vesselis maneuvered along electronic range arc AB; the azimuthfrom shore station C to the vessel is observed using a the-odolite.

HYDROGRAPHIC MANUAL

The azimuth check should not exceed 1min of arc. Observed azimuths or directions to thesounding vessel for a position fix shall be read tothe nearest 1 min of arc or better if necessary toproduce a positional accuracy of 0.5 mm at thescale of the survey.

under each of the following circumstances (whetheror not accompanied by control data):

4.4.5. Position Frequency

Frequencies of positions along soundinglines are influenced by several factors:

Scale of the survey.

Line spacing.

4. At each detached sounding.Speed of the survey vessel.

5. At each bottom sample.

The distance between successive numberedpositions on sounding lines should be about 40 mmon the hydrographic sheet and shall not exceed 50mm regardless of the scale of the survey. Positionsare taken and numbered at regular intervals to aidin detecting errors. (See 4.5.6 for sounding intervalrequirements.)

On many automated surveys, position infor-mation is obtained and recorded for every recordedsounding. To avoid congestion, position numbers areassigned only at prescribed evenly spaced intervalsand for each of the circumstances listed. The maxi-mum allowable spacing of 50 mm between positionnumbers is generally adopted for these surveys.When sextant fixes or theodolite cuts are

used for position control, numbered positionsshould be obtained more frequently—particularly ifthere is difficulty in keeping the vessel on line be-cause of wind or current or when lines must beclosely spaced. Positions may be taken less fre-quently when steering ranges or when lines are be-ing run along hyperbolic or range arcs. In areas ofeven bottom, distances between successive fixesalong distance arcs may be increased slightly butshould never exceed 50 mm on the sheet. Sextantfixes and theodolite cuts can be observed and plot-ted very rapidly, particularly where the fixes arestrong and the signals are nearby. Recording exces-sive fixes should be avoided to keep the processeddata from becoming overly congested. For exam-ple, 1.5-min intervals between fixes should not beused if 2-min intervals are adequate.

4.4.6. Position Identification

Julian dates are assigned to daily blocks ofwork for further identification of data. Julian datesbegin with 001 every January 1 and run consecutive-ly each day throughout the calendar year.

4.5. RUNNING HYDROGRAPHY

When control has been established, fieldsheets prepared, and the required data plotted onfield sheets, the hydrographer is ready to begin. Usu-ally, the first step is to make a satisfactory junctionwith a prior survey, then progress in the directionspecified in the project instructions. It may be pru-dent, however, to survey an anchorage for the vesselfirst if there is reason to doubt the charted

In addition to evenly spaced positions alongsounding lines, numbered positions shall be recorded

4-32(JUNE 1, 1981)

Conditions of wind and current.

Type of position control. (See 1.4.5.1.)

In most cases, a survey ship or launchsounds at the highest practical speed. If the scale ofthe survey is small, positions may be taken at inter-vals of several minutes; however, if the scale islarge, the intervals may be so short that it will benecessary to reduce the speed of the vessel toavoid cluttering the sheet.

1. At the beginning and end of each line.(Positions must often be plotted by dead reckoningand fixes ''created'' to ensure accurate smooth plot-ting.)

2. Whenever the speed of the soundingvessel is changed appreciably.

3. At all changes of course larger than 10º.In such cases, another position should be determinedas soon as possible after the vessel is on the newcourse.

6. At any other time a position is taken forfield edit, aids to navigation, obstructions, or to lo-cate or check a hydrographic signal.

Hydrographic positions shall be numberedconsecutively with a block of numbers assigned toeach sounding vessel. (See 1.4.5.2.) Position numberscontinue consecutively from day to day until thesurvey is completed. Detached positions such asrocks and bottom samples are included in the day-by-day numbering system. A listing of all detachedpositions must be included in the Descriptive Re-port. (See 5.3.5.(G.).)

4.5.1. Beginning Survey

HYDROGRAPHY

soundings. The decision on where to beginhydrographic operations may be logically revised bypreviously unforeseen control problems or byweather and sea conditions.

effective when strong or erratic currents or windconditions make it extremely difficult to consistentlyrun properly spaced straight parallel lines.

To start a sounding line, one navigates theship or launch to the beginning of the proposed line.Trial positions are plotted as this point is reached.The course is given to the helmsman; the recorder istold when to take the first position and sounding.For visual surveys, angle observers are advised onwhich signals to use for the fix or for theodoliteazimuthal orientation.

4.5.2. Following Proposed Sounding Lines

Line spacing is directly related to waterdepths and widens as depth increases. Maximumspacing for certain depth ranges are generallyspecified in project instructions. When the maximumspacing is exceeded, split lines should be run asnecessary to fill the void — except that wider spacingat the outer limits of depth ranges may be acceptedon even slopes. The hydrographer must use goodjudgment in running splits and should base hisdecision on the character of the bottom as well asthe distance between lines. Generally, splits shouldbe run as soon as possible after line-spacing

When electronic control systems are usedaboard nonautomated vessels, the easiest method offollowing proposed sounding lines is by steeringhyperbolic or circular loci arcs, the orientation anddirections of which vary with the shore stationgeometric configuration. When steering arcs, theposition of the vessel relative to the line can becontinually monitored by watching the digital distanceor lane counters. Departures from the line can usuallybe corrected in a timely manner by making smallcourse changes. Steering arcs can be especially

4-33 (JANUARY 1, 1980)

If the field sheet is to be plotted manuallyand the sounding line system for the survey is to beparallel straight lines, the proposed lines should belightly penciled on the sheet to guide thehydrographer. For automated surveys, parametersfor the hydrographic line equations are determined asrequired input for the computer. [See NOS TechnicalManual No. 2, "HYDROPLOT/HYDROLOGSystems Manual'' (Wallace 1971)] On larger scalenonautomated surveys, the proposed line spacing(1.4.1 and 4.3.4) should be approximately 5% lessthan the maximum spacing authorized as a safeguardagainst having to run splits later should themaximum allowable spacing be exceeded.

The hydrographer should follow the pro-posed sounding lines as closely as possible for themost efficient and effective coverage of the surveyarea. Automated vessels normally run straightparallel lines. When the survey is controlledelectronically, the position of the vessel is computedevery several seconds and displayed relative to theproposed sounding line by an electronic counter or a''left/right'' indicator. With this continually updatedinformation, minor course changes can be madeeasily and quickly to avoid significant departure fromthe lines.

When visual control is used for the survey,the first position is taken and plotted immediately,either manually or by automation. If necessary, animmediate course correction is given to the helms-man to ease the vessel over to the proposed line.Positions are then taken and plotted at shortintervals until a steering course that closely followsthe line is established. The time between positionsmay then be lengthened to the maximum allowableinterval corresponding to the scale of the survey andthe speed of the vessel.

As a survey vessel approaches the inshoreends of sounding lines or when nearing shoals,breakers, or other dangers, prudent seamanshiprequires the hydrographer to reduce speed. Fixes aretaken at any time the speed is changed for anyreason. If the vessel must begin a sounding line nearthe beach from a standstill, the fact shall be noted inthe records and the next fix taken as soon as regularsounding speed is reached.

When visual control is used, the helmsmanshould be trained to select and steer available naturalranges to stay on the proposed line. Otherwise, thevessel is maintained on the line as closely as possibleby steering compass courses - small course changesare made as required. Course changes should notexceed 10° unless a fix is taken when the change ismade (or the exact time and new course recorded).Considerable experience is required to gain the knackof making course changes of sufficient amount at thecorrect time. Changes in the direction or strength ofthe current are often indicated by ''current streaks.''These should be observed and recorded for futurereference. Changes in the strength of the current maybe expected in the vicinity of shoals and banks inoffshore areas.

HYDROGRAPIC MANUAL

represent the track as accurately as possible.Sounding lines following circular or hyperbolic arcsmay be drawn by using small pieces of clear plastictrimmed to fit arcs of various radii. Positions takenaboard vessels equipped with a HYDROPLOTSystem (Wallace 1971) are automatically computedand plotted on a real-time basis.

deficiencies or the needs for additional developmentsare discovered.

4.5.3. Turns and Changes in Course

4.5.4. Speed of Sounding VesselPosition numbers for hand-plotted ship

hydrography can often be inked when the position isplotted — frequently, on small-scale surveyssoundings may also be inked shortly after they arescaled and recorded. During launch or skiffhydrography or on larger scale surveys where dataare obtained rapidly, positions and soundings areusually inked later. When the vessel does not steeran arc, the fixes shall be plotted as quickly aspossible so that course changes necessary to followthe proposed lines can be made. Hand-plottedpositions are numbered in pencil when plotted andare inked in assigned colors as soon as practical,preferably no later than the end of the day. Insofaras possible, position numbers are placed below andto the right of the position. Position numeralsshould be about half the size of the soundingnumerals.

When there is risk of grounding.

Under certain conditions, it may not benecessary to make an accurate plot of the soundingline when the data are being gathered. If a launchis steering circular or hyperbolic arcs and soundingand position data are being logged on tape for laterplotting, rough plots on a field sheet tracing tomonitor progress are normally sufficient. Duringopen skiff operations, it may be advisable to ploton a rough worksheet to prevent water damage tothe field sheet; then replot or transfer the

Vessel speed should be as constant aspossible between positions. Each change of speedshall be recorded and a position taken when thechange was made or as soon thereafter as practical.

4.5.5. Plotting Sounding Line

4-34(JANUARY 1, 1980)

Soundings shall be plotted as precisely aspossible along the true path of the vessel. Positionfixes must be taken on course changes exceeding 10°— except that, when positions are determined foreach recorded sounding, additional fixes need beobtained only on course changes of 30° or more.When turns of approximately 90° are made or whenthe vessel is turned to a reciprocal course to begin anew sounding line, the soundings on the turn may berecorded and plotted if such data are considereduseful by the hydrographer. Soundings on turns,however, generally should be omitted unless the vesselis computer equipped and each sounding is positioneduniquely. Whether or not soundings on turns areplotted, the analog depth record must be carefullyexamined for traces of shoals or hazards that couldotherwise go undetected. A fix shall be taken at thebeginning and end of each sounding line.

Within practicality, soundings shall beobtained while the survey vessel is operated atnormal cruising speed (i.e., the most efficient speed);however, speed shall be reduced as necessary:

When submerged hazards are suspected.

When sounding in heavy seas or reducedvisibility.

When necessary to meet requirements forminimum distances between successive positions.

When required to adequately define steepfeatures.

When sounding with lead line or pole toobtain true vertical measurements (A.6.1.1 andA.6.1.2).

At all other such times required by therules of the road and prudent seamanship.

When plotting positions by hand, a finepencil line is drawn lightly between plotted positionsto show the track of the vessel. If a course changehas been made between fixes, the line drawn shall

When a line is run parallel to the shoreline,positions often cannot be obtained with sufficientfrequency to plot all course changes. In such cases,the hydrographer should draw a line that closelyapproximates the path of the launch betweensuccessive positions. Under these circumstances, anote, "SFS'' (1.2.1), should be made in the soundingrecord to indicate that the field sheet plotting mustbe used as a guide when processing the data.Positions and soundings taken in narrow windingchannels, in streams, and over mudflats are treatedin the same manner. When positions of this natureare logged for automatic plotting, a fix must be''created" (i.e., fix values for the approximateposition are scaled).

HYDROGRAPHY

interval soundings and times are scaled from thegraphic depth record and entered in the soundingrecords. (See 4.9.8. 1.)

positions on the field sheet at the end of the day.

The following guidelines may be used whenselecting sounding intervals over fairly regularbottom topography:

While uniform intervals facilitate plotting thesmooth sheet, it is more important that recordedsoundings give a true representation of the bottomconfiguration. In areas of irregular bottom, leastdepths and greatest depths between interval soundingsmust be recorded with additional intermediatesoundings as necessary to define the profileadequately. To ensure that soundings are plottedaccurately, record times of observations. Odd

The final decision as to the sounding interval,however, lies solely with the hydrographer. Selectedintervals shall, when the soundings have been

4-34a (JANUARY 1, 1980)

4.5.6. Sounding Interval

Although echo sounders produce a nearlycontinuous graphic record of the bottom profile,soundings are recorded at fixed intervals as the linesare run. Digital sounding equipment is programmedto record soundings at preselected fixed intervals.The hydrographer shall select a time interval forrecording soundings that is appropriate to the scaleof the survey, depth of water, configuration of thebottom, and speed of the vessel. (See 1.4.6. andfigure 4-21b) Where depths of water or slopes of thebottom are uniform, the minimum interval betweenrecorded soundings shall be such that all recordedsoundings can be plotted on the smooth sheetwithout congestion.

1. If the horizontal axis of the soundingnumerals is approximately parallel to the direction ofthe sounding line, one-digit numerals should bespaced about 4 mm apart, two-digit numerals spacedabout 6 mm apart, and three- and four-digitnumerals about 8 to 10 mm apart. (Rotation of thesounding numeral about the sounding line permitscloser spacing.)

2. If the horizontal axis of the numerals isapproximately perpendicular to the direction of thesounding line, numerals should be spaced 4 to 8 mmapart, depending on the depth.

3. If numerous soundings are to be shownin decimals, the decimal is considered to beequivalent to a half digit in width.

HYDROGRAPIC MANUAL

4-34b(JANUARY 1, 1980)

FIGURE 4-21 a. — Sounding Interval vs Speed

HYDROGRAPHY

shall be plotted in whole units. (See 7.3.8.1 forsmooth sheet soundings.)

plotted at the scale of the survey, portray the bot-tom configuration accurately.

4.5.7. Measuring Depths

4.5.7.1. DEPTH UNITS. These units androunding limits to be used for various areas anddepths ranges are specified in table 4-4. Soundingsare always recorded in fathoms and decimals, me-ters and decimals, or feet and decimals -fractionsshall never be used. Occasionally, soundings are re-corded in fathoms for part of the area being sur-veyed and feet for other parts. The records mustindicate which unit is being used. (See 4.8.3.5.)Only one sounding unit may be used when plotting,soundings on a field sheet or on a set of field sheetsthat will ultimately compose one smooth sheet.Special instructions will be issued for surveys onwhich soundings will be recorded and plotted inmetric units.

An adequate representation of submarine re-lief by depth curves is a problem similar to therepresentation of land topography by contour lines,except the topographer can examine the area visual-ly while the hydrographer has only measured andplotted depths as his guide. The hydrographershould make a study of characteristic bottom forms,as such forms are common within the same regionand in similar regions.

4.5.7.2. FIELD SHEET SOUNDINGS. On thefield sheet, soundings shall be plotted in black ink assoon as possible after all necessary data have beengathered. Soundings shall be reduced to the tidal orlake level datum adopted for the area using eitherpredicted or observed tide or water levels. (See1.5.4 and 4.9.3.) Significant corrections for phasedifferences or variation of the initial of the echosounder should be applied (4.9); small correctionsmay be ignored for field sheet plotting. Hand-plot-ted soundings between positions shall be properlylocated by the use of a spacing divider; odd intervalsoundings on peaks and deeps must be positionedcorrectly. Soundings shown on positions must notobscure position dots or position numbers. (See1.5.6.)

Abnormal or improbable depth curves maybe strong evidence of inaccuracies, inadequacies, orpossible errors in the hydrographic survey or theplot of the soundings. Raw position and depth data

and corrections thereto must be thoroughly exam-ined to resolve possible discrepancies where thecurve configuration is questionable.

On extensive coastal shelves, commonlyfound on the Atlantic Ocean and Gulf of MexicoCoasts of the United States, depth curves are gener-ally smooth and regular because prevailing bottomforms are caused by wave or current action on loosebottom materials. In depths greater than about 100fm on the continental slopes, bottom forms are gen-erally more like those found on land. Intervals of 25fm between depth curves are normally adequate oncontinental slopes and in deeper waters off the Pacif-ic Ocean and Alaskan Coasts.

Plotted soundings should be uniform in sizeand clearly legible. In congested areas, a selection ofrepresentative soundings should be shown; howev-

er, all soundings necessary to show the bottom con-figuration adequately must be plotted. Least depths

over shoals and dangers may be inked on the sheetin bolder figures than the surrounding soundings;notes are placed in nearby marginal areas on thefield sheet giving least depths with references tosounding record position numbers.

Drawing closely spaced depth curves accu-rately requires a careful inspection and considerationof each sounding, not only once but often severaltimes; when sketching depth curves at too wide aninterval, many intermediate soundings may not beconsidered, and important indications may be over-

Where the depth unit is the fathom and thebottom is generally flat or has a gentle slope, sound-ings shall be plotted in fathoms and decimals fordepths less than 31 fm. This is also applicable forareas where the chart sounding unit is the foot butthe survey is in fathoms. In other areas, soundings

4-35 (JUNE 1, 1981)

4.5.7.3. DEPTH CURVES ON FIELD SHEETS.

These are indispensable for a comprehensive inter-pretation and examination of a hydrographic survey.The best gage of the survey's completeness, adequa-cy, and accuracy is to be able to draw closely spaceddepth curves for the plotted soundings with an as-surance that the submarine relief is depicted accu-rately. Depth curves must be drawn on the fieldsheet by the hydrographer as the work progresses. Acareful inspection of the depth curves will disclosewhere sounding lines have not been spaced closelyenough, where additional development is required,and where there are errors that require further in-vestigation. (See 1.5.7.)

TABLE 4-4.-Depth units for scaling soundings and applying corrections.

For soundings scaled in fathomsFor soundings scaled in feet

In exposed watersIn exposed watersIn protected waters In protected watersCharacter of area or bottomDepthrange

(fm)

ApplyRecordApply RecordRecord ApplyApplyRecord

HY

DR

OG

RA

PM

C M

AN

UA

L

0.5 0.10.10.20.2 0.10.10.2Least depths over shoals and dangers0-20

In channels, established sea lanes, andfairways

0.21. 0.10.50.2 0.10.10.5

0.5 0.20.51. 0.10.20.51.

4-3

6 20-110 0.20.51. 0.21.1.1. 0.1

0.51.1.2.1.2.Over irregular bottom 0.20.5

1.2.1.1.1.2.1.2.Greater All bottom types

depths

Delinearion of appropriate low water line

Elsewhere, over regular bottom

Elsewhere, over irregular bottom

Over regular bottom

soundings to corrections to soundings to soundings to soundings to corrections tocorrections tocorrections tothe nearest the nearest the nearest the nearest the nearest the nearestthe nearestthe nearest

•Digital soundings are recorded, and computer determined correction are usually applied to the nearest tenth of the sounding unit regardless of depth or bottom character.If there is double as to which increment to use, select the more accurate.If soundings are being recorded in meters select the nearest equivalent increment from the fathoms portion of the table.In areas of depth greater than 500 fm where the slopes are very deep and the echo trace is not sharp and clear, soundings may be sealed to the nearest 5 fm.

(JUN

E 1,1981)

HYDROGRAPHY

l-fm intervals in depths between 1 and 20fm,

5-fm intervals in depths between 20 and 50fm,

10-fm intervals in depths between 50 and 100fm, and

25-fm intervals in depths greater than 100fm.

Where the bottom is relatively flat or slopesgently and is featureless, nonstandard depth curvesare drawn at a spacing of 3 to 4 cm at the scale of thesurvey. Depth curves are drawn first in pencil. Stan-dard depth curves listed in table 4-5 are then drawnin the proper color ink.

Supplemental depth curves listed in table 4-6 shall be shown in ink at the discretion of the hy-drographer. Additional depth curves necessary todisplay the bottom configuration are drawn inbrown ink. (See 1.5.7.)

4.5.8. Verification of Alongshore and Off-shore Detail

0-100/101-200/201-300,..., The hydrographer and field editor share theresponsibility for verifying map details seaward ofthe shoreline. These details are shown on the photo-grammetrically compiled shoreline manuscripts that

0-10/11-20/21-30,....,0-1/2-3/4-5,. . ., or0-1/2,. . .,

depending on the slope of the bottom. Standarddepth curves, however, must still be drawn. (See4.5.7.4.)

TABLE 4-5. - Standard depth curves

CurveCurve Curve(fm) (ft) color

(Datum of reference) OrangeGreenRedBlueRedOrange10Blue20Violet30Green40Red50GreenOrange-Violet-Green-Red-Blue-Green-Red-4.5.7.4. DEPTH CURVE INTERVAL. No sin-

gle requirement for spacing of depth curves can beprescribed that applies to all regions. In areas ofsteep slopes and irregular submarine relief, all depthcurves that the scale of the field sheet permits shouldbe drawn. A good general rule is that depth curvesshould be drawn according to these intervals:

Violet-Blue-Green-Orange-Violet-Green-

- Red-2000 Orange- Violet3000

4-37 (JUNE 1, 1981)

looked. (See 7.3.9.) Where interpretation is diffi-cult, intermediate depth curves must be drawn.

Topographic experience is a great assetwhen drawing depth curves as is the ability to rec-ognize predominating physiographic shapes. Theability to represent submarine relief by means ofcontouring can be acquired only by intensive train-ing and practice and by studies of similar workdone by experienced hydrographers.

Depth curves cannot cross or run abruptlyinto each other except at cliffs, overhangs, or otherextreme topographic features. When approachingone another, they tend to be parallel. Informationfrom sounding lines shall be sufficient to permit thedelineation of depth curves. Special care must be'exercised to avoid excessive spacing of the sound-ing lines — particularly when the direction of thelines is parallel to the depth curves.

An alternate and often preferable way ofdetermining whether sufficient soundings havebeen plotted on worksheets is to ''group" depths.Depth curves are drawn to group numbers intosmall areas easy to work with, such as:

Hydrographic field sheets are preliminaryengineering representations of the surveyor's ac-quired data and findings. Generalization of thedepth curves will not accurately portray the resultsof the field work and may prove to be misleading.Apparent irregularities or anomalies in the depthcurve patterns can be key indicators either of erro-neous data or of areas requiring additional hydro-graphic development.

See section 7.3.9 for various conventionsadopted by National Ocean Survey for drawingdepth curves on hydrographic sheets.

01235

100200300400500600700800900

100011001200130014001500

06

12183060

120

240300

180

600

HYDROGRAPHIC MANUAL

rine growth or where floating debris can be mistak-en for rocks. Limits of foul areas can usually be de-lineated with a high degree of confidence. Tide-coordinated infrared aerial photography is routinelyobtained for the delineation of the low water line inall areas where tidal datums have been establishedaccurately. These lines must be field edited for ac-curacy and completeness. Unless specified other-wise in project instructions or the hydrographerdoubts the accuracy of the photogrammetricallycompiled high or low water line, the lines need notbe developed by hydrographic methods.

TABLE 4-6. - Supplemental depth curves

CurveCurve Curve(ft) color(fm)

3 Violet0.524 Orange36 Green

360 Blue420 Green480 Red80540 Violet90

Field edit operations shall remain currentwith hydrography to avoid application of obsoletedata for smooth sheet use; however, field edit forany individual sheet must be completed althoughhydrography on that sheet cannot be completed be-fore ending the field season.

Changes discovered in field edited areaswhere hydrography has been deferred for morethan 1 yr are the responsibility of the hydrographer.Such changes shall be shown on the field sheetswith records of all observational data entered prop-erly in the hydrographic records. Each change ofthis nature must be listed and explained in the De-scriptive Report. (See ''Provisional Photogramme-try Instructions for Field Edit Surveys.'')

Pertinent items that must be verified includethe existence, the positions, and the elevations ordepths of rocks, ledges, and reefs, and the limits offoul areas, wrecks, and similar features. Modemphotogrammetric techniques used by the NationalOcean Survey produce complete, accurate, and reli-able map manuscripts. Use of color aerial photogra-phy generally permits an accurate and adequateinventory of rocks and other hazards, except whenobscured by breaking waves, turbid water, and ma- Each isolated rock and ledge, whether bare

4-38(JUNE 1, 1981)

Symbols and chart details inked in bluewhen the data were transferred from copies of shore-line manuscripts to the hydrographic field sheet areinked in black immediately after verification of thespecific feature. (See 4.2.7.) Changes to the shoreline,rocks, or other details transferred from copies ofphotogrammetric manuscripts are shown in red inkon the field sheet. Such changes made by the hy-drographer must be coordinated with the field edi-tor. Explanatory notes and references to revisorylocation data shall be included on the field sheetwhen necessary. Sufficient information is obtainedand recorded to permit any needed corrections to bemade on the manuscripts and to permit the verifier toreconcile any differences between positions of fea-tures shown both on the manuscripts and on the fieldsheets. For example, if adequate information is notfurnished, it may not be possible when verifying asurvey to determine whether there is one rockshown at different positions on the field sheet and onthe manuscript or whether the positions are for dif-ferent rocks. (See 6.3.5.) Discrepancies between theexisting physical conditions and shoreline manu-scripts must be positively resolved in the field.

support the hydrographic survey. Normally, thefield editor is responsible for the completeness andaccuracy of the details above the chart datum. (Seesection 915 of the Coast and Geodetic Survey SpecialPublication No. 249, ''Topographic Manual, Part II,Photogrammetry'' (Swanson 1949), and ''Provision-a] Photogrammetry Instructions for Field Edit Sur-veys'' (National Ocean Survey 1974).) Close coordi-nation between the field editor and hydrographermust be firmly established at the start of survey op-erations and maintained faithfully throughout toavoid duplication of effort, to prevent the occur-rence of errors of omission, and to avoid submissionof conflicting data. (See 1.6.2. and 3 2.4.)

The field editor shall be notified promptlyof actions by the hydrographer that affect detailsshown on photogrammetric manuscripts. Coordi-nated effort by both hydrographer and field editoris essential to ensure that changes are properly han-died. Failure to reconcile differences betweenmanuscripts and hydrographic sheets results in un-necessary delays during verification of the survey.The hydrographer must continually bear in mindthat changes affecting a photogrammetric manu-script which are reported only in the hydrographicrecords will probably not be seen by a photogram-metrist until the discrepancy created is discoveredin the final processing phases.

44

6070

HYDROGRAPHY

When a rock that has been verified or ade-quately located during current field edit operationsis passed on a sounding line, this fact and the esti-mated distance to the rock when abeam is entered inthe sounding records. These data are not to be usedto locate the rock but serve as a verification of itsexistence and position.

Bare rocks or rocks awash shown on priorsurveys or on published charts but which are foundto be nonexistent, incorrectly located, or have erro-neous elevations shall be fully explained in the De-scriptive Report. Recommendations shall be madefor the charting procedures to be followed.

4.5.9. Shoals and Dangers

1. A study of soundings obtained duringthe systematic survey.

2. Reports of dangers submitted by pilots,

fishermen, and other reliable sources.3. Sightings of breakers, current swirls

and eddies, kelp, or other visible evidence whilesounding.

4. An examination of aerial photographs,

particularly those in color. These often reveal thelocation of shoals or rocks. (See 4.5.8.)

The spacing of the systematic sounding linesshould provide an indication of dangers and shoalswithin the area. Such indications normally occur asbreaks in the continuity of bottom slopes. More pos-itive evidence of the existence of a shoal is foundwhere two adjacent lines of soundings contain simi-lar indications. Even slight changes from the generalsurrounding depths should be regarded as a possibleindication of a shoal. In many localities, it is not fea-sible to examine every such indication; further-more, it is not required. The hydrographer decidesHeights or depths of rocks must be deter-

4-39 (JUNE 1, 1981)

or awash, and all other hazards to navigation, in-cluding prominent rocks in a group or in a rockyarea, shall be located and described accurately andadequately. If the standard symbols shown in appen-dix B are inadequate to portray a feature, a completedescription must be entered on the field sheet. Ele-vations and depths of such features shall be deter-mined in the field when observed tide or water leveldata are available. When the height or depth of afeature relative to the water surface is measured, thedate and time must be recorded for subsequent re-duction of the measurement to the chart datum. (See''Provisional Photogrammetry Instructions for FieldEdit Surveys.'') The existence of every featureshown seaward of the shoreline on the photogram-metric manuscripts shall be verified by the hydrog-rapher. He shall also check the limits shown for kelpbeds and for rocky and foul areas and verify the se-lection of the most prominent features lying therein.Rocks and other similar features lying along or nearthe shoreline or other accurately plotted referencepoint may be verified by visual inspection at the hy-drographer's discretion; but off-lying rocks or othersimilar hazards to navigation, especially those in ornear navigable waters, must be verified by more rig-orous methods. Estimating distances and bearings tothe feature from nearby hydrographic positions is anacceptable method of verification provided that theestimates are of reasonable accuracy. The method ofverification is left to the hydrographer's judgment.

Rocks and other dangers not shown or in-correctly positioned on the manuscripts shall be lo-cated accurately and, if possible, a check measure-ment taken. If visual control is available ifpractical and safe to land on such features, the loca-tions may be determined by strong three-point fixeswith check angles; or the feature may be located bya minimum of three cuts from stations ashore orafloat that provide a strong intersections - or by sex-tant positions with the rock on range with controlstations bearing in several directions.

During electronically controlled surveys de-void of visible signals, positions shall be taken along-side or as close to the feature as safety permits. Ac-curate compass bearings and estimated distances tothe feature must be recorded. If the hydrographerhas doubt as to the accuracy of the estimated dis-tance, two or three additional positions with bear-ings and distances to the feature should be obtainedas a check.

mined accurately, and the observation time, date,and time zone noted. If a landing can be made andthe sea is calm, the height of a rock can be measuredby holding the lower end of a rod or staff at the wa-ter's edge — then read the rod or staff at the pointwhere the top of the rock and the horizon are inline. Heights must be estimated as accurately as pos-sible from a position nearby if impractical or unsafeto land.

4.5.9.1. INDICATIONS OF SHOALS AND

DANGERS. There are several sources of evidencethat shoals or submerged dangers exist in the area be-ing surveyed; the hydrographer should be aware ofall of them. This information may be obtained from:

HYDROGRAPHIC MANUAL

most probably be found should be delineated by run-ning a series of closely spaced sounding lines. Astudy of these soundings (plotted at a larger scale ifnecessary) should reveal the approximate location ofthe least depth, but may not establish the least depthon the feature. A more intensive examination of theshoalest part of the feature should be made to obtainthe least depth. (See 1.4.3.) When the bottom is visi-ble, a lead line or sounding pole can usually beplaced on the high points and the depth measured.In other areas, detection and measurement are moredifficult.

which areas need additional development (1.4.3); theChief of Party makes the final inspection to assurehimself that no additional field work is required.Hydrographers and Chiefs of Party should be guid-,ed by the considerations listed in section 1.4.3 andfrom experience in similar areas when decidingwhich areas will be developed further.

Pilots, fishermen, yachtsmen, and otherswith knowledge of the local waters should be con-suited for important hydrographic information.Each report of uncharted rocks, shoals, or obstruc-tions must be investigated. U.S. Power Squadronsand U.S. Coast Guard Auxiliary, if active in thearea, are particularly valuable sources of informa-tion for uncharted hazards. Attempts should bemade to verify or cross-check information from sev-eral sources. Individuals with local knowledge willoften guide hydrographers to uncharted features.Otherwise, approximate locations must be obtainedand plotted in pencil on the field sheet. Exact infor-mation on the location of rocks or shoals cannot al-ways be obtained. In such cases, extensive examina-tions are often required to find them.

When divers are unavailable, a short wiredrag, wire sweep, or pipe drag should be used. (SeeAF.1.4 and AF.1.5.) Alternatively, a small buoymay be anchored near the most probable least depthlocation. The buoy serves as a reference point whilethe vessel cruises slowly or drifts over the area.(Caution, for currents may carry a drifting boataround the peak of a shoal.) A second marker buoymay be used to mark the shoalest sounding recordedby the echo sounder. The final examination is thenmade by drifting over the shoalest part taking lead-line soundings. The vessel should be allowed to driftacross the feature several times, each timeoverlapping the previous path by about half thelength of the vessel. The echo sounder shall be incontinuous operation and the graphic record prop-erly annotated during the investigation. Bottomcharacteristics should be determined on these fea-tures. The lead line aids the hydrographer in resolv-ing echo sounder misinterpretation caused by kelpor by other spurious traces.

All members of a hydrographic surveyparty, when not otherwise engaged, should be alertfor visible evidence of submerged dangers. In manytropical waters, coral banks and shoals are usuallyvisible for a considerable distance when the sea iscalm, the observer is stationed well above the water,and the sun is high and at the observer's back.Breakers are clear evidence of obstructions orshoals, but current eddies indicating a shoal are lessapparent and are not always easily detected. Eddiesare caused by disturbance of the current and are al-ways seen down current from isolated shoals — thedistance depends on the depth of water and the ve-locity of the current. Eddies are more prominentwhen differences in depths between shoals and sur-rounding bottoms are large, and are most noticeableat the last of the ebb or first of the flood current.

Kelp is one of the better indications of dan-gers because it generally grows where the bottom isrocky. Each isolated growth of kelp must be investi-gated. If kelp is growing over a hazard, the factshall be entered in the hydrographic records. Alsonote whether the kelp is visible at all stages of thetide or whether it tows under and cannot be seen.

Where features are too shoal to sound safe-ly, the limits should be defined by sounding lines runas close to the feature as safety permits — in suchcases, estimates of depths covering the featureshould be made and entered on the field sheet.

4.5.9.3. RECORD OF SHOAL EXAMINATION.

When a shoal is examined by sounding along a seriesof closely spaced lines (4.3.4), all data shall be re-corded in the hydrographic records. If the leastdepth is found by drift soundings or by another

4.5.9.2. DEVELOPMENT AND EXAMINATION

OF SHOALS. When shoal indications are to be investi-gated, limits of the area where the least depth will

(JUNE 1, 1981) 4-40

When the existence of a pinnacle rock is sus-pected from the general nature of the visible terrain,a very patient and exhaustive search must be madeor the least depth may not be found. If at all possi-ble, divers or a simplified wire sweep or pipe dragshould be used to determine the least depth over thistype of feature.

HYDROGRAPHY

nonsystematic procedure, a full report of the follow-ing items must be entered in the sounding recordwhen not otherwise evident:

er parts of the wreck usually cannot be found usingordinary sounding methods. Qualified divers, if avail-able should determine least depths and describewrecks.1. The method of search used.

Large pieces of floating wreckage, logs, or otherdebris potentially hazardous to navigation that aresighted in areas where such obstructions are not com-monly encountered shall be reported immediately to thecommander of the nearest U.S. Coast Guard District.

nation.3. A statement as to whether the bottom

was visible.4. A brief description of the feature in-

4.5.12. Soundings Along Wharves and including the bottom character.Docks

5. A statement as to whether the shoal isSounding lines shall be run close to and

along the outer faces of wharves and in docks andslips within the project limits. (See 4.3.4.1.) In addi-tion, soundings shall be taken along the most likelykeel line of vessels berthing there. Several depthsalongside wharf and pier faces should be measuredby lead line or by sounding pole to determine ifsilting or shoaling is occurring. Soundings need notbe taken along small privately owned piers. Sound-ings in the vicinity of wharves and docks are shownon subplans at an enlarged scale if the scale of theregular survey is too small to show the detail ade-quately. (See 2.4.4 and 7.2.4.) The project instruc-tions may require that dock and slip areas be sur-veyed at a larger scale depending on the importanceof the area.

marked by kelp, eddies, or other visible evidence.

4.5.10. Detached Breakers

4.5.13. Aids to Navigation

4.5.11. Wrecks and Obstructions

Positions and descriptions of all nonfloatingaids and landmarks shall be submitted in accordancewith sections 1.7.1 and 5.5. If the name and descrip-tion for an aid do not agree with the data publishedin the most recent edition of the Light List (e.g., U.S.

4-41 (JANUARY 1, 1979)

2. The length of time spent in the exami-

If submerged rocks or other obstructions areevidenced by breakers and it is impractical or dan-gerous to locate the object and obtain a sounding,they must be located by intersection cuts taken fromthe sounding vessel or from shore stations. (See4.5.8.) The cuts should form a strong geometric in-tersection. The depth over the feature is estimatedand the time of observation noted. Conditions underwhich breakers form in the area must also be includ-ed; the stage of the tide or lake level and the sea con-ditions are also recorded. Submerged rocks inside agenerally foul area may be symbolized without anobserved position, provided the outline of the foularea is accurately delineated.

Whenever possible, such features should belocated during low tides and relatively calm seawhen danger of damage to the vessel is least. Smallareas around rocky points can often be examined andthe limits of foul areas determined from a skiff orother small boat. The hydrographer must be surethat other dangerous rocks lying just outside foulareas are located and shown as detached rocks.

All wrecks and obstructions not afloatshould be located and as complete information aspossible furnished. (See 1.6.4 and 4.5.9.3.) Whether awreck is totally submerged, visible at all stages of thetide, or only at some stage of the tide should be stat-ed; when possible, the wreck should be described.The description should include but not be limited tothe name, dimensions, construction material, condi-tion, and orientation of the located wreck. Any his-torical information concerning the wreck should beincluded. Sunken wrecks are treated as dangers orshoals. (See 4.5.9.2.) Least depths over wrecks arepractically impossible to determine without diver ob-servations or wire dragging the area. Masts or oth-

All aids to navigation in the project areashall be accurately located and described. (See 1.6.5.)

4.5.13. 1. NONFLOATING AIDS AND LAND-

MARKS. Data on nonfloating aids to navigation andlandmarks are essential for safe navigation in thecoastal waters of the United States. If geodetic posi-tions are not available, these aids shall be locatedphotogrammetrically or by ground survey methodsmeeting the requirements of Third-order, Class I orbetter accuracy. Where numerous minor day beaconsare subject to frequent changes in position, topo-graphic, field photogrammetric, or hydrographicmethods may be used. [See ''Photogrammetry In-structions No. 64, Requirements and Procedures forCollecting, Processing, and Routing Landmarks andAids to Navigation Data — Photogrammetric Opera-tions'' (National Ocean Survey 1971b).]

HYDROGRAPHIC MANUAL

ative to floating aids to navigation.

Azimuths of all light and day beaconranges maintained by the U.S. Coast Guard fornavigational purposes within the project area mustbe determined. If the ranges were located by pho-togrammetric methods, the hydrographer must ver-ify the azimuth of each by observing one or morevisual fixes with checks observed from a reason-able distance away from the front range — prefera-bly, the effective use of the range. Azimuths ofranges established for use in crossing bars shall bedetermined or verified by visual fixes observed onor outside the bar. 4.5.14. Bridges and Cable Crossings

Locations of bridges, overhead cables, andshore ends of submarine cables shall be deter-mined and shown on field sheets with descriptivenotes.

4.5.15. Verification of Charted FeaturesFloating aids found to be off station byan amount that makes them unsuited to markfeatures intended shall be reported immediately tothe commander of the nearest U.S. Coast GuardDistrict. Recommendations for additional aids tonavigation or for more desirable locations forexisting aids should be reported in writing to theU.S. Coast Guard and to the National Ocean Sur-vey Headquarters through the appropriate MarineCenter. Reports of this nature shall be accompa-nied by a reproduction or tracing of the fieldsheet.

Data transferred to the field sheet (4.2.8)must be compared carefully with the results obtainedduring the new survey. If a transferred sounding isobscured by new soundings, it may be overlookedand not properly investigated. Each charted dangermust be surveyed in detail to either verify it or dis-prove it. If the hydrographer fails to find a reportedshoal or danger at its charted position, the survey ofthe area must be sufficiently complete so that thefeature can be removed from the chart with confi-dence. All indications of shoals in the vicinity mustbe examined meticulously as the positions of re-ported dangers are often in error. Soundings or

Reference shall be made in the DescriptiveReport to reports made to the U.S. Coast Guard rel-

4-42(JANUARY 1, 1979)

Coast Guard 1976), the differences shall be fullyexplained in the report.

4.5.13.2. FLOATING AIDS. Positions anddepths at all floating aids to navigation in the proj-ect area shall be determined during the hydrographicsurvey. If sextants are used, aids may be located bythree-point fixes with check angles. Theodolite inter-section methods (4.4.2.2) are acceptable for locatingfloating aids, but sextant cuts from shore stations arenot. Electronic positioning systems used to locateaids must be calibrated carefully before and after theobservation at the aid — separate and immediate cali-brations are not necessary. If calibrations fail toagree or if unresolvable lane changes occur, the ob-served fix shall be rejected and a new fix observed.Procedures described in section 4.4.3.3 for determin-ing lane count by circling a buoy can be reversed tolocate a buoy. Positions of marker buoys maintainednear aids shall also be determined. Location datesare important and must be noted in the hydrograph-ic records because the aid may have been temporarilyoff station when located and subsequently replacedto its proper station.

4.5.13.3. NONFEDERAL AIDS TO NAVIGA-

TION. Aids to navigation established and maintainedprivately or by State or local governments shall belocated by the hydrographic party. Positions ofsuch aids shall be shown on both the field andsmooth sheets. The status and purpose of these aidsmust be made clear on the sheets and in the De-scriptive Report. The report should state the pur-pose of each unofficial aid, the date of its establish-ment, the agency or person who established it, andwhether the aid is maintained — if these facts canbe ascertained.

Bridge clearance data shown on nauticalcharts and in the Coast Pilots (e.g., National OceanSurvey 1976a) are usually furnished by the U.S.Coast Guard. Overhead cable clearances are provid-ed by the U.S. Army Corps of Engineers. Fieldparties shall measure overhead bridge and cableclearances only where charted values are question-able, definitive information is lacking, or there is newconstruction. When feasible, the nearest U.S. ArmyCorps of Engineers district office should be visitedfor a comparison of charted or field clearances withCorps of Engineers' data. Where National OceanSurvey and Corps of Engineers' values differ, theCorps of Engineers shall decide which value to use.[See section 5.8 of the U.S. Coast and Geodetic Sur-vey (1969a) Coast Pilot Manual. ]

HYDROGRAPHY

charted dangers cannot be removed from charts un-less there is conclusive evidence that the features donot exist.

To merely prove the existence of chartedfeatures is insufficient; positions, least depths oversubmerged features, and elevations of exposed fea-tures must be determined. If the new survey revealsa least depth deeper than the charted depth, the dis-crepancy must be explained in the Descriptive Re-port with a positive recommendation made as towhich depth should be charted and why. (See5.3.4(L).)

It is good practice to run splits (4.3.4) asnecessary for detailed examinations of shoal indica-tions as soon as possible after the indications havebeen discovered. The same vessel and depth-re-cording system used for the basic system of linesshould be used for splits. It is especially importantthat surveys be complete or ''squared off'' at theend of the season.4.6. DISCREPANCIES IN HYDROGRAPHY

Dangers, shoals, and least depths from ade-quate wire-drag surveys in relatively stable bottomareas need not be verified unless required by theproject instructions. In most areas important to navi-gation, obstructions and dangers to navigation mayhave been removed. The hydrographer must consultthe U.S. Army Corps of Engineers and the U.S.Coast Guard to learn which obstructions have beenremoved. In such cases, a new least depth over eachfeature so affected must be determined by hydro-graphic examination. Areas containing rocks andobstructions reported to have been removed byblasting should be checked by bottom sweeping.

4.5.16. Inspection of Field Sheet

After the proposed system of lines has beencompleted in an area and the soundings and depthcurves plotted on the field sheet, the results must bestudied carefully for indications of submerged fea-tures that should be more closely examined. Analogdepth records must be viewed while this study is be-ing made (4.9.8) since side echoes (4.9.8.2) are im-portant indications of shoaler depths. The study ofthe field sheet reveals where additional lines(''splits'') must be run to comply with line-spacing

If discrepancies are consistent at a number ofsuccessive crossings and the horizontal control isstrong and consistent, it is probable that the echosounder is at fault or that the datum of reference is in-correct. Vertical cast comparisons must be made in

4-43 (JUNE 1, 1981)

One of the most difficult problems encoun-tered in hydrographic surveying is finding and lo-cating charted piling. Submerged stubs of brokenpiles are almost impossible to detect by means otherthan bottom sweeping. When there is no visible evi-dence of a charted pile or dolphin, the hydrogra-pher should consult with local agencies such as theU.S. Army Corps of Engineers, the U.S. CoastGuard, or the owner of the waterfront property todetermine whether the piles have been removed.Without conclusive evidence to this effect, the areashould be examined at the lowest tide; it is usuallynecessary to use a small sweep (A.6.1.4) beforemeaningful recommendations can be made.

requirements and to obtain a better delineation ofthe bottom configuration. Critical depths transferredto the field sheet from charts or previous surveysmust be compared with the new survey. (See 4.2.8.)Additional soundings may be required to prove ordisprove the existence of features. Each discrepancymust be positively resolved in the field before thesurvey is completed.

Crosslines are run to disclose systematic andaccidental discrepancies in soundings. (See 1.4.2 and4.3.6.) Discrepancies at crossings must be recognizedas evidence of a fault of the equipment, method, orrecord that requires further study to discover thesource and to indicate the most probable correction.

Allowable differences in depths at crossingsin any area should be based on both the amount ofhorizontal displacement corresponding to the differ-ences in depth and a percentage of the depth. Incomparatively even bottom, differences of 2 to 3 ftmay be excessive because of extreme lateral dis-placement of depth contours. In areas of irregularbottom or on steep slopes, differences of several feetor fathoms may be inconsequential since depth con-tours will not be appreciably affected.

Allowable differences at crossings on thesmooth sheet are specified in section 6.3.4.3. Sinceminor corrections are ignored and predicted tides orwater levels are normally used when correctingsoundings to be shown on the field sheet, greater dif-ferences may be expected. In areas of smooth bot-tom with depths less than 20 fm, discrepanciesshould not exceed 2 ft or 0.4 fm. In areas of irregularbottom and in depths greater than 20 fm, discrepan-cies should not exceed 3% in the lesser depths andshould not exceed 1% (or less) in ocean depths.

4.6.1. Discrepancies at Crossings

HYDROGRAPHIC MANUAL

tests and checks must often be conducted to deter-mine which data set is in error and to detect andeliminate problem sources. Generally, discrepanciesare caused either by errors made in horizontal posi-tioning or by errors made when obtaining or re-ducing depths. The review of potential hydro-grahic error sources in tables 4-7 and 4-8 providesa checklist for the investigation of discrepanciesfound during the progress of the survey. In all in-stances, the field unit must obtain sufficient andconclusive evidence to resolve all discrepancies.

the vicinity of all substandard crossings to supportthe conclusion of any studies of recorded data. Pre-dicted tides or water levels used to reduce sound-ings to the appropriate chart datum must be com-pared with actual data to determine if that is thesource of discrepancy. If constant displacements ofsounding lines would bring the crossings into agree-ment, the calibration and stability of the control sys-tem, should be carefully checked and evaluated. Sur-veys with unresolved discrepancies at line crossingsare incomplete and as such will not be accepted forverification and smooth plotting.

4.7. CHARACTER OF BOTTOM4.6.2. Discrepancies at Junctions and Over-

laps 4.7.1. GeneralWhen inshore hydrography is overlapped

by work done by a larger vessel, soundings at thejunctions sometime fail to agree. Because bar checkscannot be taken from a large vessel, vertical castcomparisons must be made to determine the instru-mental error of the echo sounders. Several compari-sons in overlapping areas are required to providedata for reconciliation of possible discrepancies.The field unit must resolve the discrepancies beforeleaving the area.

The character of the bottom shall be deter-mined for nautical charting, particularly in harbors,designated anchorages, and in all other areas wherevessels may anchor. (See 1.6.3.) In addition to fur-nishing data for selecting anchorages, bottom char-acteristics shown on charts assist fishermen whenselecting areas where fish may be found and toavoid places where equipment may be damaged.

For surveys in uncharted waters, in areaswhere bottom characteristics are subject to fre-quent change, the most effective means of deter-mining the bottom character is to sample at regularfrequent intervals throughout the project area. Ex-tensive bottom sampling is not required if the proj-ect area has been surveyed previously, the charac-teristics have been adequately determined, andthere have been no significant changes in charteddepths nor reason to believe the charted character-istics are incorrect. Sufficient samples, however,must be taken to verify either that no changes haveoccurred or to indicate areas of significant changewhere additional work is necessary to accuratelydescribe the bottom characteristics.

Similar situations may arise where hydrog-raphy accomplished by different vessels joins on in-shore sheets. Where displacements of depth curvesoccur at junctions, errors probably exist in the workof one or both of the vessels. Magnitudes andsources of errors must be established by comparingboth echo sounders with vertical cast soundings.

4.6.3. Other Discrepancies and Sources of

When discrepancies arise, additional field

4-44(JUNE 1, 1981)

Error in Hydrography

Other discrepancies less obvious and moredifficult to explain or detect are frequently found.After the regular system of lines has been complet-ed over a wide area, it may be necessary to run"splits'' (i.e., reduce the line spacing). If soundingson alternate lines differ by 2 or 3 ft in areas of com-paratively flat bottom, the soundings on one systemor on both systems of lines are obviously in error. Inother instances, a vessel may have used differentecho sounders on alternate days — the soundingsobtained with each instrument are consistent withinthemselves but fail to agree with those from the oth-er. Discrepancies of this nature are generallymanifested by improbable and inexplicable shifts oranomalies in depth curves.

Sampling the surface layer is usually ade-quate to define bottom characteristics for charting.Clamshell bottom snappers or similar type grabsamplers are used to obtain as large a sample as pos-sible. (See AL.2.7.) Bottom samples shall be storedindividually in airtight labeled plastic bags recordedon NOAA Form 75-44, "Oceanographic LogSheet-M, Bottom Sediment Data." The forms areself explanatory. Data sheets and sample labels mustinclude the vessel's name, geographic location,depth, date, field description of material, type ofsampler, and pertinent remarks. The bottom sedi-

HYDROGRAPHY

TABLE 4-7.—Hydrographic surveyhorizontal positioning errors

Tidal and water level observationsStation Control1. Incorrect geodetic datum2. Use of unadjusted or incorrect geodetic

positions

3. Long periods of missing data4. Incorrect zoning4. Use of photogrammetric manuscripts that

are incorrect because of bridging errors 5. Incorrect datum determination5. Incorrect identification of photo-hydro

signals

Transducer errors7. Misidentification of control stations1. Incorrectly measured or applied coffee-

tions for draft or settlement and squat8. Excessive use of hydrographic stations to

locate other stations in the survey

Vessel control -visual

4. Unobserved or improperly applied barcheck or vertical cast data2. Geometrically weak fixes

Depth recorder errors

4. Misidentification of signals

Vessel control— electronic

Plotting errors

2. Incorrectly set angles on the manual plot

7. Geometrically weak fixes4. Distortion of the plotting material8. Use of improper operating frequencies

ment samples and original log sheet ''M'' shall bemailed to this address.

CuratorDivision of SedimentologySmithsonian InstitutionWashington, D.C. 20560

One copy of the log sheets with a transmittalletter shall be sent to the Data Control Branch, OA/C353, at NOS Headquarters. Bottom descriptionsshall also be entered into the sounding records.

4-45 (JANUARY 1, 1980)

3. Use of survey methods that fail to meetthe required accuracy criteria

6. Incorrect reduction for eccentric place-ment of electronic control system anten-nas ashore or afloat

9. Incorrectly plotted control

1. Undetected errors in the instrument, ini-tial or index (i.e., when observing theodo-

lite cuts or sextant angles)

3. Sextant tilt not compensated when usingelevated signals

6. Poor coordination of the fix event whenobserving and recording data

7. Angles or directions read or recorded in-correctly

1. Operation of nonalined or poorly adjust-ed positioning systems

2. Improper use of calibration or field checkdata

3. Undetected errors or jumps in distance orlane count

4. Attenuated or reflected signals over por-tions of the survey area

5. Electronic interferences with the position-ing system

6. Failure to correct slant ranges when nec-essary

9. Failure to reduce the electronic center ofthe ship to the transducer location

TABLE 4-8.—Hydrographic surveysounding errors

1. Incorrect predicted or real-time tide orwater levels

2. Improperly accounted time and heightshifts in the records

6. Incorrect gage, staff, and bench mark ele-vation relationship

7. Undetected tide or water level anomaliescaused by meteorological conditions

2. Failure to apply the eccentricity of thetransducer relative to the fix observationpoint

3. Inadequate or erroneous velocity correc-tions

1. Analog systems' phase errors, initial er-rors, incorrect stylus arm or belt length,incorrect stylus or paper speed, fine arcerror, recording paper skew, record misin-terpretation (i.e., presence of side echoes,silt or mud bottom, kelp or other marinegrowth, and strays), improperly ac-counted wave effects (heave), improperlymaintained voltage

2. Digital systems' incorrect threshold re-ceiving frequency, incorrect calibration(feet or fathoms), scaling errors caused bynot allowing for differences between thedigital and analog trace, improperlyaccounted heave.

1. Protractor not in adjustment or improp-erly used.

3. Automated plotter malfunction or im-proper alinement during the sheet regis-tration

Frequencies of bottom samples in variousdepths of water are specified in section 1.6.3. If a moredetailed study of the ocean floor is contemplated, bot-tom samples are usually obtained by coring or bydredging. In such cases, the project instructions willspecify sampling density and the type of sampler touse. Core samples are preserved intact in the sleeve ofthe corer or are carefully extruded into a suitable con-tainer for later analysis. Dredging samples must bepreserved in sturdy containers. All samples shall becarefully labeled and cross-referenced to detailed re-

5. Sextant angle observers not standing closeenough to each other or improperly locat-ed relative to the antenna and transducer

HYDROGRAPHIC MANUAL

cords on the place and time of sampling. Proceduresfor coring or dredging sample disposal will be in-cluded in the project instructions.

TABLE 4-9. — Sediments classified by size

TermType Grain diameter

Clay (mm)0.02-0.1Mud4.7.2. Classification of Bottom Materials

Silt

0.1-0.3Fine0.3-0.5MediumSand

Coarse 0.5-1.0

Fine 1-2MediumGravel 2-4

4-6Coarse

Fine 6-1010-20MediumPebbles20-50Coarse

50-250Stones> 250

tween tongue and cheek, it may properly be classifiedas silt. Clay is a finer grained deposit than silt andnormally feels smooth and sticky to the touch. An-other simple way to detect very fine sand is to putabout a fourth of a teaspoonful of the sample into alarge test tube, add water, and shake well. If withinless than a minute a portion of the sediment settlesout, sand is present. Ooze is not soft mud, as com-monly interpreted, but is a pelagic sediment contain-ing more than 30% organic material and is foundonly in the greater ocean depths off the ContinentalShelf on the abyssal plains.

4.7.3. Description of Bottom Materials

Colors of specimens should always be notedwhile still wet. Some sediments change in colorwhen dry. The terms ''dark'' and ''light'' should

If the material feels gritty when rubbed be-tween the fingers, between finger and cheek, or be-

4-46(JANUARY 1, 1980)

A complete description of a bottom sampleconsists of: one or more adjectives describing size orconsistency; one or more adjectives designating col-or; and one or more nouns naming the class of bot-tom material.

Descriptions should follow standard classifi-cations listed in table B-5 in appendix B. If moredetailed classifications are required by the project in-structions, use the standard abbreviations shown inpart S of Chart No. 1, United States of America Nau-tical Chart Symbols and Abbreviations (NationalOcean Survey and Hydrographic Center 1975). Whennecessary, descriptive terms not included should bewritten in full. Descriptions shall be arranged in thisorder, size or consistency, color, and noun. Bottomcharacteristics are shown on field sheets in black inkslightly below and to the right of the position dot.

In most cases, a precise classification of bot-tom materials requires a laboratory analysis; howev-er, this is impractical for hydrographic surveys and isnot a charting requirement. Careful inspection of asample by sight and touch should enable the hydro-grapher to provide a reasonably accurate descriptionof the material.

Close to shore and on the ContinentalShelf, bottoms generally consist of sands, gravels,muds, and the remains of plant and animal life.Ledge rock may be exposed in a few areas close toshore where slopes are steep. Sediments are typedaccording to the size of their particles. Table 4-9 isa general guide for classification of the sands andcoarser particles. It is not intended that the dimen-sions be measured. A careful estimation by eye issatisfactory.

Sediments larger than sand are easy to rec-ognize and simple to classify by size. Generally, sandis recognizable as even the finer grained sands feelgritty when rubbed between a finger and the palm ofthe hand. When dry, sand separates into grains visi-ble to the naked eye.

Technically, there are two classes of materialfiner than sand. These are silt and clay. For practicalpurposes, silt and clay are classified under the gener-al term, mud.

Natures of bottom materials are indicated byadjectives such as broken, sticky, hard — or by sizesuch as coarse, medium, or fine. Consistencies of bot-toms determined by feeling with a lead line or sound-ing pole (without a visual examination of the materi-al) should usually be described as ''hard'' or ''soft.''The term ''rocky'' may be used only when it isknown positively that the bottom is bedrock or con-sists of material larger than gravel, although a speci-men was not obtained for examination. "Rock" isused only when solid rock or a rock ledge is visibleto the hydrographer.

The return of an empty sampler is not suffi-cient reason to label the bottom as "hard" or as"silt". If repeated tries for a grab sample fail, the sta-tion should be labeled "no sample" unless additionalknowledge is available to the hydrographer.

Boulders

HYDROGRAPHY

To aid in sample analyses more detailedthan usually required for nautical charting purposes,one may obtain sand grain size charts and colorcharts from this company.

4.8.3. Manually Recorded Survey Data

Geophysical Instruments and Supply Co.900 BroadwayDenver, Colorado 80203

4.8. HYDROGRAPHIC RECORDS4.8. 1. General

-

Although automated data acquisition sys-tems are used for the majority of NOS hydrographicsurveys (4.8.4), it is essential that hydrographers bethoroughly familiar with basic manual data-recording techniques for these reasons:

The records must be sufficiently complete topermit the survey to be plotted accurately and thor-oughly at any future date. Explanatory and supple-mental notes shall be inserted as necessary in thefield records to make the information complete.Modem survey techniques are complex, and the re-cords must by necessity be accompanied and sup-ported by a host of associated data and reports con-taining information that cannot be shown properlyin the records or on the hydrographic sheets. (Seechapter 5.)

Information entered in the Sounding Vol-ume shall be as complete and self explanatory aspossible; it should be possible to reconstruct the sur-vey and replot all hydrographic data at any futuredate using only the information in the volume andon the graphic depth record. (Some items such asledge symbols, however, may be outlined on thefield sheet and plotted on the smooth sheet by directtransfer.)

4.8.2. Use of Abbreviations

The large volume of recorded and annotatedfield data makes it logical and convenient to abbre-viate and symbolize many of the terms and expres-sions used repeatedly. For emphasis and ease of ban-dling, these are tabulated in appendixes B and E.Those not tabulated but used during the survey

Data observed by each survey vessel shallbe recorded chronologically in a separate series ofvolumes and listings for each hydrographic sheet.Hydrographic data that will be plotted on two or

4-47 (JULY 4, 1976)

never be used alone; these terms are intended for usein qualifying the intensity of color.

Clear and comprehensive field records andreports are essential for an adequate successful hy-drographic survey. Incomplete, unintelligible, orcarelessly maintained records can seriously impairthe value and validity of the data to the point ofrendering a survey worthless. Satisfactory recordsare the direct reward of constant good judgment,attention, and care.

The chief of party shall ensure proper main-tenance, arrangement, and security of hydrographicrecords, that all necessary records and reports aresubmitted at the proper time, and that hydrographicdata are appropriately cross-referenced for ease ofuse and complete understanding. AD records andreports pertaining to one hydrographic sheet, andone only, shall be identified by the sheet registrynumber. (See 2.4.3.2.) Records and reports submit-ted on a seasonal or project basis should make refer-ence to the registry numbers of all surveys to whichthey apply.

must be defined at the beginning of the soundingrecords.

4.8.3.1. GENERAL NOAA Form 77-44,''Soundings,'' is the basic, permanently archived re-cord book for all nonautomated hydrographic sur-veys. These Sounding Volumes are the official recordof positional data and of special soundings measuredby divers, lead line, and sounding pole. Final inter-preted and scaled depths entered in the volumescombined with the graphic depth records comprisethe official record of echo soundings. Sounding Vol-es must also be used during automated surveys torecord supplemental descriptive information onsounding lines, detached positions, speed and coursechanges, and to enter notes on the passing of fea-tures, shoreline changes, and many other items thatcannot be conveniently recorded elsewhere.

Automated systems are merely extensionsof the manual recording system. The same basicprinciples apply as to the required volume, type, anddetail of field data although the records differ in for-mat.

Many surveys accomplished from smallboats, skiffs, and other nonautomated vessels requiremanual record keeping although the data will belogged for machine plotting at a later date.

Should an automated systems failure oc-cur during the course of a survey, hydrographersmust be capable of quickly reverting to manual re-cording methods.

HYDROGRAPHIC MANUAL

4.8.3.2. PAGE HEADINGS. Appropriate en-tries are made in full at the top of the first andlast record page of a day's work. If the work is di-vided between two volumes, the entries must also bemade on the last page of the first volume and firstpage of the second volume. The locality, sublocality,Julian date, name, and identification number of thesounding vessel can be entered using rubber stamps.Entries should be made on all pages if it will notinterfere with the recording of more important data.Julian dates are entered at the top of each page ofthe Sounding Volume in the identification color ofthe vessel.

4.8.3.3. INFORMATION AT BEGINNING OF

DAY'S WORK. Certain information about personnel,instruments and their adjustments, weather condi-tions, and other pertinent facts important for com-plete records of the survey shall be entered at thebeginning of each day's work.

When survey personnel are standing watchesor are otherwise rotated at regular intervals, recordthe changes using stamp 2A or 2B. When relief istemporary or is limited to less than three membersof the survey team, the fact may be recorded in theremarks column of the Sounding Volume.

Recorded data must never be erased. Cor-rections are made by crossing out erroneous entriesand making corrections above or to one side; how-ever, this prohibition does not apply to soundingsscaled from the analog depth records if congestionor ambiguity would result from using this rule.Entries rejected for any reason are indicated by an

4.8.3.4. ELECTRONIC CONTROL INFORMA-TION. The information on electronic positioning con-trol systems used is entered on stamp 3 (figure 4-27)at the beginning of each day's work and at all othertimes changes are made. These data shall include:

4-48(JULY 4, 1976)

more separate hydrographic sheets shall not be re-corded in one volume. Sounding Volumes shall benumbered consecutively as the survey progresses. Ifmore than one vessel surveys an area covered by asingle smooth sheet, a temporary series of numbersis assigned to each unit that will use more than onevolume. When the survey is completed, the recordsof each unit are grouped in proper order, the variousgroups combined, and the complete set of recordsfor the survey area numbered consecutively and per-manently. Information required on the cover label ofeach volume shall be entered in black ink.

Recorded data must be completely legible.Drafting style lettering is not required nor is it nec-essary to make entries in print; it is essential thatevery numeral, abbreviation, and word be unmistak-able. Data must be recorded systematically and, in-sofar as possible, in the form prescribed in this man-ual.

While in use, Sounding Volumes should beprotected by a suitable temporary cover. This is es-pecially important during launch hydrography whenspray, rain, or other conditions could cause damageto the records.

Sounding records are essentially time re-cords of recurring series of acts and events, with re-lated observations occasionally interspersed. Re-corded data must clearly show the relationshipbetween these events and times of occurrence. Gen-erally, each entry appears on the same horizontalline with its respective time. Occasionally, miscella-neous notes must be made at other places, then re-ferred to their corresponding times by distinctivereference notes. Several examples of manually re-corded hydrography are shown in figures 4-22through 4-25. Although space should not be wasted,recorded data should not be crowded. Soundings atirregular intervals must frequently be scaled fromanalog depth records to protray the bottom configu-ration properly. When surveying in areas of irregularbottom, soundings at regular intervals are recordedon alternate lines of the record book; when the bot-tom is smooth and evenly sloped, a sounding maybe recorded on each line.

"R'' written boldly over the entry. Soundings notplotted are indicated by the letters ''NP.''

Rubber stamps are used to record nearly allof the information required at the beginning, during,and at the end of the day's work. Header tapes canbe used instead of stamps to include the necessaryinformation on automated data listings. (See 4.8.4.)

When hydrography is controlled visually,names of key personnel and serial numbers of instru-ments used shall be recorded in the appropriatespaces of stamp 2A, ''Personnel.'' (See figure 4-26.)Instrument adjustments shall be verified and the factnoted after the number of each instrument. Stamp2A can be modified slightly for use during theodo-lite intersection surveys. If hydrography is controlledelectronically, use stamp 2B and make entries in allappropriate spaces. Punched paper tapes can be pre-pared for machine printing of these data on auto-mated survey data listings instead of using a rubberstamp. (See 4.8.4.)

FIGURE 4-22.- Manually recorded survey (NOAA From 77-44, "Sounding") using visual sextant control and showing theapplication of rules for entering corrections and remarks

HYDROGRAPHY

(JULY 4, 1976)4-49

HYDROGRAPHIC MANUAL

FIGURE 4-23.- Record of hydrography controlled by sextant fixes and Raydist

Method of data acquisition (i.e. manual range, range-azimuth, hyperbolic-visual).Name of control system.

System operating frequency.

or automatic recording).

Mode of control (such as visual, range-

JULY 4, 1976 4-50

HYDROGRAPHIC MANUAL

FIGURE 4-24.- Recorded hydrographic-visual controlled hydrography (one hyperbolic lane value and one sextant angle). Sound-ings and hyperbolic lane values recorded automatically through a digital control unit.

Names and number of shore stations.Modification may be made to stamp 3 to

fit the control system used.4.8.3.5. SOUNDING EQUIPMENT. Names and

4-51 (JULY 4,1976)

serial numbers of sounding equipment used shall beentered using stamp 4 (figure 4-28) at the beginningof the day. Equivalent information may be machineprinted on automated survey data listings. (See

HYDROGRAPHIC MANUAL

FIGURE 4-25 —Record of positions observed by the theodolite intersection method

Depth Recorder (A.6)] is used, the fact is noted im-mediately below the stamp or machine printed data.

4.8.4.) If shoal and deep-water echo sounders areused at various times during the day, each instru-ment must be identified. The source of the sound-ings must be shown in the records—times of instru-ment changes, malfunctions, component changes,and similar occurrences must be noted. If supple-mental depth recording equipment [e.g., Precision

Phase corrections and frequency checksmust also be entered. Frequency should be checkedweekly by comparing an actual count of stylus revo-lutions with the manufacturer's specifications or byusing an accurate frequency meter that is not part of

4-52(JULY 4, 1976)

HYDROGRAPHY

cording bar checks are found in section 4.9.5—asuggested alternate form for recording these dataduring automated surveys is also shown.

Comparisons between simultaneous verticalcasts and echo soundings are recorded on stamp5A. (See figure 4-30.) The lead-line number mustbe entered so the proper correction (from the com-parison of the lead line with a standard) can bemade to the vertical cast measurement.

FIGURE 4-26—Rubber stamps 2A and 2B, personnel stamps usedat the beginning of the day

When lead-line soundings are recorded, thenumber of the lead-line shall be entered either be-low the stamp or in the remarks column. A refer-ence shall be made to the volume and page wherelead-line graduation comparisons are recorded.

Deviations of the initial from the standardvalue observed during comparisons shall be notedand the observed data adjusted accordingly. The

4.8.3.6. COMPARISON OF SOUNDING EQUIP-

MENT. When graduations on lead lines or on barcheck lines are compared with a standard, the re-sults should be recorded on stamp 5. (See figure 4-29.) Calibrated steel tapes or marked distances areused to compare graduated lines for an accuracycheck. Stamp 5 is also used to enter echo soundercalibration data obtained by bar check. (SeeAF.1.3.) Detailed instructions for observing and re-

FIGURE 4-27. - Rubber stamp 3, electronic control information FIGURE 4-29. - Rubber stamp 5, a record of a bar check

4-53 (JUNE 1, 1981)

the recorder. Dial or vibrating reed types of metersbuilt in the recorders may be used to check frequen-cies throughout the day after the weekly indepen-dent check is made.

FIGURE 4-28. - Rubber stamp 4, a record of soundingequipment

Standardizations and comparisons recordedin a Sounding Volume must be indexed in the frontof the book for easy reference.

HYDROGRAPHIC MANUAL

Greenwich Mean Time (GMT) shall beused for hydrographic recording and the fact notedat the head of the time column at the beginning ofeach day's work. Time is recorded on a 24-hr basisfrom 0 (midnight) to 23 (11 p.m.). Times are record-ed in the ''Time'' column with corresponding datato which they refer entered on the same horizontalline. The time of each position, each regular intervalsounding, and each entry that will be used whenplotting data must be recorded. Depths over peaksand deeps occurring between regular intervalsoundings are also recorded in GMT.

FIGURE 4-30.— Rubber stamp 5A, a record of a simultaneouscomparison of an echo sounder

draft of the transducer at the time of comparisonmust be entered.

4.8.3.7. WEATHER AND SEA CONDITIONS.

These conditions shall be entered on stamp 6 (figure4-31) at the beginning and end of the workday andat other such times that significant changes occur.The ''weather'' entry is a general description of theprevailing conditions. ''Wind'' is recorded in termsof the direction from which it is blowing combinedwith an estimate of the force in knots. ''Sea'' state isrecorded as the average estimated height (in feet) ofthe waves or chop. If the survey continues on a24-hr basis, the weather, wind, and sea conditionsare entered in the records when each watch begins.

4.8.3.8. COLUMN ENTRIES. Figures 4-25through 4-27 illustrate manually recorded data for ahydrographic survey. Sounding Volume pages areruled in headed columns. Entries must be made inthe correct columns and should not encroach on ad-jacent columns. All data related to a specific timeentry should appear on the same horizontal line toavoid confusion—if more than one line is required,only the first entry is placed on that line. Miscella-neous entries in the remarks column may be referredto their respective times of occurrence by using cor-responding reference marks. Asterisks or similaridentifiers are used for this purpose.

Changes in sounding units must be clearlyindicated. Because only one unit is used on one hy-drographic sheet, it is more convenient to recordsoundings in the unit to be used in plotting —changes from one unit to another during soundingshould be held to the minimum consistent with theaccuracy required. (See 4.5.7.2.)

FIGURE 4-31— Rubber stamp 6, a record of weather throughoutthe day

4-54(JUNE 1, 1981)

Positions shall be numbered consecutivelyfor each hydrographic sheet in accordance with4.4.6; they are entered in the columns headed ''Posi-tion Number'' (on both left- and right-hand pagesand on the same line as the time of observation).Other entries are not made in these columns.

All times shall be recorded using a carefullyregulated clock (AL.3) or an electric clock operat-ing on a constant frequency circuit. Echo soundersoperate at constant speeds but will not measureelapsed time accurately; they shall not be used forthis purpose. Clocks must be set to the correct timeat the beginning of the day and shall be comparedwith a reliable standard at the end of the day. Gainsor losses of time shall be recorded.

Soundings shall be entered in the doublecolumn headed ''Soundings.'' If the bottom is gener-ally even and few soundings need be recorded atodd intervals, a sounding may be entered on eachline except on the line following a position. Wherethe bottom is irregular and many extra soundingsmust be scaled from the analog depth record, thesoundings at regular intervals are entered on alter-nate lines.

Soundings shall be entered in whole unitsand decimals of fathoms or of feet in accordancewith table 4-4. (See 4.5.6.) Soundings shall not beentered in mixed units of fathoms and feet (i.e., 6 fm4 ft; fractions are not used). The depth unit is indi-cated by striking out the inapplicable subheading atthe top of the double column.

HYDROGRAPHY

When soundings are obtained simultaneous-ly by two instruments, the source of each soundingmust be shown. For example, if most depths aremeasured using an echo sounder but several lead-line soundings are interspersed, each lead-linesounding is identified by the letters ''LL.'' Similar-ly, pole soundings shall be identified by the abbre-viation ''PS.'' Depths measured by lead line or polemust not be recorded unless they are true verticalmeasurements of depth.

Bottom characteristics are entered in thefirst column on the right-hand page using the ab-breviations listed in table B-5 in appendix B. Everydetermination of the character of the bottom mustbe accompanied by position data.

The heading of the vessel must always beentered. Indicate in the space at the top of the firstcolumn on the right-hand page whether a steering(psc), standard magnetic (pmc), or gyro (pgc) com-pass was used. Course changes are entered on linescorresponding to the time the change was made.Courses are recorded in degrees (clockwise fromnorth).

Several spaces should be left between posi-tions for the entry of calibration data and other cor-rections to electronic positional data. If sextant fixes,theodolite cuts, or bearings are observed at an elec-tronic position, the visual data are recorded in theremarks column and referenced to the position num-ber.

Numerical designations of the stations usedfor sextant three-point fixes are recorded vertically,in the left part of the column. Recorded numbersof signals must agree with those shown on the fieldsheet. Objects are always recorded in a clockwisedirection, that is, left object first, center objectnext, and right object last. (See figure 4-22.) Ob-served angles are recorded in the right part of thecolumn-left and right angles are recorded oppo-site the numbers of the left and right objects, re-spectively. Station numbers need not be repeatedwhen the same signals are used for successive fixes.The word ''same'' or a large letter ''S'' that coversthe three spaces usually occupied by fix data maybe used to indicate repetitions on the same page;however, signal numbers must be recorded at thetop of each new page. All station numbers must beentered if any signal in the fix is changed.

4.8.3.10. REMARKS COLUMN. Additional in-formation is entered in the remarks column as nec-essary for a thorough understanding and correctprocessing and plotting of the survey. Abbrevia-tions (appendixes B and E) may be used for manyentries. The sequence of recording may beinterrupted to enter long notes across the entirewidth of a page. As a rule, all notes should be en-tered at the time the event described occurred. Thehydrographer should place his initials under explan-atory notes entered in the record.

A great number of miscellaneous entries arerequired: these are too numerous to be discussed in-

4-55 (JUNE 1, 1981)

Electronic positioning systems normally dis-play positional data either on two dials or by twodigital counters. Readings from these types of dis-plays should be read and recorded from left to rightor from top to bottom and the values related cor-rectly to the shore stations. Rubber stamps can beused to enter headings or repetitious electronic posi-tional data in the sounding record. Electronic dataare more conveniently recorded in double columns,each column headed by the station(s) designation.Both distances or line values comprising a fix are re-corded on the same line (figure 4—23) as read fromleft to right or top to bottom from the display.

4.8.3.9. POSITION DATA. If practical, allpositional data are to be entered on the right-handpage of the Sounding Volume in the column head-ed ''Position Control Data." The first entry for po-sitional data must be on the same horizontal line asthe corresponding time on the left-hand page-theremainder of positional data is entered on follow-ing consecutive lines.

Supplemental angles, cuts, or check anglesare entered in the same column and on the nextline below the fix data. Signal numbers are enteredon the same line. The number of the left object isalways recorded first. Detached positions are fre-quently recorded without a sounding (e.g., whenlocating rocks or signals). All such positions areassigned numbers and are recorded in the samemanner as prescribed for hydrography.

Theodolite intersection location data arerecorded in the position control data column. (Seefigure 4-25.) The listing of the station numbersmust be in the same order in which observed direc-tions are radioed to the hydrographer for plotting.Once established, the order need rarely be changeduntil a theodolite is moved to a new station.

HYDROGRAPHIC MANUAL

dividually, but the following entries illustrate thevariety of information that should be recorded:

FIGURE 4-32.—Rubber stamp 7, the position of a

line beginning Statistics for each day's work are entered at

4-56(JUNE 1, 1981)

1. Latitudes and longitudes shall be notedfor the beginning of the first line of the day's work,for each detached position, and for beginnings oflines in different localities. Rubber stamp 7 (figure4-32) may be used. Scaled distances and directionsfrom nearby signals may be used instead of latitudesand longitudes.

2. The abbreviation LTLA (line turns leftabout) or LTRA (line turns right about) is enteredwhen the line turns 180° to the left or right and re-verses direction to begin a new line — LR (line re-sumes) is entered for the first position of the newline.

3. Note changes affecting information re-corded at the beginning of the day's work (e.g., per-sonnel, instruments, and weather).

4. Note the times, distances (in meters),and directions when passing important featuresnearby (e.g., aids to navigation, rocks, breakers, andkelp). Indicate whether the distance is estimated,whether the object has been previously located, orwhether the data recorded are to be used to locatethe feature.

5. Note estimated distances to the shore-line, low water line, and reef lines from the nearestrecorded position.

6. Record significant changes in speed ofthe sounding vessel. Note each sounding line startedfrom a standstill and the time that normal soundingspeed was reached. (See 4.5. 1.)

7. Indicate the scale or phase being usedon the analog depth recorder and all changes there-to. When shoal and deep water echo sounders areused alternately, each change shall be recorded.

8. Enter notes concerning the correct op-eration of the echo sounder or other electronicequipment. Various checks are required periodicallyto ensure proper operation and accuracy; the factthat these checks were made must be noted. Adjust-

ments to the stylus length of the analog depth re-corder must be entered.

9. Pertinent information received fromelectronic shore stations must be recorded and ref-erenced to time (e.g., time comparisons, changes inequipment, electronic adjustments, and repairs thatmay affect the results of the survey).

10. Enter measurements or estimates ofheights of exposed rocks and estimated depths oversubmerged features on which soundings cannot bemeasured safely. Be sure to include the time of ob-servation so that a subsequent reduction to thesounding datum can be made. (See 1.6.2.)

11. Record complete and comprehensivenotes regarding the examination of shoals includingthe method of search used, a statement as to wheth-er the bottom was visible, type of bottom, presenceof kelp or grass, least depths found, and any otherinformation that will help the verifier to ascertainwhether the investigation is adequate.

12. Each feature marked in the presurveyreview must be examined and the results noted as inentry 11. Items are identified by number or by lati-tude and longitude. Notes shall include statementsas to the amount of time spent in making the investi-gation. Specific recommendations to delete or retainfeatures on charts shall be made and be accompa-nied by the reasons for the recommendations. (See2.3.3.)

13. The beginning and end of charted fea-ture investigations shall be noted, and the featurespecifically identified.

14. Note local tidal anomalies that varysignificantly from the conditions at established tidestations to assist in zoning the tidal reducers.

4.8.3.11. INFORMATION AT END OF DAY'S

WORK. Certain entries are required to complete therecords at the end of the day's work. These entriescan be made using rubber stamps for hand-recordedsurveys or by using machine listings of the stampsfor automated surveys. (See 4.8.4.) Bar check orvertical cast data required at the end of the day maybe entered in stamp 5 (figure 4-29). Correct adjust-ment of sextants, theodolites, and clocks must beverified at the end of the day-these facts are en-tered in stamp 8 (figure 4-33.) The Officer inCharge or the Chief of Party shall certify this verifi-cation by entering initials or a signature in the ap-propriate spaces on the stamp.

HYDROGRAPHY

FIGURE 4.33. —Rubber stamp 8, verification of sextants andsounding clock

fied and grouped in a rational manner. Both fieldand registry numbers (2.4.3) are entered wherever thehydrographic sheet number is required. Rubberstamps may be used for most of the necessaryentries.

Rubber stamp 10, ''Processing'' (figure 4-35), is used as a checklist to ensure orderly and com-plete data processing. All applicable data must beentered. Space must be left at the end of each day'swork for this stamp or a machine listing.

4.8.3.12. COMPLETION OF SOUNDING RE-CORDS. Following completion of required field pro-cessing and prior to submission of the survey for ver-ification and smooth plotting, the records for eachhydrographic sheet must be indexed, cross-refer-enced, and arranged in a logical orderly manner.Procedures for correction of soundings and reductionto the appropriate datum are described in section4.9.

All records are grouped in the proper order,the various groups combined, and the complete setnumbered consecutively and permanently. Chrono-logical ordering of daily sounding records in accordi-on-type files is recommended. The hydrographershall examine each data tape, data listing, abstract,Sounding Volume, analog record, and all other sur-vey records to ensure that each is properly identifiedand explicit. Field records and computations not partof the daily sounding records must be so identi-

For automated survey data, a single index ofthe events and items listed shall be prepared and in-serted in the volume(s) accompanying the survey.References are made to the Julian date and the posi-tion number or time of the event.

4.8.4. Automated Survey Records

Most NOS hydrographic surveys are con-ducted and processed using the HYDROPLOT DataAcquisition and Processing System. (See A.7.) Thesystem is thoroughly documented in NOS Technical

Rubber stamp 9, statistics for aFIGURE 4-34. -day's work

4-57 (JANUARY 1, 1979)

the end of the day's records using stamp 9 (figure 4-34) or by using an equivalent machine listing. If aday's work is recorded in more than one SoundingVolume, the stamp is used in each volume and thestatistics for that volume entered. The totals are en-tered at the end of the day's work.

On surveys recorded by hand, the entries onthe cover labels of the Sounding Volume shall befilled in using black ink. If any ship hydrographywas run using a magnetic steering compass, a copyof the deviation table is entered on page 1 of the firstvolume of each set of records. Deviation tables arenot required for launch or small boat hydrography.Location data contained in the Sounding Volumesfor objects such as signals, rocks, landmarks, andaids to navigation shall be indexed on page 2 of thevolumes. These entries are repeated in volume 1 ofthe record set with a reference to the appropriatevolume number. References to data concerning a pre-survey review item (2.3.3) shall include the itemnumber. Calibration data for electronic control sys-tems and for echo sounders (including bar checks,vertical cast and phase comparisons, or referencesthereto) must also be indexed on page 2 of the ap-propriate volume. Other significant events or activi-ties not listed shall also be indexed.

FIGURE 4-35 .— Rubber stamp 10, a processing checklist

HYDROGRAPHIC MANUAL

copy of the listing must accompany the records ofeach. The survey data containing the tape is refer-enced under ''REMARKS."

It is frequently difficult to annotate neatlyand adequately the hard copy produced by theelectric typing devices that are connected to the au-tomated systems. Descriptive notes and information(4.8.3.10) are essential and necessary for under-standing and processing the survey. Such informa-tion that cannot be recorded accurately and com-pletely in the data tapes or on the data listingsshall be entered in NOAA Form 77-44, ''Sound-ings,'' and be referenced by time, position number,or both.

The PROCESSING /STATISTICS blockshould not be modified. The ''SQ MI'' (square nauti-cal miles of hydrography) entry is provided for usewhen tabulating statistics for Monthly Ship Accom-plishment Reports and Descriptive Reports. Thechief of party shall sign on the last line after he hasexamined the records and is satisfied that the dataare complete.The records stamps described in section

4.8.3 are often inadequate or superfluous for auto-mated survey data. For this reason and to standard-ize automated records identification, the stamps havebeen modified and the contents arranged in a formatsuitable for machine listing. The stamps are availablefrom the Marine Centers on mylar tapes in eitherASCII or BCD form. Nonchanging entries can beadded to the tapes for automatic listing (e.g., projectnumber, vessel, and year).

4.8.4.1. DATA IDENTIFICATION. All data list-ings (such as soundings, hourly heights, and velocitycorrections) shall be preceded by the DATA IDEN-TIFICATION block (figure 4-36). Every applicableentry must be made. A tape identification stamp isto be impressed on each paper tape. The ''TAPE#" entries on the DATA IDENTIFICATIONblock and on the tape identification stamp must bethe same. Identification numbers or codes are desig-nated in a logical sequential manner by the hydrog-rapher. Each tape and data listing transmitted withthe survey records is identified on the transmittal bythis number. If a tape or a listing applies to morethan one survey (e.g., tidal hourly heights), a

4.8.5. Depth Records

4.8.5.1. GRAPHIC DEPTH RECORDS. Graphicor analog records of bottom profiles produced byecho sounders are the official field records of sound-ings for manually recorded surveys and are usedto supplement the generally more accurate digi-

4-58(JANUARY 1, 1979)

Manual No. 2, ''HYDROPLOT/HYDROLOG Sys-tems Manual'' (Wallace 1971), and need not be dis-cussed in detail here.

The HYDROPLOT system acquires, pro-cesses, and plots sounding data automatically on areal-time basis. HYDROPLOT also permits the sur-vey to be plotted later using corrected and adjusteddata. Although a highly sophisticated automaticdata acquisition and processing system, the final re-sults are similar to those had the survey been re-corded and plotted by hand. HYDROPLOT pro-duces an accurate machine drawing of most of thedata required for NOS hydrographic surveys andprovides time, position, and depth records onpunched paper tape and on hard copy.

4.8.4.2. SURVEY INFORMATION, PROCESS-ING/STATISTICS, AND PERSONNEL/WEATHERBLOCKS. These blocks (figure 4-37) shall be listedafter the DATA IDENTIFICATION block on alloriginal sounding record printouts. Position andsounding data listings logged from SoundingVolumes require only the DATA IDENTIFICA-TION and SURVEY INFORMATION blocks pro-vided that the proper personnel, weather, statistics,and processing data have been entered in thevolumes.

Nonessential information should be deletedfrom the SURVEY INFORMATION and PER-SONNEL/WEATHER blocks as necessary, and ad-ditional information, such as instrument serial num-bers, entered to improve documentation.

4.8.4.3. OTHER DATA. When the data blocksare inadequate, inappropriate, or for other reasonscannot be used, they must be modified or the stampsdescribed in section 4.8.3 used. Additional informa-tion the hydrographer believes necessary to recordshall be entered by hand.

Stamp 7 (latitude and longitude, figure 4-32) shall be used for all detached positions if neces-sary to provide a reference to the position. Stamps5 and 5A, ''BAR CHECK'' and "SIMULTA-NEOUS COMPARISON'' (figures 4-29 and 4-30),may be entered on the listings (figure 4-38) or in asupplemental Sounding Volume as appropriate. Analternate method of recording bar checks and simul-taneous comparisons is discussed in section4.9.5.1.1.

HYDROGRAPHY

DATA IDENTIFICATION =======================

OPR 424 YR 70 TIME MERIDIAN GMT

REGISTRY NO(S) 9157, 9182, 9184

FIELD NO(S) MA 10-1, 2, 3 -70 TAPE # T2

TYPE OF DATA Tidal hourly heights (Tamgas Station)

SOUNDING VESSEL N/A

JULIAN DAY N/A FROM POS # TO POS #

(Tap

e nu

mbe

rs m

ust m

atch

)

Days 158 - 262

REMARKS: Type with Survey 9184

SHEET 9157,9182,9184 YR 70 DAY 158-262 VESSEL— TAPE # T2

TO#FM#

Teletypewriter printout of a data identification block (upper), for listing tidal hourly heights, and tape identification

stamp (lower)

FIGURE 4-36. -

tom profiles and other recorded hydrographic fielddata. Stamp 11, ''GRAPHIC RECORD'' (figure 4-39), shall be impressed at each end of each analogThere must be no ambiguity between bot-

TABLE 4-10.— Definitions of terms used in figure 4-3 7

Term Definition

4-59 (JANUARY 1, 1979)

tal depth listings. These analog records are frequent-ly referred to as fathograms or echograms.

←

↓

DATA Tidal Hourly Heights (Tamgas Sta)

ManualOn timeHYPR1(Sl)R2(S2)S/NSght <CorSea

Data logged by hand from Sounding VolumesData logged by hand as acquiredData recorded automatically by the HYDROPLOT systemControl station number for the slave number 1 antennaControl station number for the slave number 2 antennaSerial numberSighting angle for the hybrid control system. (See figure 4-20, angle a.)Enter sextant index correction.Enter average wave height in feet.

— —

HYDROGRAPHIC MANUAL

SURVEY INFORMATION ==========================

ACQUISITION: MANUAL ON TIME

CONTROL: VIS R/R

POSITIONING SYSTEM

FREQUENCY 1799.6

MASTER LOCATION 143

R1(S1) LOCATION 117

R2(S2) LOCATION 162

PROCESSING/STATISTICS =============

JULIAN DAY 179 VESSEL 2200

POSITIONS 208 N MI SNDG 49 SQMI 6.2

DATA INSPECTED AND COMPLETE: D.V.Dewitt Comdg

PERSONNEL/WEATHER =================

IN CHARGE J M Smith

PLOTTER •••••••••••••••••••••••••• OR (√) COMPLOT

FATHOMETER Ross S/N 362

RECORDER N D Nedbal

SGHT < na SEXT # — COR —

WEATHER CONDITION P/C VISIBILITY 8 nmi

SEA 2 FT WIND: SPD 10 DIR NE

FIGURE 4-37. Teletypewriter printout of survey information, processing/ statistics, and personnel/ weather

blocks for a day's survey work. See also table 4-10.-

4-60(JANUARY 1, 1979)

LEFT < na SEXT # — COR —

RGHT < na SEXT # — COR —

Hi Fix

HYP

HYP HYLG

HYDROGRAPHY

LEAD LINE COMPARISON

ANALOG DEPTH LEAD LINE DEPTH

17.3 ft 20. 6

@ 1 nmi N of BEAVER Point

LATITUDE 45-23.7 LONGITUDE 74-13.2

SEA Calm WIND SE 5 kt

draft 3.6QUALITY: FAIR POOR

ANALOG DEPTH GAINBAR DEPTH

ft 32.2 ft 6

8.3 12

1814.4

1814.2

8.3 12

2.3 6

FIGURE 4-38.— Lead -line comparison and bar check machine listings. Other data normally

required are found in figure 4-37.

Each echo sounder is provided with a fix

To properly relate the graphic depth recordto the other records, the operator shall make notesto indicate where lines begin, turn, end, or break,using the standard abbreviations listed in appendixesB and E. In addition, notes are added regarding in-terpretation, wrecks, and marine growth; entries aremade to identify all actions taken. The time of day

FIGURE 4-39.— Rubber stamp 11, a graphic record foridentifying bottom profiles

4-61 (JULY 4, 1976)

record, and the required information entered in allapplicable spaces. Fine-tipped felt pens are recom-mended for annotating graphic records.

BAR CHECK

GOOD

↓

marker that, when pressed or activated electroni-cally, causes the stylus to draw a line across thewidth of the recording paper. At each fixed position,the echo sounder operator shall make a fix mark;the position number is entered beside it. When a fixis rejected or missed, the fact is indicated by two orthree ''X's'' made on the fix mark.

HYDROGAPHIC MANUAL

Julian day, sounding unit indicator, and the controlmode code.

4.8.6. Analog Position Data

See section 4.9.8 for field scanning and re-cord interpretation procedures. Graphic depth re-cords shall be carefully packaged and forwarded byregistered or certified mail for final processing uponcompletion of work on the hydrographic sheet.These records shall be sent in separate shipmentsfrom the sheet and other sounding records.

4.8.5.2. DIGTAL DEPTHS. Most echo sound-ers used by NOS display depths in both digital andanalog form. Generally, digital soundings are inher-ently more accurate than those extracted from agraphic record because digital depths are free of sca-ling and mechanically induced errors; therefore, digi-tal soundings are considered as primary data thatare supplemented by analog records for these pur-poses:

Analog position records shall be annotatedas follows:

3. To adjust the effects of excessivewave action on digital soundings.

From the top, line 1 provides the ''dayrecord'' (i.e., the vessel identification number, year,

4-62(JULY 4, 1976)

Analog records of the vessel's movementsshall be obtained, when possible, during all surveyscontrolled by phase comparison type position-fixingsystems. Instruments available for this purpose pro-duce a graphic record similar to that shown in figure4-41, which is a continuous record of lane changesrecorded as the vessel maneuvers . The line drawn bythe stylus, commonly referred to as a "sawtooth re-cord,'' shows whether lane values are increasing ordecreasing; the slope of the line indicates the rate ofchange. This record is particularly useful for recon-structing accurate lane counts, when electrical inter-ference or weak signals cause the phasemeters to op-erate erratically, and for recognizing recordingblunders. Lane gains and losses are easily recognizedby using spacing dividers to check lane change ratesand to verify the annotated lane count. Frequentcomparisons between the graphic record and lanecount displays are essential for detection of losses orgains in lane count.

(GMT) shall be entered periodically on graphic re-cords where it is not evident.

Echo sounders generally record depths inmore than one phase or scale depending upon theinstrument. The first phase (A scale) is usually iden-tified by an initial trace indicating the relative depthof the transducer. Other phases must be accuratelyand positively identified by the operator on the re-cord. On some models, a circle can be drawn aroundthe scale being used on the preprinted recording pa-per; on others, it is necessary to enter notes on therecord. See appendix A for a complete discussion ofthe various echo sounders and depth-recordingequipment currently in use by NOS.

Graphic profiles of record shall be accor-dion folded into flat 10-in (25-cm) panels and filedin manila envelopes or bellows-type files that areproperly labeled for sheet number, sounding vessel,and dates and year day numbers.

1. To scale and record peaks, deeps,and other critical or revealing soundings that mayhave been missed on the regular sounding interval.

2. To correct digital soundings obvi-ously in error because of returns from kelp beds,fish, side echoes, or spurious strays.

See section 4.8.4 for a discussion of the hy-drographic records acquired by automated methodsand figure 4-40 for an example of the hard copy for-mat. On the digital record:

Line 2 provides the corrections [i.e., time,tide reducer, TRA (transducer) correction (4.9.7),electronic position value corrections, and electroniccontrol station numbers].

Line 3 lists time, depth, position number,electronic position values, and vessel heading.

Line 4 shows a depth record similar toline 3 but without a position number attached to thesounding. Refer to the " HYDROPLOT/HY-DROLOG Systems Manual'' (WALLACE 1971) for in-terpretation of the codes and other automated for-mats for sounding data. (See section A.7 for detaileddescriptions of digital sounding equipment now inuse.)

1. Lane count must be entered whencalibrations or lane checks are obtained.

2. Positions shall be marked and num-bered.

3. Every 5th or 10th lane is numbereddepending upon the rate of lane change.

4. Lane count is recorded on both sidesof a direction reversal (i.e., when an increasing lanecount changes to a decreasing lane count).

HYDROGRAPHY

2220 71 269 1 041

010201 1004 0023 100022 100025 100 000 200

010201 00228 20455 067155 073060 091

011201 00264 00456 069743 076141 090

012201 00300 00457 072377 079244 090

FIGURE 4—40.—Raw data printout of an automated record of hydrography

4-63 (JULY 4, 1976)

010301 00232

010401 00228

010501 00221

010601 00232

010701 00242

010801 00249

010901 00259

011001 00259

011101 00264

067415 073369 091

067677 073675 090

067946 073987 090

068183 074303 089

068432 074599 089

069695 074903 089

068945 075214 089

069204 075517 088

069471 075830 089

011301 00252

011401 00248

011501 0025l

01160l 00000

011701 00271

011801 00286

011901 00289

012001 00289

012101 00255

069983 076459 090

070249 076768 090

070515 077079 092

070795 077377 092

071051 077692 093

071313 078003 091

071588 078305 090

071852 078622 089

072123 078929 089

FIGURE 4-41- "Sawtooth: or analog record of a vessel positionJU

LY

4,1975JU

LY

4-64

HYDROGRAPHY

5. Detectable lane gains and losses aremarked on the record.

4.9.1.1. STANDARD NOMENCLATURE. Indiscussing the various corrections to echo soundings,standard nomenclature as defined in this section andshown on figure 4-42 will be used.

4.9. CORRECTIONS TO SOUNDINGS

Heave correction for wave action.

Datum of reference reduction for tideor water level stage.

FIGURE 4-42—Corrections to echo soundings

4-65 (JULY 4, 1976)

6. Stamp 11 (figure 4-39) is impressedon each graphic record and the appropriate entriesmade. Analog position records are maintained dailyand filed with the graphic depth records.

4.9.1. General

Observed soundings must be corrected forall departures from true depths attributable to themethod of sounding or to faults in measuring appa-ratus and must be corrected for heights of the watersurface above or below the datum of reference whensoundings were taken. When sounding operationsare in progress, hydrographers occasionally becomeso engrossed with measurements in the horizontalplane that depth measurement problems are ne-glected. An echo sounder appearing to be operatingcorrectly is not always sufficient evidence that re-corded soundings are correct. Detection of errors inboth positioning and sounding data and the accumu-lation of information necessary to correct these er-rors can often present real challenges. The final mea-sure of the quality of a hydrographic survey maydepend on these factors.

Occasionally, discrepancies are not discov-ered until the survey is verified. Available data mustbe sufficiently adequate to permit reasonable solu-tions of any problems and proper adjustments ofdiscrepancies.

Corrections to soundings, often called ''re-ducers,'' are determined and tabulated in the sameunits in which soundings are recorded. Fractionalparts of sounding units shall be recorded as deci-mals.

In those rare instances when soundings arerecorded on NOAA Form 77-44, ''Sounding,'' thenplotted by hand, vertical columns are provided inthe volumes for entering various corrections and cor-rected soundings. Each correction, with its algebraicsign, is entered on the horizontal line opposite thefirst sounding to which it applies—correctors neednot be repeated on each line, except opposite thefirst sounding on each page and when they change.(See figures 4-22 through 4-25.) Corrections onceentered are considered applicable to all following

soundings until different corrections or signs are en-tered.

Chart depths are the actual water depthsbelow the datum of reference and are the depthsshown on hydrographic smooth sheets. Chart depthsare determined by applying algebraically the follow-ing corrections and reductions to observed sound-ings:

Echo sounding instrument correction.

Velocity of sound correction.

Transducer dynamic draft correction.

Observed depths are raw uncorrected echosoundings obtained digitally or by scaling depthsfrom graphic depth records. Graphic depth recordsprovide a nearly continuous profile of the bottombelow the sounding line. Depths scaled from the re-

HYDROGRAPHIC MANUAL

Fine arc error.

Incorrect setting of initial pulse.

Stylus belt improperly adjusted.Transducers should be installed and

4-66(JULY 4, 1976)

cords are subject to human error and inaccuraciesinherent in the mechanical recording devices.

Digital depths are the more accurate ofthe two because they are determined electronicallyby multiplying the velocity of sound through waterby half the time taken by a pulse to travel from thetransducer to the bottom and back; however, theeffectiveness of digital depths is often lessened bythe inability of the system to compensate for waveaction on the vessel and to select peaks and deepsbetween the programmed sounding interval.

Heave correction (not shown) is appliedto observed soundings to compensate for the verticaldisplacement of the sounding vessel from the meanwater surface because of sea conditions. Whensoundings over regular bottom are being scaled orchecked from graphic depth records, heave effectsare compensated by visually averaging the undulat-ing depth profile in the vicinity of the sounding. (See4.9.8.1.)

Correcting heave errors in either digitalor scaled soundings over rough and irregular bottomis a more complex problem because authentic depthchanges often cannot be distinguished from heave.Soundings should not be taken in rough sea condi-tions when critical depths are required.

When seas are rough and recorded digitalsoundings are measured instantaneously and not cor-rected for the effects of heave, an excessive numberof soundings will be in error; therefore, to avoid ex-tensive hand corrections when the records arechecked, one should discontinue digital soundingand soundings should be scaled from the graphicdepth record when the effects of heave exceed 2 ft or1% of the depth, whichever is greater.

Instrument corrections are applied to ob-served depths to compensate for the errors intro-duced by the echo sounder and depth recorder. (See4.9.6.) Soundings obtained by digital methods aregenerally free of these errors and do not require sig-nificant corrections. Instrument errors in graphic oranalog depths may be attributable to one or more ofthe following sources:

Scale or phase error.Incorrect frequency (affects paper

speed and stylus arm rotation speed).

Stylus arm length error.

Variations in signal strength and timelags in the circuitry.

As a general rule, the accuracy of depthsmeasured by echo sounders is related directly to thecompetence and reliability of the technicians whooperate and maintain these instruments. Each typeof echo sounder has its unique characteristic featuresthat must be closely watched. Failure to maintainproper adjustments results in erratic observationsand unresolvable discrepancies.

Elapsed time depth is not widely used inhydrographic terminology; but it identifies a specificentity for visualizing the sounding correctionscheme. Elapsed time depth is the observed depthcorrected for instrument errors—it is equal to halfthe time taken by a sound wave to travel from thetransducer to the bottom and back multiplied by thecalibration sound velocity of the instrument.

Velocity corrections must be applied tosoundings because both digital and analog echosounders display depths based on a calibrated con-stant value for the velocity of sound through water.National Ocean Survey echo sounders are calibrated

to record depths based on a velocity of 800 fm/s,which closely approximates most actual values. Dur-ing hydrographic surveys, field measurements aremade for the determination of true sound velocitiesthroughout the water column. (See 4.9.5.) Correc-tions are then computed and applied to the sound-ings to compensate for the differences between cali-brated and true values of sound velocity. Elapsedtime depth when corrected for velocity variationsresults in the actual depth of the water below theecho sounder transducer.

Dynamic draft is the algebraic sum of thestatic draft (4.9.4.1) and the effect of vessel settle-ment and squat (4.9.4.2). Static draft is the depth ofthe transducer below the water surface and is mea-sured when the vessel is not underway. Settlementand squat corrections are determined for variousvessel speeds to compensate for vertical displace-ments and changes in attitude when underway. NOSecho sounders shall be adjusted to record initialsound pulses at zero depths; therefore, the dynamicdraft of the transducer must be added to the actualdepth below the transducer (elapsed time depth plusvelocity correction) to obtain the actual depth fromthe water surface.

HYDROGRAPHY

shimmed as necessary to ensure verticality of thesound wave cone for the average operating attitudeof the vessel.

4.9.3. Tide and Water Levels Reductions

Except as stated in section 4.9.2, all sound-ings must be corrected for the height of the tide orwater level above or below the datum of referencefor the area. (See 1.5.4.1.) Predicted tides or fore-cast water levels are often used to reduce sound-ings in the field. Final reducers are generallyderived from tide or water level automatic record-ing gages (1.5.4.2) located at primary stations orfrom supplemental gages established in the projectarea especially for this purpose. (See 2.3.1.5 andAK.) Occasionally, these reducers may be deter-mined from tide or water level values observed vi-sually on a tide staff (AK.2) for limited amounts ofhydrography. See Publication No. 30-1, ''Manual ofTide Observations'' (U.S. Coast and Geodetic Sur-vey 1965a), for detailed instructions concerningannotation and transmittal of tidal records.

4.9.1.2. STANDARD PRACTICES. Threestandard practices concerning echo-sounding cor-rections have been adopted by the National OceanSurvey:

Chiefs of Party are responsible for the prop-er field monitoring of all gages established to sup-port the project. When contract observers are hired,a reliable line of communication shall be establishedto ensure prompt notification of any gage malfunc-tion or change in the staff-gage relationship. Tidalheights and times can often be interpolated duringshort interruptions or breaks in the gage records.Accurate interpolations cannot be made for inter-ruption or invalid data periods in excess of 3 days.In such cases, tidal control may be damaged to the

extent that a resurvey of affected areas is necessary.Water level records cannot be mathematically re-constructed; however, straight-line interpretationmay be acceptable for short periods when nearbygages record steady levels during the same period.

4.9.2. Correction Units

Predicted values for tide stages and fore-cast values for water level stages are usually essen-tial to almost all operations of a hydrographic fieldparty. In addition to their possible use as prelimi-nary reductions to soundings for Field sheets,knowledge of predicted tides may be necessary forplanning beach landings, for conducting inshoreand shoal water soundings operations, and for cer-tain hydrographic feature developments and inves-tigations. Predicted tide or forecast water levelvalues may be used to reduce soundings shown onfield sheets, but the final reducers applied to deter-mine chart depths shall reflect actual tide or waterlevel stages as accurately as possible.

In ocean depths over 110 fm, correctionsmay be omitted where the algebraic sum of thetide correction and other corrections, excluding ve-locity corrections (4.9.5), is less than half of 1% ofthe depth. Water level stage corrections are appliedto all soundings in the Great Lakes regardless ofthe depth.

Although predicted times and heights ofhigh and low tides may be sufficient for some oper-

4-67 (JUNE 1, 1981)

Datum reduction is applied after all othercorrections have been made to reduce each actualdepth to the datum of reference (chart datum) forthe particular area. (See 1.6.1 and 4.9.3.) This re-duction is made by applying the difference in ele-vation of the water surface (tide or water levelstage) and the datum of reference at the time thesounding was observed.

1. NOS depth recorders are calibratedfor an assumed velocity of sound in water of 800fm/s (1463.43 m/s). This value is reasonably closeto the velocity of sound in most waters surveyed.

2. The synchronous motor that drivesthe stylus arm shaft or belt shall be operated at theproper frequency recommended by the manufactur-er. Changing frequencies to cause agreement be-tween bar checks and analog records is notpermitted. By prohibiting this practice, the hydrog-rapher can better determine the magnitude of othertypes of errors.

3.The initial setting on all depth record-ers shall be zero rather than the assumed transduc-

er depth.

Corrections to soundings are computed andapplied according to the specifications listed in ta-ble 4-4, section 4.5.7. 1. Corrections are generallydetermined to the nearest decimal that is half thatrequired for recording soundings (e.g., use 0.2where the requirement for recording is 0.5); how-ever, corrections in fathoms need not be closerthan 0.1 fm. For soundings in feet, except onshoals, banks, and other critical areas, correctionsneed be entered only to the nearest foot in depthsgreater than 20 fm.

HYDROGRAPHIC MANUAL

1. From table 2 of the Tide Tables, lookup the tide differences applicable to the area beingsurveyed. Apply these differences to the tide pre-dictions for the reference station and obtain corre-sponding times and heights of the high and lowwaters for the required period.

FIGURE 4-43—Construction of a predicted tide curve

the hydrographic field unit for survey areaswhere the tidal or water level dynamics are com-plex and difficult junctions are anticipated. Finalzoning based on real observations will also be de-termined by the Office of Oceanography prior toverification and smooth plotting of the survey.(See chapter 5 for tide and water levels report re-quirements.)

Tidal and water level reducers for sound-ings on projects where several gages are operating

may be computed by interpolation or linear re-gression techniques, provided there is evidencethat time and height variations are similarthroughout the area.

4.9.4. Dynamic Draft Correction

The static draft of the hydrographic vesselcombined with the effects of settlement and squat

The Office of Oceanography, NOS, willprovide preliminary tidal or water level zoning to

4-68(JUNE 1, 1981)

ations, values for the intermediate stages are oftennecessary. The Marine Environmental Services Di-vision, Office of Oceanography, NOS, will, uponrequest, provide predicted hourly tidal heights forreference tide stations cited in the project instruc-tions. Corrections for subordinate supplemental sta-tions may also be computed by the Marine Envi-ronmental Services Division.

If these resources are not available, pre-dicted hourly heights of sufficient accuracy can bedetermined graphically using values extracted fromthe NOS Tide Tables published annually. The pro-cedure is as follows:

2. Plot the low and high water time andheight coordinates, A and E, on cross-section pa-per. (See figure 4-43.)

3. Divide the connecting line AE intofour equal parts, points B, C, and D.

4. Plot point B vertically below B, andplot D vertically above D, making each equal toone-tenth the range of tide.

5. Draw an approximate sinusoidal orparabolic curve through points A, B, C, D, and E.This curve closely approximates the actual tidecurve permitting the required data to be readilyscaled. The falling stage of the predicted tide curveis plotted and drawn similarly.

On the tide curve thus constructed, pointscan be marked where changes in corrections occur.A tabulation of corrections and times of changecan then be extracted from the curve.

In some areas, one must establish zones be-tween adjacent stations because of significant dif-ferences in times and ranges. Procedures for mak-ing tidal time and height interpolations aredescribed in Publication No. 30-1, ''Manual of TideObservations'' (U.S. Coast and Geodetic Survey1965a). Correct zoning is critical in estuaries andin long narrow bays. Improper zoning in suchareas will be reflected in the junctions with adja-cent surveys and may cause excessive differences indepths at crossings within the survey.

When unusual tidal or water level condi-tions are observed and the stages are expected tovary significantly from those at the preselectedgage sites, the chief of party is responsible forestablishing additional gages as necessary or

obtaining series of staff observations (AK.2.1) inthe problem area. Such additional observationsshall be made for the duration of hydrography inthat area, and the nearest preselected gage mustbe in operation. Tide gages or tide staffs shall beestablished and monitored at the upper reaches ofrivers and creeks in the vicinity of the survey ifgage sites were not designated for the area.

HYDROGRAPHY

when underway are factors that must be taken intoaccount when soundings are corrected. Static draftand the combined effects of settlement and squat aredetermined individually, then combined algebraicallyfor the total dynamic draft correction.

at the beginning and end of each workday and atother such times when significant changes occur.

4.9.4.2. SETTLEMENT AND SQUAT. Trans-ducers are generally displaced vertically, relative totheir positions at rest, when a vessel is underway.Depth measurements are affected by these verticaldisplacements. Such displacements may be of suffi-cient magnitude to warrant compensation, especiallywhen accurate soundings in shoal water are mea-sured from a vessel running at moderate to highspeeds. The factors accountable for this vertical dis-placement are termed ''settlement'' and ''squat.''

4.9.4.1. STATIC DRAFT. Depths of watermeasured by echo sounders aboard NOS vessels aredepths below the transducer—not depths below thesurface. Draft, as an echo-sounding correction, refersto the depth of the transducer below the surface ofthe water when the vessel is not underway. Adjust-ments to echo sounder initial settings to compensatefor the draft and variations thereof shall not bemade while engaged in hydrography.

Squat refers to changes in the trim of thevessel when underway and is generally manifested bya lowering of the stern and a rise of the bow. Occa-sionally, the bow lowers on smaller vessels. Thischange in attitude can cause significant errors whensoundings are measured on steep slopes and the linesare normal to the depth contours.

Variations in ship's draft and depths of thewater are the two factors that determine the properfrequency of draft measurements. For soundings of20 fm or less, the draft should be observed and re-corded to the nearest 0.2 ft. Measurements and re-

cord entries shall be made with sufficient frequencyto meet this criteria. When sounding in watersdeeper than 20 fin, the draft should be observed andrecorded to the nearest 0.5 ft. In depths greater than110 fm where errors caused by improper draft ad-justments result in a small percentage of the totaldepth, an estimated average value for draft may beused to correct soundings. Draft values for smallvessels shall be observed and entered in the records

Combined effects of settlement and squat atvarious sounding speeds shall be determined to thenearest 0.2 ft at the beginning of each season foreach vessel, including auxiliaries and launches usedfor hydrographic surveying in shoal or moderatedepths. When the measurements are made, each ves-sel should be carrying an average load and be in av-erage trim. Derived values may be assumed to beconstant throughout the season. Settlement andsquat corrections of less than 0.2 ft may be ignoredwhen correcting soundings. Sounding vessel speeds

4-69 (JULY 4, 1976)

Provision must be made or special instru-ments installed to measure the draft of the transduc-ers permanently mounted in the hull. Internal draftgages may be installed on which the draft of theunits can be read directly.

The method most commonly used to mea-sure draft is to mark points on the rail or deckabove and abeam of the transducers. By measuringthe vertical distance of these marks above the trans-ducers, their drafts can be determined at any timeby measuring the vertical distance of the referencemarks above the water surface, then taking the dif-ference between the vertical distances. Referencemarks should be established on both port and star-board rails—measurements to the water surface aremade from both points and averaged to compensatefor list of the vessel. Elevations of the referencemarks above the acoustical units are determinedwhile the vessel is in drydock using an engineer'slevel and steel tape.

Settlement is the general difference betweenthe elevations of a vessel when underway and whenat rest. For lower speed nonplaning vessels, settle-ment is caused by a local depression of the watersurface. Settlement is not an increase in vessel dis-placement and, therefore, cannot be determined byreference to the water surface in the immediate vicin-ity. Vessels surveying at higher speeds may experi-ence a negative settlement or lift when planing.

Major factors that influence settlement andsquat are bull shape, speed, and depth of water be-neath the vessel. Squat does not appreciably affecttransducer depth if mounted amidships (or a littleforward of amidships as they generally are). Con-versely, settlement is generally significant at normalsounding speeds. In depths approximately seventimes the draft, settlement for a larger survey shipoften amounts to about 0.5 ft, and in extreme casesmay be as much as 1 ft; this amount increasesslightly as the depth lessens.

HYDROGRAPHIC MANUAL

and squat. Observations are repeated several times,and the average value determined.

must be entered in the hydrographic records duringsurvey operations to permit accurate corrections forsettlement and squat. 4.9.5. Velocity Corrections

Echo sounders used by the National OceanSurvey are calibrated to record soundings for an as-sumed uniform velocity of 800 fm/s. The actual ve-locity of sound through water must be determinedfor all hydrographic surveys except those in shoalareas. In such areas, bar checks (A.6.1.3), supple-mented by velocity determinations, are generallyused to determine corrections throughout the fulldepth range. In deeper waters, velocity correctionsmay be ignored when they are less than 0.5% of thedepth.

The preferred method is to set up a levelinginstrument ashore— if possible, on the end of a pieroff which are found the conditions for ideal depthand bottom type and past which the vessel can runat normal sounding speeds. A marker buoy with theshortest possible mooring scope is anchored at thepoint where the measurements will be made. Thevessel is brought alongside the marker buoy andstopped. A level rod is held over the echo sounder'stransmitting and receiving units (or over the mid-point if one is forward of the other), and the eleva-tion read from the instrument a shore. The height of the tide must be noted. The vessel is then sailed pastthe marker buoy at normal sounding speed. Withthe rod on the same spot, the elevation is readagain from the same instrument setup. The differ-ence between the two readings after correction fortidal changes is the combined effect of settlementand squat at the location of the transducers. Severalmeasurements of reasonable agreement shall bemade and averaged for a final value.

An alternate method is to select an areathat satisfies depth and bottom-type requirements,then anchor a marker buoy with a short mooringscope. The vessel is stopped alongside the markerbuoy, and the depth of water measured as accuratelyas possible with an echo-sounding instrument. Thevessel is then sailed past the marker buoy at normalsounding speed, taking another accurate soundingwhen in the same position relative to the buoy.Again, provisions must be made to record tidalchanges during the observations. The difference be-tween the echo soundings underway and stopped ascorrected for tidal changes is the value of settlement

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Either of two methods may be used to de-termine the combined effect of settlement and squat.Regardless of the method used, the tide should beeither high or low when the level is varying slowly.Tidal changes that occur during settlement andsquat determinations must be measured and appliedaccordingly.

Measurements for settlement and squatshould be made over a smooth, level, and firm bot-tom in depths of at least seven times the draft of thevessel. If the vessel will be used to survey in shoalerdepths, additional measurements should be made atthose depths.

When echo sounding, sound waves travelfrom the transducer vertically downward to the bot-tom and return through a column of water in whichthe velocity of sound varies at different depths. (SeeA.6.2.) Because depth is the product of velocity andelapsed time, the average velocity of the sound wavefrom surface to bottom must be known. Velocity ofsound in water varies with density, which is a func-tion of temperature, pressure, and (in salt water) sa-linity. Velocities used for echo-sounding correctionsare calculated from these characteristics using Wil-son's equation. (See 4.9.5.2.2.)

Hydrostatic pressure increases in a nearlydirect proportion to depth; temperature decreaseswith depth, but not uniformly; and salinity usuallyincreases with depth. The result is that the velocityof sound is seldom uniform from top to bottom, andseasonal changes within any region will change theaverage velocity.

For use in correcting echo soundings, thevelocity of sound must be known with sufficient ac-curacy to ensure that no sounding will be in errorby as much as 0.25% of the depth from this causealone. Therefore, the mean velocity must be knownto within ± 4 m/s. Temperature is the characteristicof water that most affects the velocity of sound. Tosatisfy these accuracy requirements, one must knowthe mean temperature of the water to an accuracy of± l°C and the salinity to within ± 1%o. (ppt). A suf-ficient number of salinity and temperature observa-tions must be made so that the velocity can be de-termined within the specified accuracy over theentire area sounded.

The number of observations required de-pends on the physical characteristics of the waterand the physiography of the area. A minimum of

HYDROGRAPHY

Two standard NOS methods for determin-ing velocity corrections are described in detail in thefollowing sections. The first method is by directcomparison with a standard [i.e., by comparing digi-tal and analog echo soundings with known depths atwhich a bar is suspended below the transducer (barcheck)]. Because the equipment is manhandled overthe side, bar check usage is limited to smaller surveyvessels. Larger vessels make direct comparisons bycomparing echo soundings with vertical lead-linecasts. The effects of both instrument error and ve-locity variations are included in direct comparisonresults. The effectiveness of direct comparisons isgenerally greatly reduced as the depths of the obser-vations increase because of nonverticality of the cali-brated lines on the bar or lead line when the mea-surement is made.

Velocity corrections are tabulated so theycan be applied to the soundings by a straightforwardtable look-up procedure in which the entering argu-ment is the observed depth (uncorrected for velocity)plus the dynamic draft; the output is the velocitycorrection value for that observed depth. (See4.9.5.2.5.)

4.9.5. 1. DIRECT COMPARISONS. Simultane-ous direct comparisons are made between actualdepths and observed echo soundings to determinecorrections to the observed values. The two methodsmost commonly used are bar checks and verticalcasts. Bar checks are the more accurate of the twoand should be used when possible. Observed differ-ences between actual and observed depths includethe effects of sound velocity variations, instrumentalerrors, and the static draft of the vessel.

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one serial temperature shall be observed each monthin the deepest part of the area surveyed. It is theresponsibility of the chief of party to make addi-tional observations as needed to meet the accuracyrequirements.

The second method entails combining directcomparison results with velocity corrections deter-mined from oceanographic or limnologic observa-tions for density throughout the water column. Thismethod is always used by larger vessels and byother vessels at such times when bar checks are im-practical.

See section A.9.2 for a description and dis-cussion of the various water samplers, instruments,and electronic sensors used by NOS for the determi-nation of velocity corrections.

4.9.5. 1. 1. Bar checks. Reliable and accuratebar checks can be made only under the most favor-able conditions. When the sea is calm and there islittle differential current or wind effect causing thebar to be displaced from a position vertically belowthe transducer, bar checks can be obtained in depthsas great as 15 fm. Under less favorable conditions,effective bar check depths may be reduced to 2 fm.In moderate depths where bar checks can be ob-tained over the full depth range of the survey, cor-rections to soundings can be determined that com-pensate both for the difference between thecalibrated velocity of the instrument and the actualvelocity of sound in the water and for instrumentalerrors.

2. Where all or some of the project areadepths are beyond bar check range, bar check datamust be supplemented with oceanographic observa-tions to determine velocity corrections. In suchcases, bar checks consisting of four observations aretaken at twice daily. Two comparisons aremade at the shoalest depth below the transducer atwhich the echo sounder can record. The remainingtwo comparisons are made at approximately 2 fmbelow the transducer.

I. In protected waters where bar checkresults are considered dependable and the surveydepths lie within the bar check range, bar checksshall be made at least twice daily—prior to begin-ning hydrography and again at the end of the day.Comparisons are recorded during both descent andascent of the bar at each 10 or 12 ft below the sur-face throughout the depth range of the survey. Ad-ditional observations are made at a depth of 5 or 6ft—if the sounding can be recorded.

Bar checks should always be made whenand where the water conditions are the calmest; ob-servations taken during rough sea conditions aresubject to unacceptable magnitudes of error. A smallvessel operating in exposed rough water should runto a protected area or lie in the lee of the parentship for the bar check although water densities mayvary slightly. Bar checks, however, shall not bemade in areas where temperatures or salinities varysignificantly from those at the working grounds. Ad-ditional bar checks shall be made as considered nec-essary by the hydrographer to attain the required

Launches and small boats using echo sound-ers for hydroghraphic surveying shall make barchecks and record the results as follows:

HYDROGRAPHIC MANUAL

A.6.1.1) Vertical cast comparisons are made to de-termine or verify instrumental corrections for eachecho sounder and depth recorder used on each sur-vey. It is particularly important that vertical casts bemade in areas where launch hydrography joins oroverlaps ship hydrography. In such areas, soundingsand depth contours often fail to agree. A minimumof two sets of comparisons shall be observed at dif-ferent depths to provide the data necessary to recon-cile potential discrepancies. In the field, discrepan-cies must be resolved—under no circumstances shallsurveys with unresolved discrepancies be submittedfor smooth processing.

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accuracy of sounding corrections. Changes, varia-tions, or adjustments in the sounding equipment orvariations in water properties are reasons for makingadditional comparisons.

A Direct Comparison Log similar to thatshown in figure 4-44 may be used as an alternatemethod to record bar check data and can be used toabstract the results if recorded in a Sounding Vol-ume. (See 4.8.3.6.) The following are procedures forobserving and recording bar check data:

1. The marked lines used to suspend thebar at the comparison depths shall be compared pe-riodically with a standard (i.e., a surveyor's steeltape or equivalent). When used daily, weekly com-parisons with a standard are made. When compared,the lines should be wet and under a tension equal tothe weight of the attached bar when in water. Com-parison data are entered in column B of figure 4-44and then are added algebraically to column A toobtain the Actual Depth (column C).

2. Direct comparisons should not be made until the echo sounder has warmed up in ac-cordance with the manufacturer's specifications. Thevessel must be stopped, the sea relatively calm, thebar vertical beneath the transducer, and the instru-ment operating at the proper voltage.

3. The depth recorder should be oper-ated at the same gain setting that will be used dur-ing normal sounding operations. Gain settings andthe analog scale are also recorded on the comparisonlog (figure 4-44) in columns D and E, respectively.

4. As the bar is lowered through eachsuccessive depth, corresponding analog and digitalreadings are recorded in columns F and K. Re-corded digital depths at each stage should be aver-age values of the displayed digital readings.

5. The comparisons are repeated duringthe scent by stopping the bar at each depth ob-served during the descent. Observed values are re-corded in columns G and L. Mean observed depthsare then computed by averaging columns F and G,and K and L—then entering the results in columnsH and M.

6. Data entries on the remaining col-umns for the determination of corrections to ob-served soundings are self explanatory. (See 4.9.5.1.3.)

4.9.5.1.2. Vertical casts. Because bar checkobservations from larger hydrographic survey vesselsare impractical, reliance must be placed on compar-ing echo soundings with vertical lead-line casts. (See

Similar situations frequently arise wheresounding lines run by different launches join on m-shore sheets. If a displacement of depth contoursoccurs at a junction, an error probably exists in thework of one or both launches. The magnitudes ofthe sounding errors must be established by compar-ing echo soundings from both vessels with verticalcast observations in the junctional areas.

Vertical cast observations may be recordedeither on stamp 5A (figure 4-30, section 4.8.3.6) oron the Direct Comparison Log (figure 4-44). Proce-dures for observing and recording vertical casts are as follows:

1. Lead lines shall be compared with astandard and the results entered in the records eachtime a direct comparison by. vertical cast is made.(See 4.9.5. 1. 1.)

2. Echo-sounding equipment must beproperly warmed up prior to making comparativeobservations.

3. Because vertical cast measurementsare highly susceptible to errors, observational condi-tions must be better than those required for barchecks. The vessel must be stopped, the sea rela-tively calm, and the current slack. Ideally, the bot-tom should be flat with no projections and be com-paratively firm for optimal echo soundings. Forobtaining the most accurate lead-line measurementsand minimizing the effect of variation of sound ve-locity in the determination of instrument errors, ver-tical casts are taken in the shoalest water practical.

4. At least five simultaneous compari-sons between echo soundings and lead-line depthsare observed and recorded from each side of the ves-sel for a complete vertical cast. Digital and graphicdepth records obtained during the comparison seriesshall be made part of the hydrographic records.

4--73

(1861 '

I 9N

flf)

FIGURE 4-44.—Direct Comparison Log for echo-sounding corrections

HY

DR

OG

RA

PH

Y

HYDROGRAPHIC MANUAL

5. See section A.6.1.1 for instructions onlead-line usage.

in the same area over a period of time. Series ofdata can generally be combined and average sound-ing correction curves used.

4.9.5.2. OCEANOGRAPHIC AND LIMNOLOGIC

DETERMINATIONS. Velocity of sound through wa-ter for echo-sounding corrections must be deter-mined either by collecting water samples at standarddepths for temperature and salinity measurements orby using one of the modern sophisticated electronicsensors designed to measure and display water densi-ty parameters. Several of the available sensors arecapable of recording continuous measurementsthroughout the water column. When sampling at

discrete depths, the National Ocean Survey normal-ly adheres to the standard observation depths pro-posed by the International Association of PhysicalOceanography (Jeffers 1960); these depths (in me-ters) are 0, 10, 20, 30, 50, 75, 100, 150, 200, (250), 300,400, 500, 600, (700), 800, 1000, 1200, 1500, 2000,2500, 3000, 4000, and thence at 1000-m intervals tothe bottom. (Depths in parentheses are optional.)Data for other levels are interpolated from the stan-

dard observation depths.

When Nansen bottles and reversing ther-mometers (AL.2.1, AL.2.2) are used to measure wa-ter temperatures and collect samples at variousdepths, the data are recorded and computed on''Oceanographic Log Sheet-A.'' U.S. Naval Ocean-ographic Office (1968) Publication No. 607, ''Instruc-tion Manual for Obtaining Oceanographic Data,''contains detailed instructions on the proper use ofLog Sheet-A for computing temperatures versusdepths. Log Sheet-A is available throughERL/AOML, RD/RF2. Water sample salinities aregenerally measured with induction type salinometers(AL.2.3) or by measurements of specific gravitywith calibrated hydrometers (AL.2.4).

Most electronic temperature, depth, andconductivity (TDC) or salinity, temperature, anddepth (STD) sensors and recorders now availablecommercially (AL.2.5, AL.2.6) yield precise mea-surements in excess of accuracy requirements forsound velocity corrections if properly calibrated andmaintained. In addition to the laboratory calibrationprocedures required by NOS and those recom-mended by the manufacturer, each device shall befield checked for accuracy against Nansen cast orequivalent observations at least once during each hy-drographic project and at other times considerednecessary by the Chief of Party. Each time a sensoris used, a rough check on the temperature and den-

The results of each bar check and verticalcast must be carefully compared with others taken

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6. Original vertical cast observationaldata shall be entered in the records of each applica-ble hydrographic survey to substantiate the echosounding correction values.

4.9.5.1.3. Corrections to soundings from barcheck data. Computations for echo-sounding cor-rections from bar check data are relatively simpleand straightforward:

1. Remove the effects of draft correctionfrom the bar check data by adding the vessel draftto the mean observed depths before comparing ob-served depths with actual depths (i.e., add the draftto columns H and M and record the results in col-umns I and N). See figure 4—44.

2. Total corrections for velocity varia-tions and residual instrument errors are determinedby subtracting column I from column C (analogsounding corrections) and column N from columnC (digital sounding corrections), then entering theresults in columns J and P, respectively.

3. From these data, a sounding correc-tion curve is constructed by plotting correctionsversus mean observed depths plus draft in a man-ner similar to that shown in figure 4-45, section4.9.5.2.6. When digital echo sounders are used, fi-nal correction curves are developed by plottingmean observed depths plus draft listed in column Non the vertical scale against their correspondingdigital corrections (column P) on the horizontalscale. A smooth curve is faired through the plottedpoints. When only analog records are available, thesounding correction curve is plotted in a similarmanner—except that the mean observed depthsplus draft (column 1) are plotted against the corre-sponding corrections (column 1).

4. Final incremental sounding correc-tions are then scaled from the curve and tabulat-ed for application as shown in example 1, section4.9.5.2.6.

5. Analog errors with respect to digitalsoundings (column Q) are determined bysubtracting the values in column P from those incolumn J. This correction is applied to intermedi-ate scaled analog depths inserted into digital sound-ing lists and reflects the instrumental errors. (Seesection 4.9.6.)

HYDROGRAPHY

from many sources nationally and are processedautomatically, International Standard Depths areused; but when serial temperatures and salinitiesare observed in relatively small project areas andwhen the winch registering sheave is graduated infathoms, observations may be taken at the follow-ing approximate depths: 0, 2, 5, 11, 16, 27, 41, 55,82, and 109 fm.

Depths can be checked or measured direct-ly by lashing a sensor to a lead line or by similarlymarking the sensor conductor cable. Erratic read-ings often result from bad connections to a sensorfrom salt deposits on a conductivity sensor or froma faulty sensor. Manufacturer's specificationsshould be observed rigorously for adjusting, clean-ing, and care of equipment.

4.9.5.2.1. Selection of layers. Layer thick-nesses need not always be chosen in a uniformmanner. Experience has proven that 10-m layers inthe upper 200 m, 40-m layers from 200 to 400 rndeep, and 400-m layers in greater depths are usual-ly satisfactory; however, in areas where the chang-es in temperature are not great and are relativelyregular with respect to depth, thicker layers maygive sufficient accuracy. When changes in tempera-ture are irregular and are large with respect todepth, smaller layers must be selected to attain therequired accuracy. The first layer is irregular andis dependent on the draft of the vessel. (See4.9.5.2.3.)

Once temperatures and salinities have beendetermined for the proper depths, velocity correc-tions for the sounded water column are computedusing the ''summation of layers'' method. Velocitiesof sound at mid-depths of specified layers are com-puted either by graphical or by numerical methods(described in the following sections). Correctionscomputed for each layer of depth are then summedalgebraically to arrive at total velocity correctionsapplicable to given depths. A graph of observeddepth plus draft versus correction is then plottedand used to scale corrections for even correctionintervals (table 4-4, section 4.5.7. 1) according tosurvey requirements.

4.9.5.2.2. Determination of velocities at layermid-depths. The velocity of sound through water iscomputed by using the Wilson (1960) equation andthe temperature and salinity values observed ateach sampling depth:

Vµ=1449.14+Vρ+Vφ+Vσ+Vτ+Vστρ

Velocity corrections seldom vary apprecia-bly over relatively short periods of time throughoutmost project areas. It is, therefore, practical to aver-age computed velocities from several casts at layermid-depths for final corrections; however, under spe-cial circumstances such as in areas of upwelling, ex-tensive estuarine discharge of fresh water, or in areassuch as the Gulf Stream or Great Lakes where largetemperature variations occur, series of regional ve-locity curves are required. Regional curves must becarefully studied to determine how they can be bestgrouped by area or time or to permit drawing of aver-age curves. It is also desirable to take frequent tem-perature observations in such areas with a bathy-thermograph, thermistor, or similar sensor to disclosethe existence of temperature inversions and to assistin the selection of appropriate depths for sampling.Steep temperature or salinity gradients in the watercolumn require closer spacing of Nansen bottles.

Using this equation, velocities of soundmay be determined in one of three ways:

2. By using the ''Sound Speed and Struc-ture Form'' nomogram also included in table 12; or

Because oceanographic data are assembled

(JUNE 1, 1981)4-75

sity shall be made against a surface bucket sampleto avoid gross errors. Surface sample values forthis check may be determined by using a hydrome-ter and thermormeter. If differences between sensorvalues and surface check values exceed 1C° or 1%o

(ppt salinity), corrections shall be computed andapplied to all sensor data. Instruments shall also berecalibrated or adjusted as necessary.

1. By using table 12 in U.S. Naval Ocean-ographic Office Special Publication No. 68, ''Hand-book of Oceanographic Tables'' (Bialek 1967), tolook up and sum algebraically the equation vari-ables;

3. By using an available program for cal-culating velocities if the hydrographic party isequipped with a digital computer. (See ''HYDRO-

where Vµ is the velocity of sound through water inmeters per second, Vρ is a correction for pressure(depth), Vφ is a correction for the variation ofgravity with latitude, Vσ is a correction for salini-ty, Vτ is a correction for temperature, and Vστρ isa simultaneous correction for the combined effectsof temperature, salinity, and depth.

HYDROGRAPHIC MANUAL

4.9.5.2.6. Sample computation of velocity cor-rections The following examples illustrate methodsused for computing velocity corrections:4.9.5.2.3. Layer corrections. When the veloci-

ty of sound has been determined for each layer mid-depth, a correction for each layer can be computed.A correction factor based on a calibrated sound ve-locity of 800 fm/s is then obtained from table C-7.For echo sounders calibrated at other velocities, fac-tors can be calculated by using the formula:

factor = A–CC

where A is the actual velocity at the layer mid-depthand C is the velocity for which the instrument hasbeen calibrated.

Multiply each layer thickness by the factorto derive the layer correction. Exercise cautionwhen computing the first layer correction. If thislayer includes the depth from the surface to thetransducer, correction factors are multiplied by thelayer thickness minus the vessel draft instead of thetotal layer thickness. Although in many areas the ef-fects of draft may be negligible, it should be consid-ered before ignoring it in the calculations. A draftthat results in a layer correction of less than 0.1% ofthe depth is considered negligible. In column G, enter the cumulative

sums of the layer corrections from column F.4.9.5.2.4. Corrections versus applicable depths.Layer corrections are summed algebraically to givethe correction applicable to the depth at the bottomof each layer (i.e., when using 10-m intervals, thecorrection at an actual depth of 70 m is equal to thesum of the first seven layers.)

4.9.5.2.5. Velocity correction table. Correc-tions for the corresponding actual depths are scaledfrom the correction versus applicable depth curve atspecific correction intervals. It should be noted,however, that observed depths to which the correc-tions apply are not the same as the actual depths. Theobserved depth is the actual depth minus the

4-76(JUNE 1, 1981)

PLOT/HYDROLOG Systems Manual'' (Wallace1971).)

Example 1. Table 4-11 has been computedfor a salinity, temperature, depth sensor (STD) cast(AL.2.6) taken at 35° latitude.

In column A, the mid-depths of eachlayer are entered following the selection of layerthicknesses.

In columns B and C, tabulate the tem-peratures and salinities observed at each mid-depthfrom the STD cast data.

In column D, enter the velocities ofsound for each mid-depth as computed using one ofthe methods described in section 4.9.5.2.2.

In column E, the correction factors foreach tabulated velocity, relative to the calibratedvalue of 800 ftn/s, are interpolated from table C-7(appendix C) or as described in section 4.9.5.2.3.

In column F, each factor tabulated incolumn E is multiplied by its respective layer thick-ness and the product entered. Note that the layerthickness for the first layer correction is 6 m for avessel with a 4-m draft.

In column H, the maximum depth ofeach layer is entered as the applicable actual depthfor the corresponding computed velocity correction.

If the data were obtained by a tempera-ture, depth, conductivity sensor (TDC) cast (AL.2.5)and conductivities rather than salinities were mea-sured, computations are similar except that the ob-served conductivity values must be converted to sa-linity values prior to calculating velocities in columnD.

Columns G and H are converted to thesounding unit assigned to the survey, then plotted onNOAA Form 75-21, ''Velocity Corrections,'' asshown in figure 4-45. For the example, soundings arein fathoms. Velocity correction curves for greaterdepths can be shown on the same graph used for theshoaler water curve by applying an appropriate ratioto the shoal water scales. In this example, the ratio

When sampled depths are not equal topreselected layer mid-depths, computed velocitiesare plotted against their depths. Velocities for layermid-depths are scaled from a smooth curve faired tothe plotted points.

Up to this point, computations are in metricunits. Corrections and applicable actual depths arenow converted to the sounding units for the survey.The summed corrections are plotted against applica-ble actual depths in the proper units and a smoothcurve faired through the points.

correction (figure 442), and the velocity correctiontable for each vessel should be so constructed. Cor-rection intervals are dependent upon the depth ofwater and character of the area. (See table 44 andsection 4.9.2.)

HYDROGRAPHY

TABLE 4-11.— Example of velocity correction computations, STD cast *

Tempera- AccumulativeMid-depth of Salinity Mid-depth ApplicableCorrection Layercorrectioneach layer velocityture factor layer Corr actual depth

(m/s)(C) (‰)(m) (m)(m) (m) (m)

19.6 1519.4 +0.03855 +0.23 101518.7 +0.03807 +0.38 +0.611516.8 +0.37+0.03677 +0.981509.5 +0.03179 +0.32 + 1.301492:4 +0.20+0.02010 + 1.501481.5 +0.13+0.01265 + 1.631484.5 +0.15+0.01470 + 1.781488.3 +0.17+0.01729 + 1.951492.7 +0.20+0.02030 +2.151497.0 +0.02324 +0.23 +2.38 1001499. 4 +0.02488 +0.25 +2.63

1201500.7 +0.02577 +0.26 +2.89130+ 3.151501.5 +0.02632 +0.26

1502.0 +0.02667 +0.27 +3.421502.0 +0.02667 +0.27 + 3.691502.0 +0.02667 +0.27 + 3.961501.6 +0.02638 +0.26 +4.221501.3 +0.02618 +0.26 +4.481500.9 +0.02590 +0.26 +4.74 1901500.1 +0.02536 +0.25 +4.991499.3 +0.02481 +0.99 + 5.981494.4 +0.02146 +0.86 +6.84 2801491.3 +0.01934 +0.77 +7.61 3201489.2 +0.01791 +0.72 + 8.33 3601485.5 +0.01538 +0.62 +8.951481.9 +0.01292 + 5.17 + 14.121494.5 +0.01470 + 5.88 +20.001489.8 +0.01832 +7.33 +27.331495.8 +0.02242 +8.97 + 36.301501.5 +0.02632 + 10.53 +46.831507.6 +0.03049 + l2.2O + 59.03

* Computed for echo according taken with an instrement calibreated for a velocity of sound of 800 fm/s and taken by a verssd with a draft of 4.0 m or 2.2 fm

or scale factor of 10 as shown on the form was se-lected. Note that the velocity correction which willbe applied is zero at the depth of the transducer.

Plied from the depth for which the correction is+ 0.05 fm to the depth for which the correction is+0.15 fm.

a. Determine the required soundingcorrection intervals from table 4-4. (See 4.5.7. 1.)

-

4-77 (JULY 4, 1976)

170

2600

400800

12001600200024002800

200240

Velocity corrections are scaled from thePlotted curves at the appropriate correction inter.vals, then tabulated in a Velocity Correction Table(table 4-12):

b. Scale the actual depths from thegraph at the points where the curve crosses the cor.rection values for the required correction interval,and enter these depths in column J. (See table 4-12.)In shoaler waters where corrections are applied tothe nearest 0.1 unit, the depth range for a discretecorrection is from the depth where the curve crossesa correction value 0.05 unit less than the discretecorrection to the depth where the curve crosses acorrection value 0.05 unit more than the discretecorrection value (e.g., a 0.0-fm velocity correction isapplied from the depth for which the correction is0.05 fm to the depth for which the correction is+ 0.05 fm); a + 0.1 fm velocity correction is ap-

c. Tabulate in column L the appro-priate velocity correction values for the scaleddepths.

d. Subtract the corrections in columnL from the actual depths in column J for the appli-cable depths in column K. The values listed in col.umn K are the entering arguments for determiningvelocity corrections.

To determine a velocity correction, findthe nearest discrete depth in column K that isgreater than or equal to the observed sounding plusdraft to be corrected; the corresponding entry in col.umn L is the correction to be applied to the sound-ing. From the example shown in table 4-12, the ve.locity correction is + 2.0 fm for an observedsounding of 77.2 fm and a draft of 2.2 fm.

Example 2. The method used to com.pute velocity corrections from Nansen cast data var.ies slightly from example 1. The Velocity Correction

2200180014001000

600380340300260220195185175165155

145135125115105

9585756555453525155

19.218.515.910.7

7.78.49.3

10.411.512.112.412.512.512.4

12.312.111.911.711.411.1

9.58.57.86.75.44.23.93.73.53.3

33.633.733.833.934.034.134.334.434.634.734.935.035.235.435.6

35.735.835.936.036.136.136.236.236.136.034.535.235.135.135.035.0

203040

6050

708090

140150160

110

180

+0.23

A B C D E F G H

FIGURE-4-45-Velocity correction curve plotted from data in columns G and H in table 4-11

JULY 4.1976 4-78

HYDROGRAPHIC MANUAL

HYDROGRAPHY

TABLE 4-12.—Example of a Velocity Correction Table(derived from figure 4-45). The draft is 2.2 fm.

K LTo applicable depthTo actual depth Velocity correction 4.9.5.3. COMBINING OCEANOGRAPHIC DE-

TERMINATIONS WITH DIRECT COMPARISONS. Glen-erally, in other than shoal waters, the best and mostaccurate method of determining sounding correctionsis to combine oceanographic observations with directcomparisons. Significant information can be obtainedby comparing bar check data (if the depth recorderhas been adjusted to eliminate major errors) withvelocity corrections derived from oceanographic orlimnologic observations. The displacement of the barcheck velocity correction curve relative to the curvederived from temperature and salinity data (figure4-47).indicates the sum of the draft and the residualinstrument error. The shapes of the curves, in the-ory, should be identical. Major variations in theshapes or slopes occurring in common depths indi-cate a malfunction in the sounding system that mustbe remedied.

from surface(fm)(fm) (fm)

3.2 0.03.25.6 5.5 +0.18.2 8.0 0.2

11.0 10.7 0.313.6 13.2 0.416.3 15.8 0.521.2 0.620.632.0 31.2 0.846.0 45.0 +1.055.6 54.4 1.262.6 1.461.270.0 68.4 1.678.0 76.2 1.885.4 83.6 +2.093.4 91.2 2.2

101.0 98.6 2.4108.0 105.4 2.6

112.2115.0 2.8132.0135.0 +3.0186.0190.0 4.0250.0255.0 5.0324.0330.0 6.0

412.0 405.0 7.0485.0 278.0 8.0560.0 551.0 9.0

Velocity corrections derived by combiningdirect comparisons with oceanographic data are de-termined as follows:

630.0 620.0 +10.0690.0 679.0 11.0745.0 733.0 12.0

787.0800.0 13.0852.0 838.0 14.0900.0 885.0 15.0945.0 929.0 16.0990.0 973.0 17.01035.0 1017.0 18.01080.0 1061.0 19.01120.0 1100.0 +20.01158.0 1137.0 21.01195.0 1173.0 22.01232.0 1209.0 23.01265.0 1241.0 24.01295.0 1270.0 25.0

Computation Table shown in table 4-13 illustratesthe method to be used.

In columns AA, BB, and CC enterthe oceanographic data determined from the cast.

4. The Velocity Correction Table is then

4-79 (JULY 4, 1976)

J

In column DD, compute the velocityof sound for each Nansen bottle depth by one of themethods described in section 4.9.5.2.2 and enter theresults.

In column D, plot the computed ve-locities in column DD against their respective actualdepths (figure 4-46); then fair a smooth curvethrough the plotted points. Scale the interpolatedvelocities for the selected layer mid-depths and enterthem.

In columns E, F G, and H, deriveand tabulate as described in example 1 for the sub-sequent plotting of the velocity correction curve andcompilation of the Velocity Correction Table.

1. Plot the correction curve, based onoceanographic data, in accordance with section4.9.5.2.6. (See figure 4-47.)

2. Plot at the same scale the curve fromdata obtained by direct comparison. Depths scaledfrom an analog record for comparison must be cor-rected for all known instrument errors (i.e., initialerror, stylus arm length error, and fine are error).Note that the plotted curves should be based ondata averaged from a series of observations.

3. Measure the average displacement (don figure 4-47) of the bar check curve from theoceanographic curve. The displacement is equal tothe combined residual instrument error plus draftand will be applied separately as a sounding correc-tion. (See 4.9.7.) For vessels where the draft variessignificantly or bar checks were not taken, draft isdetermined for each comparison and applied sepa-rately. The shapes of the two curves in commondepths should be nearly identical if the echo sounderis calibrated properly and the direct comparisons aremade carefully and accurately.

CC DD HAA ABBActual depthDepthLayerCast-depth Velocity Md-depth mid-depth CorrectionSalinity

correctioncorrectionfactorof layers velocity(m) (°C) (%o) (m)(m/s)

+0.2621.36 1526.7 1526.7 +0.2635.81 +0.0435451526.4 +0.6921.35 35.79 1526.8 +0.43+0.043349

+1.1235.77 1525.9 +0.4321.02 1526.0 + 0.0429925+1.551525.6 +0.43+0.0427935.75 1525.920.92 35

+0.39 +1.941519.5 +0.0386220.59 35.77 1525.335.77 1517.1 1513.7 +0.35 +2.2917.61 +0.0346647 5535.7715.12 1509.9 1511.1 +0.03288 +0.33 +2.62

1509.2 +0.36+0.03158 +2.9813.86 35.71 1506.0951507.7 +0.31+0.03056 +3.29142 35.6612.62 1502.8 85

+3.5935.61 1506.2 +0.30+0.0295395190 1501.512.061505.2 +0.29+0.02885 +3.88287 11.38 35.53 1500.7 105

1499.4 1504.3 +0.02823 +0.28 +4.16385 10.59 35.41+0.281498.2 1503.610.03 +4.44+0.02775448 35.30+0.27+0.02748 +4.711496.3 1503.2538 9.12 35.25+0.27+0.02714719 35.16 1492-8 1502.7 +4.98743

6.02 1490.2 1502.3 +0.02686 +0.27 + 5.2535.019011502.1 +0.27 + 5.521490.034.97 +0.026731086 5.211501.8 +0.27 + 5.791490.54.20 34.96 +0.0265213691501.6 +0.26+0.02638 +6.051496.434.941853 3.681501.3 + 6.311500.5 +0.02618 +0.263.41 34.9421531501.0 +7.35+0.02597 + 1.041500.7 + 1.03 + 8.38+0.025771500.6 + 1.03 +9.41+0025701500. 1 +1.01 +10.42+0025361499.7 +0.02509 + 1.00 + 11.421495.2 +8.80+0.02201 +20.221490.0 +0.01846 +27.60+ 7.381490.6 +001887 +7.59 + 35.191495.4 +0.02215 +44.05+8.861501.1 +54.47

+66.28

• Computed for echo sounding with an instrument calibrated for a velocity of sound of 100 fm/s taken by a vessel with a draft of 4.0 fm or 2.2 fm

derived from the oceanographic curve as describedin section 4.9.5.2.6.

4.9.6. Instrument Error Corrections

Soundings shall be corrected for errors in-troduced by mechanical and electronic faults in thedepth recording system. (See 4.9. 1. 1.) Digital depthsare nearly free of these errors and generally do notrequire corrections of this nature; corrections for in-strument errors must be applied to depths scaledfrom analog records.

Translating the bar check curve to theoceanographic curve has several advantages over atranslation in the opposite direction:

Although digital depths may comprise thepnmary depth data for a hydrographic survey(4.8.5.1), it is imperative that instrumental errors inanalog depth records be kept to an absolute mini.mum. Careful calibration and adjustment proceduresmust be strictly observed, and continual diligenceexercised by hydrographers and recorder operators.The following sections discuss the various types ofinstrument errors common to most analog recorders.See section A.6 for more details and calibration pro-cedures for specific instruments.

4-80(JULY 4, 1976)

10001400180022002600

+0.02604+0.029531506.2

+10.42 + +11.81

1. The resulting curve and correctiontable give a more meaningful profile of the actualvelocity of sound correction.

2. Bar check errors are not propagatedinto the oceanographic velocity correction curve. Aslight depth error when observing temperatures andsalinities has little effect on the velocity determina-tion because of the slow rate of change in velocitywith depth. Depth errors made during a bar checkor caused by poor line calibration severely impactthe results of that check. For this reason, bar checksare logically grouped and average curves drawn.

3. Several vessels working in close prox-imity can share a common velocity curve if theirdrafts are the same or if the difference in correctionscaused by neglecting the draft layer of water is insig-nificant.

4.9.6.1. INITIAL ERRORS. In the setting ofthe initial pulse, errors are manifested by noncoinci-dence of the trace of the leading edge of the trans-mitted outgoing sound pulse with the zero line on

HYDROGRAPHIC MANUAL

TABLE 4-13.—Example of velocity correction computations, Nansen cast•

Temperature

0

192838

71

15

45

6575

102030405060708090

100110120130140150160170180190200240280320360400800

12001600200024002800

115125135145155165175185195220260300340380600

GFD E

HYDROGRAPHY

FIGURE 4-46.—Velocity versus a depth curve plotted from columns AA and DD in table 4-13The depths in parentheses are for the deep water curve.

4-81 (JULY 4, 1976)

HYDROGRAPHIC MANUAL

FIGURE 4–47.—Velocity correction curve with combined observations

4-82(JULY 4,1976)

(For

dee

p w

ater

,add

a 0

to th

ese

figu

res)

HYDROGRAPHY

the chart recording paper. Most analog depth re-corders are equipped with an initial setting adjust-ment that allows the instrument operator to main-tain the initial pulse at zero. Nonzero settings areidentified easily when scanning analog records. (See4.9.8.) Corrections for initial errors must be appliedto scaled depths of peaks and deeps that occur be-tween interval soundings.

Unfortunately, the initial trace is registeredonly on the first scale (''A'' scale) or depth range ofthe recorder. When sounding in deeper waters andrecording on wales other than the A-scale for ex-tended periods of time, the scale setting shall be fre-quently switched to the A-scale, momentarily, tocheck the initial setting. This check is performed asoften as necessary to ensure that the initial setting isnot fluctuating in a manner that precludes accuratedetermination of corrections. Digital depths are not.subject to initial setting errors.

4.9.6.2. PHASE ERRORS. These are disagree-ments between recorded soundings common to morethan one phase or scale setting of the analog depthrecorder (i.e., soundings in phase overlap depths).Such errors are caused by improper calibration ofthe instrument. Necessary adjustments should bemade only by qualified electronic technicians.

Digital phase checkers . (A.6.3.1.4) providethe best means of detecting and measuring phaseerror. ''True depths'' are simulated electronically andrecorded on the graphic depth record. The phaseerror is the difference between the simulated sound-ing and the recorded value. Otherwise, phase errorscan be detected readily by comparing soundings freeof other instrumental errors that occur in the over-lapping depths between adjoining scales. Althoughnot as accurate, bar checks made at depths commonto more than one phase can be used to determinethe error. Phase error is compensated by applying aconstant correction to all soundings scaled from ananalog depth record at a particular scale. Digitaldepths are not subject to phase error.

The scale of the depth lines is computedand printed on the recording paper on the assump-

4-83 (JULY 4, 1976)

Errors caused by incorrect stylus armlengths can be detected by making a careful visualcomparison of a single trace of the stylus with a finearc that is preprinted on the recording paper. Thepreferred method of comparison is to transfer a se-ries, of points from a preprinted arc on the recordingpaper to a mylar or other suitable clear plastic over-lay. The overlay is then placed over an actual stylustrace on the graphic depth record to determine ifthere is a significant deviation between the two. Ifthe two traces conform exactly, the stylus arm iswithin ± 0.5% of being correct; and the recordedsoundings are correspondingly accurate to within± 0.5% of the depth range within the particularscale or phase used. Deviations between the twotraces at the center of the graphic depth record aredirectly proportional to the errors in stylus armlengths. A deviation of 0.4 mm at the center of atrace is equivalent to a 1.6-mm error in arm lengthand causes a 1% error in depth throughout the scale.If the printed fine arc bulges outward from the sty-

tion that the radius of the rotating stylus arm willbe maintained at its constant calibrated length. Er-rors in the recorded sounding traces occur if the sty-lus arm radius is too long or too short. (See figure4-48.) If the arm is too long, scaled analog depthsare greater than actual depths; conversely, if the armis too short, scaled values are less than actualdepths. Ile magnitude of the depth error is propor-tional to the error in the length of the stylus arm.Stylus arm error corrections are applied to scaledsoundings as a percentage of the relative depth in each scale and vary from zero at the top of eachscale to a maximum at the bottom of each scale (notas a percentage of the entire depth).

4.9.6.3. STYLUS ARM LENGTH ERRORS. Onsome echo sounders, such as the Raytheon DE-723,depths are determined graphically by the length ofthe stylus arm and the angle through which it ro-tates in the interval between the transmitted and re-ceived acoustical pulses. Various angular rotationvalues correspond to fixed depths. FIGURE 448.Echo sounder stylus arm-length error. The

effective length here is too long causing recorded depthsto be greater than actual depths.

HYDROGRAPHIC MANUAL

in use, various ways by which frequency can bemeasured or checked include:

lus trace as shown in figure 4−48, the arm is toolong, the scaled values are greater than the actualdepths, and a negative correction is required.

A dial-type frequency meter.4.9.6.4. STYLUS BELT LENGTH ERRORS.

These occur only in soundings scaled from analogrecorders equipped with a recording stylus.mountedon an endless moving belt [e.g., Ross Sounding Sys-tern (A.6.3.2)]. These errors are easily detected bygenerating simulated depths with a digital depthchecker, then comparing simulated and recorded val-ues. Most endless belt-type recorders are equippedwith the internal circuitry necessary for digital depthchecking. Stylus belt length error effects are similarto those of incorrect stylus arm length (4.9.6.3);therefore, when detected they must be corrected im-mediately.

Variations in frequency from the standard60 Hz shall be noted in the sounding recordsuchvariations must be corrected or adjusted immedi-ately. Recorder frequency shall never be varied in anattempt to compensate other analog recorder errors.

4.9.6.5. FINE ARC ERRORS. These are re-vealed by a divergence of the stylus trace from theprinted fine arc on the recording paper. A fine arcerror may be present even when the stylus arm ra-dius is at the proper length. (See figure 4−49.) Thiserror is generally caused by misalinement of the re-cording paper and the corresponding displacementof the stylus arc center from the paper axis. Adjust-meats to the analog recorder to elimmate a fine arcerror must be made by a qualified electronics techni-cian at its first indication.

4.9.7. Transducer Correction

The final transducer (TRA) correction is thealgebraic sum of the corrections for the combinedeffects of dynamic draft and instrument errors. TheTRA correction is a time, vessel, echo sounder de-pendent variable that must be applied to all ob-served analog and digital soundings.

The form shown in figure 5−7 [5.3.5(D)] ora similar version should be used to list TRA correc-tions; the listing must be included in the DescriptiveReport for survey verification reference.4.9.6.6. FREQUENCY ERRORS. Variations in

frequency of the recorder power supply (usually 60Hz) that drives the synchronous motor, which inturn drives the stylus arm shaft or belt, generateserrors in scaled soundings. If the operating fre-quency is too high, the arm or belt moves too fastcausing recorded depths to be too deep; conversely,low frequencies result in recorded depths that aretoo shallow. When available, constant frequencypower sources should be used for analog depth re-corders. Depending upon the particular instrument

4.9.8. Scanning Analog Depth Records

4.9.8.1. CHECKING RECORDED DEPTHS.Hydrographers shall carefully inspect all graphic an.alog depth records (echograms, fathograms) to en-sure that each important sounding has been scaledand recorded properly. (See 1.5.3.)

Digital soundings, when taken, shall be con-sidered the primary sounding data because of theirgreater accuracy; graphic depth records comprisesupplemental information and will be used for:

3. Adjusting digital soundings for theeffects of heave (wave action).

FIGURE 4-49.¾Echo sounder fine-arc error 4. Determining the presence of shoals

4-84(JULY 4, 1976)

Counting the- number of stylus revolu-tions (on the fathoms scale) in a set time intervaland comparing the revolutions with the manufactur-er's specifications and with the linear measurementof paper travel.

The position of a vibrating reed on areed frequency meter.

1. Scaling and recording peaks, deeps,and other important soundings that occur betweenthe normal digital sounding interval (1.4.3).

2. Correcting digital soundings that dif-fer significantly from analog soundings because ofstray returns, side echoes, fish, and similar reasons.

HYDROGRAPHY

When the bottom is extremely irregularmaking it impractical to scan and plot soundingsthat reveal every irregularity, soundings are selectedto show the general topographic character of thebottom.

There are no rigid specifications that defineacceptable differences between digital depths anddepths scaled from graphic records. Close agree-ment, however, is essential since depths must bescaled from the graphic record to supplement digitaldata. The hydrographer must continually exercisesound judgment because acceptable differences varywith the depth of the water, the relative importanceof the area, and the degree of bottom irregularity.For guidance, if digital depths agree to within ± 0.5ft or ± 0.2 fm of scaled depths, the differences gen-erally need not be taken into account; but differ-ences should not exceed ± 0.2 ft or ± 0.1 fm underthe following circumstances:

TABLE 4-14.-Time tolerances for scaling peaks and deeps *

Sounding interval Scale time to nearest Tolerance

5 $ ± 0.5 $10 $ ± 1 $15 $ ± 2 $20 $ ± 2 $30 $ ± 5 $

1 min ± 10 $5 min ± 1 min

10 min ± 2 min

* From Pacific Marine center (1974) OPORDER

4-85 (JULY 4, 1976)

and hazards that are undetectable in the digital re-cords.

Graphic records are used to verify plottedsoundings that appear doubtful when compared withother soundings on adjacent lines or that showabrupt changes in slope contrary to the generalcharacteristics of the area. Inspecting or scanningthe bottom profiles should be conducted as soon aspossible after the lines have been run so the hydrog-rapher can determine whether additional develop-ment work in the area is necessary.

In addition to scanning depth records forrequired intermediate soundings, each sounding,whether determined by digital methods or scaledand entered manually into a sounding record, shallbe checked for accuracy. If the scan for complete-ness and the check for accuracy are carried out inseparate steps, only competent and experienced per-sonnel should be assigned to check the individualsoundings for accuracy. Recorded soundings shall bescanned and checked prior to inking the soundingson the final field sheet.

When the bottom is irregular or the tracepartially obscured by kelp, grass, strays, or side ech-oes, a considerable amount of experience is requiredfor proper interpretation of the graphic record. Re-gardless of the character of the bottom, graphic re-cords often display spurious marks, attributable toechoes from fish, vegetation, debris floating at vari-ous depths, turbulence in the water, abrupt changesin temperature or density of the water, noises gener-ated in the sounding vessel, and instrumental faults.(See 4.9.8.2.) Skill is required to ensure that eachtrace is correctly identified and that the greatestvalue and most accurate results are extracted fromthe records.

Graphic depth records should first be exam-ined to determine whether the initial trace has variedby an amount sufficient to require correction. Neces-sary corrections should be entered in the soundingrecords at the appropriate places. When soundingshave been recorded on more than one scale (phase),each scale change shall be correctly labeled on thegraphic record and noted in the sounding records. Ifa template must be used when scaling soundings, thepaper speed should be checked at each template set-ting. If a template is not used, several paper speedchecks should be made at random during the day'swork. If there is evidence of incorrect speed, a de-

tailed examination is necessary to determine the lo-cation and magnitude of the required corrections.

Soundings are then scaled from the analogrecord at the selected interval and compared withthe recorded soundings; the latter are corrected asnecessary. Significant peaks and deeps between inter-val soundings shall be scaled and entered with thetimes of their occurrence.

For standardizing the scanning and check-ing of graphic depth records and for meeting theInternational Accuracy Standards for HydrographicSurveys (International Hydrographic Bureau 1968),the time tolerances in table 4-14 are specified toscale peaks and deeps.

$$

$$$$

1. On shoals and other hazards.2. On navigable bars.3. In dredged channels.4. At critical places in natural channels.

min min

HYDROGRAPHIC MANUAL

Poor scanning techniques, careless scanning,scanning by inadequately trained personnel, and im-proper interpretation are major sources of defectivedata discovered during the verification of hydro-graphic surveys.

A section of the same graphic record isshown in figure 4-50(B). Note the unbroken bottomtrace. The depression below the unidentified echoindicates current scour around a probable sub-merged obstruction. In this case subsequent wire-drag investigation revealed the presence of a wreckwith kelp growing on top.

Kelp recordings probably cause the greatestdifficulties when interpreting bottom profiles. Sincekelp seldom grows in depths greater than 15 fm, dif-ficulties from this source are encountered in rela-tively shoal water, usually in areas of irregular bot-tom. Kelp traces often resemble side echoes and areusually detached from the bottom trace as seen infigure 4-50(C), or the kelp echo may blend with thebottom trace as shown in figure 4-50(D). Actualbottom profiles can sometimes be traced throughkelp echoes by viewing the graphic record at a slantto accentuate shading differences in the trace. Be-cause clear lines of separation cannot always beseen, doubtful soundings must be investigated using

"Stray'' echoes are marks on the graphicdepth records or spurious digital soundings resultingfrom sources other than the bottom below the ves-sel. Traces from fish, kelp, grass, or electrical noiseare properly classified as strays by the hydrographer.Unfortunately, what appears to be a stray may be,in fact, only too real. There are no rules of thumbthat hydrographers can rely on to distinguish straysfrom actual bottom echoes. To continually and suc-cessfully differentiate between the two, surveyorsmust rely upon experience, good judgment, andluck. A sounding must never be classified as a stray

4-86(JULY 4, 1976)

5. For soundings that delineate the lowwater line.

On steep slopes, digital and scaled depthsmay vary substantially because of the nature of thereturning echo and the recording devices. In theseareas, digital depths are generally accepted. When scaling depths from bottom profilesfor insertion in the digital record tapes, the differ-ence between digital and analog values at the timeof the sounding must be determined. This differenceis applied to scaled analog soundings to obtain theproper digital depth. Values are easily determined bymeasuring the differences between analog and digitaldepths for soundings immediately before and imme-diately following the time in question, then calculat-ing the average. Particular attention must be paid tovariations in the initial setting and to other knowninstrumental errors present during the record period.If a data-acquisition system is not equipped to com-pensate for the effects of heave (wave action) on thevessel, the digital soundings must be so adjusted.

4.9.8.2. INTERPRETING ANALOG DEPTH

RECORDS. Although echo-sounding depth recordershave been used for many years, correct interpreta-tion of bottom profiles remains a major problem onmany surveys. When recorded traces on the graphicrecord cannot be attributed with reasonable cer-tainty to reflections from the bottom or from ob-structions, they should not be recorded as sound-ings. Herein lies a major problem-differences ofopinion frequently arise even among the most experi-enced hydrographers when identifying ambiguous orunclear bottom traces.

if there is any reasonable doubt that it may be anobject dangerous to navigation. Hydrographers, must often investigate a rea-sonable number of representative strays, using a leadline to verify or disprove the interpretation of thebottom trace. Although this procedure may not en-sure infallible results, it does provide tangible evi-dence on which to base an interpretation. Under cer-tain circumstances, it may even be advisable to wiredrag or wire sweep the bottom with a modifiedtrawl sweep (A.6.1.4) or pipe drag before rejectingapparent strays. In many areas, depth recorders arean imperfect means of obtaining soundings totalreliance should not be placed on their measurements.Supplemental lead-line or pole soundings are re-quired to clarify certain traces, substantiate doubtfulleast depths, and, in areas of dense grass, even tomeasure depths for the basic development.

Strays caused by excessive gain settings, er-ratic operation of a depth recorder, or other phe-nomena about which only the hydrographer has per-sonal knowledge should be adequately annotated onthe bottom profile or in the sounding records. Whengain settings are too high, strays recorded on thegraph from various sources are generally identifiableas such. Figure 4-50(A) shows a typical recording ofa stray caused by an overly high gain setting. Straysof this nature can also be generated by faulty electri-cal circuitry aboard the vessel, by mechanical vibra-tions, and by heavy percussions on the hull.

FIGURE 4-50-Typical bottom profiles (fathograms)

a lead line or sounding pole. Although not practicalto investigate all such soundings in a foul area, thelimiting features must be carefully sounded. Each Interpretation in kelp or grass becomes

indication of a pinnacle in or adjacent to a navigablewater must be examined.

(JULY 4,1976)4-87

HYDROGRAPHY

HYDROGRAPHIC MANUAL

The presence of side echoes and strays oftencreates a special problem when digital echo soundersare used. Digital depths are recorded when the re-turning echo reaches a certain intensity or signal re-sponse level. Echoes from fish, kelp, turbulence, anddebris often reach this intensity and are recordedrather than the actual bottom return. Returns froma steep slope may or may not actuate the digital re-corder. Weak side echoes frequently appear on theanalog record but are not recorded-where the leastdepth over a feature is involved, the sounding fromthe analog trace must be scaled. Figure 4-51(D)shows such an example where both an analog recordand a digital record were obtained. The weaker sideecho over the ridge at the second sounding to theleft of position 2192 was not strong enough to berecorded digitally. The least depth had to be scaledfrom the analog record and entered later in the datafile.

In areas of heavy marine growth, the bot-tom trace may be completely obscured as in figure4-50(D). The top of the profile usually has a raggedappearance compared with the smooth bottom; butin some instances, the top of the grass may appearto be no more irregular than the bottom profile. Infigure 4-51(A), the bottom is easily identified in thegaps between traces from the grass permitting thebottom profile to be determined with assurance. Un-less actual bottom soundings can be identified withsufficient frequency for a basic survey, supplementallead-line or pole soundings must be obtained.

Side echoes recorded in deep water generateadditional unresolvable dilemmas when interpretingthe graphic record. The first echo return from asloping bottom may not necessarily be from a pointdirectly below the sounding vessel; it may be fromthat part of the bottom lying the shortest distancefrom the transducer. Under this condition, the re-corded depth is less than the actual depth. In the-ory, when the slope of the bottom is more than halfthe angular beam width of the echo sounder, bottomechoes cannot reach the ship and produce a trace. Inpractice, however, echo traces are obtained overslopes steeper than half the beam width since theparticles forming the sea bed are rough and do notreflect as would a flat surface. Experience has shownthat the best traces from a steep slope are obtainedwhen the survey vessel sails in a direction towardthe shallower water and approximately normal tothe depth contours.

Echo traces caused by fish over shoals, rockpinnacles, and coral heads can be extremely difficultor even impossible to identify as such. Unless de-tailed and complete examinations of these featuresprove that echoes were caused by fish, the assump-tion must be made that the shoalest soundings re-sulted from small outcrops that form part of thebottom.

Side echoes produce traces that may be de-tached from the bottom trace, blend with the bot-tom trace, or mask it completely. Side echoes cannotalways be distinguished from fish or turbulent water.Occasionally, side echoes are the only indications ofboulders, pinnacles, or other submerged obstruc-tions. Side echoes should neither be ignored nor ini-tially accepted as vertical soundings. Such soundingsshould be noted in the remarks column; unless they

If the bottom is undulating or slopessteeply, hyperbolically shaped side echoes often ap-pear on the recorded bottom profile. In the follow-ing hypothetical case, a survey vessel with a 40°

4-88(JULY 4, 1976)

more difficult when higher transducer frequencies areused. Echoes from the bottom may be completelymasked by kelp or vegetation when very high fre-quency transducers are used. In such cases, manylead-line, or pole soundings are required to substanti-ate the hydrographer's interpretation of the actualbottom profile.

Areas where the growth of kelp is suspectedshould be investigated at low water or by a diver toresolve interpretation problem . Echoes from fish are generally easy to dis-tinguish in open seas over regular bottoms—unlessthe fish are lying very near the bottom. In suchcases, fish echoes are usually distinct from the bot-tom; and the bottom echo trace is clearly visible. Ifin doubt as to whether fish are present, the depthrecorder should be switched to slow speed and thegain setting increased to enhance the actual continu-ous bottom profile. Low frequency echo soundersgenerally amplify and enhance a profile if largedense schools of fish are below.

come from previously identified shoaler features, ad-ditional lines should be run to obtain least depths.Typical side echo recordings are shown in figure 4-51(B), and another example of a kelp echo return isshown in figure 4-51(C).

Side echoes representing shoalest depths ob-tained on isolated features should be accepted andplotted as least depths thereon after reasonable ef-forts fail to obtain a shoaler sounding.

FIGURE 4-51.-Common problems of bottom profile interpretation

4-89 (JULY 4,1976)

HYDROGRAPHY

HYDROGPAPHIC MANUAL

transducer beam width is sounding from left to rightin depths of approximately 1400 fm. [See figure 4-52(vertical scale not shown).] Prior to reaching posi-tion 1, the vessel was sounding over relativelysmooth firm bottom. Nearing position 1, the for-ward edge of the acoustical beam strikes shoal Aand records an echo both from the shoal and fromthe bottom directly below the ship. Because theslant distance to the shoal is greater than the verti-

cal distance, a side echo, deeper than the sea bottombelow, is recorded.

equal. Again, the side echo masks the bottom pro-file. The depth recorded at position 3 is the actualdepth because the vessel is directly over the crest ofthe shoal. Then, moving forward, the actual bottomis not recorded again until the distance becomes lessthan the slant distance to shoal B when the vessel ispast position 4. Note that depression C has beentotally masked out and remains undetected. This hy-pothetical case has been simplified by consideringthe problem in only two dimensions. Uncertaintiesbecome considerably more complex when additionalfeatures to the left and right of the vessel's path areThe slant distance to the shoal from posi-

tion 1 is equal to the vertical distance to the bottomcausing the two traces to intersect. Between posi-tions 1 and 2 the bottom echo is masked by theside echo from the shoal because the slant distanceis less. If shoal A were an isolated bottom feature,the side echo would crest at position 2, which is theonly point on the side echo where the apparentdepth and the actual depth are equal. Shoal B, how-ever, is then detected by the leading edge of theacoustical beam just prior to reaching position 2.The new side echo begins to rise from a point belowthat caused by shoal A, then intersects with theother trace at position 2 where the two distances are

introduced.

Actual bottom profiles cannot always be determined with certainty because echo traces do notalways represent actual physical conditions. Hydrog-raphers must then follow a prudent conservativecourse when scaling soundings by joining crests witha smooth curve and making the assumption that thecurve represents the bottom. When the bottom isextremely rough, the graphic depth record may liter-ally be a maze of hyperbolically shaped side echoes,so complex that only indications of general depthscan be extracted.

Irregular profiles resulting from swells orchoppy seas are simils, to profiles of sand waves.When irregular profiles are caused by rough sea con-ditions, readings should be taken along a line repre-senting the average depth, not from tops of peaks.Sounding records and analog depth records mustcontain sufficient notes that describe the cause of theirregular profile. If this information is unrecorded,an examination of the bottom trace may reveal thecause. Chop or swell is usually apparent over theentire line; the character of the graph changes whenheading with or into the sea.

4.9.9. Final Field Soundings

4-90(JULY 4, 1976)

FIGURE 4-52.-Hypothetical example of deep water sideechoes

Reduced field soundings are calculated bythe hydrographic party for surveys on which thedata are plotted manually on the field sheets. Afterall check scanning of the analog depth records hasbeen completed and all corrections have been en-tered in the sounding record and checked, recordedsoundings shall be reduced by the algebraic sum of the corrections; the corrected soundings are then en-tered in the column headed "field'' (See figures4-22 and 4-23.) These soundings must be entered inthe same unit when recording, whether feet or fath-oms. Because only one unit is used on a smoothsheet, recorded soundings must sometimes be con-

HYDROGRAPHY

cords have been scanned and checked for accuracyand corrections and additions made to the automat-ed data listings, the original records, tapes, reports,and printouts are sent to the appropriate MarineCenter for processing when the sheet has been com-pleted.

On automated surveys, listings or tabula-tions of final reduced soundings by the field partyare not required. After the depth profiles and re-

TABLE 4-15. -Conversion of reduced soundings

Reduced soundings in To be plotted on Reduced soundings in To be plotted on Sounding Record Smooth sheet in Sounding Record Smooth sheet in

(fm) (fm)(ft)(ft) (ft)(ft)

-1.3-0.5 -3-3.2 -0-0.8-3.4-2.3

-0-2 -0.7-2.2 -0.3-0.2-1.3

-1 -0.1 0-1.2 -0.20.4-0.8

-0 00.5-0.1-0.71.0-0.3

00 1.1-0.2 0.01.60.2

0 00.1 1.70.3 22.20.7

01 2.30.20.82.81.7

02 2.91.8 0.3 33.42.7 0.4

03 4 3.52.8 0.5

4.03.7 0.6

04 4.13.8 0.74.64.7

054.8 0.8 4.750.9 5.25.7

05.35.8

6 15.96.4

4-91 (JUNE 1, 1981)

verted. Conversions shall be made as shown in table4-15, and the results entered in the double columnheaded ''Office'' (figures 4-22 and 4-23).

5

51

2

3

4

5

6

7

8

9

2

1

HYDROGRAPHIC MANUAL

SPECIAL SURVEY TECHNIQUES4.10.1 General

reefs, rocks awash, heavy kelp, and other unsafeconditions shall be used to determine the limits. Asa general rule, the hydrography should be conduct-ed to the 1-fathorn curve or within 100 meters ofthe shore, whichever is feasible. Where conditionsdo not permit extending the survey to these limits,it would be desirable to include in the DescriptiveReport a simple statement briefly describing condi-tions that prevented nearshore operations. In somecases it will be obviously desirable and practicableto extend hydrography to the beach to develop afavorable landing area. Such cases should be obvi-ous in the course of the survey and by examiningthe T-sheets.

4.10.

Operational requirements occasionally maysuggest usage of survey techniques differing fromthose used for standard basic hydrographic sur-veys. Such techniques may greatly enhance the ef-ficiency of surveying an area without causing anoverall lowering of the survey quality or the fail-ure of the survey to satisfy the requirements. Spe-cial techniques may be required in areas where re-cent photogrammetry is not available and/ordevelopment of the 0-foot curve or inshore watersis not required. Other techniques are used in per-forming a reconnaissance of an area of questionableadequacy. Still others are required to resolve thestatus of unconfirmed charted features and obstruc-tions.

4.11.2.2. SHOALS AND DANGERS TO NAVI-

GATION. Within the sounding area, the develop-ment of shoals and dangers to navigation shall bebasic as instructed in sections 1.4.3, 4.5.9, and4.5.10. This includes all shoals and other dangers tonavigation that are covered or surrounded by navi-gable water. All detached shoals or indicationsthereof shall be investigated, developed, or areasdelimited as required by basic hydrographic tech-niques. Those shoals or dangers which are the ex-tension of nonnavigable waters shall be delimited.The technique of delimiting areas applies only tothose features which cannot be safely developed bystandard methods. Hydrography shall be run towithin 50 meters of a delimited area. Foul areasshall be delimited by fairing a line through: (1) thepositions of the outer off-lying rocks which riseabove MLLW (2) the margins of dense kelp beds,or (3) the line at which breakers form.

It is the purpose of these sections to pro-vide guidance for such special surveys. This guid-ance will be referred to, as appropriate, by anyproject instructions requiring its implementation.

4.11. NAVIGABLE AREA SURVEYS4.11.1.General

The Navigable Area Surveys (NAS) aredesigned to provide contemporary hydrographicsurveys for updating existing nautical charts orconstructing new charts. This type of basic surveyis primarily designed toward meeting charting re-quirements in areas of increased commercial inter-est where scarce or obsolete data exist. Byrestricting the area of coverage of these surveys,yet retaining the basic hydrography concept withinthe surveyed waters, there will normally be a morerapid progression of field work and availability ofdata. The coverage is reduced by normally omit-ting requirements for: (1) development of the0-foot curve and foul near shore areas not consid-ered navigable and (2) complete field edit of thesurvey area.

4.11.2. Hydrogiraphy

Hydrography shall, in general, be basic ex-cept as outlined herein or by the project instruc-tions. 4.11.2.4. LANDMARKS. Landmark verifica-

tion or location shall be done in accordance withsections 4.5 and 5.5.

4.11.2.1. INSHORE LIMITS. General inshorelimits shall be designated by Headquarters; howev-er, onsite deviations may be determined by the hy-drographer and approved by the Chief of Party.Factors such as surf, the foul nature of an area,

4.11.2.5. AIDS TO NAVIGATION. All float-ing and nonfloating aids to navigation in the proj-ect area shall be verified or located in accordance

4-92(JUNE 1, 1981)

4.11.2.3. CHART TOPOGRAPHY. A compari-son of topography as depicted on the most recentchart edition with the actual topography will beaccomplished to determine wherein the chart doesnot present a true picture of the area. When dis-crepancies are discovered and are within the fieldunit's capabilities, they should be resolved. Other-wise, recommendations should be made to secureupdating photography. Such resolution of item dis-crepancies is imperative if the charts are to remaincontemporary in their presentations.

HYDROGRAPHY

with sections 1.6.5 and 4.5.13. To prevent confusion,the latest edition of the chart, corrected via Notice toMariners, should be used. Any discrepancies, once ver-ified, should be reported to the local U.S. Coast GuardDistrict and a copy submitted to National Ocean Sur-vey Headquarters, through the appropriate MarineCenter.

4.11.2.6. MISCELLANEOUS. All other dataand activities pertinent to a basic survey shall be con-ducted.

4.11.3. Data Processing

4.12. CHART EVALUATION SURVEYS

4.12. 1. General

The Chart Evaluation Survey (CES)program is designed to:

2. Evaluate the adequacy/accuracy ofhydrographic information on existing charts.

4.12.2.Operations

4.12.2. 1. DEFICIENCY INVESTIGATIONS.Copies of the latest chart editions will be furnishedwith discrepancy items annotated for resolution. Allavailable background data describing these discrep-ancies will be provided by the Marine Chart Divi-sion, NOS. All indicated items shall be disposed of aswell as any items brought out through local contacts;i.e., U.S. Power Squadrons, U.S. Coast Guard, U.S.Coast Guard Auxiliaries, port authorities, U.S. ArmyCorps of Engineers, and knowledgeable individuals.These contacts may also be of value in resolvingassigned items. The Chief of Party is given the lati-tude to resolve deficiencies by the most expeditiousand effective means available. Since many of theassigned items will be difficult to resolve using stan-dard hydrographic methods, the use of an improvisedwire drag or sweep is encouraged. The records mustbe clearly and accurately annotated to indicate thetype of rig employed, the extent of the area investi-

Not all procedures will be required in each instance,but accomplishment of these program objectives willrequire one or more of the following operations: de-ficiency investigations, reconnaissance hydrography,waterfront planimetry verification, harbor recon-naissance, landmark verification, aids to navigationverification, Coast Pilot inspection, tide/water levelobservations, and user evaluation/public relations ef-fort. This section will describe each technique, theeffort required by the technique, and the desired re-sults of each portion of the program.

A unit assigned to Chart Evaluation Surveyswill progress through areas of NOS charting respon-sibility as rapidly as possible while fulfilling all pre-scribed objectives and requirements. To the extentpossible, Chart Evaluation Surveys will be coordi-nated with the chart printing schedule and planned

4-93 (JUNE 1, 198 1)

All data processing shall be completed as forany basic survey and in the same format with no spe-cial priorities assigned to the Navigable Area Sur-veys.

1. Resolve all deficiencies reported or dis-covered. (A deficiency is defined as charted informa-tion that can be made more complete through fieldinspection, or information which should be but is notcharted.)

3. Verify or revise information publishedin the appropriate Coast Pilot. 4. Conduct user evaluation and public re-lations efforts to provide an awareness of NOS prod-ucts and obtain user input.

so as to provide the new revision data in a timelymanner most beneficial to the users. Control for these surveys shall be by the bestavailable methods, including the use of charted land-marks and fixed aids, to navigation that have beenverified or located to not less than third-order posi-tional accuracies.

Normally accompanying the project instruc-tions will be a series of charts with items identified(marked and numbered) for investigation along witha listing defining each item. Additional deficienciesmay be found during the survey and these shall be in-vestigated and resolved as well. Also included willbe itemized tide/water level information- eitherwhere a staff or gage is required, bench mark infor-mation, and where and what predictions are to beused for reducing hydrographic data to chart datumor, perhaps, what maintenance shall be performed insupport of another NOS program. Where extensive hydrographic surveying isauthorized and for any reconnaissance soundinglines, the Chief of Party shall ensure that adequatecorrectors are determined in accordance with provi-sions in section 1.5.4. Bottom samples are not required unless spec-ified.

The project instructions shall specify whichof the following techniques shall be applied to thesurvey. Time frames, extent of effort, and area limitswill be described in the instructions.

HYDROGRAPHIC MANUAL

gated, and the time spent. Proper resolution of a sub-merged feature after it has been located includes thedetermination of a least depth. Techniques effectivein accomplishing this objective include the use of di-vers as well as drift soundings employing a lead line.Where resources permit and the project area appearsto warrant it, side scan sonar may be furnished. In-stances occasionally arise which would indicate thatresolution of an assigned item is impossible or im-practicable. These items should be evaluated on acase-by-case basis by the Chief of Party. Factorswhich should be considered are proximity to vesseltraffic areas, surrounding depths, existing control,and likelihood of resolution. If, in the opinion of theChief of Party, resolution of an item does not meritthe anticipated expense in time and manpower, thatitem may be omitted from the investigation list.When possible, the Hydrographic Surveys Division,OA/C35, should be notified of items not investigatedprior to leaving an area. In all cases, a statement de-scribing the factors affecting the decision should beincluded-in the Descriptive Report.

within the field unit's capabilities, they should be re-solved. U.S. Army Corps of Engineers' surveys, con-struction drawings, private surveys, and city orcounty maps shall be utilized wherever possible toeliminate duplication of effort. However, when printsfrom other Federal sources are used, verification ofinformation shown thereon must be made to ensurethat the resulting revision of the chart will be correctand adequate. When discrepancies are found whichrequire corrections that are beyond the capability ofthe field party, recommendations should be made onways to accomplish their resolution, such as securingchart updating photography.

4.12.2.4. HARBOR RECONNAISSANCE. Re-connaissance soundings shall be taken in active slipsand along pier faces to verify the charted depths andcontours. Adequate data shall be collected and re-corded to permit evaluating charted hydrography.One sounding line should be run approximatelywhere the keel of the pertinent vessel would travelin approaching and mooring to the pier. Lead linesoundings are required close to pier and wharf facesto prevent false side echoes from being received andrecorded on the echogram. To verify charteddepths, reconnaissance soundings shall be taken inother portions of the inner harbor outside of regular-ly maintained project areas.

4.12.2.2. RECONNAISSANCE HYDROGRAPHY.Reconnaissance hydrography, as related to ChartEvaluation Surveys, is primarily for the purpose ofevaluating the nonmaintained charted depth informa-tion although maintained areas should be checkedalso. This may range from just a few sounding linesto somewhat extensive operations in areas wheredangers to navigation are known to exist or are foundto exist. Since each situation is different, general guid-ance will be provided with each project with the fi-nal determination of survey effort left to the Chief ofParty. If extensive hydrography is required, the Hy-drographic Surveys Division, OA/ C35, should benotified through the appropriate Marine Center for adecision on what further action should be undertakenand the scope of this action. Reconnaissance hydrog-raphy should generally be conducted at the scale ofthe largest scale chart or manuscript available for thearea.

4.12.2.5. LANDMARK VERIFICATION. Allcharted landmarks shall be evaluated for their exis-tence, accuracy of position, and usefulness for navi-gation. Recommendations should be made regardingthe deletion and/or addition of landmarks. Any land-marks to be charted shall be located in accordancewith provisions of the Hydrographic Manual. Land-marks can be verified by observing a multiobject sex-tant fix from a position along the shore. This initialfix will indicate charted landmarks misplotted in onedirection. The fix should be plotted on the chart be-ing verified and appropriate rays drawn through thelandmarks observed. Subsequent fixes are then ob-served ensuring a minimum ray intersection angle of30° at each charted landmark. Two intersecting raysshould prove or disprove the adequacy of the chart-ed landmark position. Should this method indicate aninaccurately charted feature, methods described insection 4.5.13.1 should be followed.

4.12.2.6. AIDS TO NAVIGATION VERI-

FICATION. All floating and nonfloating aids to navi-gation shall be checked for charted accuracy. Toprevent unnecessary effort, the latest edition of theWhen discrepancies are discovered and are

4-94(JUNE 1, 1981)

4.12.2.3. WATERFRONT PLANIMETRY VERI-

FICATION. The waterfront planimetry depicted onthe chart shall be compared with the existing condi-tions in sufficient detail to determine whether or notthe chart presents a true picture of the area. Carto-graphic factors such as the scale of the chart must begiven, due consideration; i.e., features that can andshould be shown on a scale of 1-5,000 will not neces-sarily be depicted on a 1:20,000 or smaller scale chart.

HYDROGRAPHY

chart, corrected through the latest Notice to Mariners,should be used. Any discrepancies should be resolvedand reported in accordance with section 4.5.13.

4.12.2.7. COAST PILOT INSPECTION. The ap-propriate Coast Pilot shall be examined for accuracyand completeness in the areas of operation, as well asen route. If modifications are required, reports shall besubmitted in accordance with section 5.8.

4.12.2.8. TIDE/WATER LEVEL OBSERVA-

TIONS. For any specified hydrography or item discrep-ancy investigations, tide/water level requirementswill be issued with the project instructions.

Contact with the user should be oriented withthe objective of obtaining input as to the adequacy ofthe existing chart layout, scale, format, color, etc., andto inform the public of the mission of NOS and themany products and services provided by this Agency.Results of these contacts should be included in the De-scriptive Report in detail sufficient to provide NOS(Marine Chart Division) support for future chart andsurvey planning.

Predicted tides are the only tidal data avail-able to the mariner for reducing his observed depths tothe chart datum; therefore, the accuracy of the pre-dicted tides in the project area may require verificationif so directed in the project instructions. This can be ac-complished in several ways. A site having a flat bottomis selected near an offshore entrance to a harbor or oth-er area of critical navigation within the working area.On a range, near a buoy, or using a marker installed bythe survey party, depths are determined at the predict-ed times of low water, high water, and midway be-tween during normal meteorological conditions.Depths should also be measured before and after thepredicted tides to determine the actual times of highand low water and any differences noted. Depth obser-vations should be made using a calibrated lead line orother calibrated direct means and the measurement lo-cation should vary as little as possible. At a number ofstation locations selected from table 2 of the tide tables,a bubbler tide gage should be installed and operated fora minimum of 3 days (installation of a staff is not re-quired). Care should be taken to ensure the orifice willnot be subject to movement while in operation. Theanalog record will be annotated for time, data, andweather (including unusual meteorological condi-tions). Any particular requirements such as locationand priority will be furnished in the project instruc-tions.

4.12.3. Data Processing

Because of the special nature of these surveysand the need to reduce the time between field acquisi-tion and office processing of the charting data, it is in-tended that the data will not be processed through theMarine Centers. Instead, the survey party will be re-sponsible for field processing the data to a point where

the responsible cartographer in the Marine Chart Di-vision, OA/C32, can apply the data directly to thechart with a minimum of additional data reduction orverification required. Extreme care must be exercisedby the field party to assure that the plotting of data onchart overlays or plotting sheets is done accuratelyand is in accordance with provisions of the Hydro-graphic Manual. A concise and yet comprehensiveDescriptive Report must be included with each chartrevised so that the office cartographer can readily de-termine and evaluate the merits of proceduresemployed by the field hydrographer in his data reduc-tion. All appropriate correctors shall be applied tosoundings. The use of correctors determined fromreal-time tide/water level observations is preferredover predicted tides if they are available. All revisionsand notations to land and water features shall be madeon the latest edition of the largest scale chart of eacharea. It is not mandatory that chart notations are colorcoded. It is, however, essential that each notation belegible and complete. If the hydrographer chooses touse a color code, he should ink all change and additionnotes in red ink, all deletion notes in green ink, and allconfirmation notes in blue ink. It is important that allinspection and revision notes be inked on the chart bythe hydrographer as the field work progresses. If a

In most instances, a real-time reduction of hy-drography can be accomplished in Chart EvaluationSurveys and still achieve the objectives of these sur-veys.

4.12.2.9. USER EVALUATION PUBLIC RELA-

TIONS EFFORT. Every effort shall be made to contact

4-95 (JUNE 1, 1981)

Water level requirements in nontidal areas areless complex and can generally be satisfied using tem-porary gage installations.

users through the news media and local organizations.Names and addresses of suggested contacts will befurnished, when available, and will generally include:U.S. Army Corps of Engineers; U.S. Coast Guard;U.S. Coast Guard Auxiliaries; U.S. Power Squadrons;port authorities; commercial fishing organizations;Sea Grant Marine Advisers; pilots' associations; localnewspapers, radio, and television; etc. Liaison will bemaintained with the NOS Public Affairs Officer.

HYDROGRAPHIC MANUAL

4.12.4. Data Distribution

4.12.5.3. DESCRIPTIVE REPORT TEXT. De-scriptive Report texts are typed on letter-size (8½ X11 in) paper with left-hand margins of 1.25 in to permitbinding. The text must be clear and concise. All infor-mation required for a complete understanding of therecords shall be included, but verbosity shall beavoided.

4.12.5. Descriptive Report

The ''Type of Survey'' entry shall be ChartEvaluation. ''Field No.'' should be struck out andthe appropriate chart number indicated. ''OfficeNo.'' should be entered with N.A.

B. AREA SURVEYED. Briefly describethe area covered by the survey and the adjacentcoast. State the general locality, approximate limits,and inclusive dates of the survey.

The ''Locality'' entry pinpoints the imme-diate area of the survey. Again, specific geographicnames are used as reference (e.g., Approaches toChincoteague Inlet, Northern Portion of Lake St.Clair, or NW of Cape Kumukahi).

C. SOUNDING VESSEL. List all ships orlaunches by letter designations and electronic dataprocessing (EDP) numbers that were used to obtainthe soundings. Include in this section a narrative de-scription of any unusual sounding vessel config-urations and problems encountered.

4.12.5.2. TITLE SHEET. Information for the ti-tle of a survey shall be furnished on NOAA Form77-28, ''Hydrographic Title Sheet.'' Entries are madeon all applicable spaces on the form. (See figure 4-54.)Since the Title Sheet is often referred to for informa-tion pertaining to the survey, be sure all entries are ac-curate.

The entries required on the Title sheet are self-explanatory. ''State,'' ''General Locality,'' and ''Lo-cality'' entries shall be identical to those on the CoverSheet. The ''Date of Survey'' entries are the inclusivedates of the field work. The name(s) listed in Summarize the methods used to determine,

4-96(JUNE 1, 1981)

color code is used, it must be briefly described inthe Descriptive Report.

Upon completion of a chart area, the report,records, field sheets, and other associated data shallbe forwarded to the Hydrographic Surveys Divi-sion, OA/C35. All tidal records shall be forwardedto the Tides and Water Levels Division, OA/C23.All data transmitted should be clearly labeled andindexed (e.g., the folder containing graphic depth re-cords should be indexed by date and position num-bers). NOAA Form 61-29, Letter Transmitting Datashall be used for all data submissions.

A modified Descriptive Report as describedherein is required for each chart investigated. Forgeneral guidance in preparing any Descriptive Re-port, refer to section 5.3.

4.12.5.1. COVER SHEET. NOAA Form76-35A, ''Descriptive Report,'' shall be used as the out-side cover sheet; appropriate entries are made to iden-tify the survey. (See figure 4-53).

The ''State'' entry is the name of the stateor territory nearest the center of the chart.

The ''General Locality'' in which the sur-vey was performed must be defined by a well-known geographic name (e.g., Sumner Strait, Gulfof Mexico, or Lake Huron).

the ''Surveyed by'' entry are those who were actuallyin charge during the surveying operations.

If a field party has not completed all requiredwork on a field sheet prior to transferring the data toanother unit or to NOS Headquarters, enter a com-plete explanation in the ''Remarks'' section. OtherDescriptive Reports or special reports containing in-formation or data pertinent to the survey should bereferenced under ''Remarks.''

Each text shall be entitled ''Descriptive Re-port to Accompany Chart Evaluation Survey ofChart "(insert chart number). The scaleand year of the survey, the names of the survey ves-sel or party, and the Chief of Party are listed.

When reference is made to a hydrographicfeature on the field sheet, the latitude, longitude, andposition number of the feature shall be given. Toprovide uniformity of reports, the text is arrangedunder the following lettered headings in order ap-pearing here.

A. PROJECT. Include the project number,and date of original instructions, and the dates of allchanges, supplemental instructions, amendments,and pertinent letters.

D. SOUNDING EQUIPMENT ANDCORRECTIONS TO ECHO SOUNDINGS. Iden-tify by type and serial number all echo-sounding in-struments used by each survey vessel. State the typeof other sounding equipment used and the generalareas and depths in which each was used. Discussany faults in the equipment which affected the accu-racy of sounding.

HYDROGRAPHY

showing the locations and dates.NOAA FORM 76-35A

U.S. DEPARTMENT OF COMMERCE

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

NATIONAL OCEAN SURVEY

DESCRIPTIVE REPORT(HYDROGRAPHIC)

Chart EvaluationType of Survey

Chart No. 11383

N.A.Office No

A copy of the Abstracts of Corrections toEcho Soundings should be inserted at the end ofthe Descriptive Report (4.12.5.4(B)); substantiatingfield observations, computations, and graphs are in-cluded with the field records (See 4.9.)

LOCALITY

FloridaState

General Locality Gulf of Mexico E. SURVEY SHEETS. List all charts,overlays, and blowups and state the scale and areaof the sheets. Since no further processing of thesesheets will be applied, they must be neatly, clearly,and accurately plotted.

Pensacola Bay.Locality

1976F. CONTROL STATIONS. List the con-

trol stations on the sheet that have beenmonumented and described; state the surveyingmethods used to establish horizontal positions forhydrographic signals and stations. Define the gener-al areas in which each method was used and indicatethe datum used. If a geodetic control report is notavailable, copies of the appropriate geodetic ab-stracts; and computations shall be included with thesurvey records for verification of the positions. Ex-plain in detail:

CHIEF OF PARTYCdr J. W. Dropp, Comdg

LIBRARY & ARCHIVES

DATE

FIGURE 4-53. - Descriptive Report cover sheet

evaluate, and apply the following listed correctionsto the echo soundings:

1. Velocity of sound through water.

3. Other instrument corrections.

4. Corrections determined from directcomparisons (bar checks and vertical casts).

3. Any known photogrammetric prob-lems that could contribute to position inaccuracies.

If salinity, temperature, depth (STD) sen-sors; temperature, depth, conductivity (TDC) sen-sors; or similar instruments were used for velocitydeterminations, identify each instrument by serialnumber and provide the most recent dates of cali-bration or field check.

Refer to section 4.12.5.4(D) for control list-ings to be appended to the Descriptive Report.

G. HYDROGRAPHIC POSITION CON-

TROL. State the method or methods of sounding lineposition control used for the survey and explain in de-tail any known difficulties experienced with the con-trol system that may have degraded the expected po-sition accuracy. Electronic control equipment shall

List the positions of the stations observedfor velocity corrections with the date of observa-tion; or prepare letter-size 8½ X 11 in) chartlets

4-97 (JUNE 1, 1981)

2. Variations in the instrument initial.

5. Settlement and squat.

If unusual or unique methods or instrumentswere necessary for the determination of corrections toecho soundings, describe them in sufficient detail toprovide subsequent users of the survey a full under-standing of the data. It must be emphasized that sound-ing corrections be determined and reported in a stan-dard manner (4.9) unless extenuating circumstancesarise; extensive analysis of data acquired by nonstan-dard methods can be extremely time consuming.

When applicable, specify the vessels, areas,depths, and items for which any particular groupof corrections are to be applied.

1. Unconventional survey methods, ifused, for determining the positions of horizontalcontrol stations.

2. Anomalies in the control adjustmentor in closures and ties.

FIGURE 4-54.—Hydrographic Title Sheet

4-98(JUNE 1, 1981)

HYDROGRAPHIC MANUAL

HYDROGRAPHY

Visible Wreck, PA1964 USPS Report

be identified by manufacturer, model, and compo-nent serial numbers for each vessel and shore station.

Dangerous Sunken WrecksNM 45/64

Dangerous Sunken Wreck, PALocal Report, Delaware Bay,Pilots AssociationItems to be discussed in detail in this sec-

tion include, but are not limited to: The geodetic position should be completedto show the position of the item as charted and theactual position as surveyed. A specific description ofthe positioning methods used shall be stated. Themethod of item investigation is the single most im-portant portion of this form. Confidence in the hy-drographer's recommendation is frequentlydependent on the detailed description containedwithin the method of item investigation. For this rea-son, specific information describing the investigationshall be included. The least depths obtained over sub-merged features and the baring height of visible ha-zards shall be listed. Standard techniques employedshall be referenced to the source of that technique(Hydrographic Manual, NOAA Diving Manual,PMC OPORDER, AMC OPORDERS, etc.). Anyunique survey method must be specifically described.Conditions of the investigation such as weather, wa-ter clarity, time spent, etc., can be important.

5. Discovery and treatment of systematicerrors in the position data.

A copy of the Abstract of Corrections toElectronic Position Control shall be inserted at theend of the Descriptive Report (4.12.5.4(C)), andthe substantiating field observations, computations,and other pertinent data shall be included in thesurvey records. (See 4.8.)

H. WATERFRONT PLANIMETRYVERIFICATION. Specifically describe shorelineareas that have experienced significant modificationand reference those survey sheets included which de-lineate the change. State the methods used in verify-ing the charted planimetry or acquiring revision data.

I. HARBOR RECONNAISSANCE. Statethe accomplishment of the investigation of harborareas with a brief discussion of significant observa-tions.

J. DEFICIENCY INVESTIGATIONS.Each numbered deficiency item that lies within thelimits of the survey must be completely discussed.The standard format (see figures 4-55 and 4-56)shall be completed for each item and transmittedwith the Descriptive Report. It is important that theform be completely and thoroughly filled out. Mosttop sections of the form are self-explanatory. Theitem description should reflect the abbreviated itemdesignation and the source of that item. This infor-mation will be specified in the original instructionrequest or determined locally. For example:

Copies of telegrams or letters that havebeen submitted recommending immediate changesto the charts and items for inclusion in the LocalNotice to Mariners shall be included in the De-scriptive Report.

K. CHANNEL AND SHOAL INVESTI-GATIONS. Channels and shoals found and investi-gated during the survey shall be listed. Leastdepths or clearances for these features must be giv-en. Reference to the appropriate position numbersand development overlays should be made.

Submerged Pile, PAChart Letter 1775 (73)

4-99 (JUNE 1, 1981)

Briefly describe the methods for calibratingthe electronic control systems. Evaluate, to the extentpossible, the adequacy of the calibration data appliedto raw position data throughout the survey area.

1. Unusual or unique methods of operat-ing or calibrating electronic positioning equipment.

2. Equipment malfunctions, substandardoperation, and probable causes.

3. Unusual atmospheric conditions thatmay have affected data quality.

4. Weak signals or poor geometric con-figuration of the control stations.

Limits of an investigation (area covered,width of a wire sweep, etc.) should be stated. Fre-quently a sketch can clarify details of an investiga-tion which are otherwise difficult to explain.References to individuals in the area may be perti-nent. Charting recommendations must be positiveand explicit. Recommendations should includewhether or not the item should be charted, and thesymbolization to be used. If the hydrographer isunwilling to make a positive statement after anonsite investigation, it is most unlikely that the of-fice cartographer will be able to rely on such a rec-ommendation.

HYDROGRAPHIC MANUAL

CHART # 18661 ITEM # 34

ITEM DESCRIPTION: Submerged Pile, PA

SOURCE: Chart Letter 1775 (73)

185OZ-1905Z4/7/77 (JD97)INVESTIGATION DATE: TIME: VESSEL: DA 2

OIC: ENS Kenny

REFERENCES:

Position No.: 7028, 7029 Volume: 3, pg. 27

Velocity TRA Correctors Applied

Predicted Actual Tide Correctors Applied

LatitudeGEODETIC POSITION Longitude

38° 01 ' 05'' 121° 30' 50''Charted:

38° 01' 04.7" 121° 30' 51.7''Observed:

POSITION DETERMINED BY:

The pilings were searched for and found visually. There is a row ofpilings approximately 25 feet offshore and extending approximately 100feet. Fixes were taken on the northernmost and southernmost piles, bothof which were awash at the time of observation with the predicted tide2.0 feet above MLLW. Most piles in between were uncovered approximately2 feet. The pilings are visible at MLLW but most are covered at MHW.

CHARTING RECOMMENDATION:

Delete " Piling" presented charted in the same vicinity.

Compilation Use Only

APPLIED ASCHART

FIGURE 4—55.—Deficiency Item Report

4-100(JUNE 1, 1981)

Sextant and visual observation.

METHOD OF ITEM INVESTIGATION:

Chart "Piles" from 38° 01' 04.7" N, 121° 30' 51.7" W to 38° 01' 06.3" N, 121° 30' 50.6" W.

HYDROGRAPHY

CHART # 11388 ITEM # 7

ITEM DESCRIPTION: Shoal Rep. 1971

SOURCE: LNM 37/71

1700Z-1735ZINVESTIGATION DATE: TIME: VESSEL: PE 13/15/76 (JD75)

OIC: LTJG Dreves

REFERENCES:

20-21Position No.: NA Volume: 1, pg-

Velocity TRA Correctors Applied

Predicted Actual Tide Correctors Applied

LongitudeLatitude

86° 30. 4'30° 22. 5'

Observed: NANA

POSITION DETERMINED BY:

The area surrounding the charted position of the reported 12-foot shoalwas searched for a circle of a 100-meter radius with lines run in 30-meterintervals. General soundings in the area of the shoal were 30 feet andconsistent with the gradual inshore shoaling. The fathometer was keptrunning the entire period of the search with no unusual features. Theannotated fathogram is included with survey records. Water clarity allowedbottom visibility to 40 feet and no features or obstructions could be seen.

CHARTING RECOMMENDATION:

The charted ''Shoal Rep. 1971'' should be removed. Careful search by thehydrographer indicates that such a shoal is not existent. The reportundoubtedly was errant in its position with the reporting vessel probablyinshore from the reported position.

Compilation Use Only

CHART APPLIED

FIGURE 4-56.—Deficiency Item Report

4-101 (JUNE 1, 1981)

GEODETIC POSITION

Charted:

Sextant fixes and visual references to Buoy BW "CB"

METHOD OF ITEM INVESTIGATION:

HYDROGRAPHIC MANUAL

R. PUBLIC RELATIONS EFFORTS.Generally describe the unit's efforts in the area ofpublic relations. Describe the more successful eventsand mention particularly cooperative individuals orgroups.

P. TIDE/WATER LEVEL OBSERVA-TIONS. Describe the methods used and the resultsof all comparisons to predicted tides. State the

W. REFERRAL TO REPORTS. List all re-ports, records, and forms not included with the surveyrecords or Descriptive Report that have been

4-102(JUNE 1, 1981)

L. RECONNAISSANCE HYDROGRA-PHY. Compare the reconnaissance hydrographywith the latest edition of the largest scale chart ofthe area, identifying the chart by number, edition,and date. State the quality of general agreement be-tween the reconnaissance soundings and the chart-ed depths, and give conclusions or opinions as tothe reasons for significant differences.

M. LANDMARK AND NONFLOATINGAIDS VERIFICATION. Copies of NOAA Form76-40, ''Report on Nonfloating Aids or Landmarksfor Charts,'' that contain the required informationon landmarks within the survey limits that arerecommended for charting shall be attached to theDescriptive Report (4.12.5.4(F)). State the accom-plishment of this task.

N. AIDS TO NAVIGATION. Referenceshall be made to any correspondence with the U.S.Coast Guard regarding the location or establish-ment of floating aids in the surveyed area. The loca-tion and description of each floating aid shall beentered in the hydrographic records. A separate list-ing of floating aids by geographic position and char-acteristic need not be entered here. However, acomparison shall be made with data in the latest edi-tion of the Light List and with the largest scalechart of the area. The hydrographer shall state theresults of this comparison, and indicate whether theaids adequately serve the apparent purpose forwhich they were established.

List all aids to navigation located during thesurvey that are not shown in the Light List. Statetheir apparent purpose, whether and by whom theaids are maintained, and whether or not such main-tenance is seasonal, if known. Give the position anddescription of each such aid and the date of estab-lishment, if known.

List all bridges and overhead cables notshown on the chart. State bridge and cable clear-ances measured by the survey party or as deter-mined from other sources. Mention any submarinecables, pipelines, and ferry routes in the area. Listthe position of each terminal if not shown on con-temporary shoreline manuscripts.

O. COAST PILOT INSPECTION. Statethe accomplishment of this task. Copies of the CoastPilot report and/or NOAA forms 77-6 should be at-tached to the Descriptive Report (4.12.5.4(G)).

observed or user reported acceptability of predictedtides for this area.

Q. USER EVALUATION. State the resultsof the user evaluation effort. Carefully describe anyrecommendations for changes in chart layout, insets,scale, format, color, etc., and provide the justifi-cations for such recommendations.

S. STATISTICS. List the total number ofitems investigated, the total number of positions, andnautical miles of sounding lines run by each launchor ship during the survey. A tabulation of statisticsfor each day is not required. A summary of other sur-vey statistics such as the number of tide comparisons,landmarks added, landmarks deleted, open houses,etc., should also be included.

T. MISCELLANEOUS. Provide informa-tion of significant scientific or practical value result-ing from the survey which is not covered in previoussections. Where new silted areas are detected, thediscussions should include the size of the areas, ap-parent thickness, and reference to typical depth pro-files by date. Unusual submarine features such as ab-normally large sand waves, mounds, valleys, andescarpments should be described. Discuss anomoloustidal conditions encountered such as the presence ofbores and extremely fast currents not previously re-ported. If special reports have been submitted onsuch subjects, refer to them by title, author, and dateof preparation or publication.

U. RECOMMENDATIONS. Specificcharting recommendations should be included withthe individual discrepancy items. Recommendationsfor new basic hydrography, tides or tidal current sur-veys, or shoreline updating photography should be

stated and justified. Recommendations for futureChart Evaluation Surveys should be included.

V. AUTOMATED DATA PROCESS-ING. List by program name, number, and versiondate all routines used for automated data acquisitionand processing. If any of the acquisition or processingmethods used differ from those described in currentNOS manuals or instructions, each difference must belisted and explained, and the data format defined.

HYDROGRAPHY

submitted separately, but which are necessary for acomplete evaluation and understanding of the surveyrecord. Give the title and the date on which the re-port was forwarded.

For substantiating these corrections tosoundings, the following supporting material shall beassembled and separately bound or arranged in a ca-hier and included with the survey data thataccompanies the hydrographic sheet and DescriptiveReport:

A. FIELDTIDE/WATER LEVEL NOTE.A field tide or water level note shall be inserted inthe Descriptive Report for each applicable survey.(See figure 5.5.) The note should state: 1. Copy of the settlement and squat ab-

stract.2. Abstracts of bar checks, vertical cast

comparisons, and echo sounder phase comparisons.

4. Nansen cast observations.

C. ABSTRACTS OF CORRECTIONS TOELECTRONIC POSITION CONTROL. When allor any portion of the hydrographic survey is con-trolled by an electronic positioning system or by dis-tance measuring equipment, an abstract of correc-tions to be applied to the observed data shall becompiled and inserted into the Descriptive Report.(See figure 5-8.) Supporting data shall be assembledand separately bound or arranged in a cahier and in-cluded with the survey data that accompanies thehydrographic field sheet and Descriptive Report.(See 4.8.)

D. LIST OF STATIONS. A numerical listof stations used for controlling the hydrographic sur-vey shall be included as a separate sheet and insertedin the Descriptive Report. (See figure 5-9.) The fol-lowing information shall be given for each station:

9. Recommendations, if any, for zoningand time corrections. 1. Station number (001-999).

B. ABSTRACT OF CORRECTIONS TOECHO SOUNDINGS. Abstracts, in tabular form,for velocity and other corrections to be applied tothe echo soundings shall be included as separateentries in the Descriptive Report. (See figure 5.7.) A

3. Longitude (to nearest thousandth of asecond).

4. Name and type of station (3.1), that is:

4-103 (JUNE 1, 1981)

4.12.5.4. SEPARATES FOLLOWING TEXT.Various tabulations and other information are re-quired on separate sheets which are inserted in theDescriptive Report. Those applicable shall befurnished and inserted in the order listed below.

The first page of the text and the attached in-serts shall be numbered consecutively. The approvalsheet is always placed last.

1. How the tide/water level correctionswere derived and the zones or items to which thesecorrections were applied. (If automated computa-tions for tides corrections to soundings were madebased on multigage observations, the program num-ber and gage sites must be given.)

2. The name, geographic locale, latitude,and longitude of each gage.

3. Dates of gage installations and remov-als, and any problems experienced with gage opera-tions.

4. Staff value equivalent to the zero lineon analog tide records. (In the Great Lakes, the ele-vation of the reference mark (zero electric tape gageor ZETG) on the electric tape gage shall be noted.)

5. Significant differences in comparativeobservations (AK.2.3), in tide or water level times,or in ranges or unusual fluctuations between adjacentgages.

6. The time meridian used for records an-notation.

7. Observations of unusual tidal, waterlevel, or current conditions.

8. A tabulation of missing hourly heights,if any, that may be required for reduction of sound-ings to the datum of reference.

similar abstract can be easily constructed for correc-tions determined solely by bar checks taken through-out the depth range.

The Sounding Correction Abstract shows thedates, times, vessels, and instrument serial numbers towhich the corrections apply. If the same correc-tions apply to more than one survey, a copy of the ab-stract and applicable correction tables (4.9) are in-cluded in the Descriptive Report for each survey.

3. Copies of calibration data for STD,TDC, or other sensors used for velocity determin-ations.

5. All other basic data, computations,graphics, and material needed to verify the final cor-rections.

2. Latitude (to nearest thousandth of asecond).

HYDROGRAPHIC MANUAL

(a) Basic or supplemental (include yearof establishment).

(b) Photogrammetric or hydrographic.

E. ABSTRACT OF POSITIONS. TheAbstract of Positions shall be assembled for eachhydrographic survey vessel that worked on thefield sheet. (See figure 5-10.) Each vessel is identi-fied by its data-processing number, and the workaccomplished is listed by Julian dates, inclusive po-sition numbers, control codes, and electronic con-trol station numbers.

If chart sections are submitted, separateforms for landmarks to be deleted need not be pre-pared. The following procedures are used:

F. REPORT ON LANDMARKS ANDNONFLOATING AIDS TO NAVIGATION.NOAA Forms 76-40, ''Report on Nonfloating Aidsor Landmarks for Charts,'' shall be prepared as re-quired herein and copies attached to the DescriptiveReport. Separate forms 76-40 are submitted for:

1. Landmarks to be charted.

2. Landmarks to be deleted.

3. Nonfloating aids to navigation.

A separate NOAA Form 76-40, ''Non-floating Aids or Landmarks for Charts,'' shall beused to report the positions of all nonfloating aids tonavigation on a chart-by-chart basis. The geograph-ic positions of all nonfloating aids, including pri-vately maintained lights and beacons, shall beverified or determined in the field. Applicable partsof the requirements stated for form 76-40 shall befollowed in compiling this report. If contemporaryshoreline mapping of the area has been undertaken,copies of form 76-40 for new aids or aids to be de-leted shall be sent to the Photogrammetry Division,OA/C34; otherwise, the forms are sent to the Ma-rine Chart Division, OA/C32. For additional detailsconcerning landmarks and aids to navigation see:

Objects of special importance or extraordi-nary prominence are indicated by an asterisk (*)preceding the name of the object. When selectingobjects of special importance, the total area andchart coverage must be carefully considered. Flag-staffs, flagpoles, and other structures of a temporarynature are not listed as landmarks unless they are ofa very permanent and prominent nature and thereare no other suitable objects in the area. Recom-

4-104(JUNE 1, 1981)

5. Source; that is, volume and page num-ber for published geodetic control or, if new, a ref-erence to abstracts of field observations.

The hydrographer shall evaluate all chartedlandmarks from seaward to determine which are ade-quate and most suitable for the purpose intended andto determine which charted landmarks no longer existand thus should be deleted from the charts. If there aremore prominent objects in the area which would serveas better landmarks, their positions shall be deter-mined and listed among the landmarks to be charted.

Reports on landmarks must be completewithin themselves. Avoid additional references togeodetic, photogrammetric, or other data not readi-ly available to other users. The report shall statepositively whether or not a seaward inspection hasbeen made to evaluate the landmarks. If the reportshave been assembled without the benefit of a sea-ward inspection, the reason for omission shall befully explained.

mended charting names should be short, general,and shown in capital letters (5.5.1.2). If the objectwas used as a hydrographic signal, a note is made tothis effect and the station number indicated.

When a large number of landmarks are re-ported, or the hydrographer or field editor consid-ers it necessary to clarify the tabulated data, a copyof the chart of the area should be cut into letter-sizesections, appropriately annotated, and submittedwith the copies of NOAA form 76-40. (See figures5-11 and 5-12.) The area inspected is outlined onthese chart sections and a recommendation madefor each charted or plotted landmark within theoutlined area.

1. New landmarks shall be plotted andidentified by the landmark symbol (A) together withthe name recommended for charting. The geo-graphic datum of the chart must be known and con-sidered in the plotting.

2. Charted landmarks recommended forcontinuance are checkmarked (A). If the positionhas been verified in the field, the word ''verified'' isentered beside the checkmark.

3. Charted landmarks recommended fordeletion shall be indicated by an X in a circle (A),the word ''delete'' entered, and the reason for therecommendation given.

Names and notations on these chart sectionsshall be typed or lettered legibly in red ink. Caremust be taken that such notations always appear onthe same section of the chart section as the land-marks to which they refer.

HYDROGRAPHY

chart, corrected through the latest Notice to Mariners,should be used. Any discrepancies should be resolvedand reported in accordance with section 4.5.13.

4.12.2.7. COAST PILOT INSPECTION. The ap-propriate Coast Pilot shall be examined for accuracyand completeness in the areas of operation, as well asen route. If modifications are required, reports shall besubmitted in accordance with section 5.8.

4.12.2.8. TIDE/WATER LEVEL OBSERVA-

TIONS. For any specified hydrography or item discrep-ancy investigations, tide/water level requirementswill be issued with the project instructions.

Contact with the user should be oriented withthe objective of obtaining input as to the adequacy ofthe existing chart layout, scale, format, color, etc., andto inform the public of the mission of NOS and themany products and services provided by this Agency.Results of these contacts should be included in the De-scriptive Report in detail sufficient to provide NOS(Marine Chart Division) support for future chart andsurvey planning.

Predicted tides are the only tidal data avail-able to the mariner for reducing his observed depths tothe chart datum; therefore, the accuracy of the pre-dicted tides in the project area may require verificationif so directed in the project instructions. This can be ac-complished in several ways. A site having a flat bottomis selected near an offshore entrance to a harbor or oth-er area of critical navigation within the working area.On a range, near a buoy, or using a marker installed bythe survey party, depths are determined at the predict-ed times of low water, high water, and midway be-tween during normal meteorological conditions.Depths should also be measured before and after thepredicted tides to determine the actual times of highand low water and any differences noted. Depth obser-vations should be made using a calibrated lead line orother calibrated direct means and the measurement lo-cation should vary as little as possible. At a number ofstation locations selected from table 2 of the tide tables,a bubbler tide gage should be installed and operated fora minimum of 3 days (installation of a staff is not re-quired). Care should be taken to ensure the orifice willnot be subject to movement while in operation. Theanalog record will be annotated for time, data, andweather (including unusual meteorological condi-tions). Any particular requirements such as locationand priority will be furnished in the project instruc-tions.

4.12.3. Data Processing

Because of the special nature of these surveysand the need to reduce the time between field acquisi-tion and office processing of the charting data, it is in-tended that the data will not be processed through theMarine Centers. Instead, the survey party will be re-sponsible for field processing the data to a point where

the responsible cartographer in the Marine Chart Di-vision, OA/C32, can apply the data directly to thechart with a minimum of additional data reduction orverification required. Extreme care must be exercisedby the field party to assure that the plotting of data onchart overlays or plotting sheets is done accuratelyand is in accordance with provisions of the Hydro-graphic Manual. A concise and yet comprehensiveDescriptive Report must be included with each chartrevised so that the office cartographer can readily de-termine and evaluate the merits of proceduresemployed by the field hydrographer in his data reduc-tion. All appropriate correctors shall be applied tosoundings. The use of correctors determined fromreal-time tide/water level observations is preferredover predicted tides if they are available. All revisionsand notations to land and water features shall be madeon the latest edition of the largest scale chart of eacharea. It is not mandatory that chart notations are colorcoded. It is, however, essential that each notation belegible and complete. If the hydrographer chooses touse a color code, he should ink all change and additionnotes in red ink, all deletion notes in green ink, and allconfirmation notes in blue ink. It is important that allinspection and revision notes be inked on the chart bythe hydrographer as the field work progresses. If a

In most instances, a real-time reduction of hy-drography can be accomplished in Chart EvaluationSurveys and still achieve the objectives of these sur-veys.

4.12.2.9. USER EVALUATION PUBLIC RELA-

TIONS EFFORT. Every effort shall be made to contact

4-95 (JUNE 1, 1981)

Water level requirements in nontidal areas areless complex and can generally be satisfied using tem-porary gage installations.

users through the news media and local organizations.Names and addresses of suggested contacts will befurnished, when available, and will generally include:U.S. Army Corps of Engineers; U.S. Coast Guard;U.S. Coast Guard Auxiliaries; U.S. Power Squadrons;port authorities; commercial fishing organizations;Sea Grant Marine Advisers; pilots' associations; localnewspapers, radio, and television; etc. Liaison will bemaintained with the NOS Public Affairs Officer.

HYDROGRAPHIC MANUAL

4.12.4. Data Distribution

4.12.5.3. DESCRIPTIVE REPORT TEXT. De-scriptive Report texts are typed on letter-size (8½ X11 in) paper with left-hand margins of 1.25 in to permitbinding. The text must be clear and concise. All infor-mation required for a complete understanding of therecords shall be included, but verbosity shall beavoided.

4.12.5. Descriptive Report

The ''Type of Survey'' entry shall be ChartEvaluation. ''Field No.'' should be struck out andthe appropriate chart number indicated. ''OfficeNo.'' should be entered with N.A.

B. AREA SURVEYED. Briefly describethe area covered by the survey and the adjacentcoast. State the general locality, approximate limits,and inclusive dates of the survey.

The ''Locality'' entry pinpoints the imme-diate area of the survey. Again, specific geographicnames are used as reference (e.g., Approaches toChincoteague Inlet, Northern Portion of Lake St.Clair, or NW of Cape Kumukahi).

C. SOUNDING VESSEL. List all ships orlaunches by letter designations and electronic dataprocessing (EDP) numbers that were used to obtainthe soundings. Include in this section a narrative de-scription of any unusual sounding vessel config-urations and problems encountered.

4.12.5.2. TITLE SHEET. Information for the ti-tle of a survey shall be furnished on NOAA Form77-28, ''Hydrographic Title Sheet.'' Entries are madeon all applicable spaces on the form. (See figure 4-54.)Since the Title Sheet is often referred to for informa-tion pertaining to the survey, be sure all entries are ac-curate.

The entries required on the Title sheet are self-explanatory. ''State,'' ''General Locality,'' and ''Lo-cality'' entries shall be identical to those on the CoverSheet. The ''Date of Survey'' entries are the inclusivedates of the field work. The name(s) listed in Summarize the methods used to determine,

4-96(JUNE 1, 1981)

color code is used, it must be briefly described inthe Descriptive Report.

Upon completion of a chart area, the report,records, field sheets, and other associated data shallbe forwarded to the Hydrographic Surveys Divi-sion, OA/C35. All tidal records shall be forwardedto the Tides and Water Levels Division, OA/C23.All data transmitted should be clearly labeled andindexed (e.g., the folder containing graphic depth re-cords should be indexed by date and position num-bers). NOAA Form 61-29, Letter Transmitting Datashall be used for all data submissions.

A modified Descriptive Report as describedherein is required for each chart investigated. Forgeneral guidance in preparing any Descriptive Re-port, refer to section 5.3.

4.12.5.1. COVER SHEET. NOAA Form76-35A, ''Descriptive Report,'' shall be used as the out-side cover sheet; appropriate entries are made to iden-tify the survey. (See figure 4-53).

The ''State'' entry is the name of the stateor territory nearest the center of the chart.

The ''General Locality'' in which the sur-vey was performed must be defined by a well-known geographic name (e.g., Sumner Strait, Gulfof Mexico, or Lake Huron).

the ''Surveyed by'' entry are those who were actuallyin charge during the surveying operations.

If a field party has not completed all requiredwork on a field sheet prior to transferring the data toanother unit or to NOS Headquarters, enter a com-plete explanation in the ''Remarks'' section. OtherDescriptive Reports or special reports containing in-formation or data pertinent to the survey should bereferenced under ''Remarks.''

Each text shall be entitled ''Descriptive Re-port to Accompany Chart Evaluation Survey ofChart "(insert chart number). The scaleand year of the survey, the names of the survey ves-sel or party, and the Chief of Party are listed.

When reference is made to a hydrographicfeature on the field sheet, the latitude, longitude, andposition number of the feature shall be given. Toprovide uniformity of reports, the text is arrangedunder the following lettered headings in order ap-pearing here.

A. PROJECT. Include the project number,and date of original instructions, and the dates of allchanges, supplemental instructions, amendments,and pertinent letters.

D. SOUNDING EQUIPMENT ANDCORRECTIONS TO ECHO SOUNDINGS. Iden-tify by type and serial number all echo-sounding in-struments used by each survey vessel. State the typeof other sounding equipment used and the generalareas and depths in which each was used. Discussany faults in the equipment which affected the accu-racy of sounding.

HYDROGRAPHY

showing the locations and dates.NOAA FORM 76-35A

U.S. DEPARTMENT OF COMMERCE

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

NATIONAL OCEAN SURVEY

DESCRIPTIVE REPORT(HYDROGRAPHIC)

Chart EvaluationType of Survey

Chart No. 11383

N.A.Office No

A copy of the Abstracts of Corrections toEcho Soundings should be inserted at the end ofthe Descriptive Report (4.12.5.4(B)); substantiatingfield observations, computations, and graphs are in-cluded with the field records (See 4.9.)

LOCALITY

FloridaState

General Locality Gulf of Mexico E. SURVEY SHEETS. List all charts,overlays, and blowups and state the scale and areaof the sheets. Since no further processing of thesesheets will be applied, they must be neatly, clearly,and accurately plotted.

Pensacola Bay.Locality

1976F. CONTROL STATIONS. List the con-

trol stations on the sheet that have beenmonumented and described; state the surveyingmethods used to establish horizontal positions forhydrographic signals and stations. Define the gener-al areas in which each method was used and indicatethe datum used. If a geodetic control report is notavailable, copies of the appropriate geodetic ab-stracts; and computations shall be included with thesurvey records for verification of the positions. Ex-plain in detail:

CHIEF OF PARTYCdr J. W. Dropp, Comdg

LIBRARY & ARCHIVES

DATE

FIGURE 4-53. - Descriptive Report cover sheet

evaluate, and apply the following listed correctionsto the echo soundings:

1. Velocity of sound through water.

3. Other instrument corrections.

4. Corrections determined from directcomparisons (bar checks and vertical casts).

3. Any known photogrammetric prob-lems that could contribute to position inaccuracies.

If salinity, temperature, depth (STD) sen-sors; temperature, depth, conductivity (TDC) sen-sors; or similar instruments were used for velocitydeterminations, identify each instrument by serialnumber and provide the most recent dates of cali-bration or field check.

Refer to section 4.12.5.4(D) for control list-ings to be appended to the Descriptive Report.

G. HYDROGRAPHIC POSITION CON-

TROL. State the method or methods of sounding lineposition control used for the survey and explain in de-tail any known difficulties experienced with the con-trol system that may have degraded the expected po-sition accuracy. Electronic control equipment shall

List the positions of the stations observedfor velocity corrections with the date of observa-tion; or prepare letter-size 8½ X 11 in) chartlets

4-97 (JUNE 1, 1981)

2. Variations in the instrument initial.

5. Settlement and squat.

If unusual or unique methods or instrumentswere necessary for the determination of corrections toecho soundings, describe them in sufficient detail toprovide subsequent users of the survey a full under-standing of the data. It must be emphasized that sound-ing corrections be determined and reported in a stan-dard manner (4.9) unless extenuating circumstancesarise; extensive analysis of data acquired by nonstan-dard methods can be extremely time consuming.

When applicable, specify the vessels, areas,depths, and items for which any particular groupof corrections are to be applied.

1. Unconventional survey methods, ifused, for determining the positions of horizontalcontrol stations.

2. Anomalies in the control adjustmentor in closures and ties.

FIGURE 4-54.—Hydrographic Title Sheet

4-98(JUNE 1, 1981)

HYDROGRAPHIC MANUAL

HYDROGRAPHY

Visible Wreck, PA1964 USPS Report

be identified by manufacturer, model, and compo-nent serial numbers for each vessel and shore station.

Dangerous Sunken WrecksNM 45/64

Dangerous Sunken Wreck, PALocal Report, Delaware Bay,Pilots AssociationItems to be discussed in detail in this sec-

tion include, but are not limited to: The geodetic position should be completedto show the position of the item as charted and theactual position as surveyed. A specific description ofthe positioning methods used shall be stated. Themethod of item investigation is the single most im-portant portion of this form. Confidence in the hy-drographer's recommendation is frequentlydependent on the detailed description containedwithin the method of item investigation. For this rea-son, specific information describing the investigationshall be included. The least depths obtained over sub-merged features and the baring height of visible ha-zards shall be listed. Standard techniques employedshall be referenced to the source of that technique(Hydrographic Manual, NOAA Diving Manual,PMC OPORDER, AMC OPORDERS, etc.). Anyunique survey method must be specifically described.Conditions of the investigation such as weather, wa-ter clarity, time spent, etc., can be important.

5. Discovery and treatment of systematicerrors in the position data.

A copy of the Abstract of Corrections toElectronic Position Control shall be inserted at theend of the Descriptive Report (4.12.5.4(C)), andthe substantiating field observations, computations,and other pertinent data shall be included in thesurvey records. (See 4.8.)

H. WATERFRONT PLANIMETRYVERIFICATION. Specifically describe shorelineareas that have experienced significant modificationand reference those survey sheets included which de-lineate the change. State the methods used in verify-ing the charted planimetry or acquiring revision data.

I. HARBOR RECONNAISSANCE. Statethe accomplishment of the investigation of harborareas with a brief discussion of significant observa-tions.

J. DEFICIENCY INVESTIGATIONS.Each numbered deficiency item that lies within thelimits of the survey must be completely discussed.The standard format (see figures 4-55 and 4-56)shall be completed for each item and transmittedwith the Descriptive Report. It is important that theform be completely and thoroughly filled out. Mosttop sections of the form are self-explanatory. Theitem description should reflect the abbreviated itemdesignation and the source of that item. This infor-mation will be specified in the original instructionrequest or determined locally. For example:

Copies of telegrams or letters that havebeen submitted recommending immediate changesto the charts and items for inclusion in the LocalNotice to Mariners shall be included in the De-scriptive Report.

K. CHANNEL AND SHOAL INVESTI-GATIONS. Channels and shoals found and investi-gated during the survey shall be listed. Leastdepths or clearances for these features must be giv-en. Reference to the appropriate position numbersand development overlays should be made.

Submerged Pile, PAChart Letter 1775 (73)

4-99 (JUNE 1, 1981)

Briefly describe the methods for calibratingthe electronic control systems. Evaluate, to the extentpossible, the adequacy of the calibration data appliedto raw position data throughout the survey area.

1. Unusual or unique methods of operat-ing or calibrating electronic positioning equipment.

2. Equipment malfunctions, substandardoperation, and probable causes.

3. Unusual atmospheric conditions thatmay have affected data quality.

4. Weak signals or poor geometric con-figuration of the control stations.

Limits of an investigation (area covered,width of a wire sweep, etc.) should be stated. Fre-quently a sketch can clarify details of an investiga-tion which are otherwise difficult to explain.References to individuals in the area may be perti-nent. Charting recommendations must be positiveand explicit. Recommendations should includewhether or not the item should be charted, and thesymbolization to be used. If the hydrographer isunwilling to make a positive statement after anonsite investigation, it is most unlikely that the of-fice cartographer will be able to rely on such a rec-ommendation.

HYDROGRAPHIC MANUAL

CHART # 18661 ITEM # 34

ITEM DESCRIPTION: Submerged Pile, PA

SOURCE: Chart Letter 1775 (73)

185OZ-1905Z4/7/77 (JD97)INVESTIGATION DATE: TIME: VESSEL: DA 2

OIC: ENS Kenny

REFERENCES:

Position No.: 7028, 7029 Volume: 3, pg. 27

Velocity TRA Correctors Applied

Predicted Actual Tide Correctors Applied

LatitudeGEODETIC POSITION Longitude

38° 01 ' 05'' 121° 30' 50''Charted:

38° 01' 04.7" 121° 30' 51.7''Observed:

POSITION DETERMINED BY:

The pilings were searched for and found visually. There is a row ofpilings approximately 25 feet offshore and extending approximately 100feet. Fixes were taken on the northernmost and southernmost piles, bothof which were awash at the time of observation with the predicted tide2.0 feet above MLLW. Most piles in between were uncovered approximately2 feet. The pilings are visible at MLLW but most are covered at MHW.

CHARTING RECOMMENDATION:

Delete " Piling" presented charted in the same vicinity.

Compilation Use Only

APPLIED ASCHART

FIGURE 4—55.—Deficiency Item Report

4-100(JUNE 1, 1981)

Sextant and visual observation.

METHOD OF ITEM INVESTIGATION:

Chart "Piles" from 38° 01' 04.7" N, 121° 30' 51.7" W to 38° 01' 06.3" N, 121° 30' 50.6" W.

HYDROGRAPHY

CHART # 11388 ITEM # 7

ITEM DESCRIPTION: Shoal Rep. 1971

SOURCE: LNM 37/71

1700Z-1735ZINVESTIGATION DATE: TIME: VESSEL: PE 13/15/76 (JD75)

OIC: LTJG Dreves

REFERENCES:

20-21Position No.: NA Volume: 1, pg-

Velocity TRA Correctors Applied

Predicted Actual Tide Correctors Applied

LongitudeLatitude

86° 30. 4'30° 22. 5'

Observed: NANA

POSITION DETERMINED BY:

The area surrounding the charted position of the reported 12-foot shoalwas searched for a circle of a 100-meter radius with lines run in 30-meterintervals. General soundings in the area of the shoal were 30 feet andconsistent with the gradual inshore shoaling. The fathometer was keptrunning the entire period of the search with no unusual features. Theannotated fathogram is included with survey records. Water clarity allowedbottom visibility to 40 feet and no features or obstructions could be seen.

CHARTING RECOMMENDATION:

The charted ''Shoal Rep. 1971'' should be removed. Careful search by thehydrographer indicates that such a shoal is not existent. The reportundoubtedly was errant in its position with the reporting vessel probablyinshore from the reported position.

Compilation Use Only

CHART APPLIED

FIGURE 4-56.—Deficiency Item Report

4-101 (JUNE 1, 1981)

GEODETIC POSITION

Charted:

Sextant fixes and visual references to Buoy BW "CB"

METHOD OF ITEM INVESTIGATION:

HYDROGRAPHIC MANUAL

R. PUBLIC RELATIONS EFFORTS.Generally describe the unit's efforts in the area ofpublic relations. Describe the more successful eventsand mention particularly cooperative individuals orgroups.

P. TIDE/WATER LEVEL OBSERVA-TIONS. Describe the methods used and the resultsof all comparisons to predicted tides. State the

W. REFERRAL TO REPORTS. List all re-ports, records, and forms not included with the surveyrecords or Descriptive Report that have been

4-102(JUNE 1, 1981)

L. RECONNAISSANCE HYDROGRA-PHY. Compare the reconnaissance hydrographywith the latest edition of the largest scale chart ofthe area, identifying the chart by number, edition,and date. State the quality of general agreement be-tween the reconnaissance soundings and the chart-ed depths, and give conclusions or opinions as tothe reasons for significant differences.

M. LANDMARK AND NONFLOATINGAIDS VERIFICATION. Copies of NOAA Form76-40, ''Report on Nonfloating Aids or Landmarksfor Charts,'' that contain the required informationon landmarks within the survey limits that arerecommended for charting shall be attached to theDescriptive Report (4.12.5.4(F)). State the accom-plishment of this task.

N. AIDS TO NAVIGATION. Referenceshall be made to any correspondence with the U.S.Coast Guard regarding the location or establish-ment of floating aids in the surveyed area. The loca-tion and description of each floating aid shall beentered in the hydrographic records. A separate list-ing of floating aids by geographic position and char-acteristic need not be entered here. However, acomparison shall be made with data in the latest edi-tion of the Light List and with the largest scalechart of the area. The hydrographer shall state theresults of this comparison, and indicate whether theaids adequately serve the apparent purpose forwhich they were established.

List all aids to navigation located during thesurvey that are not shown in the Light List. Statetheir apparent purpose, whether and by whom theaids are maintained, and whether or not such main-tenance is seasonal, if known. Give the position anddescription of each such aid and the date of estab-lishment, if known.

List all bridges and overhead cables notshown on the chart. State bridge and cable clear-ances measured by the survey party or as deter-mined from other sources. Mention any submarinecables, pipelines, and ferry routes in the area. Listthe position of each terminal if not shown on con-temporary shoreline manuscripts.

O. COAST PILOT INSPECTION. Statethe accomplishment of this task. Copies of the CoastPilot report and/or NOAA forms 77-6 should be at-tached to the Descriptive Report (4.12.5.4(G)).

observed or user reported acceptability of predictedtides for this area.

Q. USER EVALUATION. State the resultsof the user evaluation effort. Carefully describe anyrecommendations for changes in chart layout, insets,scale, format, color, etc., and provide the justifi-cations for such recommendations.

S. STATISTICS. List the total number ofitems investigated, the total number of positions, andnautical miles of sounding lines run by each launchor ship during the survey. A tabulation of statisticsfor each day is not required. A summary of other sur-vey statistics such as the number of tide comparisons,landmarks added, landmarks deleted, open houses,etc., should also be included.

T. MISCELLANEOUS. Provide informa-tion of significant scientific or practical value result-ing from the survey which is not covered in previoussections. Where new silted areas are detected, thediscussions should include the size of the areas, ap-parent thickness, and reference to typical depth pro-files by date. Unusual submarine features such as ab-normally large sand waves, mounds, valleys, andescarpments should be described. Discuss anomoloustidal conditions encountered such as the presence ofbores and extremely fast currents not previously re-ported. If special reports have been submitted onsuch subjects, refer to them by title, author, and dateof preparation or publication.

U. RECOMMENDATIONS. Specificcharting recommendations should be included withthe individual discrepancy items. Recommendationsfor new basic hydrography, tides or tidal current sur-veys, or shoreline updating photography should be

stated and justified. Recommendations for futureChart Evaluation Surveys should be included.

V. AUTOMATED DATA PROCESS-ING. List by program name, number, and versiondate all routines used for automated data acquisitionand processing. If any of the acquisition or processingmethods used differ from those described in currentNOS manuals or instructions, each difference must belisted and explained, and the data format defined.

HYDROGRAPHY

submitted separately, but which are necessary for acomplete evaluation and understanding of the surveyrecord. Give the title and the date on which the re-port was forwarded.

For substantiating these corrections tosoundings, the following supporting material shall beassembled and separately bound or arranged in a ca-hier and included with the survey data thataccompanies the hydrographic sheet and DescriptiveReport:

A. FIELDTIDE/WATER LEVEL NOTE.A field tide or water level note shall be inserted inthe Descriptive Report for each applicable survey.(See figure 5.5.) The note should state: 1. Copy of the settlement and squat ab-

stract.2. Abstracts of bar checks, vertical cast

comparisons, and echo sounder phase comparisons.

4. Nansen cast observations.

C. ABSTRACTS OF CORRECTIONS TOELECTRONIC POSITION CONTROL. When allor any portion of the hydrographic survey is con-trolled by an electronic positioning system or by dis-tance measuring equipment, an abstract of correc-tions to be applied to the observed data shall becompiled and inserted into the Descriptive Report.(See figure 5-8.) Supporting data shall be assembledand separately bound or arranged in a cahier and in-cluded with the survey data that accompanies thehydrographic field sheet and Descriptive Report.(See 4.8.)

D. LIST OF STATIONS. A numerical listof stations used for controlling the hydrographic sur-vey shall be included as a separate sheet and insertedin the Descriptive Report. (See figure 5-9.) The fol-lowing information shall be given for each station:

9. Recommendations, if any, for zoningand time corrections. 1. Station number (001-999).

B. ABSTRACT OF CORRECTIONS TOECHO SOUNDINGS. Abstracts, in tabular form,for velocity and other corrections to be applied tothe echo soundings shall be included as separateentries in the Descriptive Report. (See figure 5.7.) A

3. Longitude (to nearest thousandth of asecond).

4. Name and type of station (3.1), that is:

4-103 (JUNE 1, 1981)

4.12.5.4. SEPARATES FOLLOWING TEXT.Various tabulations and other information are re-quired on separate sheets which are inserted in theDescriptive Report. Those applicable shall befurnished and inserted in the order listed below.

The first page of the text and the attached in-serts shall be numbered consecutively. The approvalsheet is always placed last.

1. How the tide/water level correctionswere derived and the zones or items to which thesecorrections were applied. (If automated computa-tions for tides corrections to soundings were madebased on multigage observations, the program num-ber and gage sites must be given.)

2. The name, geographic locale, latitude,and longitude of each gage.

3. Dates of gage installations and remov-als, and any problems experienced with gage opera-tions.

4. Staff value equivalent to the zero lineon analog tide records. (In the Great Lakes, the ele-vation of the reference mark (zero electric tape gageor ZETG) on the electric tape gage shall be noted.)

5. Significant differences in comparativeobservations (AK.2.3), in tide or water level times,or in ranges or unusual fluctuations between adjacentgages.

6. The time meridian used for records an-notation.

7. Observations of unusual tidal, waterlevel, or current conditions.

8. A tabulation of missing hourly heights,if any, that may be required for reduction of sound-ings to the datum of reference.

similar abstract can be easily constructed for correc-tions determined solely by bar checks taken through-out the depth range.

The Sounding Correction Abstract shows thedates, times, vessels, and instrument serial numbers towhich the corrections apply. If the same correc-tions apply to more than one survey, a copy of the ab-stract and applicable correction tables (4.9) are in-cluded in the Descriptive Report for each survey.

3. Copies of calibration data for STD,TDC, or other sensors used for velocity determin-ations.

5. All other basic data, computations,graphics, and material needed to verify the final cor-rections.

2. Latitude (to nearest thousandth of asecond).

HYDROGRAPHIC MANUAL

(a) Basic or supplemental (include yearof establishment).

(b) Photogrammetric or hydrographic.

E. ABSTRACT OF POSITIONS. TheAbstract of Positions shall be assembled for eachhydrographic survey vessel that worked on thefield sheet. (See figure 5-10.) Each vessel is identi-fied by its data-processing number, and the workaccomplished is listed by Julian dates, inclusive po-sition numbers, control codes, and electronic con-trol station numbers.

If chart sections are submitted, separateforms for landmarks to be deleted need not be pre-pared. The following procedures are used:

F. REPORT ON LANDMARKS ANDNONFLOATING AIDS TO NAVIGATION.NOAA Forms 76-40, ''Report on Nonfloating Aidsor Landmarks for Charts,'' shall be prepared as re-quired herein and copies attached to the DescriptiveReport. Separate forms 76-40 are submitted for:

1. Landmarks to be charted.

2. Landmarks to be deleted.

3. Nonfloating aids to navigation.

A separate NOAA Form 76-40, ''Non-floating Aids or Landmarks for Charts,'' shall beused to report the positions of all nonfloating aids tonavigation on a chart-by-chart basis. The geograph-ic positions of all nonfloating aids, including pri-vately maintained lights and beacons, shall beverified or determined in the field. Applicable partsof the requirements stated for form 76-40 shall befollowed in compiling this report. If contemporaryshoreline mapping of the area has been undertaken,copies of form 76-40 for new aids or aids to be de-leted shall be sent to the Photogrammetry Division,OA/C34; otherwise, the forms are sent to the Ma-rine Chart Division, OA/C32. For additional detailsconcerning landmarks and aids to navigation see:

Objects of special importance or extraordi-nary prominence are indicated by an asterisk (*)preceding the name of the object. When selectingobjects of special importance, the total area andchart coverage must be carefully considered. Flag-staffs, flagpoles, and other structures of a temporarynature are not listed as landmarks unless they are ofa very permanent and prominent nature and thereare no other suitable objects in the area. Recom-

4-104(JUNE 1, 1981)

5. Source; that is, volume and page num-ber for published geodetic control or, if new, a ref-erence to abstracts of field observations.

The hydrographer shall evaluate all chartedlandmarks from seaward to determine which are ade-quate and most suitable for the purpose intended andto determine which charted landmarks no longer existand thus should be deleted from the charts. If there aremore prominent objects in the area which would serveas better landmarks, their positions shall be deter-mined and listed among the landmarks to be charted.

Reports on landmarks must be completewithin themselves. Avoid additional references togeodetic, photogrammetric, or other data not readi-ly available to other users. The report shall statepositively whether or not a seaward inspection hasbeen made to evaluate the landmarks. If the reportshave been assembled without the benefit of a sea-ward inspection, the reason for omission shall befully explained.

mended charting names should be short, general,and shown in capital letters (5.5.1.2). If the objectwas used as a hydrographic signal, a note is made tothis effect and the station number indicated.

When a large number of landmarks are re-ported, or the hydrographer or field editor consid-ers it necessary to clarify the tabulated data, a copyof the chart of the area should be cut into letter-sizesections, appropriately annotated, and submittedwith the copies of NOAA form 76-40. (See figures5-11 and 5-12.) The area inspected is outlined onthese chart sections and a recommendation madefor each charted or plotted landmark within theoutlined area.

1. New landmarks shall be plotted andidentified by the landmark symbol (A) together withthe name recommended for charting. The geo-graphic datum of the chart must be known and con-sidered in the plotting.

2. Charted landmarks recommended forcontinuance are checkmarked (A). If the positionhas been verified in the field, the word ''verified'' isentered beside the checkmark.

3. Charted landmarks recommended fordeletion shall be indicated by an X in a circle (A),the word ''delete'' entered, and the reason for therecommendation given.

Names and notations on these chart sectionsshall be typed or lettered legibly in red ink. Caremust be taken that such notations always appear onthe same section of the chart section as the land-marks to which they refer.

HYDROGRAPHY

gathered while sailing along assigned lines (e.g., In-ternational Hydrographic Bureau 1974). Track linesare normally required only when there is a specificneed for the data, and are controlled using themost accurate positioning system available to thevessel. LORAN-C ground wave positions providethe minimum accuracy desired. If accurate longrange navigation equipment is not available, otherstandard methods, with some refinements, may beused to follow and control the line. Because the re-quirements for each track line survey are unique,the following discussion is limited to generalities.

It is important that the names of the aidsentered on the form be identical with those givenin the Light List and that the Light List number begiven. The position of each aid should be plottedon the largest scale chart of the area and comparedwith the charted position. Significant differencesshall be reported to the U.S. Coast Guard DistrictHeadquarters and to NOS Headquarters throughthe appropriate Marine Center.

Track line surveys are plotted either onOcean Survey Sheets (OSS series) or on U.S. NavyBathymetric Charts (to be specified in the projectinstructions). Limits of the OSS series weredesigned to conform closely to the U.S. NavyBathymetric series. The OSS, however, are twicethe scale of the U.S.N. Bathymetric Charts.

G. COAST PILOT REPORTS. The CoastPilot Report and/or copies of NOAA form 77-6shall be completed and attached as a separate. Anysupporting documentation should be attached tothe appropriate item report.

Thirty OSS are used to span the area fromlatitude 0°30'S to 72°30'N. The sheets are turned180° for use in southern latitudes. The MercatorProjection is used for these sheets; the sheets be-tween the Equator and the 65th parallel are at ascale of 8 in = 1° longitude, and the sheets to thenorth thereof are at a scale of 4 in = 1° longitude.The scale 8 in = 1° longitude causes the naturalscale to vary from approximately 1:548,000 at theEquator to 1:232,000 at the 65th parallel. Projec-tions are ruled at 30-min intervals with 1-min grad-uations on the central and outer latitude andlongitude lines of the sheet. The larger scale sheetscover 5° longitude sectors with the smaller scalesheets covering 7.5° sectors. Each sheet overlapseach adjoining sheet by 30 min of latitude and 15min of longitude. Natural scales and a sheet indexare shown on the margins. OSS series projectionson paper and Stable base polyester drafting filmcan be ordered from the Marine Centers.

H. DISCREPANCY ITEM REPORTS.The report forms for discrepancy items shall becompleted and attached as a separate. Supportivedocumentation of page size should be attached tothe appropriate item report. Larger documentationshould be included with the other survey recordsand appropriate reference made in the item report.

I. ABSTRACT OF DOCUMENTATION.All sources of information pertinent to the surveyshould be considered part of the survey and trans-mitted with other supportive data.

J. APPROVAL SHEET. The Chief ofParty shall furnish, on a separate sheet attached tothe Descriptive Report, a signed statement of ap-proval of the field sheet and all accompanying re-cords. Include a statement concerning the amountand degree of personal supervision of the fieldwork and frequency with which he examined thefield sheet and other records. State whether thesurvey is complete and adequate or if additionalfield work is recommended. Cite additional infor-mation or references that may be of assistance forverifying and reviewing the survey.

Stamp 30 (figure 4-57) shall be impressedon the lower right-hand corner of each OSS andall applicable entries made as follows:

SPECIAL SURVEYS4.13.

4.13.1 Track Line Surveys

National Ocean Survey vessels occasionallyconduct track line surveys on extended voyagesfrom port to project areas for bathymetric mappingor for other research projects. Track line surveysare merely continuous records of sounding data Opposite ''Field number,'' enter the field

4-105

"Photogrammetry Instructions No. 64,Requirements and Procedures for Collecting, Pro-cessing, and Routing Landmarks and Aids to Navi-gation Data–Photogrammetric Operations'' (Na-tional Ocean Survey 1971b).

Opposite ''Registry no.,'' enter the regis-try number if assigned. Otherwise, enter the surveyproject number.

Opposite ''BC index no.,'' enter the U.S.Navy Bathymetric Chart series number from theseries index and identify the quadrant in which theOSS lies (figure 4-58).

(JUNE 1, 1981)

HYDROGRAPHIC MANUAL

TABLE 4-16.– Ocean Survey Sheets

(OSS) series numbers and limits

00°30'S to 03°30'NOSS-1

03°00'N to 07°00'NOSS-206°30'N to 10°30'NOSS-3

10°00'N to 14°00'NOSS-413°30'N to 17°30'NOSS-5

OSS-6 17°00'N to 20°30'N20°00'N to 23°30'NOSS-7

23°00'N to 26°30'NOSS-826°00'N to 29°30'NOSS-9

29°00'N to 32°30'NOSS-1032°00'N to 35°30'NOSS-11

35°00'N to 38°00'NOSS-12

37°30'N to 40°30'NOSS-13

OSS-14 40°00'N to 43°00'N

42°30'N to 45°30'NOSS-15

OSS-16 45°00'N to 47°30'NOSS-17 47°00'N to 49°30'N

49°00'N to 51°30'NOSS-1851°00'N to 53°30'NOSS-1953°00'N to 55°00'NOSS-2054°30'N to 56°30'N FIGURE 4-57. — Enlargement of rubber stamp 30, oceanographic

survey sheet data stampOSS-21

56°00'N to 58°00'NOSS-2257°30'N to 59°30'NOSS-2359°00'N to 61°00'NOSS-2460°30'N to 62°30'NOSS-2562°00'N to 63°30'NOSS-2663°00'N to 64°30'NOSS-27 Soundings are logged at intervals not to ex-

ceed 5 min in depths over 100 fm and at intervalsnot to exceed 2 min in depths under 100 fm. In ad-dition, depths of all intermediate peaks and deeps

OSS-28* 64°00'N to 67°30'NOSS-29 67°00'N to 70°30'N

70°00'N to 72°30'NOSS-30

* Sheets 28 through 30 are at a scale where 1° of longitude equals 4 in.

number as a two-letter vessel identifier, the scale atthe central latitude of the sheet (1:519,000 as 519),the sequential sheet number for the project, and thelast two digits of the calendar year.

A B

D C

Positions are taken and recorded hourlyand when significant changes in the course or speed

4-106(JUNE 1, 1981)

Opposite ''Control curves plotted by,''enter the method or type of automatic plotter usedto draw line of position arcs on the sheet.

Opposite ''Type of control,'' enter the pri-mary control system in upper case letters and auxil-iary or supplemental systems in lower case letters.

Opposite ''Rate or station,'' enter all navi-gational rates and stations used for lines of positionon the sheet with the colors used to draw the corre-sponding arcs.

When using U.S. Navy Bathymetric Chartsfor track line surveys, the recorded soundings aregenerally not plotted in the field. Processing re-quirements and data disposal for track line surveyswill be included in the project instructions.

of the vessel are made. Distance log or revolutioncounter readings and ship's courses shall be record-ed with the fix data.

FIGURE 4-58. — Subdivision of a U.S. Navy Bathymetric Plot-ting Sheet into four Ocean Survey Sheets (OSS) and letteridentifications

HYDROGRAPHY

seamount is ''an elevation of the sea floor having anearly equidimensional plane less than 60 nauticalmiles across the summit'' (Bruder 1963). Significantuncharted features discovered during track line sur-veys shall be reported immediately to the director ofthe vessel's Marine Center who in turn shall informNOS Headquarters. Significant features include un-charted seamounts, submarine valleys, and othersimilar physiographic phenomena. Reports shouldinclude the general characteristics, the approximatesize, and the geographic location of the feature.

All position data for track line surveys shallbe recorded on NOAA Form 77-15, ''Dead Reck-oning Abstract,'' and on magnetic or punched papertape, depending on the vessel's capability. Positionsare identified by sequential serial numbers followed

by a cruise letter. Cruise letters begin with the letter''A'' at the beginning of each calendar year andprogress through the alphabet— letters ''I'' and ''O''are not used. Serial numbers are reset to 1 at the be-ginning of each cruise. Bottom cores, bathyther-mograph profiles, and similar events shall also beassigned serial numbers and be recorded on NOAAForm 77-2, ''Marine Operations Log.''

Frequent checks on the depth recorder shallbe made to ensure that the recorded soundings areon the proper scale. For example, a sounding checkshould be made when recording on the 4000-fmrange to ensure that the correct 400-fm scale is beingused. Position numbers are assigned when simulta-neous comparisons of soundings are made; all graph-ic records and tabulated data for these comparisonsshall be included as part of the permanent surveydata.

Astronomic observations should be madewith navigation sextants read to the nearest 10 s—the time of each observation is recorded to the near-est 0.2 s using an accurate stopwatch. The stop-watch must be compared with an accuratechronometer or with another acceptable time stan-dard such as WWV, National Bureau of Standards(Fort Collins, Colorado) radio station, before and af-ter the observations. WWV and WWVH (Maui,Hawaii) broadcast continuous time signals on thefrequencies 2.5, 5, 10, 15, 20, and 25 MHz. When seaand sky conditions permit, each observer makes aseries of six measurements to each star or other bodyto be used for the position. A recorder should beassigned to each observer.

Commanding officers may be authorized bythe appropriate Marine Center to develop one sea-mount per track line, if encountered, provided con-trol is consistent and geometrically strong — two sea-mounts may be authorized when engaged on otherocean surveys. Developments should be complete tothe extent necessary to determine that the feature isa seamount. The officially accepted definition of a

4-107 (JUNE 1, 1981)

shall be recorded—times of occurrence are enteredto the nearest minute. All soundings shall be loggedto the closest 1 fm, even in areas of indistinct re-turns. Unless specified otherwise in the project in-structions, velocity corrections are applied from ap-plicable historical tables as the soundings are taken.

Shore ties must be made at the beginningand ending of every track line by accurately fixingthe vessel's position with reference to fixed objectsof known position. Three-point fixes with check an-gles, cross bearings, or radar ranges are acceptablefor shore ties, in that order of preference.

Analog depth records shall be removedfrom the depth recorder each time a plotter sheethas been completed or the sounding line continueson to a new sheet. The following notations shall bemade in addition to the record stamps routinely re-quired: beginning position number and its GMT, thelast position number and its GMT, and the generaldirection of the sounding line (N S), (W E).

4.13.1.1. ASTRONOMIC OBSERVATIONS.When other control is not available, astronomicsights are used to position vessels on track or cruiselines. Observations are similar to those used for rou-tine surface navigation, except that sights are takenwith greater precision and care and are computedand plotted more accurately. Observation and com-putation procedures and the use of astronomic sightsare described in ''American Practical Navigator, anEpitome of Navigation'' (Bowditch 1962); Dutton'sNavigation and Nautical Astronomy (Beito 1957); andDutton's Navigation and Piloting (Dunlap andShufeldt 1969) and are not repeated here. The infor-mation contained herein is limited to the refinementsfor observations and the best methods of using thedata. There is no NOAA form for computationswith H.O. Pub. No. 229, ''Sight Reduction Tablesfor Marine Navigation'' (U.S. Naval OceanographicOffice 1970). For attaining required precision, com-putations are made to the nearest 0.1 s of time and tothe nearest 0.1 min of arc. Each computation mustbe checked and the sheets bound in chronologicalorder for shipment to NOS Headquarters with thesurvey records. Smooth copies of the computationsare not required.

HYDROGRAPHIC MANUAL

Log readings or revolution counter read-ings are recorded at 10-min intervals during morn-ing and evening star sight observations. Star sights,when taken underway, must be advanced (run up)or retired (run back) to a selected dead-reckoningposition.

3. Direction of the wind and whether itis blowing into the observer's eyes.

4. Rate of change in altitude of the star.

For best results, celestial bodies to be ob-served should be selected so that lines of positionwill plot in a symmetrical quadrilateral. Whenmore than four stars are observed, it is preferableto combine lines of position to a resultant rectangu-lar figure of error with sides roughly north-southand east-west. The stars should be of about thesame magnitude and about the same altitude. Ob-servations on bodies at altitudes between 15º and20º usually give the best results, but altitudes be-tween 10º and 35º may be considered satisfactory.

Because of observational errors, the linesof position (corrected for the run of the ship be-tween sights) normally will not intersect at apoint. Three lines of position generally form a tri-angle of error. The probable position of the vesselderived from a series of morning or evening starsights is based on the assumption that there is anerror common to all sights—approximately equalin magnitude and in the same direction with re-spect to the stars observed. It is not especially nec-essary that the magnitude of this error be small,but for best results it must be symmetrical. Whendetermining the most probable position of the ship,the directions of the observed bodies must alwaysbe considered. For unweighted observations, theprobable position should be equidistant from thelines of position and lie either toward or awayfrom each star of the series—never away fromsome and toward others.

Two methods are used to find the mostprobable position; when a series of more than threesights is observed, a combination of methods isused. The first method is to move each line of posi-tion either away from or toward the objects ob-served by an equal distance to bring them as closeas possible to a common intersection. (See A and Cin figure 4-59.) In practice, the lines of position

1. Relative distinctness of the horizon be-low each star observed.

2. Disturbing effects of the roll and pitchof the vessel.

4-108(JUNE 1, 1981)

Each star sight is used independently todetermine the probable position of the ship. Theresults may be compared and weighted, if neces-sary, for the final position. Observations taken bydifferent observers with different sextants or at dif-ferent times of the day should never be combinedto determine a probable position. Each observer'ssights should be plotted on separate sheets of pa-per. The dead-reckoning position, the final positionof the ship, and the lines of position (after beingrun up or run back) are inked. The name of eachstar observed and its direction are indicated along-side each line of position. Observed lines of posi-tion and the distance and direction each was runup or back are left in pencil. The final position isthen transferred to the plotting sheet. If one ob-server obtained the astronomic position, the finalplot may be made directly on the plotting sheet.(See 4.13.1.)

Several factors influence the accuracy ofastronomic observations. A change of 1 min in alti-tude moves the line of position 1 nmi. At the Equa-tor, the altitude of a celestial body on the primevertical changes 1 min of arc in 4 s of time. Forother latitudes and azimuths, the error in positioncaused by an error in time is less and varies withthe cosine of the latitude and the sine of the azi-muth. Greater errors in astronomic sights on celes-tial bodies are more likely in an east or westdirection than in a north or south direction—an er-ror in time affects the line of position proportion-ately more because the bodies change faster inaltitude and make accurate observations more diffi-cult. A distinct and clear horizon is essential for ac-curate observations. Evening star sights are madeas early as possible, and morning sights as late aspossible to assure a well-illuminated horizon. Atthe time of observation, each observer should rateeach set of sights as ''excellent,'' ''good,'' ''fair,'' or"poor.'' Ratings should be based on these factors:''poor.

5. Relative distinctness of stars of differ-ent magnitudes.

When selected stars are arranged symmetri-cally and are at approximately the same altitude,some observational errors will be partly eliminatedin the final plot. Accidental errors of observation arenot eliminated by a systematic arrangement. Officialobservations should be made only by experiencedpersonnel able to obtain consistently good results.

HYDROGRAPHY

should be combined by drawing the bisectrix be-tween them. From the figure of error thus formed,the most probable position is determined as de-scribed. (See figure 4-59(E).)

need not actually be moved; the probable positionis determined by using dividers and visualizing thetransfer of the line of position. Be certain to adopta position on the correct side of each line of posi-tion considered (i.e., the position must lie either to-ward or away from each star of the series).

When possible, observations should be madeon the Sun at least five times a day. The first and lastobservations are made when the altitude of the Sunis between 12° and 25° the noon sight should betaken at local apparent noon, and the other two ap-proximately halfway between the noon sight and theearly morning and late afternoon sights. A meridianaltitude sight should be taken independently by twoor more observers. Individual Sun sights are not runup in the final plot, but are used as separate lines ofposition at the times of observation to which thetrack line, as a whole, is adjusted.

The second method is to draw bisectricesbetween intersecting lines of position. Each bisectrixis drawn so that it is either toward or away from thetwo objects observed. In the triangle of errorformed by three lines of position, the threebisectrices intersect at a point, as shown in figure 4—59(B). For four lines of position from stars in fourdirections, two bisectrices are drawn—each be-tween two opposite lines of position as shown in fig-ure 4—59(D). Where two opposite lines of positionare from stars in the same direction, a mean lineshould first be drawn between them. This mean lineand the other two lines are treated as three lines andthe bisectrices drawn as in figure 4—59(B).

4.13.1.2. DEAD RECKONING. This is naviga-tion by account, or reckoning, from the last knownposition (i.e., the position of a vessel at any instantis determined by applying the course steered anddistance traveled from the last known well-deter-mined position). Dead-reckoning is used to plottrack or cruise lines between observed positions andto substantiate other position data. When electronicpositioning systems fail and weather conditions donot permit celestial fixes, dead reckoning must beused.

When more than four stars are observed inone series, the lines of position in the same generaldirection should be combined to reduce the data tonot more than four lines of position. Assuming allobservations to be of equal weight, the lines of posi-tion from two stars in the same general direction

-

_7/ '' A B I''~

/I.

A

To attain greater accuracy, one appliesseveral refinements when determining hydrographicpositions by dead reckoning. Engine speeds shouldbe maintained at a constant rate. Although the valueof constant speed is reduced when the vessel must bestopped for other observations, maintaining constantspeed is helpful when reconciling track line plots be-tween fixed positions. Vessels should be equippedwith accurate submerged electric logs. Revolutioncounters are read and the values recorded at eachfixed position; these readings may be useful if a dis-tance log fails to function properly. Courses must besteered very closely—within 1° if possible. Only themost competent helmsmen should steer the vessel

FIGURE 4–59. — Probable position of a ship from astronomicobservations

4-109 (JUNE 1, 1981)

Dead reckoning positions are not precise—positional uncertainty increases proportionally withthe distance run from the last fixed position. Errorsmay be introduced in a number of ways. Those fac-tors affecting the course include steering errors, in-correct allowance for compass error, leeway, andthe effects of currents; those affecting distance trav-eled are inaccurate distance logs, unknown log fac-tors, and incorrect allowance for current.

HYDROGRAPHIC MANUAL

when automatic steering is not used. Officers onwatch must check the course being steered at fre-quent intervals. All compass errors must be deter-mined accurately.

4.13.2. Tag Line Surveys

When detailed surveys of important docks,anchorages, or restricted areas are needed, ''tagline'' surveys often prove to be the most efficientand accurate method. Depending upon the requiredline spacing and sounding interval, a special scale isselected that allows each sounding to be shown. Forguidance, a scale of 1 in = 100 ft is generally ade-quate for sounding lines spaced 25 ft apart withsoundings taken at intervals of 25 ft along the lines.Dead-reckoning positions are most accurate

when operating in dead calm seas; however, thiscondition seldom exists. Trials should be made todetermine the effects of leeway caused by winds ofdifferent velocities from various angles to the ship'sheading. Graphs can be prepared from these data tobe used when estimating course changes to compen-sate for leeway.

The following example is but one of manydifferent methods that can be used to execute a sat-isfactory tag line survey:

Allowances must also be made for the setand drift of the current. In addition to oceanic cur-rents, persistent winds generate surface currents. Es-timates of wind-driven currents may be based on thefollowing:

Dead-reckoning positions should becorrected for all known factors affecting course anddistance before they are plotted. Differences be-tween dead-reckoning positions and positions deter-mined by other methods are termed dead-reckoningclosures. These differences are adjusted by distribut-ing the errors proportionally with times betweenfixed positions. Adjustments are not always linearbecause Sun sights, electronic lines of position, or

(JUNE 1, 1981) 4-110

A complete record of events must berecorded on NOAA Form 77-15, ''Dead Reckon-ing Abstract,'' as the line is run. All control data tobe used in plotting and adjusting the dead reckon-ing line should be entered in this abstract. Eachevent must be recorded promptly and correctly andreferenced to time. Data shown on the abstracts,the line-of-position computations, and theastronomic sights may all be used to make final ad-justments of the plot.

other recorded data must be considered and evalu-ated. Supplemental data obviously in error shouldbe rejected. Soundings along the track often have tobe compared with charted soundings for additionalguidance when making the final adjustment.

1. A diagram of the area to be surveyed isprepared at the selected scale (figure 4–60); pro-posed sounding lines P, Q,..., U are plotted on thediagram.

2. Base line A, B,.... is plotted on the dia-gram. A and B may be existing control stations ornew stations located by sextant fixes or other meth-ods of equivalent accuracy.

3. Intersections of proposed sounding lineextensions with the base line are laid out on theground, temporarily marked, and for identificationpurposes assigned a letter or number. The diagrammay be used later as a base for the final soundingplot.

4. Point C is a distant control station usedfor azimuth control if the base line is too short foran accurate initial azimuth.

5. A sextant and lead line or echo sounderare used aboard a light skiff powered by a lowhorsepower outboard motor. The only specialequipment needed is a sturdy metal reel largeenough to hold the necessary length of small wirethat will be used to measure the distances from thebase line. The reel should be equipped with a strongbrake and a geared crank for winding in the wire atthe end of each sounding line. The tag line shouldbe made of 3/32-in pliable stranded wire. Readilyidentifiable marks are attached to the wire at 100-ftintervals using crimp-type electrical splicers. Col-ored cloth is inserted between the wire strands tomark intervals of 25 ft.

1. Observations have shown that persis-tent winds set up wind-driven surface currents withvelocities equal to approximately 2% of that of thewind in both coastal areas and the open ocean.

2. The direction of wind-driven currentsin the Northern Hemisphere is about 20° to the rightof the wind in coastal areas; theoretically, this de-flection is probably closer to 40° to the right of thewind in the open ocean. Coastal wind-driven cur-rents do not always follow this rule— speciallywhen near the shore where the current direction de-pends primarily on the angle between the wind di-rection and the coastline.

HYDROGRAPHY

• FIGURE 4–60.—Layout of a tag line survey •

(JUNE 1, 1981)4-111

6. An observer stands on each point alongthe base line (A, 1, 2,..., 5) as the survey progresses,and using a sextant sets the angles a1, a2,...., a5 fromazimuth station C to the azimuth of the soundingline. The observer then indicates to the skiff byprearranged signal its position relative to the pro-posed sounding line; he may also select a range ob-ject in the background to keep the skiff on line.

7. The zero end of the tag line issecured at the proper point on the base line andthe reel manned by an operator aboard the skiff.The

skiff is run slowly in reverse and the tag line playedout over the bow. By braking the reel as eachsounding interval mark appears, the skiff is stoppedat the proper distance.

8. The coxswain maintains the proper ten-sion on the tag line and maneuvers the skiff onto thesounding line as directed by the observer ashore.The leadsman takes a sounding when signaled bythe observer—the recorder enters the appropriatesounding time, sounding, tag line distance, and linenumber in the records.

5. FIELD REPORTS

PERIODIC ADMINISTRATIVEREPORTS

5.1.

Periodic reports are required from the fieldto keep NOAA and NOS management informed ofthe general activities, status, progress, and accom-plishments of all hydrographic survey units. Thefollowing periodic reports shall be submitted in ac-cordance with the indicated citations and relatedreferences:

Type of survey;General locale;

Scale of sketch;Project number;Inclusive dates of survey;

Name of Chief of Party.

In addition to these reports, each Chief ofParty shall compile and submit a Monthly Activi-ties Report and a Monthly Survey Status Report inaccordance with the appropriate Marine Center di-rectives, that is:

The Atlantic Marine Center OPORDERS(1975-1980); and

The Pacific Marine Center (1974) OPORDER.

5.1.1. Monthly Progress Sketch

Symbols shown in the upper portion of fig-

5-1 (JUNE 1, 1981)

1. Season's Report from the NationalOcean Survey (1971a) ''Operations Manual'' (NOSManual No. 1, chapter 77, section 61).

2. Cruise Report from the NationalOceanic and Atmospheric Administration (1972)"NOAA Circular 72-134'' (NOAA Directives Manu-al, chapter 17, section 17).

3. Special Report from the NationalOcean Survey (1971a) ''Operations Manual'' (NOSManual No. 1, chapter 77, section 63).

4. Monthly Ship Accomplishment Re-port from the National Ocean Survey (1971a) ''Op-erations Manual'' (NOS Manual No. 1, chapter 77,section 64). See also sections 5.1.1 and 5.1.2 forprogress sketch requirements.

Vessels conducting hydrographic, tidal cur-rent, wire drag, or ocean investigation surveys shallsubmit a Monthly Progress Sketch for each projectworked on during the month. The sketch shall besent with a transmittal letter to the appropriate Ma-rine Center as soon as possible after the end of themonth. Vessels engaged only in oceanographic re-search and development projects or other projectsof a special nature need submit only one progress

sketch upon completion of each project or segmentof a continuing project that has been completedduring any one calendar year unless specified oth-erwise in the project instructions.

Progress sketches shall be drawn on a du-rable transparent drafting material that permits easyreproduction. Only black ink should be used. Thesketch and title must be neat and legible.

The scale to be used is generally stated inthe project instructions; if not, the scale should bethat of the published chart which covers the entirework area of the season. Dimensions of the sketchshould not be larger than needed to show the workaccomplished during the reporting season.

Each progress sketch shall contain a titleand legend giving the following information:

Name of vessel or party; and

Scales may be given as ratios or by refer-ring to a chart from which the projection has beentraced. A labeled projection with sufficient shore-line and geographic names shall be shown on thesketch for easy identification of the general locale.Progress for all types of work accomplished shouldbe added at the end of each month. The informa-tion should be generalized, using standard symbolsas shown in figure 5-1. The principal objective isto report areas surveyed in such a way that infor-mation can be transferred quickly and easily to theprogress charts maintained at the Marine Centersand at Headquarters. (See figure 5-2.)

Sheet limits are shown and identified onprogress sketches as survey sheets are started andregistry numbers assigned (2.4.3.2); if this informa-tion would create congestion and confusion, thesheet layout should be submitted on an accompany-ing transparent overlay.

HYDROGRAPHIC MANUAL

Combined Operations

Magnetic station

Water level gageTide gage

Hydrography

Area surveyed or

Field edit

Wire drag areas

Control surveys

New stations Recovered stations

Identified on photos

Each bottom sample retained for analysisshall be numbered consecutively and the methodused to obtain the sample indicated on the sketch asC for core; S, snapper cup; SF, scoopfish; and D,dredge. Dashed lines are used to show dredgingroutes.

Measured line

Main schemeStation numbers are shown beside current

station symbols and the methods of current measure-ments indicated by letters such as A for AanderaaSystem, G for Grundy System and D for droquetracking.

Intersection directions

Observed one direction

In addition to the graphic data, a table of sta-tistics showing a numerical listing of the monthly ac-complishments shall be included on the sketch. Anew Monthly Progress Sketch is prepared at the be-ginning of each calendar year for each projectassigned to the hydrographic party.

Oceanographic Projects

(See text for use of letters to supply additional

information.)

Tide gage Bottom sample5.1.2. Season's Progress Sketch

Salinity, temperature,depth sensor cast For each project, a Season's Progress Sketch

shall be prepared on a transparent durable material,using the same guidelines stated for the MonthlyProgress Sketch, and be submitted with the Season'sReport. The information shown on the Season'sProgress Sketch is a summation of all progressshown on the monthly sketches. A page-size repro-duction of the final Monthly Progress Sketch may beused.

Nansen bottle cast

Bathythermograph (BT)Expendable BT

Current station ©

Oceanographic station Biological sample

FIGURE 5-1-Symbols to be used for drawing progresssketches

The title shall state ''Progress Sketch To Ac-company Season's Report'' and include the date on

ure 5-1 are used to report progress on hydrographicand combined operations projects. Different symbols

5-2(JUNE 1, 1981)

shall be used to distinguish between hydrography ac-complished in consecutive months. Additional sym-bols may be used as necessary to report other accom-plishments, but such symbols must be explained in alegend. Oceanographic observations made as part ofa combined operations survey are shown on the samesketch. Unless specified in the project instructions,horizontal control accomplishments are not shownon a monthly basis. (See 5.1.2.)

Vessels assigned to oceanographic projectsshall use the symbols shown in the lower part of fig-ure 5-1 to report progress. The symbol for Nansencasts or the equivalent is supplemented by letters andnumbers to identify the water samples retained. Anoceanographic station occupied for the determina-tion of salinity shall be identified by the letter S, foroxygen by the letter O, for phosphate by the letter P,and for nitrates by the letter N. Sample bottle serialnumbers are shown also (e.g., S 105-121 indicatesthat salinity samples numbered inclusively from 105to 121 were obtained at that station).

Temperature andsalinity station

FIELD REPORTS

FIGURE 5-2. —Monthly Progress Sketch

5-3 (JANUARY 1, 1980)

PROGRESS SKETCHOPR - 469

UPPER COOK INLET , ALASKAMAY 15 -AUGUST 22,1974NOAA Ship RAINIER

K.WILLIAM JEFFERS, CDR, NOAACOMD G

From Chart 16660 ( formerly C&GS 8553)

HYDROGRAPHIC MANUAL

which field work was closed in addition to the infor-mation shown in the title of the Monthly ProgressSketch.

cable to the survey and to give, in concise form, re-quired information on certain standard subjects.General statements and detailed tabulation of self-ev-ident data (such as inshore rocks and shoals or rocksor coral heads already shown on the field sheet)serve no purpose and should not be included.

Recoverable control stations established bythe hydrographic party (3.1.1) are shown on a sepa-rate sketch that is then attached to the Season's Re-port. This sketch shall be prepared in accordancewith instructions on pages 191 and 192 of Coast andGeodetic Survey Special Publication No. 247, ''Manu-al of Geodetic Triangulation'' (Gossett 1959), usingthe symbols shown in figure 5- 1.

5.2. PHOTOGRAMMETRICPRECOMPILATION FIELD REPORTS

These shall be prepared to describe photo-grammetric field operations conducted prior to thecompilation of coastal maps and shoreline manu-scripts. Supporting operations of this nature includerecovering or establishing horizontal control stationsand placing targets on the stations prior to aerialphotography. Observing and reporting tidal stages insupport of tide-coordinated photography may also berequired. In surveys of large extent or of a complicat-

ed nature, it may be advisable to prepare specialreports on certain phases of the work covering theentire project. Cross-references to each of these andto all other pertinent reports shall be included. [See5.3.4(S).]

Reports on these field activities shall be pre-pared in accordance with individual photogrammet-ric job instructions and ''Photogrammetry Instruc-tions No. 22, Field Recovery and Identification ofHorizontal and Vertical Control'' (U.S. Coast andGeodetic Survey 1965b).

5.3. DESCRIPTIVE REPORT

The various data required on separate sheetsshall be arranged in the sequence described herein.

5.3.1. Cover SheetThe Descriptive Report serves as a narrative

document that describes the conditions under whichthe work was performed and discusses various fac-tors affecting the adequacy and accuracy of the re-sults. The primary purposes are to direct attention toimportant results and to supplement the hydrograph-ic sheets and sounding records with information thatcannot be shown clearly, concisely, and graphicallyon the sheets or in tabular form. The report shouldassist the cartographers compiling and verifying asurvey, then charting the results. It serves to refer-ence and index all records and reports appli-

The ''State'' entry is the name of the Stateor territory nearest the center of the hydrographicsheet.

The ''General Locality'' in which the surveywas performed must be defined by a well-known geo-graphic name (e.g., Sumner Strait, Gulf of Mexico,or Lake Huron).

5-4(JANUARY 1, 1980)

A daily journal or log sheet shall bemaintained by the hydrographer. Without a carefullyprepared journal, satisfactory Descriptive Reportscannot be written from memory or compiled by anindividual lacking personal knowledge of the fieldwork. To complete the tabulations or abstracts de-scribed in section 5.3.5, the hydrographer must eval-uate and tabulate data daily while the data are beingacquired, rather than waiting until the sheet is com-pleted or the field season has ended. The inclusion ofthese tabulations permits standardization of data-col-lection methods and forms and results in more com-prehensive and understandable field data. Notesmade on the field sheet to supplement the daily jour-nal shall, when applicable, be included in the De-scriptive Report.

The Descriptive Report for a special projectshould include all data, computations, and formsthat would ordinarily be assembled as separate re-ports, with the exception of those submitted individ-ually such as Coast Pilot notes and forms fornonfloating aids and landmarks for charts (NationalOcean Survey 1976a). (See 5.5.)

NOAA Form 76-35A, ''Descriptive Re-port'' shall be used as the outside cover sheet; appro-priate entries are made to identify the survey. (Seefigure 5-3.)

A separate Descriptive Report shall be writ-ten for each hydrographic survey sheet completed.This report furnishes all data necessary to completeoffice processing of the survey and plotting of thesmooth sheet. The original and two copies shall beforwarded to the Marine Center with the field sheetand other survey records as soon as field work hasbeen completed.

FIELD REPORTS

NOAA FORM 76-35A

U.S. DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

NATIONAL OCEAN SURVEY

DESCRIPTIVE REPORT(HYDROGRAPHIC)

If a field party has not completed all re-quired work on a field sheet prior to transferring thedata to another unit or to a Marine Center, enter acomplete explanation in the ''Remarks'' section. Oth-er Descriptive Reports or Special Reports contain-ing information or data pertinent to the surveyshould be referenced under ''Remarks.''

HydrographicType of Survey

FA 10-2-72Field No.

H-9286Office No

5.3.3. Index of SheetsLOCALITY

If two or more smooth sheets are needed forthe project area, a copy of the approved smooth sheetlayout (2.4.1) shall be included in the Descriptive Re-port. The subject survey should be indicated on thesheet layout sketch and the adjoining sheets identifiedby both field and registry numbers.

AlaskaState

Ernest SoundGeneral Locality

Petersen Island toLocality

Brownson IslandTide or water level stations must be clearly

shown and identified by name. Separate sheet layoutsshowing the division between visually and elec-tronically controlled hydrography and the amount ofhydrography accomplished each month should be in-cluded. If necessary for clarity, a full layout of all in-sets, overlays, and partial field sheets shall be includ-ed to portray the coverage of the hydrographic sheet.

1972

CHIEF OF PARTYCapt R. H. Houlder, Comdg

LIBRARY & ARCHIVES

DATE

The scale of the index should be such thatthe sketches or drawings can be shown readily onletter-size paper (8½ X 11 in). A reduced copy ofthe smooth sheet layout will be furnished by theMarine Center on request.

FIGURE 5-3.— Descripitive Report cover sheet

The ''Locality'' entry pinpoints the imme-diate area of the survey. Again, specific geographicnames are used as reference (e.g., Approaches toChincoteague Inlet, Northern portion of Lake St.Clair, or NW of Cape Kumukahi).

5.3.4. Descriptive Report Text

This is typed on letter-size (8½ X 11 in)paper with left-hand margins of 1.25 in to permitbinding. The text must be clear and concise. All in-formation required for complete understanding ofthe records shall be included, but verbosity shall beavoided.

5.3.2. Title Sheet

Information for the title of a survey shallbe furnished on NOAA Form 77-28, ''Hydro-graphic Title Sheet.'' Entries are made on all appli-cable spaces on the form. (See figure 5-4.) Sincethe Title Sheet is often referred to for informationpertaining to the survey, be sure all entries are ac-curate.

The entries required on the Title Sheet areself explanatory. ''State," "General Locality,'' and''Locality'' entries shall be identical to those on theCover Sheet. The ''Date of Survey'' entries are the When referring to a hydrographic feature on

5-5 (JUNE 1, 1981)

inclusive dates of the field work. In addition to thename or hull number of the surveying vessel or fieldparty in the ''Vessel'' entry, the identification num-ber assigned to the vessel for electronic data process-ing purposes shall be shown. The name(s) listed inthe ''Surveyed by'' entry are those who were actual-ly in charge during sounding operations.

Each text shall be entitled ''DescriptiveReport To Accompany Hydrographic SurveyH ——(Field No.——)." (Insert registry andfield numbers.) The scale and year of the survey,the names of the survey vessel or party, and theChief of Party are listed.

HYDROGRAPHIC MANUAL

REGISTER NO.

H-9286HYDROGRAPHIC TITLE SHEET

FIELD NO.INSTRUCTIONS - The Hydrographic Sheet should be accompanied by this form.filled in as completely as possible, when the sheet is forwarded to the Office. FA 10-2-72

AlaskaState

Ernest SoundGeneral locality

Petersen Island to Brownson IslandLocality

March 23 to April 21, 19721:10,000Scale Date of survey

OPR-465Instructions dated Project No.

NOAA Ship FAIRWEATHER (2020) Launches FA-1 (2021) and FA-5 (2025)

Captain R. H. Houlder

M.C. Grunthal, A.N. Bodnar, Jr. , D.B. McClean

Soundings taken by echo sounder, hand lead, pole

Graphic record scaled by

MCG, ANB, RCM, RHCGraphic record checked byPMC - Geber

Automated plot by Protracted by

J. L. StringhamVerification by

Soundings in fathoms feet MLW MLLWLWD

See paragraph G for special methods used toREMARKS:

locate control stations.

NOAA FORM 77-28 SUPERSEDES FORM C&GS-537.

FIGURE 5-4.—Hydrographic Title Sheet

(JUNE 1, 1981) 5-6

at

NOAA FORM 77-28(11-72)

U.S. DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

February 28 , 1972

Vessel

Chief of party

Surveyed by

MCG, ANB, DBM, RCM

N/A Digital Plotter

FIELD REPORTS

the field sheet, the latitude and longitude and posi-tion number of the feature shall be given. To pro-vide uniformity of reports, the text is arranged un-der the following lettered headings in the orderappearing here.

to echo soundings, describe them in sufficientdetail to provide the survey verifiers a full un-derstanding of the use and application of data.Sounding corrections must be determined andreported in a standard manner (4.9) unless ex-tenuating circumstances arise; extensive analysisand validation during verification of data ac-quired by nonstandard methods can be extreme-ly time consuming.

A. PROJECT. Include the project num-ber, the date of original instructions, the dates ofall changes, supplemental instructions, amendments,pertinent letters, and purpose of the survey.

B. AREA SURVEYED. Briefly describethe area covered by the survey and the adjacentcoast. State the general locality, approximate limits,and inclusive dates of the survey. A copy of each Abstract of Corrections

to Echo Soundings is inserted at the end of theDescriptive Report (5.3.5(D)); substantiating fieldobservations, computations, and graphs are in-cluded with the field records. (See 4.9.)

C. SOUNDING VESSEL. List all ships orlaunches by letter designations and electronic dataprocessing (EDP) number that were used to obtainthe soundings. Include in this section a narrativedescription of any unusual sounding vessel configu-rations and problems encountered.

E. HYDROGRAPHIC SHEETS. Statehow and where the field sheets were preparedand where it is anticipated the field recordswill be sent for verification and smooth plot-ting. Information on the projection and elec-tronic control parameters for all automated sur-veys is inserted at the end of the DescriptiveReport. (See 5.3.5(A).)

D. SOUNDING EQUIPMENT ANDCORRECTIONS TO ECHO SOUNDINGS. Iden-tify by type and serial number all echo-sounding in-struments used by each survey vessel. State thetype of other sounding equipment used and thegeneral areas and depths in which each was used.Discuss any faults in the equipment that affectedthe accuracy of sounding.

Include any irregularity in projection,scale, or other salient properties of the fieldsheet that should be brought to the attention ofthe office cartographers; such information ishelpful during verification.

Summarize the methods used to determine,evaluate, and apply the following listed correctionsto the echo soundings:

F. CONTROL STATIONS. On the sheet,list the control stations that have been monu-mented and described; state the surveying meth-ods used to establish horizontal positions for hy-drographic signals and stations. Define the gener-al areas in which each method was used andindicate the datum used. If a geodetic control re-port is not available when the survey is submit-ted for processing, copies of the appropriate geo-detic abstracts and computations shall be includedwith the survey records for verification of thepositions. Explain in detail:

If salinity, temperature, depth (STD) sen-sors; temperature, depth, conductivity (TDC) sen-sors; or similar instruments were used for velocitydeterminations, identify each instrument by serialnumber and provide the most recent dates of cali-bration or field check.

3. Any known photogrammetric prob-lems that could contribute to position inaccuracies.

If unusual or unique methods or instrumentswere necessary for the determination of corrections

(JUNE 1, 1981)5-7

List the positions of the stations observedfor velocity corrections with the dates of observa-tion or prepare letter-size (8½ X 11 in) chartletsshowing the locations and dates.

When applicable, specify the vessels,areas, and depths for which any particulargroup of corrections are to be applied.

1. Unconventional survey methods, ifused, for determining the positions of horizontalcontrol stations.

2. Anomalies in the control adjustmentor in closures and ties.

1. Velocity of sound through water.2. Variations in the instrument initial.3. Other instrument corrections.4. Corrections determined from direct

comparisons (bar checks and vertical casts).5. Settlement and squat.

HYDROGRAPHIC MANUAL

Refer to section 5.3.5(F) for control listingsto be appended to the Descriptive Report.

changes. Discrepancies between photogrammetricand hydrographic locations of detail seaward of theshoreline must be mentioned and resolved. Controlstations seaward of the shoreline will be noted hereand described adequately on the field sheet.

G. HYDROGRAPHIC POSITION CON-TROL. State the method or methods of soundingline position control used for the survey and ex-plain in detail any known difficulties experiencedwith the control system that may have degradedthe expected position accuracy. Electronic controlequipment shall be identified by manufacturer,model, and component serial numbers for each ves-sel and shore station.

I. CROSSLINES. State the percentage ofcrosslines run (1.4.2) and discuss any discrepancies atcrossings. If the magnitude of discrepancy varieswidely over the sheet, make a quantitative evaluationof the disagreements area by area.

A special note on the crossing agreementsmust be included if the vessel and sounding equip-ment used to run the regular system of lines werenot used for the crosslines. In all cases, methodsused to reconcile significant differences at crossingsmust be explained.

Briefly describe the methods for calibratingthe electronic control systems. Evaluate, to the ex-tent possible, the adequacy of the calibration dataapplied to raw position data throughout the surveyarea.

J. JUNCTIONS. If the survey junctionswith prior surveys, list each prior survey by regis-try number, scale, and date. List each contempo-rary survey with which junctions were made orthat have a common area by registry or field num-ber. Discuss the agreement or disagreement indepths at junctions. If the hydrographer believesthat an adjustment to soundings and depth contoursshould be made, the recommendation should be in-cluded here. Comprehensive statements must bemade on the agreement or disagreement of sound-ings between the new survey and other contempo-rary surveys in the area.

Items to be discussed in detail in this sec-tion include but are not limited to:

5. Discovery and treatment of systematicerrors in the position data.

A copy of the Abstract of Corrections toElectronic Position Control shall be inserted at theend of the Descriptive Report (5.3.5(E)) and thesubstantiating field observations, computations, andother pertinent data shall be included in the surveyrecords. (See 4.8.)

Compare the results of the new surveywith those shown on the most recent prior sur-veys of the area, identifying prior surveys byregistry number, dates, and scales. State the qual-ity of general agreement between the new andthe old surveys and give conclusions or opinionsas to the reasons for significant differences. Listimportant features or depths on prior surveys—their existence having been disproved—and iden-tify those that should be deleted from the charts.

If any of the shoreline or topographic detailswere plotted inaccurately or have changed since thedate of photography on which the map was basedand were revised by the hydrographer, identify therevisions on the field sheet in red and explain the

(JUNE 1, 1981) 5-8

1. Unusual or unique methods of operat-ing or calibrating electronic positioning equipment.

2. Equipment malfunctions, substandardoperation, and probable causes.

3. Unusual atmospheric conditions thatmay have affected data quality.

4. Weak signals or poor geometric con-figuration of the control stations.

H. SHORELINE. Give the source ofshoreline details shown on the field sheet by listingall topographic sheets or shoreline manuscriptsused. (See 1.6.1 and 3.2.) State whether the shore-line details have been field edited and whether thechanges or corrections noted during field edit havebeen transferred to the field sheet. List and explainall areas on the field sheet where field edit was notaccomplished.

K. COMPARISON WITH PRIOR SUR-VEYS. Each numbered presurvey review item thatlies within the limits of the survey must be listed,referred to by its presurvey review item number,and discussed unless directed otherwise in thepresurvey review. State positively whether or notthe feature should be charted, its position replotted,or its symbolization revised. The least depthsobtained over submerged features shall be listed to-gether with the position number, latitude, longi-tude, and description of the feature. (See 2.3.3.)

FIELD REPORTS

Compare the new survey with recent sur-veys in the area made by the U.S. Army Corps ofEngineers or with other surveys within the projectarea by authoritative public or private organiza-tions. Surveys other than those by NOS must beidentified by date, scale, and sheet number, andshall be forwarded with the survey records. Astatement should be included as to whether thesesurveys meet NOS standards.

Tabulate and describe newly found dangersto navigation, listing the latitude, longitude, andposition number of each item. Mention specificallyeach danger reported to the U.S. Coast Guard.(See 5.9.)

Dangers and shoals investigated or foundby wire drag, wire or pipe sweep, diver, or by oth-er equivalent methods are listed separately. Leastdepths and clearances over these features must belisted. Include copies of telegrams or letters thathave been submitted recommending immediatechanges to the charts and also include items for in-corporation into the U.S. Coast Guard Local Noticeto Mariners (e.g., Commander, Third Coast GuardDistrict 1976).

Recommend necessary changes to pub-lished charts (e.g., format and coverage) of the sur-vey area. Mention special shoal investigations con-ducted and list the positions used. Hydrographicfindings of special note should be included in thissection.

M. ADEQUACY OF SURVEY. Statewhether the survey is sufficiently complete and ad-equate to warrant its use to supersede prior surveysfor charting. Identify any part of the survey that isincomplete or substandard in any way.

In addition to (but not in lieu of) a compar-ison with the named edition of the chart, the fieldunit may take into account Notice to Mariners is-sued since the chart publication date. Any chartcomparison item which is dependent upon a Noticeto Mariners should be identified in the DescriptiveReport with the source Notice to Mariners.

In addition to (but not in lieu of) a compar-ison with the named edition of the chart, the fieldunit may take into account later editions of thechart. This situation is most likely to arise whenthe field work is accomplished during more thanone field season. When a later edition of the chartis also used, it needs to be clearly documented inthe Descriptive Report. Identify the chart by num-ber, edition, and date, and give similar information,without duplication, to that required for prior sur-veys. Charted features bearing the notation ''re-ported," "PA," "ED,'' or ''PD'' must be mentionedspecifically in this section and a positive recom-mendation made as to whether (and how) the fea-ture should be charted in the future. When thecharted feature is a numbered Presurvey Reviewitem, it should be referred to by its Presurvey Re-

List all aids to navigation located duringthe survey that are not shown in the Light List.State their apparent purpose, whether and bywhom the aids are maintained, and whether or notsuch maintenance is seasonal, if known. Give the

5-9 (JUNE 1, 1981)

Include bare rocks as well as subsurface featuresand depths.

L. COMPARISON WITH THE CHART.Comparison of the survey with the chart by thefield unit and processing office and quality controlshall be with the edition of the chart as listed in theproject instructions. If the comparison is not madewith the edition of the chart named in the projectinstructions, a reason for this shall be included inthe Descriptive Report. The field or office shouldrecommend a change to the project instructions ifthey feel the named edition should be changed.

If the project instructions do not specifycomparison with a specific edition of the chart, thelatest edition of the chart available (for public dis-tribution), at the time of commencing field work,shall be used.

view number. Mention how the depths were deter-mined. Similar recommendations shall be made forfeatures such as charted pilings, wrecks, and ob-structions that may not be mentioned specifically.

N. AIDS TO NAVIGATION. Referenceshall be made to any correspondence with the U.S.Coast Guard regarding the location or establish-ment of floating aids in the surveyed area. The lo-cation and description of each floating aid shall beentered in the hydrographic records. A separatelisting of floating aids by geographic position andcharacteristic need not be entered here. A compari-son, however, shall be made with data in the latestedition of the Light List (U.S. Coast Guard 1976)and with the largest scale chart of the area. Thehydrographer shall state the results of this compari-son and indicate whether the aids adequately servethe apparent purpose for which they wereestablished.

HYDROGRAPHIC MANUAL

5.3.5. Separates Following Text

P. MISCELLANEOUS. Provide informa-tion of significant scientific or practical value result-ing from the survey that is not covered in previoussections. Where new silted areas are detected, the dis-cussion should include the size of the areas, apparentthickness, and reference to typical depth profiles bydate. Unusual submarine features such as abnormallylarge sand waves, mounds, valleys, and escarpmentsshould be described. Discuss anomalous tidal condi-tions encountered such as the presence of bores andextremely fast currents not previously reported. Ifspecial reports have been submitted on such subjects,refer to them by title, author, and date of preparationor publication.

5. Significant differences in comparativeobservations (AK.2.3), in tide or water level times,

5-10(JUNE 1, 1981)

position and description of each such aid and thedate of established, if known.

A copy of NOAA Form 76-40, ''Report onLandmarks for Charts and Nonfloating Aids to Nav-igation'' (5.5), should be included in the DescriptiveReport for those located during the survey.

List all bridges and overhead cables notshown on the chart. State bridge and cable clearanc-es measured by the survey party or as determinedfrom other sources. Mention any submarine cables,pipelines, and ferry routes in the area. List the posi-tion of each terminal if not shown on contemporaryshoreline manuscripts.

O. STATISTICS. List the total number ofpositions, nautical miles of sounding line, and squarenautical miles of hydrography run by each ship orlaunch during the survey. A tabulation of statisticsfor each day is not required.

A summary of other survey statistics such asbottom samples and the number of tide, current,temperature and salinity, or magnetic stationsshould also be included. Copies of NOAA Form 75-44, ''Oceanographic Log Sheet-M, Bottom Sedi-ment Data,'' for the survey shall be appended tothe Descriptive Report.

Q. RECOMMENDATIONS . If any part ofthe survey is considered inadequate for charting, ex-plain and submit recommendations as to additionalfield work required and methods necessary to makethe survey adequate. Mention present or plannedconstruction or dredging in the survey area that mayaffect the survey results. Include recommendationsfor further investigations of unusual features or seaconditions of interest in excess of routine chartingrequirements. For clarity, recommendations shouldbe made for special insets to be shown on the smoothsheet or on the published chart of the area.

R. AUTOMATED DATA PROCESSING.List by program name, number, and version date allroutines used for automated data acquisition andprocessing. If any of the acquisition or processingmethods used differ from those described in currentNational Ocean Survey manuals or instructions,each difference must be listed and explained and thedata format defined.

S. REFERRAL TO REPORTS. List allreports, records, and forms not included with thesurvey records or Descriptive Report that have beensubmitted separately but which are necessary for acomplete evaluation and understanding of the sur-vey record. Give the title and the date on which thereport was sent to the Marine Center.

Various tabulations and other informationare required on separate sheets that are inserted inthe Descriptive Report. Those applicable shall befurnished and inserted in the subsequent order.

The first page of the text and the attachedinserts shall be numbered consecutively. The ap-proval sheet is always placed last.

A. HYDROGRAPHIC SHEET PROJEC-TION AND ELECTRONIC CONTROL PARA-METERS. A sheet listing the necessary projectionand electronic control parameters is required for allsurveys scheduled for automated smooth plotting.Each Marine Center, because of differences in auto-mation equipment, prescribes the required formats.

B. FIELD TIDE OR WATER LEVELNOTE. This note shall be inserted in the Descrip-tive Report for each hydrographic survey. (See fig-ure 5-5.) The note should state:

1. How the tide or water levelcorrections were derived and the zones in whichthese corrections were applied. (If automated com-putations for tidal corrections to soundings weremade based on multigage observations, the programnumber and gage sites must be given.)

2. The name, geographic locale, latitude,and longitude of each gage.

3. Dates of gage installations and remov-als and any problems experienced with gage opera-tions.

4. Staff value equivalent to the zero lineon analog tide records. (In the Great Lakes, the eleva-tion of the reference mark (zero electric tape gage orZETG) on the electric tape gage shall be noted.)

FIELD REPORTS

FIELD TIDE NOTE

Field tide reduction of soundings was based on predicted tidesfrom Juneau, Alaska, corrected to Willoughby Island, GlacierBay, and were interpolated by PDP8/E computer utilizing AM 500.All times of both predicted and recorded tides are GMT.

Two Bristol Bubbler Tide Gages were installed at two loca-tions in the project area. Location and period of operationare as follows :

SITE LOCATION PERIOD

SEBREE ISLAND

WILLOUGHBY ISLAND

SEBREE ISLANDGage (S/N 68A14940) was installed and began operation 12 Sep-tember. The staff was installed and leveled 13 September.Excellent records were obtained for 34 days with no inter-ruptions. The marigram reads 5.6 ft greater than the staff.

LEVELSIn a comparison of level records, the greatest observed dif-ference at a station was a 0.023-ft rise in the Sebree Is-land tide staff. The Willoughby Island tide staff had neg-ligible shifts of less than 0.004 ft in its staff.

25-30 min later than Sebree Island(used as the reference station).

Correctors applied to sheet FA-20-2-73 fromthe northern limit to latitude 58°/45.0'N.

Sebree Island -

Willoughby Is. Correctors applied to sheet FA-20-2-73 fromlatitude 58°/45.0'N to the southern limitof the sheet and to sheet FA-20-3-73 fromthe northern end of Willoughby Island to aline extending from STAR 1938 on the southend on Willoughby Island to STRAW 1938 onthe west point of Strawberry Island.

-

FIGURE 5-5.—Field Tide Note

5-11 (JUNE 1, 1981)

WILLOUGHBY ISLANDGage (S/N 64A11033) was installed and began operation 12 Sep-tember. Excellent records were obtained with the exception of a loss of 1 day from 1500 hr 26 September to 1600 hr 27 September. The trace was lost because of a disengaged clutchon the take-up reel. The marigram reads 12.4 ft greater thanthe staff.

58°/45.2'N136°/09.2'W

34 days12 September-15 October

58°/36.4'N136°/07.2'W

48 days12 September-29 October

GAGEWILLOUGHBY ISLAND

ZONINGSuggested zoning based on field observations is as follows:

HYDROGRAPHIC MANUAL

NOAA FORM 76-155 SURVEY NUMBER

H-9310GEOGRAPHIC NAMES

1Cape Island Creek

2

3

Cape May

Cape May Canal

Cape May Harbor 4

Cape May Inlet 5

Cedar Creek 6

Linger Point 7

Middle Thorofare

Mill Creek 9

Schellenger Creek 10

Schellenger Landing 11

Sewell Point 12

Spicer Creek Canal 13

Two Mile Beach 14

Upper Thorofare

16

17

18

19

20

21

22

23

24

25

NOAA FORM 76-155 5UPERSEDFS C&G5 197

5-12(JUNE 1, 1981)

(11-72)

8

15

FIGURE 5-6.— List of Geographic Names

U.S DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

FIELD REPORTS

or in ranges or unusual fluctuations between adja-cent gages.

F. LIST OF STATIONS. A numerical list ofstations used for controlling the hydrographic sur-vey shall be included as a separate sheet and insertedin the Descriptive Report. (See figure 5-9.) The fol-lowing information shall be given for each station:

1. Station number (001-999).

5. Cartographic code (appendix B).6. Control station antenna elevation.

8. Name and type of station (3.1), that is:

b. Photogrammetric or hydrographic.

H. BOTTOM SAMPLES. All copies ofNOAA Form 75–44, ''Oceanographic Log Sheet-M,Bottom Sediment Data,'' that tabulate the bottomcharacteristics in the survey area shall be inserted.

4. Nansen cast observations.

5-13 (JUNE 1, 1981)

6. The time meridian used for recordsannotation.

7. Observations of unusual tidal, waterlevel, or current conditions.

8. A tabulation of missing hourlyheights, if any, that may be required for reduction ofsoundings to the datum of reference.

9. Recommendations, if any, for zoningand time corrections.

C. GEOGRAPHIC NAMES LIST. A listof Geographic Names that occur on the field sheetshall be prepared and inserted (figure 5-6). Namesshould be listed alphabetically. The list may be pre-pared either on a plain sheet of paper or on NOAAForm 76-155, ''Geographic Names." If NOAAForm 76-155 is used, add the word ''field'' in paren-theses to the title and do not enter any information incolumns A through K. (See section 5.7 for additionalrequirements on geographic names.)

D. ABSTRACT OF CORRECTIONS TOECHO SOUNDINGS. Abstracts, in tabular form,velocity and other corrections to be applied to theecho soundings shall be included as separate entriesin the Descriptive Report. (See figure 5-7.) A similarabstract can be easily constructed for corrections de-termined solely by bar checks taken throughout thedepth range.

The Sounding Correction Abstract showsthe dates, times, vessels, and instrument serial num-bers to which the corrections apply. If the same cor-rections apply to more than one survey, a copy of theabstract and applicable correction tables (4.9) are in-cluded in the Descriptive Report for each survey.

For substantiating these corrections tosoundings and facilitating timely office processing ofthe field data and plotting of the smooth sheet, thefollowing supporting material shall be assembled andseparately bound or arranged in a cahier and includ-ed with the survey data that accompanies the hydro-graphic sheet and Descriptive Report:

1. Copy of the settlement and squatabstract.

2. Abstracts of bar checks, vertical castcomparisons, and echo sounder phase comparisons.

3. Copies of calibration data for STD,TDC, or other sensors used for velocity determina-tions.

5. All other basic data, computations.

graphics, and material needed to verify the final cor-rections.

E. ABSTRACTS OF CORRECTIONS TOELECTRONIC POSITION CONTROL. When allor any portion of the hydrographic survey is con-trolled by an electronic positioning system or by dis-tance-measuring equipment, an abstract ofcorrections to be applied to the observed data shallbe compiled and inserted into the Descriptive Re-port. (See figure 5-8.) Supporting data shall be as-sembled and separately bound or arranged in acahier and included with the survey data thataccompanies the hydrographic field sheet and De-scriptive Report. (See 4.8.)

2. Octant plotting position of the stationnumber.

3. Latitude (to nearest thousandth of asecond).

4. Longitude (to nearest thousandth of asecond).

7. Transmitting frequency (to nearest hun-dredth of a kilohertz); use 000000 for other stations.Electronic distance-measuring stations may be iden-tified as such in the type/name or source columns.

a. Basic or supplemental (include yearof establishment).

9. Source, that is, volume and page num-ber for published geodetic control or, if new, a refer-ence to abstracts or field observations.

G. ABSTRACT OF POSITIONS. This shallbe assembled for each hydrographic survey vesselthat worked on the field sheet. (See figure 5–10.)Each vessel is identified by its data-processing num-ber, and the work accomplished is listed by Juliandates, inclusive position numbers, control codes, andelectronic control station numbers.

(JUN

E 1, 1981)

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5-14

FIGURE 5-7.—Sounding Correction Abstract

FIELD REPORTS

ELECTRONIC CORRECTOR ABSTRACT

VESSEL : 2126 SHEET : RA-20-3-73

TIME DAY PATTERN 1 PATTERN 2

150

151

154

158

FIGURE 5-8 — Electronic (position) Corrector Abstract

5.4 FIELD EDIT REPORT

J. APPROVAL SHEET. The chief of partyshall furnish, on a separate sheet attached to the De-scriptive Report, a signed statement of approval ofthe field sheet and all accompanying records. In-clude a statement concerning the amount and degreeof personal supervision of the field work and fre-quency with which he examined the field sheet andother records. State whether the survey is completeand adequate or if additional field work isrecommended. Cite additional information or refer-ences that may be of assistance for verifying and re-viewing the survey.

The contents of the report are essential dur-ing the final review of the shoreline manuscript andfor the resolution of discrepancies that may appearduring hydrographic verification and chart compila-tion; frequently, the report provides invaluable refer-ence, explanatory, and corroborative material for

5-15 (JUNE 1, 1981)

I. LANDMARKS FOR CHARTS. Includeall copies of NOAA Form 76-40, ''Report onNonfloating Aids or Landmarks for Charts,'' thatcontain the required information on landmarks with-in the hydrographic sheet limits which arerecommended for charting. Copies of NOAA Form76-40 prepared by the field editor may be used forthis purpose. (See 5.5.)

A separate Field Edit Report shall be pre-pared and submitted for each shoreline manuscriptwithin the project area (3.2.4) no later than 10 work-days after field work has been completed on thatmanuscript. Refer to ''Provisional PhotogrammetryInstructions for Field Edit Surveys'' (NationalOcean Survey 1974) for detailed directions on assem-bly and content of the report. The reportaccompanies other pertinent manuscript data and in-formation including the Discrepancy Print, FieldEdit Sheet, supporting annotated aerial photographyand accompanies other miscellaneous data in accor-dance with the photogrammetric instructions.

-00009-00006-00002-00007

+00012+00009+00007-00002-00002

-00005+00005+00005

-00002+00002+00002

-00015-00015-00015-00015

135415140816154006160000

101746130300131000145600155500

+00003+00004+00001-00006-00006

-00008-00005-00008

090545103836143000

+00011+00007+00007

112816140730154700

(JUN

E 1, 1981)

H - 7953STATION LIST:

CRT ELEV F. KHZ TYPE/NAMELONGITUDE SOURCESTA 0 LATITUDE------

243 0002 000000 Photo T-13042

243 0005 000000 Photo T-13045

139 0010 179960 SPIT 2 1973 Ecc

139 0003 179850 RANGE 1842

139 0004 179960 SMITH 3 1956

243 0013 000000 Sextant

139 0009 179850 POPPY 1973

243 0011 000000 Photo T-13042

243 0008 000000 Sext T-13045

243 0003 000000 Photo T-13043

243 0006 000000 Photo T-13043

243 0007 000000 Photo T-13043

243 0005 000000 Photo T-13044

243 0010 000000 Photo T-13042

243 0002 000000 Photo T-13045

243 0007 000000 Sextant

Class II001 7 58 38 51070 136 12 29730

002 7 58 45 00800 136 10 26740

003 5 58 45 07820 136 09 37490

004 5 58 45 00180 136 09 22430

005 7 58 45 00520 136 09 14150

006 1 58 43 51080 136 00 45200

007 3 58 45 12200 136 01 28890

008 7 58 43 23960 136 03 26650

009 7 58 36 30950 136 06 34320

010 7 58 38 36330 136 02 35350

018 4 58 46 47550 136 08 32880

020 4 58 38 58770 135 59 13320

022 6 58 37 51160 135 55 18340

200 7 58 41 30190 135 59 14900

201 7 58 41 37810 135 59 18560

202 7 58 41 46150 135 59 19240

203 7 58 41 57070 135 59 17380

204 5 58 42 07500 135 59 04350

205 5 58 42 25760 135 58 38060

206 7 58 42 28730 135 58 29310

207 7 58 42 34420 135 57 59830

208 7 58 42 40140 135 58 17260

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Vol. II p. 3

Vol. III p. 2Vol. I p. 3

Vol. III p. 3Vol. III p. 4243 0006 000000 Sext

243 0009 000000 Photo T-13042

243 0011 000000 Photo T-13044

243 0008 000000 Photo T-13044

243 0012 000000 Photo T-13044

243 0003 000000 Photo T-13044

FIGURE 5-9. Station List-

-

5-16

HYDROGRAPHICAL MANUAL

ABSTRACT OF POSITIONS: H-1314

VESSEL: 3030

DAY POSITIONS CTRL REMARKS:Sl M S2

04116 2001-2316 126 Hydro---

Control Codes (CTRL)

Visual01 -Theodolite03 -Range - range04 -

05 Hyperbolic-

08 Hypervisual-Range - visual09 -

FIGURE 5-10. — Abstract of Positions

5-17 (JUNE 1, 1981)

09804117 2317-2502 126 Hydro---09801118 2503-2717 Bottom SamplesVIS--- ---

VESSEL: 3031

DAY POSITIONS CTRL REMARKS:Sl M S2

05106 0001-0182 126 Hydro21309808108 0183-0362 H-V Hydro09808108 0363-0511 213

213H-V 126 Hydro

01109 0512-0610 VIS--- --- Detached Positions

DAY POSITIONS CTRL REMARKS:Sl M S2

09112 4001-4204 R-V Hydro---09804113 4250-4370 126 DP MLLW line09804114 4371-4593 ---

---098 126 Hydro

01117 4701-4657 VIS098 --- Bottom Samples

VESSEL: 3032

HYDROGRAPHIC MANUAL

5.5.

5.5.1. Preparation of Reports on Landmarks

5.5.1.2. STANDARDIZATION OF NOMEN-CLATURE. It is essential for charting purposes that thenomenclature used and the method of reporting land-marks be standardized. Cartographers should nothave to interpret these data because they cannot seethe object in the field and do not know what is mostprominent about the landmark. If a landmark is re-ported on Form 76–40 (figures 5–11 and 5–12) as a''Tall yellow tank,'' the cartographer cannot tellwhether the landmark is prominent because it is atank, because it is yellow, or because it is tall. The

Objects of special importance or extraordi-nary prominence are indicated by an asterisk (*) pre-ceding the name of the object. When selecting objectsof special importance, the total area and chart cover-

5-18(JUNE 1, 1981)

cases in litigation. The Field Edit Report shall be ap-proved by the chief of party designated by the hydro-graphic survey project instructions.

A copy of each form must be provided to the hydro-graphic survey verifier.

The hydrographer shall evaluate all chartedlandmarks from seaward to determine which are ade-quate and most suitable for the purpose intended andto determine which charted landmarks no longer existand thus should be deleted from the charts. If there aremore prominent objects in the area that would serveas better landmarks, their positions shall be deter-mined and listed among the landmarks to be charted.

Preliminary 76–40 forms are assembled rou-tinely during the photogrammetric compilation of theshoreline manuscripts and are provided as an aid tothe field editor and the hydrographer. (See 5.5.) Posi-tions of charted landmarks are determined in the of-fice as a check, and descriptions and positions of newobjects that appear to have value as a new landmark tobe charted are listed. (See figures 5-11 and 5-12.)

Reports on landmarks must be complete andstand alone. Avoid additional references to geodetic,photogrammetric, or other data not readily availableto other users. The report shall state positively wheth-er or not a seaward inspection has been made to evalu-ate the landmarks. If the reports have been assembledwithout the benefit of a seaward inspection, the reasonfor omission shall be fully explained.

age must be carefully considered. Flagstaffs, flag-poles, and other structures of a temporary nature arenot listed as landmarks unless they are of a very per-manent and prominent nature and no other suitableobjects are in the area. Recommended charting namesshould be general and short (5.5.1.2); they should beshown in capital letters. If the object was used as a hy-drographic signal, a note is made to this effect and thestation number indicated.

5.5.1.1. SUPPORTING CHART SECTIONS.When a large number of landmarks are reported or thehydrographer or field editor considers it necessary toclarify the tabulated data, a copy of the chart of thearea should be cut into letter-size sections, appropri-ately annotated, and submitted with the copies ofNOAA Form 76–40. (See figures 5–11 and 5–12.) Thearea inspected is outlined on these chart sections and arecommendation made for each charted or plottedlandmark within the outlined area.

If chart sections are submitted, separate formsfor landmarks to be deleted need not be prepared. Thefollowing procedures are used:

1. New landmarks shall be plotted and iden-tified by the landmark symbol ( ) together withthe name recommended for charting. The geographicdatum of the chart must be known and considered inthe plotting.

2. Charted landmarks recommended forcontinuance are checkmarked ( √√ ). If the position hasbeen verified in the field, the word ''verified'' is en-tered beside the checkmark.

3. Charted landmarks recommended fordeletion shall be indicated by a cross in a circle ( ⊗⊗);the word ''delete'' is entered, and the reason for therecommendation is given.

Names and notations on these chart sectionsshall be typed or lettered legibly in red ink. Care mustbe taken that such notations always appear on thesame section of the chart section as the landmarks towhich they refer.

REPORT ON LANDMARKS ANDNONFLOATING AIDS TONAVIGATION

Copies of NOAA Form 76-40, ''Report onNonfloating Aids or Landmarks for Charts,'' are usu-ally prepared by the field editor, checked by the hy-drographer, and submitted for processing with thephotogrammetric data. Detailed instructions are con-tained in ''Photogrammetry Instructions No. 64, Re-quirements and Procedures for Collecting, Process-ing, and Routing Landmarks and Aids to NavigationData—Photogrammetric Operations'' (NationalOcean Survey 1971b). [See also 5.3.5(I).] SeparateForms 76-40 are submitted for:

1. Landmarks to be charted.2. Landmarks to be deleted.3. Nonfloating aids to navigation.

HOAA FORM 76-40 U.S.DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

ORIGINATING ACTIVITY(8-74)

LANDMARKS FOR CHARTSReplaces C&GS Form 567.

REPORTING UNIT STATE LOCALITY DATE(Field Party Ship or Office)

5/74WHITING Miami BeachFla.

The following objects HAVE HAVE NOT been, inspected from seaward to determine their value as landmarks.

OPR PROJECT NO. JOB NUMBER SURVEY NUMBER DATUM

NA 1927POSITION

PH-7113OPR-419 METHOD AND DATE OF LOCATION(See Instructions on reverse side)

TP-00423CHARTS

AFFECTEDLATITUDE LONGITUDEDESCRIPTIONOFFICECHARTING //

D.M.Neters

35.27

09-05

278.49

33.86

D.P.Meters

01.21

33.70

14-93

416.03

37-05

1032.20

8o-o8

80-08

8o-o8

8o-o8

FIELD(Record reason for deletion of landmark or aid go navigation.Show triangulation station names, when applicable, In parentheses)

NAME 0 /

54T

CUPOLACupola on large white bldg ,east end of Fisher Island 25-45

CHIMNEYChimney on power plant, SouthDolphin Point 25-46.8

TANKSouth Miami Beach, Water Tank,(Green), 1934 ht=133(138) 25-46

TOWERMiami Beach Radio Station (WKAT)tower, 1971 ht=207(212) 25-47

75E(C)6402 V-VIS1248847-SC

P-8-L3/21/75 "

Triang- Recc v"

" "

1085.34 8/12/74 3/19/75

3/22/75

1041.95

FIGURE 5–11.—Side 1 of NOAA Form 76–40, ''Nonfloating Aids or Landmarks for Charts.'' See also figure 5-12.

HYDROGRAPHIC PARTYGEODETIC PARTYPHOTO FIELD PARTYCOMPILATION ACTIVITYFINAL REVIEWERQUALITY CONTROL & REVIEW GRP.COAST PILOT BRANCH(See reverse for responsible personnel)

xTO BE CHARTED

TO BE REVISED

TO BE DELETED

x

x

0 ///

5-19(JU

LY

4, 1976)

9

FIE

LD

RE

PO

RT

S

(JUL

Y 4, 1976)

RESPONSIBLE PERSONNEL

TYPE OF ACTION NAME ORIGINATOR

OBJECTS INSPECTED FROM SEAWARD

NOAAC.D. Schorlein, Lt;

PHOTO FIELD PARTY

HYDROGRAPHIC PARTY

GEODETIC PARTY

OTHER (Specify)

J.E. Wolf, Photo Party 62 FIELD ACTIVITY REPRESENTATIVE

Coast. Map Div; AMCS.T. Walker, OFFICE ACTIVITY REPRESENTATIVE

POSITIONS DETERMINED AND/OR VERIFIED

REVIEWERFORMS ORIGINATED BY QUALITY CONTROL

AND REVIEW GROUP AND FINAL REVIEW

ACTIVITIES

QUALITY CONTROL AND REVIEW GROUP

REPRESENTATIVE

INSTRUCTIONS FOR ENTRIES UNDER 'METHOD AND DATE OF LOCATION'

(Consult Photogrammetric Instructions No. 64,

FIELD (Cont'd)OFFICE1. OFFICE IDENTIFIED AND LOCATED OBJECTS H

YD

RO

GR

AP

HIC

MA

NU

AL

Enter the number and date (including month,day, and year) of the photograph used toIdentify and locate the object.EXAMPLE: 75E(C)6042

8-12-755-2

0

FIELD1. NEW POSITION DETERMINED OR VERIFIED

Enter the applicable data by symbols as follows:P - PhotogrammetricFieldF

LV12

-

Vis VisualityLocated -Verified

Field IdentifiedTriangulation 56 TheodoliteTraverse-

PlanetableIntersection 78

34

-

SextantResection-

A. Field positions* require entry of method oflocation and date of field work.EXAMPLE: F-2-6-L

8-12-75

*FIELD POSITIONS are determined by field obser-vations based entirely upon ground survey methods.

HOAA FORM 76-40 (8-74) SUPERSEDES NOAA FORM 74-40 (2-71) WHICH IS OBSOLETE ANDEXISTING STOCK SHOULD BE DESTROYED UPON RECEIPT OF REVISION.

FIGURE 5–12.—Side 2 of NOAA Form 76–40, ''Nonfloating Aids or Landmarks for Charts.'' See also figure 5-11.

-

-

-

**PHOTOGRAMMETRIC FIELD POSITIONS are dependententirely, or in part, upon control establishedby photogrammetrIc methods.

III. POSITION VERIFIED VISUALLY ON PHOTOGRAPHEnter 'V-Vis ' and date.EXAMPLE: V-Vis

8-12-75

II. TRIANGULATION STATION RECOVEREDWhen a landmark or aid which is also a tri-angulation station is recovered, enter 'TriangRec ' with date of recovery.EXAMPLE: Triang Rec

B-12-75

B. Photogrammetric field positions** requireentry of method of location or verification,date of field work and number of the photo-graph used to locate or identify the object.EXAMPLE: P-8-V

8-12-7574L(C)2982

FIELD REPORTS

In table 5-1 is the standardization of termsthat shall be used when practical.

hydrographer must interpret the data and report it inproper form. Although the following standardizationof nomenclature is general, it shall be followed inso-far as practical.

Generally, an object's utilization is non-essential charting information unless knowledge ofthe use contributes to the identification of the object.When reporting buildings as landmarks, avoid inso-far as possible using a charting name that indicatesthe function of the building. It is preferable to use aterm such as DOME, TOWER, or SPIRE that de-scribes the shape of the top of the building. Thename describing the function, such as schoolhouse orcourthouse, may follow in lowercase letters.

Company names usually are omitted fromthe chart unless these names or abbreviations are vis-ible on the landmark in letters large enough to serveas identifying features to the mariner.

It is important that the names of the aids en-tered on the form be identical with those given in theLight List (U.S. Coast Guard 1976) and that the LightList number be given. The position of each aid shouldbe plotted on the largest scale chart of the area andcompared with the charted position. Significant differ-ences, shall be reported to the U.S. Coast Guard Dis-trict Headquarters and to National Ocean SurveyHeadquarters through the appropriate Marine Center.

Names of especially well-known buildingsare shown in parentheses following the names of thelandmarks [e.g., DOME (STATEHOUSE), TOWER(EMPIRE STATE BLDG)].

If two similar objects are close together, theword ''twin'' shall be omitted if the objects arecharted as two separate landmarks. Where indicatedby a single landmark symbol, "twin'' is used. 5.6. TIDE AND WATER LEVEL STATION

REPORTS AND RECORDSIf only one of a set of closely grouped ob-jects is to be charted, the name of the object isfollowed by a descriptive legend in parentheses. In-clude the number of objects in the group [e.g.,STACK (TALLEST OF FOUR) or STANDPIPE(NORTHEAST OF THREE)].

The following reports and information shallbe submitted promptly after the installation, remov-al, inspection, or servicing of a tide or water levelstation:

The geographic relationship of a landmarkwith respect to other topographic features is not es-sential and should not be included in the descriptionbecause this is shown graphically on the chart. NOAA Form 76-77, ''Leveling Record—

5-21 (JANUARY 1, 1980)

In general, descriptive terms are omittedfrom the name recommended for the chart. Colorsdescribing an object are particularly objectionablebecause of their temporary nature. Information onthe material from which an object is built is notvaluable on the chart because from even a short dis-tance away the mariner may not be able to identifyan object by its material. The adjective ''tall'' is un-necessary; if the object were not tall it would not bea prominent landmark. If a descriptive term is neces-sary to distinguish a charted landmark from otheruncharted objects in the vicinity, the descriptive termis entered in capital letters.

5.5.2. Report on Nonfloating Aids to Navi-gation

A separate NOAA Form 76-40, ''Non-floating Aids or Landmarks for Charts,'' shall be-used to report the positions of all nonfloating aids tonavigation on an areal basis when a hydrographicproject has been completed or work has ended forthe field season. (See 4.5.13 and figures 5-11 and5-12.) The geographic positions of all nonfloatingaids, including privately maintained lights and bea-cons, shall be verified or determined in the field. Ap-plicable parts of the requirements stated in section5.5.1 for Form 76-40 shall be followed in compilingthis report. If contemporary shoreline mapping of thearea has been undertaken, copies of Form 76-40 fornew aids or aids to be deleted shall be sent to thePhotogrammetry Division; otherwise, the forms aresent to the Marine Chart Division. For additionaldetails concerning landmarks and aids to navigation,see the following:

''Photogrammetry Instructions No. 64,Requirements and Procedures for Collecting, Pro-cessing and Routing Landmarks and Aids to Navi-gation Data— Photogrammetric Operations'' (Na-tional Ocean Survey 1971b).

''Provisional Photogrammetry Instructionsfor Field Edit Surveys'' (National Ocean Survey 1974).

NOAA Form 77-12, ''Report—Tide Sta-tion.''

NOAA Form 77-75, ''Great Lakes WaterLevels Station Report.''

HYDROGRAPHIC MANUAL

Landmark classifications, definitions, and rulesTABLE 5-1. -

BUILDING(See house).

CHIMNEYThat projecting part of a building for discharging smoke or effluvium to the outer air. This term is to be used only

where the building is the prominent feature and the charting of some specific part of it is desirable (e.g., the tallestchimney of a large factory).

CUPOLAA small turret or dome-shaped tower rising from a building; used in cases where the building is the prominent object

and the cupola is small as compared to the building.

DOMEA large cupola or rounded hemispherical form, or a roof of the same shape, whether rounded or many-sided.

FLAGPOLEA single staff flagpole rising from the ground and not attached to a building or other structure.

FLAGSTAFFA single flagpole rising from a building or other structure. Flagstaffs are not usually desirable for use as landmarks

because they may not be permanent. Although desirable that the most prominent definitive part of a building (such as aflagstaff) be pointed at when making visual survey observations, it may not be the most important part of the buildingfor charting purposes. Wherever possible, indicate for use on the chart that part of the building from which the flagstaffrises, such as TOWER, CUPOLA, and DOME.

FLAGTOWERAny scaffold-like tower on which flags are hoisted, such as a U.S. Coast Guard skeleton steel flagpole. Do not use

the term ''SIGNAL TOWER.''

GAS TANK or OIL TANK

LOOKOUT TOWER

MONUMENTDo not use ''obelisk'' or other similar terms.

RADOMEDome-shaped structure used to enclose radar apparatus (may also have a cylindrical base with a dome top).

RADAR TOWERA tower or structure used to elevate parabolic or mattress-type radar reflectors.

RADIO MASTA general term used to include any polelike structure for elevating radio antennae.

SPIREGenerally, a slender pointed structure that surmounts a building. Do not use the term ''steeple.'' SPIRE is not appli-

cable to a short pyramid-shaped structure rising from a tower or belfry.

STACKAny tall smokestack or chimney more prominent than surrounding buildings or structures.

STANDPIPE

5-22(JANUARY 1, 1980)

Although it is desirable to locate a house or building by observations on a specific point, such as the west gable orthe flagstaff, such terms are not desirable for charting purposes if the structure itself is the landmark. Use HOUSE orBUILDING followed by a description of the point either in capitals or in lowerease letters, according to whether or notthe description should be shown on the chart. Where the outline of the building should be shown on the chart, the no-tation ''chart outline'' is made on Form 76-40. (See figures 5-11 and 5-12.)

Since this tank differ in shape and size from water tanks, the compound name shall be used.

HOUSE or BUILDING

Any tower surmounted by a small house from which a watch is habitually kept, such as a U.S. Coast Guard lookouttower or a fire lookout tower. Do not use this term to describe an observation tower or parts of buildings from which awatch is not kept.

A tall cylindrical structure, usually part of a waterworks system, with a height several times greater than its diame-ter.

FIELD REPORTS

TABLE 5-1.–Concluded

TANKA container for water. Its base rests on the ground or other foundation, and its height is not much greater than

its diameter.

TANK (elevated)

TELEVISION TOWER

TOWER1. A part of a structure higher than the other parts but having vertical sides for the greater part of its height.

3. The top of a skyscraper, high in proportion to its horizontal size; rising above its surroundings.

TREEDo not use the terms ''lone tree'' or ''conspicuous lone tree.'' These characteristics are assumed; otherwise, the

tree would not serve as a landmark.

WATER TOWERA decorative structure that encloses a tank or standpipe (infrequently used).

WINDMILL(Self explanatory).

EXAMPLES

CHIMNEY, schoolhouse (Mt. Vernon H.S.)CUPOLA, schoolhouse (Normal School, 98 ft high)FLAGPOLE (Green Hill Country Club)LOOKOUT TOWER, fire (110 ft high)SPIRE, church ( Nanticoke Church Spire)STACK (Aiea Mill)STACK (at Hot House)

specified in the project instructions. The differenttypes of investigations, field procedures to follow,and instructions for the assembly and submission ofthe Geographic Names Report are described in''Photogrammetry Instructions No. 63, Instructions—Geographic Names and Object Names for Photo-grammetric Maps—Field and Office.'' (U.S. Coastand Geodetic Survey 1969b).

GEOGRAPHIC NAMES REPORT If a separate or detached unit is ashore con-ducting field edit or other supporting survey opera-tions, information on geographic names usually can

5.7.

5-23 (JUNE 1, 1981)

A container for water. The tank is elevated high above the ground or rests on a foundation or skeletal frame-work.

A tall slender structure for elevating television antennae.

2. An isolated structure with vertical sides (not otherwise classified); high in proportion to the size of its base; simplestructural form.

4. Any structure, whether or not its sides are vertical, with its base on the ground; high in proportion to the size of itsbase.

STACK (TALLEST OF FOUR)STACKTANK (BAY STATE CO.) ( 275)TANK (SOUTH) (southernmost of the three tanks)TANK (125 ft high)TANK ( GRAMP, 294)TOWER (CITY HALL)

Tide Station.'' A detailed sketch showing the loca-tion of all station bench marks, the gage, and thestaff shall be provided on pages 4 and 5.

A page-size section of a large-scale nauti-cal chart or map (e.g., 1:24,000 U.S. GeologicalSurvey quadrangle) indicating the station site.

If possible, photographs of the generalarea of the station with closeup snapshots of thegage and staff installations.

Original tidal and water level records aresubmitted directly to NOS Headquarters (OA/C23) for analysis and datum determination, and a copy ofthe transmittal letter is sent to the appropriate Ma-rine Center. Copies of the records will be furnishedto the Marine Center after inspection for complete-ness and accuracy.

Detailed instructions for gage installationand operation, bench mark and leveling require-ments, and the reports listed are found in Publica-tion 30-1, ''Manual of Tide Observations'' (U.S.Coast and Geodetic Survey 1965a).

Complete or extensive field investigationsof geographic names shall be conducted only when

Although the project instructions may notspecifically require a complete geographic names in-vestigation, the hydrographer should be continuallyalert for new names and discrepancies in chartednames throughout the project area. It is particularlyimportant that all geographic names not only becorrect in name but also in spelling and application.The hydrographer should take every opportunity tocheck both charted names and those in the Coast Pi-lots against local usage. If a published name differsfrom local usage, the hydrographer should ascertainfrom independent sources how well the local nameis established and, if possible, the origin.

HYDROGRAPHIC MANUAL

be gathered with little or no extra effort during thecourse of the daily work. The correct geographicnames of water features such as channels, sloughs,rivers, inlets, bays, reefs, rocks, shoals, and small off-lying islands and their special features are of equalimportance with the correct names of interior land-forms and bodies of water. Copies of NOAA Form76-155, ''Geographic Names'' (figure 5-6), shall besubmitted to the NOS Chief Geographer on a proj-ect or seasonal basis, whichever occurs first. Thenames are listed alphabetically and appropriate datain columns A through K are entered.

5.9. DANGERS TO NAVIGATION REPORT

Discoveries of uncharted shoals, obstruc-tions, wrecks, or other submerged features consid-ered dangers to navigation must be reported imme-diately by radio, telephone, or telegraph to thecommander of the nearest U.S. Coast Guard Dis-trict and to the appropriate Marine Center. Themessage shall be in this form:

COAST PILOT REPORTS5.8.

A statement of all such reported dangersshall also be included in the Descriptive Report.(See 5.3.4(L).) Negative reports are required.

When a floating aid to navigation is found tobe off station to an extent that it does not serve itspurpose adequately and creates a danger to naviga-tion, the facts should be reported immediately to thenearest U.S. Coast Guard District.

The necessity for prompt action in these situ-ations cannot be overemphasized. Verbal communi-cations and radio messages must always be confirmedin writing. Copies of all correspondence with theU.S. Coast Guard shall be forwarded to the Chart In-formation Branch, OA/C322 through the appropri-ate Marine Center.

5.10. CHART INSPECTION REPORT

Each field party, while en route to and fromthe project area, shall obtain data for revision ofcharts. The fact that time and circumstances do notpermit obtaining precise field locations and informa-tion on new features should not deter the hydrogra-pher from furnishing all practical information on ob-served changes.

Coast Pilot Reports shall be assembled in ac-cordance with the Coast Pilot Manual and submittedin duplicate. (See 1.7.1.) Where appropriate, NOAAForm 77-6, ''Coast Pilot Report,'' may be used inplace of a more lengthy narrative report.

5-24(JUNE 1, 1981)

A Geographic Names Report, when re-quired, shall be prepared and submitted for theportion of all projects surveyed during the fieldseason as soon as practical after work on each proj-ect has ended. The report shall be prepared in ac-cordance with Photogrammetric Instruction No.63. Refer to section 5.3.5(C) for Descriptive Reportgeographic names requirements.

The Coast Pilots, published annually byNOS contain narrative information of importanceto the navigator. This information cannot be shownconveniently on the nautical charts and is notreadily available elsewhere.

Revision data and reports collected andsubmitted by hydrographic field parties are amongthe most important sources of information forupdating the Pilots. Special efforts shall be madeby all field units to collect all data pertinent toCoast Pilot publications so the published informa-tion in the project area can be updated completelyand accurately. The opportunity should be taken atall ports of call and during passages between portsto verify or revise the information contained in thelatest editions of the Pilots. Mere revisions of thepublished text are not sufficient; new informationthat will increase the value of the Pilot publicationsshould be obtained whenever possible.

Pilot Reports shall be compiled and submit-ted as soon as practical after the data have beencollected. If the Pilot information for an area is ad-equate and no revisions are recommended, a briefreport stating this fact shall be submitted.

''(Object) covered by (depth of water) at(tidal or water level datum) discovered; Chart No.———; Latitude ———; Longitude ———;distance——— nautical miles (or meters), bearing ———degrees true from (charted object)."

A tracing of the field sheet or largest scalechart available showing the exact location of thenewly discovered danger shall be prepared andsent to Chart Information Branch, OA/C322,through the appropriate Marine Center, at the ear-liest opportunity. A description of the hazard andthe method of location shall accompany the trac-ing. (See 1.6.4.)

Floating wreckage, logs, derelicts, or othersimilar objects that are menaces to navigation shallalso be reported promptly to the commander of thenearest U.S. Coast Guard District.

FIELD REPORTS

REPORT ON VISIT TO AUTHORIZEDCHART SALES AGENT

5.11.

National Ocean Survey authorized chartsales agents provide valuable assistance to the mari-ner by stocking the most recent editions of charts ofthe area. Field units are occasionally required tovisit and familiarize the agents with NOAA servicesand to provide assistance and advice to the agent onhis stock of charts. Special instructions and report-ing forms will be issued for required inspection visits.

Each chief of party must contact local mem-bers; of the U.S. Power Squadrons and U.S. CoastGuard Auxiliaries at every possible opportunity. Aslocal knowledgeable users, they can furnish first-hand information on chart conditions and deficien-cies. Chart inspection data submitted should consistof the following classes of information:

5.12. SPECIAL REPORTS ANDPHOTOGRAPHS

Miscellaneous reports of a special nature inaddition to those listed in this chapter and in otherNOAA/NOS manuals are desirable and necessaryfrom all hydrographic field units. These reports shallbe prepared and submitted for all items of uniqueinterest or historical documentation. Although theneed for special reports generally will be included inthe project instructions or identified by separatememorandums, the chief of party should preparesuch additional reports he considers necessary. Itemsthat should be handled by special reports includebut are not limited to:

1. Landmarks to be added or deleted.

3. Bridges or tunnels to be added ordeleted.

Equipment trial and evaluation.

7. Channel depths. Report indicationsof shoaling in dredged channels.

Chart inspection notes should be accompa-nied by sections of charts showing corrections in redink. The method of submitting such data is dis-cussed in detail in sections 7 and 8 of the Coast PilotManual (U.S. Coast and Geodetic Survey 1969a).

5-25 (JULY 4, 1976)

New landmarks, waterfront construction,and other shoreline changes are frequently added tocharts by photogrammetric methods without a fullhydrographic survey of an area. Advance informa-tion on erroneous or incomplete chart data is ex-tremely useful when scheduling aerial photographyand compiling the survey.

2. Waterfront improvements andchanges.

4. Removal of piling. When markingpiers and other structures for deletion, state whetherpiles have been removed. The feature will be re-tained as ruins if definitive information is not pro-vided.

5. Rocks, shoals, and other obstruc-tions. Include discrepancies between charts and ob-served conditions and provide information gatheredlocally on reported obstructions. Where not feasibleto obtain positions and soundings on such reporteddangers, the report should include recommendationsfor future surveys.

6. Aids to navigation. Positions of float-ing aids should be verified. Description, numbering,and light characteristics should be checked.

8. Cable areas. Report new submergedcable areas and overhead cables not currently shownon the chart.

Innovative operational procedures andresults.

Geodetic, magnetic, gravity, and othersimilar field operations.

Other observations and operations notusually associated with hydrographic surveying.

Photographs of field activities, personnel,and equipment (particularly snapshots that portrayactual field operations) are of considerable value.Each chief of party should designate a responsibleperson with an interest in photography to take suchphotographs whenever practical. A good-qualitycamera should always be used to assure sharp repro-ductions and enlargements. The negatives of eachpertinent photograph should be sent to the appropri-ate Marine Center, with a recommended caption.The Marine Center shall provide copies to NOSHeadquarters.

PART TWO

Final Data Processing

6. VERIFICATION AND SMOOTH PLOTTING

6.1. DEFINITION AND PURPOSE

Utilization of sophisticated data acquisitionand processing systems does not lessen the inherentresponsibilities of a verifier. The high standards de-scribed in chapter 7 for the completeness and clarityof the cartographic presentation of hydrographicdata must be adhered to rigorously. A slight knowl-edge of equipment and survey methods now in gen-eral use and a casual awareness of the contents ofthis and other pertinent manuals are not sufficient.A verifier must be thoroughly knowledgeable about allphases of hydrography and automated data processingand must be capable of applying correctly the princi-ples involved.

VERIFICATION WORK SCHEDULES

A verifier's primary duty is to carefullycheck every phase of a survey for accuracy and forconformance to established specifications, conven-tions, and guidelines. His task extends beyond cor-recting obvious errors and providing a complete re-cord of a survey; he must also detect and correcterrors of a less evident nature that may affect theaccuracy of a smooth sheet and the correspondingfinal data listings. Specific areas of discrepancy arefrequently not revealed until the final verificationstages. Because the factors affecting the plotted dataare so complex, verifiers often find it necessary toreview analog depth records, velocity correctiondata, echo sounder calibration data, tidal informa-tion, calibration of electronic control systems, andcomputer input data—then make other adjustments

(JULY 4, 1976)6-1

Each registered hydrographic survey shallbe verified to ensure that the survey data to besmooth plotted and stored in the hydrographic databank are as accurate as possible and provide a truerepresentation of the surveyed area. Although mod-ern verification procedures rely heavily on high-speed automated techniques for batch processing thevoluminous survey data, human judgment and inter-cession are still required during the verification pro-cess. Verifiers must be continually alert for lost orerroneous data that could compromise the quality ofa survey. They must make frequent value judgmentswhen assessing various data, and must be preparedto make final comprehensive statements as towhether or not surveys meet basic hydrographicstandards and specifications.

Field survey data are processed through asequence of both computer and automatic plotteroperations and manual verification checks; the typesand applications of these checks depend on the con-trol system, method of sounding, and other equip-ment used to acquire the data. The timing of eachverification check is important. All errors and omis-sions in field survey data must be systematicallyfound and corrected to avoid unproductive repeti-tious work by the verifier and to not waste time onautomation equipment.

as necessary to eliminate discrepancies and provide atrue cartographic representation of the survey area.

6.2

Because of the difficulties encountered whenscheduling the large number of plotting and verifica-tion phases through which each survey mustprogress, it may not be possible for one verifier tocomplete all stages. Assignments of the variousphases therefore must be made giving considerationto the degrees of difficulty of the work and to therelative capability, experience, and judgment of anindividual verifier. As each step of the verificationprocess is completed, each unresolved problem orunusual situation must be documented to provideinformation and guidance to those assigned to thelater stages of the work. A summary of significantchanges to the raw survey data shall be prepared toaccompany the completed smooth sheet.

Close working relationships must be main-tained between survey verifiers and those responsiblefor automated data processing (Electronic Data Pro-cessing Branches). Such relationships help to ensurean efficient application of the many corrections andchanges to preliminary data found during each phaseof verification. All corrections and changes made bythe verifier must either be clearly indicated in theSounding Volumes, on the data listings or printouts,or be tabulated in a neat orderly manner that is easyto follow. Such notes made by verifiers become thebasis for detailed instructions that list remedial ac-tions and reprocessing requirements. Such lists ofinstructions must be inspected and approved by the

HYDROGRAPHIC MANUAL

M) are useful in shallow waters and where mechani-cal cable handling equipment is not available. Longertow cables (200 m to 10,000 m) are steel armored,high-density cables designed to achieve maximumtow depth and minimum noise interference at giventow speeds.

Depth of the transducer towfish is controlledby the length of cable deployed, vessel towing speed,and vessel course. Tow depths can be increased bythe use of a depressor or suitable weights.

Al.3. Side Scan Sonar

AI.3.1.2. Side Scan Transducers. The towfishconsists of individual modular port and starboardtransducers whose vertical beam may be varied in10º ± 2º increments from 0º to 20º by means of mi-nor external mechanical adjustments to the trans-ducer modules. (See figure AI-2.) The tail finassembly consists of two individual breakaway tailfins, separating when they strike a submerged ob-ject. The towfish parts are capable of operation inwater depths to 7,500 feet. Separate identical leftand right channel plug-in circuit boards are housedin the nose of the towfish.

AI-2(JUNE 1, 1981)

The graphic recorder contains most of theelectronics for the system as well as the graphicmechanism. Most recorders are designed to operatefrom 24 V d.c. or 110 to 220 V a.c. power supply.(See figure AI-1.)

The following discussion is limited to a de-scription of the side scan sonar system currently usedby the National Ocean Survey for hydrographic andbathymetric surveying. The technical manual pub-lished by the manufacturer is a necessity for satisfac-tory operation and maintenance of the system.

AI.3.1. KLEIN ASSOCIATES, INC; SIDE

SCAN SONAR SYSTEM. The Klein side scan sonarsystem consists of the following components:

1. Dual Channel Hydroscan Recorder2. 50-kHz Dual Channel Towfish.3. 100-kHz Dual Channel Towfish.4. Lightweight Tow Cable - 300 feet.5. Lightweight Tow Cable - 600 feet.6. Armored Tow Cable - 2,000 feet.7. Towfish Stablizer Depressor.8. Operation and Maintenance Manual,

Recording Paper, Breakaway Tail Assemblers, andSpare Parts.

The Klein side scan system can be operatedfrom both small and large ships. The system is imper-vious to marine environments including temper-atures of 0ºC to 50ºC. The equipment will operatefrom both 24 V d c. ±10% and 120 V a.c. 60 Hz ±10%. The service manual (Klein Associates, Inc.-1977) includes all necessary instructions, schematics,parts lists, troubleshooting, and general maintenanceinstructions. This manual is available as Klein PartNo. 521-01 from Klein Associates, Inc., Route 111,RFD 2, Salem, New Hampshire 03079.

FIGURE AI-1.— Klein Hydroscan Dual Channel Side Scan SonarRecorder (courtesy of Klein Associates, Inc., Salem, NewHampshire)

AI.3.1.1. Side Scan Recorder. The Klein re-corder contains the patented Hands-Off-Tuningfeature which provides automatic adjustment, mak-ing uniform results across the sonar chart. Switchesare provided for each channel to additionally permitmanual selective tuning. Three event mark featuresare included: an internally generated 2-minute mark,a pushbutton on the recorder control panel, and aremote event mark pushbutton.

Both recording channels print simultaneous-ly, reading outward from the center of the record intrue left/right perspective. The range of the systemusing the 100-kHz towfish is at least 1,500 feet portand starboard at speeds up to 6 knots. At a 5-knottow speed the 50-kHz towfish range is at least 2,000feet. The range of the side scan system is also depen-dent on the operational environment, target, and thetow speed.

EQUIPMENT AND INSTRUMENTS

speed. Both of these decrease the area which can besearched in a given period of time. It should bepointed out that speed over the ground is very im-portant in side scan operations. Slow, constant speedcan often be maintained by moving into the current.

AI.3.1.3 Tow Cable Assemblies. Lightweighttow cable assemblies consisting of a polyurethanejacket and a Kevlar strength member are provided.The minimum breaking strength is 6,000 pounds.The core consists of four conductors, two of whichare individually shielded and used for the right andleft channel signal returns, while the other two arefor power and trigger pulses. The entire core is ad-ditionally shielded. A 300-foot and a 600-foot light-weight cable are provided. The 2,000-foot cablehas the same core as the lightweight cable and usesa dual-armored steel jacket providing a breakingstrength in excess of 15,000 pounds.

Another environmental factor limiting useof side scan is sea state. This factor is most influen-tial in water under 40 feet, but decreases withdepth. Sea surface return is so strong with wavesof only 2 and 3 feet in less than 40 feet, that it can-not be completely tuned out. As a result, targets onthe bottom may be lost. One recourse is to lowerthe towfish below the interference. This would, ofcourse, endanger the towfish in shallow water. An-other means is by use of a recently developedtowfish with a variable vertical beam (20º or 40º).The 20º setting is useful to minimize sea clutter.

AI.3.1.4. Operations Considerations. Al-though automatic tuning is available in the controlcircuitry manual tuning is superior when employedby a trained operator. Experience has shown thatproperly adjusted, manual controls strongly print aknown target which might have been entirelyoverlooked among other returns on automatic tun-ing. Herein lies a problem, for if the manual tuning isnot properly adjusted, it is worse than the automatictuning for search. Manual tuning requires constant at-tention, and some skill to know, or feel, when propertuning has been achieved. It is important to developskill in hand tuning by working near a known targetfor a short period of time. This known target may beattached to an implanted buoy anchor line.

FIGURE AI-2.— Klein Side Scan Sonar Towfish (courtesy ofKlein Associates, Inc., Salem, New Hampshire)

AI-3 (JUNE 1, 1981)

Environmental conditions limit the use ofthe sonar. The pulse repetition frequency is limitedby the time required for the acoustic signal to reachthe limit of the search band and return to the towfish.This physical limitation is in direct conflict with thedesire to gain resolution on a target by getting asmany separate pulses as possible to bounce off thetarget. There are two solutions to this problem: First,limit search path width; second, move at very slow

HYDROGRAPHIC MANUAL

Each detached position used to locate struc-tures and objects (such as beacons, buoys, rocks)and to position other hydrographic data (such assubmerged rocks, obstructions, least depths overshoals) must be checked by the verifier. When a hy-drogapher has observed so many detached positionsthat congestion occurs delineating limits for shoalsor reefs, the size and shape of piers, or other fea-tures, the verifier should retain only the most criticaldata—the remainder are rejected and excised fromthe data file.

Verifiers must exercise precaution and useevery resource available to detect and list for correc-tion every erroneous position prior to orderingsounding overlays. When this phase of verification is

6-4(JULY 4, 1976)

speed—or when a position deviates from the dead-reckoned track without a recorded correspondingchange of course. Other errors in positioning may becaused by incorrect visual angles, theodolite direc-tions, or undetected electronic system lane jumps orother anomalies that may not become apparent untildepth discrepancies are noted on sounding overlays.(See 6.3.4.)

''Weak'' positions are likely to occur onelectronically controlled surveys (4.4.3) if the controlwas inadvertently used beyond the limits of strongintersections or where the signal parallels, crosses,reflects, or otherwise attenuates from landmasses.Under these conditions, sextant or theodolite fixesmay have been observed as a check on the electroniccontrol. Where visual fixes are available or wherejunctions are made with visually controlled hydrog-raphy and conflicts in depths occur, positions lo-cated by visual methods are generally accepted andappropriate adjustments should be made to thosecontrolled by electronic methods. In such cases, thesurvey Descriptive Report is consulted for the hy-drographer's recommendations.

Estimated positions are frequently neededwhere it is not feasible to obtain geometric fixes(e.g., in narrow winding creeks or sloughs, arms,high-banked channels, and in other restricted areaswhere similar conditions prevail). Estimations basedon dead reckoning are also used occasionally whenpositioning ends of sounding lines and when survey-ing in docking areas or along waterfront structureswhere it is impractical to control hydrographic linesconventionally. These positions are pricked on thefield sheet and subsequently recorded as geographicpositions by latitude and longitude. Except for posi-tions in docks and around piers, which generally aresmooth plotted as subplans (7.2.4) at enlargedscales, pseudo fixes (forced positions) must be scaledby the verifier for automated plotting, if not alreadydone by the hydrographer.

Survey vessels equipped with fully auto-mated HYDROPLOT systems usually record elec-tronic positional data for each sounding. Vessels notequipped with a HYDROPLOT system or that areconducting visually controlled hydrography furnishposition control data only for numbered positions;interval soundings between fixes are plotted by timeand course. Positional data from either system maybe adversely affected by electrical interference toelectronic control. Such interference in phase-comparison measurements is manifested by sporadic"lane jumps" and "dial roll" when electronic receiv-ers attempt to lock onto a spurious signal from out-side the system. Super high frequency systems aresubject to a number of distance-measuring errors.Signal reflection (multipath measurements), phaseinterference bands, line-of-sight interference, and im-proper voltage are among the causes that affect dis-tance readout. Powerful radar transmissions in thevicinity of super high frequency operations fre-quently cause significant signal blockage.

Lane jumps and dial roll are usually detect-able on the analog position record or sawtooth re-cording. (See 4.8.6.) Otherwise, the verifier must bealert for pronounced irregularities in dead-reckonedpositions, poor agreement of depths at sounding linecrossings, or depth contour anomalies. Positions inerror usually are replotted to agree with time andcourse of the vessel; such replotting must be notedon the appropriate data lists so the correct data willbe input for updated machine plots of the positionoverlays. Judgment is often required; however, cor-rections to positions must not be applied capri-ciously just to force agreement with dead reckon-ings. When spacings between soundings and posi-tions are relatively constant and the course of a ves-sel is erratic, irregularity may be attributed to poorsteering or to the effects of sea conditions. Whensuch conditions exist, the soundings should generallybe assumed to be positioned correctly.

Inshore preliminary position overlays arecompared with the field sheets for changes made bythe hydrographer and with photogrammetricallycompiled shoreline manuscripts to detect and resolvediscrepancies in the shoreline, datum line (1.6.1),electronic control correctors, and other hydrographicand topographic details. (See 6.3.5.)

VERIFICATION AND SMOOTH PLOTTING

Plotting and checking a position determinedby a hyperbolic positioning system is best accom-plished by scaling each line of position separatelyusing a dependable variable scale device. Variablescales are available commercially. When only a fewpositions need to be plotted or checked, an engi-neer's scale can be used by skewing the scale be-tween the plotted position arcs to match the scalevalues with the difference in arc values.

Smooth position overlays are the final plotsof positions that accompany each smooth sheet.Normally, a smooth overlay is not plotted until aftercompletion of the sounding verification phase (6.3.4);previously undetected errors are often discoveredduring sounding verification making necessary fur-ther adjustment of positional data.

6.3.3.2. RESOLVING ERRONEOUS VISUALPOSITIONS. Erroneous sextant positions will nor-mally be resolved by the hydrographer in the fieldand the data corrected accordingly. Resolution ofundetected errors becomes the verifier's responsibil-ity.

(JULY 4, 1976)6-5

done thoroughly and efficiently, expensive electronicdata processing time is not wasted; and potentialproblems that could surface at later stages of verifi-cation are often eliminated. All major positional er-rors, deficiencies, or unusual methods that have beendiscovered must be thoroughly documented for theinformation and guidance of those involved in thesucceeding stages of verification and quality control.

6.3.3.1. CHECKING MACHINE-PLOTTED PO-SITIONS. A sufficient number of machine-plotted po-sitions on each smooth sheet shall be checked to en-sure overall plotting accuracy. Each position neednot be checked — the number of positions to bechecked is a judgment matter. Checking methodsdepend on the positioning system used for the sur-vey.

Visual sextant fixes are checked by plottingpositions with three-arm protractors. (See A.9.1.1.)Plastic protractors cannot be adjusted and should bechecked for error at least daily when in use. Indexand other scale errors can be determined and ap-plied to observed angles for accurate plotting orchecking of positions. Plastic protractors have a ten-dency to warp, particularly near the ends of thearms; the usable portion must be determined andmarked or the fiducial line rescribed. Plastic protrac-tors may be used to the full limit of the arm length,but no protractor with an index error greater than 3min either arm shall be used for verification orposition plotting. To plot a three-point fix lying verynear one of the three stations, one lays the threelines out on a piece of drafting film that can then beused as the protractor.

When electronic positioning systems areused in the range-range mode, positions are plottedor checked manually by using an Odessey protrac-tor. (See A.9.1.2.) The concentric circles inscribed onthe transparent plastic base permit placing the centerover the position by measuring the proper incre-ments from each of the nearest distance circles. Be-fore using an Odessey protractor, the circular scalesmust be checked carefully with a beam compass and

meter bar, taking into account the system operatingfrequency and resultant lane width.

When a "split fix'' (two angles without acommon center object) is observed in the field, apsuedo three-point fix must be created to providesuitable input for a machine plot. An observed posi-tion is plotted by constructing the intersection of theloci of the angles. Then the values for a legitimatethree-point fix are scaled from the sheet for use onthe next plot.

When only one angle was recorded or ac-cepted, the position of the vessel must be plotted onthe locus of the angle at a point that coincides withthe speed and course made good. The quality of aposition of this nature depends on the vessel main-taining a steady speed and course and on the geo-metric strength and accuracy of the single line ofposition. It may be necessary to defer the determina-tion of final positioning values until the soundingoverlays have been constructed (6.3.4) so as to ad-just the soundings to be in agreement with othersurrounding hydrography. If a series of positionscannot be resolved, it may be necessary to rejectthat portion of the sounding line. ''Swingers'' andother geometrically weak fixes (4.4.2) that are de-tected and noted during the machine-plotting phasereceive similar treatment as positions for which onlyone angle was observed.

Estimated positions are used when the hy-drographer could not observe a strong three-pointfix — such positions must be verified with a suspi-cious and critical eye. Estimated positions are oftenused close inshore where normal fixes are not avail-able. The distance from a beach, structure, or stationshould have been estimated and entered in the re-

HYDROGRAPHIC MANUAL

cords. Positions of line ends and beginnings can beplotted by dead reckoning on the extended line, pro-vided that a speed change affecting the positioninginterval did not occur during the period over whichthe last three reliable fixes were taken.

tered above or alongside in a clear and concise man-ner. Typical errors that repeatedly occur in recordedpositional data include:

c. A wrong object was observed or asignal misidentified.

Human blunders contribute heavily to theoccurrence of sextant position errors. In most cases,erroneous positions can be salvaged if the contribu-tory cause can be recognized. Original data shown inthe field records must never be erased or otherwiseobliterated; a single line is used to cross out errone-ous data, and the revised or corrected data are en-

(JULY 4, 1976) 6-6

Structures and objects such as beacons,buoys, rocks, and piers are often referenced in thesounding records (by distance and direction) whenthe survey vessel passes the feature. These notes, toprovide a check on the survey, must state positivelyon which side of the object the launch passed andthe time of occurrence. See figure 4–24 (4.8.3.1) foran example of a proper entry where ''can buoy 7''was 20 m abeam of the survey vessel at 20h 31m 50s

GMT. Skillful evaluation of the data is required toresolve the occasional discrepancies that can resultfrom such estimates. Survey vessels often cannotsafely get close to rocks and reefs when locatingthem. In such cases, the vessel stands off the feature,several positions of the vessel are taken, and a dis-tance and direction to the feature are estimated fromeach position. When possible, sextant cuts or bear-ings to the feature should have been observed. Whenestimated positions disagree, a verifier must evaluatewhether an incorrect estimate was entered or other"standoff'' positions were determined and plotted,yet inadvertently not recorded.

Estimated positions are often used to plotsoundings observed after a vessel makes a sharp turnthen continues to record soundings. The forwardmomentum of a vessel varies with its size, hullshape, and speed; such variations should be reflectedon field plots and by information provided by thehydrographer.

Occasionally, good fixes are not available,especially when sounding in narrow winding water-ways. A hydrographer in such cases should have es-timated the vessel position on the field sheet, usingthe adjacent features of the shoreline as a reference—in such cases, the note ''See field sheet'' (SFS) willhave been entered in the sounding records. To ma-chine plot an estimated position, a verifier mustscale a pseudo fix if not already determined by thehydrographer.

1. Entry of an incorrect station numberfor an observed object because:

a. A change in observed objects wasnot reported or recorded;

b. A recorder misunderstood the sta-tion number; or

2. Minutes and degrees of an observedangle were reversed (e.g., an observed angle of30°50 ' was recorded as 50°30 ').

3. Transposition of numbers (e.g., anobserved angle of 54°30 ' was recorded as 45°30 ').

4. A sextant angle was read incorrectly.Angular errors commonly result from misreading anadjacent vernier division by 20 or 30 min, dependingon the type of sextant. Other misreading errors in-clude: 10' on the drum of a Navy-type sextant; 1°on any sextant; 2°, 4°, or 6° when a 1°, 2°, or 3° in-crement is erroneously applied on the wrong side ofthe longer 5° or 10° division; 5° and 10° for the samereason as for 10 ', 20 ', 30 ', and 1°. Although errorsof this nature occur repeatedly in field observations,recorded angles must not be corrected or adjustedunless the substituted value is confirmed by otherfactors.

5. A recorder may have misunderstoodthe reported value of an observed angle and re-corded a 15 for a 50, a 7 for an 11, a 5 for a 9, orvice versa.

6. A station position may be in error.Occasionally, a more careful evaluation of a controlstation location by hydrographic methods may dis-close previously undetected errors.

6.3.3.3. RESOLVING ERRONEOUS ELEC-TRONIC POSITIONS. These positions stem from amultiplicity of causes, many of which admittedly re-main unknown. Weak positions occur on electroni-cally controlled surveys when the hydrographerpushes the control system beyond the limits of geo-metrically strong intersections and acceptable lanewidths. When discrepancies between visually con-trolled and electronically controlled hydrographyoccur in junctional areas, visual observations areusually more reliable and are generally accepted. Seesection 4.4.3 for a discussion of potential sources of

VERIFICATION AND SMOOTH PLOTTING

errors in electronic positioning systems.

When discrepancies in electronic positionsoccur, one or more of the following actions usuallywill identify the source of error:

6.3.4.1. SOUNDING OVERLAYS.

6.3.4.1.1. Preliminary sounding overlay. Incontrast to a field sheet, which is plotted during sur-vey operations (using preliminary and possibly un-corrected data), a preliminary sounding overlay isplotted using corrected data. Before the initial pre-liminary sounding overlay is plotted, the verifiershall make every effort to eliminate errors and shalltake the actions necessary to ensure that the plotwill conform with hydrographic standards and speci-fications. Preliminary sounding overlays and theiraccompanying excess sounding overlays are used todetect and correct errors in the observed hydro-graphic data and any other errors that may haveoccurred. Original data must not be adjusted or al-tered unless the changes are justifiable and can besupported by other evidence. When completed,sounding overlays should have all discrepancies re-solved insofar as practical. Except for the degree ofneatness and totality of detail, sounding overlaysshould closely resemble a completed smooth sheet.

Every effort must be expended to resolvequestionable electronic positioning data; however,changes to correction values applied by the fieldparty should be made only with sound justification,and must be thoroughly documented and supportedin the verifier's report.

Specific actions to be taken prior to produc-ing a sounding overlay include:

6.3.4. Verification of Soundings

3. Analog depth records and digitaldepth listings shall be reviewed for the accuracy andadequacy of the soundings selected to portray thebottom. Particular attention must be given to the

6-7 (JULY 4, 1976)

1. Check carefully both digital and ana-log (sawtooth) position records for indications oflane jump, dial roll, erroneous recording of values atpositions, and evidence of external interference.

2. Check for line-of-sight obstructionsthat may have been present between shore stationsand the vessel, for indications of landmass-inducedsignal attenuation, and for evidence of electronic sig-nal reflection.

3. Review and check each calibrationobservation and computation.

4. Determine whether the position isgeometrically strong based on the angle of intersec-tion of the lines of position and the lane divergencefactor.

5. Check shore station elevations to de-termine if significant slant range corrections to theobserved electronic values are needed.

This verification to be plotted on smoothsheets is one of the most detailed and arduousphases of final data processing. As is the case in po-sition verification, successive sounding overlays aremachine plotted, each new needed overlay being acorrected and refined version of its predecessor. Inareas where intensive investigations result in a den-sity of soundings that would cause confusion andcongestion if all were shown at the smooth sheetscale, excess sounding overlays are used as neces-sary. In addition, other plotted soundings that causecongestion and do not reveal important informationfor the delineation of bottom features should be con-sidered excess and deleted from the plot. Althoughthe information shown on sounding overlays mustbe displayed in a neat manner, the emphasis shouldbe toward accuracy and completeness. Preliminarysounding overlays are work sheets and do not de-mand the more exacting drafting standards requiredfor smooth sheets. These overlays provide verifiers

with a graphic means of viewing the final results ofhis checks and his applications of depth corrections,junctional soundings, shoreline and datum line com-parisons, depth contours, topographic detail, and fordetermination of the existence of previously unde-tected deficiencies or errors.

1. Tidal or water level reducers enteredin the computer listings for application to soundingsmust be checked against verified tidal hourly heightsor verified water levels. Whether time and range cor-rections are to be applied to hourly heights must bedecided. Final determination and application of cor-rect tidal or water level reductions to soundings isthe responsibility of the Marine Center.

2. Velocity and transducer (TRA) cor-rections (4.9) and the Abstract of Corrections toEcho Soundings [5.3.5.(D)] compiled by the fieldunit and included in the survey Descriptive Reportmust be carefully checked. Some of the errors morefrequently encountered include algebraic sign rever-sals, faulty interpretation and abstraction of correc-tion data, and corrections entered in an improperformat or applied to the wrong vessel.

HYDROGRAPHIC MANUAL

printouts of sounding data shall indicate whichsoundings have been excessed.

6.3.4.2. DATA LISTINGS AND PRINTOUTS.When checking and correcting hydrographic datalistings and computer printouts, each verifier uses acode to identify his work; when more than one workphase is completed on a single listing or printout byone verifier, each phase is to be marked in a differ-ent color. Raw field data listings, final data listings,and new verification data-processing printouts mustaccompany each survey. Required listings include:

Other preliminary intermediate listings andprintouts may be destroyed with the approval of theappropriate Marine Center review board followingfinal inspection. (See chapter 8.)6.3.4.1.2. Excess sounding overlays. These

are assembled for the following basic purposes:

3. To show soundings that influence thedelineation of depth contours.

Soundings are generally excessed by com-puter subroutines for preliminary plots, but the veri-fier should not hesitate to reinsert excessed sound-ings where he believes a better choice could havebeen made. The most critical soundings must beshown on the regular sounding overlay and on thesmooth sheet; the less critical are shown on the ex-cess sounding overlay to clarify certain bottom fea-tures, reveal discrepancies, and (if necessary) justifythe placement of depth contours. Final listings or

Allowable differences in depths at crossingsare based on the amount of horizontal displacementcorresponding to the difference in depth, rather thana set percentage of the depth. Generally, in area offlat or gently sloping bottom and in depths of less

6-8(JULY 4, 1976)

time, placement, and scaling of least depths, com-pensation for wave action, and the interpretation ofquestionable traces, side echoes, or strays. All cor-rections to soundings are entered in the data file andapplied before the sounding overlay is plotted.

4. On inshore surveys, preliminary posi-tion overlays and accompanying field sheets are usedas guidance for the placement of needed insets andsubplans to the best advantage. Areas where inten-sive development of the bottom was conducted areexamined to determine how many excess soundingoverlays will be needed to show all soundingsclearly. On offshore surveys where the depth unit isfathoms, the overlays are used as guidance when se-lecting the proper depth unit and to determinewhether sounding numerals need be rotated to avoiddeleting (as excess) too many soundings. At thisstage, revisions are made to the projection parame-ters to center the hydrography within the edges ofthe final smooth plot.

5. Verifiers shall review each DescriptiveReport and other related reports to become com-pletely familiar with all field records connected witha survey. As the verification progresses, revisionsand appropriate explanatory notes that affect thecompleted survey are penciled lightly in the Descrip-tive Report. Following approval of the survey by theappropriate Marine Center review board and priorto final administrative approval, the penciled notesand changes are inked.

1. To avoid confusion and congestion ofsoundings in areas of intensive hydrographic devel-opment.

2. To show all soundings that are in therecords but are not plotted on the regular soundingoverlay or smooth sheet.

1. All raw data listings, including thosewith revisions to original entries—such listings orsounding volumes (if used) become original officialsurvey records and are archived accordingly.

2. Final computer printouts correspond-ing with the final position overlay, smooth sheet,and excess sounding overlays.

3. A finalized listing of all horizontalcontrol stations.

4. Velocity and TRA corrections andfinal verified data listings of tide or water level re-ductions.

5. Additional listings and printouts, asneeded, to clarify the resolution of unusual condi-tions or problems encountered during verification.

6.3.4.3. CROSSLINES. Regular systems ofsounding lines are usually supplemented by a seriesof crosslines to check positional accuracy and vali-date soundings. (See 1.4.2 and 4.3.6.) Systematiccrossing discrepancies usually indicate a fault withthe sounding equipment, which requires study todetermine the most probable cause and proper cor-rective actions. Sounding discrepancies caused byhorizontal displacement may be attributed to ques-tionable control. Otherwise, discrepancies may becaused by one or a combination of factors involvingthe observation or compilation of control, echo-sounding corrections, or faulty reductions to the da-tum of reference.

VERIFICATION AND SMOOTH PLOTTING

viewpoint, minor irregularities in soundings shouldnot be overemphasized. Significant bottom features,however, should not be masked by injudicioussmoothing of the curves. When more than one in-terpretation of depth curves can be deduced fromthe available sounding data, the depth curves shallbe the most prudent representation from a safe nav-igational standpoint.

than 20 fm, discrepancies of one unit in feet or 0.2units in fathoms can be expected occasionally; and,except where the natural delineation of depthcurves is affected, such differences do not justifyextensive investigation. Where considerable areasof hydrography are in disagreement, the verifiermust carefully review each phase of the survey toresolve the problem satisfactorily; his report shallpoint out all unresolved discrepancies and includecross references as needed.

6.3.4.6. PHOTOBATHYMETRY. Water depthsand bottom curves are often obtained by photogram-metric methods where the water is shallow andclear. (See 3.2.1.) Photobathymetric surveys are par-ticularly advantageous in areas where coral pinna-cles or other formations prevent running systematicpatterns of sounding lines or prove dangerous toshallow-draft sounding launches. In most instances,photobathymetry will junction with or overlap con-ventional hydrography; but when two soundingmethods are used, occasional conflicts are expectedand must be resolved during the verification process.Merging these data together can best be done on thesounding overlay after the hydrographic data havebeen verified. When discrepancies between hydro-

Depth curves should eventually delineatenatural bottom configurations. From a cartographic

6-9 (JUNE 1, 1981)

6.3.4.4. DEPTH CURVES. With the excesssounding overlays in proper registry with the pre-liminary sounding overlay and with their soundingstaken into consideration, depth curves are first pen-ciled lightly on the preliminary sounding overlayby the verifier. No single requirement for the spac-ing of these study curves can be prescribed for allareas and water depths, but they must be spacedclosely enough to delineate the bottom configura-tion completely and accurately. Depth curves areindispensable for interpreting and examining a hy-drographic survey; drafting closely spaced depthcurves carefully and accurately requires inspectionand consideration of each sounding. Merely delin-eating the standard curves specified in tables 4–5and 4–6 is generally inadequate for study purposes.When drawing depth curves, incorrect soundingsare easily detected; anomalous or improbable con-figurations are strong evidence that a further inves-tigation of the plotted soundings is required.

The ability to represent submarine relief bymeans of depth curves is acquired only by trainingand experience. The shoalest depth curves shouldbe drafted first, then continued in sequence to themaximum depths. To avoid confusion, a verifiershould always bear in mind that he is separatingshoal water from the deeper water; depth curvesgenerally are drawn to include soundings of equaldepth or less. When completed, depth curvesshould be continuous and extend to the limits ofhydrography or approach the shoreline. Depthcurves must never overlap, touch, or be drawnthrough a numeral or symbol. Lines are broken atsoundings as necessary to avoid unnatural bottomconfigurations. Verifiers should not overlook a hy-drographer's interpretation of depth curves, partic-ularly those he drew using his local knowledge anddirect observations.

Preliminary study depth curves, which aredrawn in pencil, must rigorously follow the sound-ings so as to graphically depict potential deficien-cies. Because sounding overlays are used as guid-ance when constructing smooth sheets, the colorsand conventions prescribed for standard depthcurves are to be followed. (See 7.3.9.)

Plotting halves of sounding units on thesounding overlay is occasionally desirable in flat orgently sloping bottom areas to eliminate unnaturaldepth curves.

6.3.4.5. LEAST DEPTHS. Variations in newlydetermined least depths from previously surveyedvalues must be investigated in detail. Analog depthrecords and position data must be closely scannedand checked for errors or omissions. The Descrip-tive Report must be reviewed to see if the hydrog-rapher made specific mention and recommendationsconcerning the feature. Occasionally, shoalestsoundings are overlooked and not included in thedigital data, or erroneous corrections were appliedto the observed depths. A verifier must also evalu-ate whether or not an adequate search was made todetermine a least depth. Significant differences withprior survey least depths not mentioned in the hy-drographer's portion of a Descriptive Report shallbe included in the verification report.

HYDROGRAPHIC MANUAL

Soundings and other details on the transpar-ent photobathymetric overlay are transferred to thesounding overlay only when necessary for adequateverification. Photobathymetric data, however, areshown on the smooth sheet in accordance with sec-tion 7.3.8.3. Where junctional discrepancies cannotbe resolved, the most reliable soundings shall be re-tained and a butt junction made. Photobathymetricinformation generally is compiled on the topographicor shoreline survey of the area. A copy of the reportthat describes the compilation shall be attached to theDescriptive Report of the hydrographic survey.

6.3.4.7. COMPARISON WITH ADJOININGSURVEYS. After a preliminary sounding overlay hasbeen plotted, the verifier shall make a comparisonwith adjoining contemporary surveys to determinethe completeness and relative agreement of the hy-drographic findings. Descriptive Reports for ad-joining surveys should be inspected to guardagainst gross errors in velocity of sound correc-tions. A hydrographer's interpretation of the com-parisons stated in the Descriptive Report must bereviewed. It must be borne in mind that a hydrog-rapher's evaluation may have been based on pre-liminary uncorrected data. Consistent differences insoundings, corresponding displacements of depthcurves, and gaps in coverage must be described inthe verifier's report. If a survey is incomplete, defi-ciencies shall be noted for investigation when fieldwork on the project is resumed.

In a satisfactorily completed junction,depth curves must be in coincidence, soundingsnecessary to further define depth curves must beaccurately transferred, and depths must be in goodagreement. If depth curves and depths do notagree because of bottom changes or other causes, abutt junction is generally made. In this case, adashed line is drawn in color to show the buttjunction, and a note in the same color is entered toindicate the superseded soundings.

6.3.5. Verification of Shoreline, Hydro-graphic, and Topographic Features

On inshore surveys, preliminary positionoverlays and preliminary sounding overlays shall becompared in detail with the appropriate shorelinemanuscripts to detect and resolve discrepancies in

Positions of submerged features or breakersand the notes relating thereto generally should be

6-10(JUNE 1, 1981)

graphic and photobathymetric data arise and can-not be resolved by a combined review of the workby the verifier and the photogrammetrist, the hy-drographic data are generally accepted.

the shoreline, reference datum line (MLW, MLLW,LWD), and other hydrographic and topographicfeatures shown thereon. Class I (final) shorelinemanuscripts must be used for this purpose. Shorelinemanuscript data need not be transferred to the over-lays. Satisfactory comparisons can be made merelyby placing one transparent sheet in registry over theother. Depending on the complexity of the survey,on the amount of shoreline and topographic details,and on the revisions recommended by the hydrogra-pher as shown on the field sheet and in the Descrip-tive Report, one may find it desirable or necessary totransfer data from the shoreline manuscript to thesounding overlay for satisfactory comparison andevaluation. In this case, the cartographic standardsand symbolization specified in chapter 7 for smoothsheets should be followed, although minor depar-tures may be made for expediency.

Although all discrepancies between photo-grammetric surveys and hydrographic surveysshould have been resolved in the field, some occasion-ally escape detection or are not resolved clearly andconcisely. Resolution of these discrepancies rests withthe verifier if the hydrographic field unit has left thearea. There are no set rules—only generalities can bestated as guidance toward a satisfactory solution.

Photogrammetric locations of shoreline, ref-erence datum lines (MLW and MLLW when deter-mined by tide-coordinated aerial photography), andobjects awash or that uncover at the charting datumare usually more accurate and are accepted over hy-drographic locations—unless there is unmistakableevidence of error in the shoreline manuscript. Errorsin rock positions are among the most common. A veri-fier must examine carefully all available records to as-certain whether there are actually two rocks orwhether the same rock is being shown at two loca-tions. When a feature is clearly visible on aerial photo-graphs and its position on the shoreline map has beenverified, the photogrammetric location generallyholds; however, if a hydrographer detected and inves-tigated a discrepancy in the field and resolved it satis-factorily, the hydrographic determination takesprecedence. In cases where a feature was located indifferent positions by two different methods (each ap-pearing reliable), the feature must be shown at bothpositions in the interest of safe navigation. Additionalfield investigations shall be recommended by the veri-fier to resolve such discrepancies.

VERIFICATION AND SMOOTH PLOTTING

6.3.6. Wire-Drag Comparisons

6.3.7. Prior Survey Data

6.3.7.1. COMPARISON WITH PRIOR SURVEYDATA. The most recent prior hydrographic surveysof the area used for charting most of the soundingsshall be carefully compared with the present survey.This comparison serves two important purposes. Pri-marily, it is necessary to determine whether the pres-ent survey is adequate to supersede prior surveys,and the comparison is used to transfer important dataneeded to supplement the new survey. Secondly, thecomparison serves to reveal whether the character ofthe bottom is stable or transient; it provides a recordof bottom changes that may be useful when schedul-ing future revision surveys. Locations of important shoals, rocks, and

other obstructions and their least depths shall be com-pared. When differences in position are found for thesame feature, the reliability of the present method oflocation must be evaluated with respect to earliermethods; the most probable position should be ac-cepted. If the least depth on a permanent feature isneither verified nor disapproved by a survey, the pri-or least depth must be transferred. Wherever possible,

6.3.7.2. EVALUATING PRIOR DATA. Whencomparing a prior survey with a new survey, differ-ences in least depths, individual depths, general hy-drography, and in other details are often revealed.Some differences are caused by natural changes, cul-tural changes, or by errors in plotted data. Since eachsignificant difference must be evaluated, the surveyverifier must carefully judge each case before accept-

6-11 (JUNE 1, 1981)

accepted from the hydrographic data if it has beendetermined that the identical feature is involved. Ex-ceptions to this policy may be exercised when a sub-merged feature was determined during the course ofa photobathymetric survey. Elevations of bare rocksor rocks awash are accepted from the most crediblesource. Proximity to the feature, if known, and avail-ability of accurate tidal or water level data at thetime of observation will help determine credibility.Verifiers must be sure that the elevation shown foreach rock has been accurately corrected for tidal orwater level stage. Supervisors should check a sam-pling of rock elevations on applicable sheets to en-sure accuracy.

If wire-drag surveys have been made in thearea, the results of the two surveys shall be comparedand correlated. Except where a hydrographic surveyhas revealed shoaler soundings, items such as verifiedsoundings, groundings, bottom characteristics, andwreck or obstruction notations are transferred fromwire-drag surveys. Such data are entered in greenink; the grounding circle is omitted. Wire drag clear-ance depths are not transferred. Each discrepancybetween hydrographic survey soundings and wire-drag effective depths must be resolved. Notation offeatures transferred to the smooth sheet shall bemade as described in section 6.3.7.3. (See figure 7–7.)

ing or rejecting data. Each verifier must be thorough-ly familiar with procedures and techniques used inhydrographic surveying and expected accuraciessince NOS began hydrographic surveying in 1834.

Unless there is sufficient evidence to showotherwise, the most recent basic survey findings willsupersede prior survey data. When a discrepancy isdiscovered that cannot be resolved logically, exten-sive research into the prior survey records to prove ordisprove data will not be undertaken. When doubtsarise as to which information will be shown on asmooth sheet, the safest and most conservative course,from a marine navigational viewpoint, shall be taken.

6.3.7.3. RETENTION OF PRIOR DATA. Impor-tant soundings or features on prior surveys that wereneither verified nor disproved by a new survey shallbe brought forward and shown on the new smoothsheet. (See figure 7-7.) The notation ''from H–—(year)'' shall be placed near such items with a leaderand arrow pointing to the sounding or feature.Where transferred items are scattered over largeareas of the smooth sheet, a group notation ''De-tached Soundings in (color) from H–—– (year)"shall be placed in a marginal area, preferably near thetitle block. Slanted lettering is to be used for all suchnotes. Red ink is preferred if not already used forphotobathymetry, but most other colors may be usedas necessary. The color selected should uniquelyidentify the intended source. The repetitive use of aparticular color to identify data carried forward fromseveral sources may cause confusion in determiningthe actual source of retained prior survey informa-tion. If all available colors have already been utilized,then the group notation should be appropriately for-matted so as to eliminate confusion, One suggestedformat is: ''Detached soundings in (color) (east/westof longitude X) from H-xxxx (19xx).''

It is emphasized that the note should clearlyand uniquely state the source of the retained priordata. Green ink is reserved for wire drag survey databrought forward. Notations for wire-drag surveys areindicated by the initials ''WD'' entered after the year.

HYDROGRAPHIC MANUAL

When rocks shown on a prior hydrographicor topographic survey have not been verified by thenew survey, have been located in a slightly differentposition, or are somewhat different in character, allavailable information should be consulted and thefollowing rules applied for disposition of the feature:

6.3.8. Geographic Datums

Verifiers shall identify the geographic datumto which a prior survey was referenced and make ad-justments as necessary to permit comparison at thedatum used for the most recent survey.

During the early years of survey operations,many detached triangulation networks wereestablished in the United States — each referenced toa datum based on independent astronomic observa-tions within the network. Hydrographic and topo-graphic surveys conducted within such areasconsequently were based on these independent localdatums. Upon completion of the first transcontinen-tal arc of triangulation, the various detached net-works were connected, then a coordinated networkbased on a single geographic datum was establishedfor the whole country. Station MEADES RANCHin central Kansas was selected as the reference pointfor this single geodetic datum. In 1901, the adopteddatum was officially named the ''United States Stan-dard Datum.'' When Canada and Mexico adoptedthis datum, it was renamed the ''North AmericanDatum.''

In 1927, a unified adjustment of all first-or-der triangulation in the United States was initiated,and the ''North American Datum of 1927'' wasadopted. Use of this datum has been extended intoAlaska where several independent datumspreviously had been used. Modern hydrographicsurveys in waters bordering the continental UnitedStates are now made on this geographic datum. Sur-veys in the Caribbean Sea areas, the Hawaiian Is-

6-12(JUNE 1, 1981)

shoalest depths from both surveys are shown; but ifthere is insufficient space on the smooth sheet, thedeeper of the two should be treated as an excesssounding and not shown. If a retained sounding isfrom a prior survey, the note "Least depth——(units) from present survey" is to be added to thepresent survey in black ink with a leader indicatingthe feature

Occasionally, a group of soundings must betransferred from a prior survey to complete hydrog-raphy in a gap or small unsurveyed area of a new sur-vey. Similarly, a new survey may have to besupplemented by transferring ledge, reef, or rock de-lineations if both the new hydrographic and photo-grammetric surveys are deficient.

1. If the position of what is presumably thesame rock differs between a present and a prior sur-vey, the newer position is generally accepted as cor-rect provided the positioning method is consideredto be more accurate and conclusive.

2. When an adequate examination madeduring the present hydrographic survey in the vicini-ty of a rock or rocks shown on the prior survey failsto disclose or verify existence of the rock, the dispo-sition recommendation made by the hydrographershould be followed.

When general statements in a DescriptiveReport indicate that certain rocks shown on old sur-veys could not be found, these rocks should not bedeleted but should be transferred either as rocksawash or as submerged rocks, depending on the cir-cumstances in each case. Without proof of an ade-quate examination, general statements of this naturecan be accepted only as evidence that such rockswere not visible at the time of a cursory examination.

3. Bare rocks on a prior topographic orhydrographic survey that are not shown or are notdisproved on the new hydrographic or topographicsurvey should be carried forward as rocks awash un-less more specific information is available.

4. Rocks shown as being awash on a priorsurvey but shown as being submerged on a new sur-vey, should be considered to be rocks awash (the saf-est course) unless the new survey shows clearly that

the rock was not visible at the low water datum orunless it is known that submergence has occurredsince the last survey. When revising a new survey,the rock awash symbol is shown in black ink and anote made in the sounding record.

5. Submerged rocks shown on prior sur-veys, when not disproved by the new survey, shouldbe carried forward with caution. On some prior sur-veys, submerged rock symbols may have been usedto indicate rocky bottom areas rather than individualsubmerged rocks that are dangerous to navigation.

6. Generally, the delineation inshore of thereference datum line on the new survey should be ac-cepted as correct — except that significant rocksshown awash on prior topographic or hydrographicsurveys which were neither located nor disprovedon the new survey should be brought forward in anappropriate color.

VERIFICATION AND SMOOTH PLOTTING

Many older hydrographic surveys list thegeographic position of a triangulation station thatlies within the surveyed area. Positions of these sta-tions were shown in the lower margin of the sheet;however, the reference datum was not always indi-cated. On later surveys, both the geographic posi-tion of the reference triangulation station and thegeographic datum were listed.

6.3.9. Datum Ticks

1. Geographic position data used for plot

6.3.10. Chart Comparison

FIGURE 6-1.— Change of datum shown on a hydrographic sheet

6-13 (JUNE 1, 1981)

lands, and other South Pacific islands may be basedon independent datums; these are specified in theproject instructions.

Before comparing surveys made in variousyears, the geographic datums must be correlated.Never assume that an unlabeled projection on anolder survey was referenced to any specific datum—differences in datums must always be determined be-fore comparing surveys or transferring data. TheU.S. Standard or North American Datum was shownby a complete projection (in color) on many of theolder surveys. Others (figure 6-1) show only one ortwo marked projection intersections (ticks) on theU.S. Standard Datum or the NA Datum of 1927.

If a prior survey does not show the NA1927 Datum, this datum shall be established beforetransferring data to the new survey. To establishthe NA 1927 Datum, select at least three widelyseparated triangulation stations within the sheetlimits for which geographic positions are availableon the NA 1927 Datum. Two methods can then beused to determine the datum differences:

ting an original survey are best determined fromold registers, records, or publications. The mean ofthe differences between positions on the NA 1927Datum and the datum used for an older survey isthe correction to be applied. Position differencesfor each of the three stations should be nearlyequal. If a significant variance is found, an investi-gation should be made for possible errors in com-putations or for failure to identify common stationson the two datums. The position of the NA 1927Datum relative to the original projection can bedetermined by back plotting NA 1927 values forone of the triangulation stations or by followingthe rule that, if the latitude (N) and longitude (W)on the old datum are greater than the correspond-ing values on the new datum, the new projectionwill be north and west, respectively, of the oldprojection. If the old values are smaller, the datumshift is to the south and east.

2. This method is applicable where geo-graphic position data used for plotting the selectedtriangulation stations on the prior survey are notavailable. A graphic method of determining the da-tum differences is used. Arcs based on the NA1927 values of latitude and longitude are swungfrom the selected triangulation stations shown onthe survey, and tangents to the arcs are drawn par-allel to the projection. Datum differences betweenthe tangents to the arcs and the original projectioncan then be scaled. An average of the differences isused to plot the datum tick.

Extreme care shall be exercised when de-termining the proper relation of the NA 1927 Da-tum to the original projection. Distortion in theoriginal projection must be measured and appliedcarefully to all distances plotted. Plotting of the da-tum tick (in colored ink) is to be verified by anoth-er person. Each person enters initials and the datebeside the tick. Each tick shall be identified by lati-tude and longitude and be labeled ''NA 1927 Da-tum.'' If only approximate datum differences can bedetermined, the datum tick note includes the abbre-viation ''approx.''

The verifier shall carefully check the hy-drographer's comparison of the survey with thechart for errors or omissions. Comparison of thesurvey sheet with the chart by the verifiers shall bewith the edition of the chart as listed in the projectinstructions. (See 5.3.4. (L.)). Charted items thatwere disposed of satisfactorily during the compari-

HYDROGRAPHIC MANUAL

Some faults lie in lack of training or care-less supervision—others reflect the aptitude of theverifier and his attitude and approach toward thework. To produce a verified survey and smoothsheet that will conform to National Ocean Surveystandards, a competent verifier should have hadfield experience and must be thoroughly familiarwith all parts of this manual.

The following is a partial list of the mostcommon deficiencies on both manual and automat-ed surveys:Errors, omissions, and additional recom-

mendations are to be tabulated and entered in theverification reports (6.6); references to these datamust be entered in paragraph L of the DescriptiveReport text. (See 5.3.4.) To avoid confusion, achart section identifying the items may be submit-ted with the list. If the comparison reveals an un-charted danger or condition important to naviga-tion not previously reported, the feature must bereported immediately by radio telephone or tele-graph to the nearest Commander, U.S. CoastGuard District with a copy to the Chart Informa-tion Branch, OA/C322, for possible inclusion in thenext Notice to Mariners. (See 5.9.)

2. Errors in recorded observations of anykind were not detected and corrected.

3. Signal location errors or misidentifica-tions were not detected.

4. Positions of signals were entered orplotted incorrectly.

QUALITY CONTROL6.4.

7. Soundings were selected poorly or im-properly to portray a complex feature.

6.5.

These can be grouped into three generalcategories: (1) inadequate or inaccurate field datawith which a verifier has to work, (2) unrecog-nized or unresolved discrepancies in the field data,and (3) substandard verification practices and pro-cedures. 13. A feature is shown at two locations.

6-14(JUNE 1, 1981)

son with prior surveys need not be repeated here.Extensive research to resolve apparent discrepan-cies is not usually required of the verifier, particu-larly if an item was charted by approximate posi-tion or depth based on reported information.Marine chart compilers have more complete infor-mation on such items and are better equipped tomake appropriate charting judgments. Such items,however, shall be individually identified and re-ported by the verifier.

Procedures for quality control shall be de-veloped by each Marine Center or other processingarea to ensure that the procedures established forverifying surveys are sound and are so designed toassure that the final product meets the specifica-tions prescribed for smooth sheets. (See chapter 7.)It must be emphasized that the quality of surveyverification extends beyond specifications and de-pends primarily on the methods and thoroughnessof the verification processes. Final approval of averified survey by a Marine Center indicates thatadequate verification and inspection have beenperformed. Hydrographic surveys that fail to meetthe requirements of this manual and of the projectinstructions shall not be submitted to NOS Head-quarters without specific recommendations for ad-ditional field work.

COMMON DEFICIENCIES OFVERIFIED SURVEYS

1. Positions were plotted incorrectly be-cause of improper editing of logged positional dataor because of failure to calibrate or register the au-tomated plotter.

5. Sounding line positions plotted fromweak fixes were not properly adjusted to conformto supplemental information.

6. Soundings are spaced incorrectly (e.g.,at the inshore end of a line or where a line beganfrom a standing start, where a line began or endedon an uneven position or sounding interval, andwhere the spacing does not agree with recordedspeed and course values).

8. Soundings have been spaced at exces-sively wide or unnecessarily close intervals.

9. The shoreline has been transferred in-accurately, and various symbols (particularly rocksymbols) have been drafted carelessly.

10. Depths appearing erroneous or exces-sive differences at crossings were not checked.

11. Analog depth records were misinter-preted; erroneous digital depth values in kelp orgrass were not corrected; soundings were not ad-justed for the effects of strays or sea conditions.

12. The shoreline has been transferred toa smooth sheet from other than class-I shorelinemanuscripts.

VERIFICATION AND SMOOTH PLOTTING

14. Sounding corrections were determinedor applied incorrectly.

5. Copy of the Headquarters-approvedtide or water level note, as appropriate.

6. Reports or notes needed to understandthe survey or to clarify procedures or results.16. Depth contours have not been shown

in accordance with standard NOS conventions.

17. Bottom characteristics have been over-ly condensed and significant information omitted.

20. Soundings were not corrected for in-strument errors.

VERIFICATION REPORTS6.6.

When a hydrographic survey verificationhas been completed, a verification report shall beprepared and appended to the Descriptive Report.The verification report is a summary of pertinentfacts about a survey and an evaluation of the detailedcomparisons made with prior surveys and the charts.The report shall include a description of unusual pro-cessing procedures, major changes or adjustments todata, and a list of complete work statistics. Specificstatements must be included that evaluate the ade-quacy of the survey to supersede prior survey dataand charted information. The verification reportserves as a guide to the chart compiler and identifiesareas where additional field work is needed to satis-factorily complete a survey. Subject matter pertinentto the report should consist of the following:

1. NOAA Form 77-27, ''HydrographicSurvey Statistics.'' (See figure 6-2.)

2. A narrative account of the verifica-tion procedures and findings.

6-15 (JUNE 1,1981)

15. Erroneous elevations were determinedfor rocks or were incorrectly reduced to the chart da-tum.

18. Inshore sounding lines parallel to theshoreline do not follow the actual path of the vessel.

19. Erroneous tidal or water level reducerswere applied.

3. Documentation of all problems en-countered and nonstandard procedures used duringverification of the survey. Justify any procedurethat may have compromised the quality of thedata.

4. Statement(s) as to whether any of thefollowing data entered in the Descriptive Report bythe hydrographer were revised during verification: (a)projection parameters, (b) electronic position controlparameters, (c) list of stations, (d) tide or water level re-duction values, and (e) corrections to soundings. If

the revisions were not entered on the Descriptive Re-port listings by the verifier, include them here.

7. Control and shoreline. When the originof the horizontal control is described adequately in theDescriptive Report, reference the pertinent section. Ifnecessary, add supplementary information deter-mined during verification.

Statement(s) as to the source of shorelinedata. Identify the numbers, the survey dates, and theclassification of the shoreline manuscripts used for thefinal comparison.

8. Hydrography. Make a summary evalu-ation of the hydrography. Include specific state-ments regarding agreement of soundings at crossingsand completeness and confidence with which depthcontours could be drawn. List any discrepancieswith respect to photogrammetric surveys. A state-ment is to be made evaluating the adequacy of devel-opment of the bottom configuration and thedetermination of least depths. Each significant defi-ciency shall be described.

9. Condition of survey. Comments in thissubmission are directed toward deficiencies in field-work procedures, in the survey records, and in theDescriptive Report. Mention specifically each casewhere a procedure was erroneously used or failed tocomply with the requirements of this manual or oth-er pertinent documents. Include constructive criti-cism that should be brought to the attention of thehydrographer. If the condition of the survey isfound to be satisfactory, state only that the smoothsheet and accompanying overlays, hydrographic re-cords, and reports are adequate and conform to therequirements stated in this manual.

10. Junctions. Adjoining surveys are ref-erenced by registry number, year, and their posi-tion relative to the present survey. Junctions shallbe evaluated and their adequacy discussed. Impor-tant irreconcilable discrepancies must be describedand probable causes stated. Where butt junctionswere necessary because of disagreements in depths,the condition shall be specifically described.

11. Comparison with prior surveys. In hy-drographic surveys, the results of comparisons be-tween the most recent prior survey and the presentsurvey shall be summarized in a brief introductory

HYDROGRAPHIC MANUAL

RECORDS ACCOMPANYING SURVEY: To be completed when survey is registered.

RECORD DESCRIPTION AMOUNT RECORD DESCRIPTION AMOUNT

SMOOTH SHEET 1 BOAT SHEETS 1

DESCRIPTIVE REPORT 1 OVERLAYS ( POS 1, Control 1) 2

DESCRIPTION DEPTHRECORDS

HORIZ CONTRECORDS PRINT OUTS

ABSTRACTS/SOURCE

DOCUMENTS

1 1 2

CAHIERS 1VOLUMES 9

BOXES

AccordionENVELOPES

T-SHEET PRINTS (List)

1079810795,T - 10791,

SPECIAL REPORTS (List)

Control and Photogrammetric Report

OFFICE PROCESSING ACTIVITIESThe following statistics will be submitted with the cortographer's report on the survey.

AMOUNTSPROCESSING ACTIVITY PRE-

EVALUATION TOTALSVERIFICATION

1991POSITIONS ON SHEET

POSITIONS CHECKED 45 3

POSITIONS REVISED 35 3

DEPTH SOUNDINGS REVISED 300 5

DEPTH SOUNDINGS ERRONEOUSLY SPACED -

SIGNALS ERRONEOUSLY PLOTTED OR TRANSFERRED -

TIME (MANHOURS)

TOPOGRAPHIC DETAILS 24 4

JUNCTIONS -

VERIFICATION OF SOUNDINGS FROMGRAPHIC RECORDS 40 2

SPECIAL ADJUSTMENTS -

ALL OTHER WORK 136 76

TOTALS 206 93

ENDING DATEPRE VERIFICATION BYW. H. Guy, R. R. Hill , B. J. Stephenson

BEGINNING DATE4-30-70

VERIFICATION BY

B. J. Stephenson

BEGINNING DATE

5-19-75

4-24-75

ENDING DATE

6-20-75

BEGINNING DATE ENDING DATEEVALUATED BY6-23-75 7-7-75B. J. Stephenson

FIGURE 6–2.— NOAA Form 77-27, ''Hydrographic Survey Statistics''

6-16(JUNE 1, 1981)

TAPE ROLLS PUNCHED CARDS

24 0

VERIFICATION

U. S. DEPARTMENT OF COMMERCENATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

HYDROGRAPHIC SURVEY STATISTICSHYDROGRAPHIC SURVEY NO. H-9050

(742 - 20 - 2 - 69)

NOAA FORM 77-27(9 -72)(PRESC BYHYDROGRAPHICMANUAL 20-26-94, 7-13

VERIFICATION AND SMOOTH PLOTTING

A.

Date:

Signed:

Title: Chief, Verification Branch

B.

Date:

Signed:

Title: Chief, Processing Division

FIGURE 6–3.— Verification approval sheet

6-17 (JUNE 1, 1981)

APPROVAL SHEETFOR

SURVEY H-

All revisions and additions made on the smooth sheet

during verification have been entered in the magnetic

tape records for this survey. A new final position

printout has/has not been made. A new final sounding

printout has/has not been made.

The verified smooth sheet has been inspected, is complete,

and meets the requirements of the Hydrographic Manual.

Exceptions are listed in the verifier's report.

HYDROGRAPHIC MANUAL

6-18(JUNE 1, 1981)

paragraph. Changes in shoreline, bottom configura-tion, and general depths should be described. Statewhether such changes are attributable to natural,artificial, or less-detailed or less-accurate methodsused during prior surveys. The magnitude of signif-icant shoreline changes and bottom changes shallbe indicated. Other items discussed individuallythat have been charted from the preceding surveyor earlier surveys must be disposed satisfactorily.

In each discussion, there shall be a state-ment made that the prior survey is superseded —however, such a statement must be qualified whenit is necessary to carry forward and retain specifieddetails from a prior survey.

12. Comparison with chart. The chartnumber and edition shall be entered beside thisheading for ready reference. Discussion of thecomparison is to be subdivided as follows:

a. Listing of the unresolved discrep-ancies between the new survey and the charteddata. (See 6.3.10.) Do not include items discussedpreviously in the comparison with prior surveys oritems that have been disposed satisfactorily by anadequate hydrographic investigation. Where chart-ed data from sources other than NOS surveys havenot been disproved by the present survey, a specif-ic recommendation to retain the data on the chartshould be made. The discussion should be conclud-ed with a statement as to the adequacy of the pres-

ent survey to supersede the charted hydrography.This statement may require qualification because ofthe verifier's recommendation to retain certaincharted features.

b. Controlling depths. Notes of con-trolling depths are usually based on data furnishedby the U.S. Army Corps of Engineers. Discuss thecomparison of the survey with these notes.

c. Aids to navigation. The adequacywith which the charted positions of aids to naviga-tion mark the features or serve the purposes intend-ed should be stated. Definite recommendationsshould be made when new unmarked dangers arenoted or when shoals and channels have beenshifted in position and are not properly marked bythe charted buoys and fixed aids. Also, differencesbetween the charted positions and present surveypositions of nonfloating aids to navigation shouldbe noted.

13. Compliance with instructions. Make abrief statement as to whether the survey adequatelycomplies with the project instructions; note anysignificant exceptions.

14. Additional field work. Each survey isevaluated as an inadequate, an adequate, a good, oran excellent basic survey. Recommendations shallbe made as to whether or not additional field workis needed. If additional field work is recommended,each item or area is to be clearly described or ref-erenced to another specific discussion in the report.Further work, when needed, usually consists of ex-aminations of shoal indications or of questionablecharted information, disposal or clarification of dis-crepancies, and further development of outstandingfeatures or inadequately developed areas.

15. An ''Approval Sheet.'' This shall beincluded to attest that the verified and smooth-plot-ted survey, the Descriptive Report, and the verifi-er's report have been inspected by a designatedverification supervisor, and meets the requirementsand specifications stated in this manual, except asnoted. (See figure 6-3.)

In wire-drag surveys, discuss separatelythe comparison made with wire-drag surveys.Comparisons shall be made with both contempo-rary wire-drag surveys that have been reviewedand prior wire-drag surveys in the area. Wherethere are no conflicts between present surveydepths and effective depths of the wire-drag sur-veys, only a simple statement need be made to thateffect. Discrepancies arising as a result of bottomchanges should be identified as such. Wire-dragsurveys, however, are not generally superseded byordinary hydrographic surveys; thus statements tothat effect need not be made.

VERIFICATION AND SMOOTH PLOTTING

A.

Date:

Signed:

Title: Chief, Verification Branch

B.

Date:

Signed:

Title: Chief, Processing Division

FIGURE 6–5.— Verification approval sheet

6-19 (JULY 4, 1976)

APPROVAL SHEETFOR

SURVEY H-

All revisions and additions made on the smooth sheet

during verification have been entered in the magnetic

tape records for this survey. A new final position

printout has/has not been made. A new final sounding

printout has/has not been made.

The verified smooth sheet has been inspected, is complete,

and meets the requirements of the Hydrographic Manual.

Exceptions are listed in the verifier's report.

HYDROGRAPHIC MANUAL

paragraph. Changes in shoreline, bottom configura-tion, and general depths should be described. Statewhether such changes are attributable to natural,artificial, or less-detailed or less-accurate methodsused during prior surveys. The magnitude of signifi-cant shoreline changes and bottom changes shall beindicated. Other items discussed individually thathave been charted from the preceding survey or ear-lier surveys must be disposed satisfactorily.

6-20(JULY 4, 1976)

In each discussion, there shall be a state-ment made that the prior survey is superseded —however, such a statement must be qualified when itis necessary to carry forward and retain specifieddetails from a prior survey.

In wire-drag surveys, discuss separatelythe comparison made with wire-drag surveys. Com-parisons shall be made with both contemporarywire-drag surveys that have been reviewed and priorwire-drag surveys in the area. Where there are noconflicts between present survey depths and effectivedepths of the wire-drag surveys, only a simple state-ment need be made to that effect. Discrepancies aris-ing as a result of bottom changes should be identi-fied as such. Wire-drag surveys, however, are notgenerally superseded by ordinary hydrographic sur-veys; thus statements to that effect need not bemade.

12. Comparison with chart. The chartnumber and edition shall be entered beside thisheading for ready reference. Discussion of the com-parison is to be subdivided as follows:

a. Listing of the unresolved discrep-ancies between the new survey and the charted data.(See 6.3.10.) Do not include items discussed previ-ously in the comparison with prior surveys or itemsthat have been disposed satisfactorily by an ade-quate hydrographic investigation. Where charteddata from sources other than NOS surveys have notbeen disproved by the present survey, a specific rec-ommendation to retain the data on the chart shouldbe made. The discussion should be concluded with astatement as to the adequacy of the present survey

to supersede the charted hydrography. This state-ment may require qualification because of the verifi-er's recommendation to retain certain charted fea-tures.

b. Controlling depths. Notes of con-trolling depths are usually based on data furnishedby the U.S. Army Corps of Engineers. Discuss thecomparison of the survey with these notes.

c. Aids to navigation. The adequacywith which the charted positions of aids to naviga-tion mark the features or serve the purposes in-tended should be stated. Definite recommendationsshould be made when new unmarked dangers arenoted or when shoals and channels have been shiftedin position and are not properly marked by thecharted buoys and fixed aids. Also, differences be-tween the charted positions and present survey posi-tions of nonfloating aids to navigation should benoted.

13. Compliance with instructions. Makea brief statement as to whether the survey ade-quately complies with the project instructions; noteany significant exceptions.

14. Additional field work. Each surveyis evaluated as an inadequate, an adequate, a good,or an excellent basic survey. Recommendations shallbe made as to whether or not additional field workis needed. If additional field work is recommended,each item or area is to be clearly described or refer-enced to another specific discussion in the report.Further work, when needed, usually consists of ex-aminations of shoal indications or of questionablecharted information, disposal or clarification of dis-crepancies, and further development of outstandingfeatures or inadequately developed areas.

15. An ''Approval Sheet.'' This shall beincluded to attest that the verified and smooth-plotted survey, the Descriptive Report, and the veri-fier's report have been inspected by a designated ver-ification supervisor, and meets the requirements andspecifications stated in this manual, except as noted.(See figure 6-5.)

SMOOTH SHEET7.

DEFINITION AND PURPOSE7.1.

Sheets must be protected at all times fromcreasing, defacing, or smudging. A protective covershould be kept over the entire sheet exposing onlythe small area where work is actually being done.Avoid getting fingerprints on plotting surfaces be-cause ink does not adhere well to oily areas.

Smooth sheet scales are generally identicalto those of the corresponding field sheets. In somecases, however, it may be desirable to smooth plotat a smaller scale to avoid an oversize smooth sheetor to combine two adjacent surveys. Authorizationto plot surveys at reduced scales must be obtainedfrom the Director, NOS. Such reductions may beauthorized where;

7.2. GENERAL SPECIFICATIONS

Smooth sheets shall be plotted only on sta-ble polyester drafting films specifically authorized bythe Director, NOS, for this purpose. Arkwrite Draft-ing Film No. 2102W (manufactured by the Diazo

1. A smaller scale will not significantlyreduce the value of a survey.

7-1 (JULY 4, 1976)

A smooth sheet is the final, neatly drafted,accurate plot of a hydrographic survey. In contrastto the field sheet plotted during field operationsfrom preliminary field data, the smooth sheet isplotted from verified or corrected data. The smoothsheet and survey information shown thereon shallconform to the cartographic standards and conven-tions described in this chapter. Unless specified oth-erwise in the project instructions, verified hydro-graphic surveys are smooth plotted by the MarineCenter Processing Divisions.

Each smooth sheet shall be accompanied bya smooth position overlay (6.3.3) drawn at the samescale. Smooth position overlays show each horizon-tal control station within the sheet limits that wasused during the survey and all hydrographic posi-tions that portray the sounding line system. Elec-tronic position lattices are also shown provided thelines can be drawn without obscuring position dotsand numbers. Otherwise, control stations and lat-tices must be drafted on separate horizontal controloverlays. (See figures 7-6 and 7-7.)

Supplemental overlays are used for develop-ments, insets, and excess soundings that cannot beshown on a basic smooth sheet in a clear and un-congested manner

Following inspection and administrative ap-proval, a smooth sheet becomes the official perma-nent graphic record of a survey and is the principalauthority for hydrographic data to be charted.Smooth sheets are referred to frequently duringchart compilation; photographic copies are often fur-nished to surveyors, engineers, geologists, lawyers(for use in the courts), and others with interests inmarine surveys. Field sheets are usually discardedafter final administrative approval of smooth sheetsand Descriptive Reports.

7.2.1. Sheet Material

Specialty Company, Fiskeville, R.I.) or equivalent isapproved. The film is 0.0075 in thick, semitranspar-ent, and matte finished on both sides.

Overlays are constructed on 0.003-in-thickstable polyester drafting film that is semitransparentand matte finished on one side. Ageproof Polyfilm(manufactured by the Dietzgen Corporation, DesPlaines, III.) or equivalent is authorized for overlays.

7.2.2. Sheet Size and Layout

Smooth sheet sizes shall conform to thespecifications contained in section 1.2.4. Overlaysshould generally be the same size as the smoothsheets they accompany. Smooth sheet limits shouldconform closely to those shown on the approvedsheet layout (2.4) with respect to area coverage, ori-entation, and size. Field sheet limits usually arecompatible with smooth sheet limits. Small limitshifts shall be made as necessary to ensure sufficientmargins (7.2.3) and space for title blocks. Occasion-ally, original sheet layouts must be modified whenunforeseen factors are introduced during field opera-tions. Most of these factors and considerationsthereof are discussed in 7.2.3 and 7.2.4. Skewed pro-jections should be considered to avoid using ''dogears'' to show control stations beyond the sheet lim-its, and at other times when necessary for marginalrequirements.

HYDROGRAPHIC MANUAL

Dog-ear usage can usually be avoided bycareful planning when laying out the sheets. (See2.4.)

7.2.4. Insets and Subplans

Smooth plotting at scales larger than thoseplanned is generally confined to subplans as de-scribed in section 7.2.4.

7.2.3. Sheet Margins and Extensions

Where soundings are taken in small docksand along the sides and ends of small piers andwhere they are located by reference distances to oralong pier faces, enlarged plans (figure 7-7) shall beshown nearby with arrows pointing to the area onthe original scale plot. Such plans need not containa scale or be surrounded by a margin. Each plan

FIGURE 7–1.— Smooth sheet, dog ear or temporary extension

(JULY 4, 1976) 7-2

2. Publication of a chart at a scalelarger than the survey scale is not anticipated.

3. Hydrography has not revealed shoalsor submarine features that cannot be shown ade-quately at reduced scales, on subplans, or on over-lays.

When determining final smooth sheet sizesand limits of hydrography to be shown on eachsheet, remember that soundings and other hydro-graphic information are not to be plotted closer than7.5 cm (3 in) to the final cut edge of the sheet. Dataplotted near the edges may become obscured or de-stroyed because of repeated handling. Marginal areasmay also be needed for labeling projection line orelectronic control lattice values. Space for the sheettitle, about 15 by 20 cm (6 by 8 in), must be re-served. The exact placement of a tide block on asheet is not critical and is selected where most con-venient and attractive.

Although automated computation and ma-chine drafting has largely reduced the need to ploteach horizontal control station used to position avessel, extensions of smooth sheets to show controlstations beyond sheet limits must occasionally beused for manual position plotting and verification.(See 2.4.4.) When possible, oversize sheets should beused to include such control stations, then trimmedto a standard size following final inspection.

If an oversize sheet is impractical, controlstation may be plotted on "dog ears" that shouldnot extend more than about 15 cm (6 in) from theedge of the sheet. They are attached securely to a smooth sheet or a smooth position overlay by apply-ing strips of masking tape to the underside of thesheet.

When control stations necessary to manu-ally plot hydrographic positions lie beyond the sheetlimits, three fine-inked lines to each station aredrawn on the sheet. These lines should intersect atthe stations at geometrically strong angles andlengths so each station can be replotted accuratelyafter final trimming of a sheet or removing the dogear. Such leader lines shall be hand drafted to avoideffacing soundings and other hydrographic details.(See figure 7-1.) Each line must be annotated withthe station symbol, number, and name.

These are used to extend survey coverage ofsmooth sheets as necessary and to combine contem-porary small detached surveys of the same project.Small congested areas shall be shown at enlargedscales in subplans in otherwise blank spaces on thesmooth sheet. (See 6.3.4.1 and figure 7-2.) Scalesand extents of subplans must be large enough toshow the hydrography clearly and to include controlstations used.

Enlarged subplans, such as those made toinclude the water area of a small bay, cove, inlet, oranchorage area, shall be surrounded by a heavy mar-gin in black ink. Each subplan includes the scale,name of the water area, if any, and at least one la-beled meridian and parallel. Subplans are furtherdefined by enclosing the area with a fine dashed inkline, then drawing an arrow leading to the subplan.Details shown in enlarged subplans may be omittedfrom the original scale.

If a smooth sheet is plotted by hand, insetor subp1an scales can be conveniently enlarged byusing the original smooth sheet projection lines andchanging their values in the subplan area. Onsmooth sheets to be plotted by automated methods,projection lines must be omitted in the subplan area.A unique set of projection parameters for the sub-plan must be derived for a proper automated plot.

SMOOTH SHEET

FIGURE 7–2.— Subplan of a small cove on a smooth sheet

ceptions are discussed in the following sections.

7.2.5.2. LETTERING ORIENTATION. Sym-bols and lettering shall be aligned with parallels oflatitude so they can be read from the south to theextent practical. Where geographic names cannotbe lettered in an east-west direction, they shall bealigned at an angle or along a curve so they can beread from the south. (See 7.3.12.3.)

7.2.5. Drafting Standards

Regardless of the direction of the soundingline, sounding numerals are consistently orientednormal to an east-west projection line — except indeep-water areas where it may be necessary to plotthree- or four-digit soundings at an angle. On east-west lines where soundings are spaced very close-ly, two-digit soundings may be shown at an angleto the line to avoid congestion. In such cases, ori-entation of these soundings shall be as consistent aspossible and easily readable from the south. (Seefigure 7-3.)

Both vertical and slant-style lettering areused on smooth sheets. Vertical characters shall beused for:

2. Position numbers and soundings.

4. Projection line labels.

7-3 (JUNE 1, 1981)

shall show, in figures, the principal dimensions ofthe pier.

Approved smooth sheets are official gov-ernment documents retained permanently in theNational Ocean Survey archives. Standards of ac-curacy for smooth plotting and detailing, alongwith clarity and neatness of drafting, must reflectthe high standards of accuracy of the collecteddata. Manual drafting should not be artistic, butshall be neat, clearly legible, and in accordancewith the standards adopted for hydrographicsmooth sheets as specified in this chapter. Charac-ters drafted mechanically must be placed to avoidclutter and congestion insofar as possible.

7.2.5.1. CHARACTER OF LETTERING. Whenconstructing smooth sheets and supporting overlaysby automation methods, mechanical plotting capa-bilities shall be fully utilized to accomplish as muchof the lettering and symbol drafting as possible. Oth-erwise, on manually processed or automated smoothsheets, mechanical lettering sets or guides shall beused for lettering all signal names and numerals, butnot position numbers, soundings, bottom characteris-tics, buoy designations, and rock elevations. Gener-ally, descriptive notes and penciled geographicnames should be in freehand lettering. Geographicnames are entered on smooth sheets in ink using let-tering templates following approval of the list ofnames by the NOS Chief Geographer. (See 5.3.5(C)and 5.7.) See appendix B and the figures in this chap-ter for lettering character examples. Informationoriginating from the present hydrographic and topo-graphic surveys is generally shown in black ink—ex-

1. Names and descriptions of topograph-ic features that in general include all features abovethe high water line (or above low water datum inthe Great Lakes).

3. Control station and signal names andnumbers.

5. Title block in formation.

HYDROGRAPHIC MANUAL

FIGURE 7–3.—Three- and four-digit soundings plotted at an angle

Slant-style characters shall be used for:

4. Bottom characteristics.

7.2.6. Drafting Materials

As a rule, station designations should notbe placed in water areas, particularly along ruggedcoast lines; but if such location cannot be avoided,relatively unimportant soundings in generally flat

Special inks are needed for modern plasticdrafting films; ordinary waterproof drawing inks willnot bond. Most commercial inks are unsatisfactory

7-4(JUNE 1, 1981)

1. Names of hydrographic features; ingeneral, all features below mean high water (or be-low low water datum in the Great Lakes); and re-lated descriptive notes.

2. Elevations of bare rocks, rocks awash,piling, and other similar objects.

3. Official names and designations of allaids to navigation.

7.2.5.3 PLACEMENT OF LETTERING. For an-notations, lettering shall be placed on smooth sheetsin such a manner that there can be no doubt as tothe item or feature it describes. Control stationnames, dates of establishment, identification num-bers, and most other descriptive annotations areplaced in the land areas if possible to ensure optimalclarity of hydrographic detail. (See also 4.2.5.)Where practical, annotations should be separatedfrom feature symbols by the space of one letter, andbe either on line with the symbol or placed as a sub-script. Where an identification or annotation mustbe placed so that doubt could arise as to its refer-ence, a fine inked arrow or leader, in the same coloras the name, must be drawn to the symbol. Exten-sive usage of offset names, descriptions, and designa-tions is undesirable and should be avoided.

areas may be omitted to allow space. Where roomexists for only a hydrographic signal number, thenumber may be placed there provided the com-plete station designation is shown on a nearby un-used portion of the sheet.

Where hydrographic detail is too congest-ed to permit normal station identification, a capitalletter (A, B, C, . . .AA, BA, CA, . . .— omit I andO.) may be used to reference the full station nameor number with a reference placed in an unusedpart of the sheet. Arrows can be used to offsetnumbers and descriptions provided they are nottoo long and do not cross congested hydrography.Arrows and leader lines should be broken whencrossing a sounding.

7.2.6.1. SELECTION AND USE OF INK.Selecting and applying proper inks during smoothsheet drafting are important and require judgmentand experience. Ink quality is critical because im-proper inks result in faint, nonphotographic, or wa-tery detail that usually becomes illegible with age.Bottles of coagulated or otherwise aged inksshould be discarded. Waterproof drawing inks aremost often used on paper drafting surfaces;pigmented inks, when used, must be stirred orshaken to homogeneous consistency. When colorintensity becomes weak, use new ink. Green ink isespecially perishable and deteriorates rapidly.

SMOOTH SHEET

ing surface, and lines from such pencils are oftentoo dim to allow sharp clear reproduction. Softpencil points become blunt quickly and often re-sult in smearing the plotting surface with a layerof graphite that inhibits proper penetration of ink.Inked soundings deteriorate rapidly on graphite-coated sheets.

Types of pencils used on mylar smoothsheets for geographic names, junction notations,unverified high water lines, and similar detailsvary with the individual. Those with a heavyhand should use a 3H or 4H pencil as lightly aspossible — those with a light hand can use up to a6H. Care should be taken to keep pencil pointssharp to maintain fine narrow lines applying as lit-tle graphite as possible. Pencil lines should neverbe drawn so firmly that permanent indentationsare made on the paper or drafting film; such in-dentations may result in damage to the graineddrafting surface and in tears or ruptures of thesheet.

7.2.7. Drafting Instruments and Plotters

7.3. CARTOGRAPHIC SPECIFICATIONSAND CONVENTIONS

The following sections contain specifica-tions and conventions for the cartographic repre-sentation of data on smooth sheets. See also appen-dix B, ''Hydrographic Sheet Cartographic Codesand Symbols,'' for additional details.

7.3.1. Projection

The polyconic projection shall be used forall smooth sheets unless a different projection is au-thorized by the project instructions for special sur-veys. Projections are machine drafted at the MarineCenters as an integral part of the verification andsmooth plotting process. Projections shall be shownby (1) black tick marks connected by fine blue linesor (2) continuous lines fine enough so that soundingswill not be obscured. See sections 1.2.2 and 4.2.6for additional details and projection line spac-

7.2.6.2. SELECTION AND USE OF PENCILS.Proper drawing pencils are essential for gooddrafting. Pencils that are too hard can mar the draft-

7-5 (JUNE 1, 1981)

because of their tendency to ''bleed'' after an inkfixative has been applied; but Pelikan Drawing Ink,"Special Shades, 50 Series'' (manufactured by Gun-ther Wagner, Germany, and distributed by Koh-i-noor Rapidograph, Inc., Bloomsbury, N.J.) hasproven satisfactory and should be used.

Special pressurized ball-point pens are ap-proved for machine-drafted detail on overlays pro-vided the information is sufficiently dense and darkfor easy sheet reproduction.

Standard characters for inked lettering arespecified in appendix B. Freehand and mechanicalpens shall be carefully selected and used to con-form with these standards insofar as possible. Expe-rienced draftsmen are familiar with the varioustypes of pens available and acquire proficiencywith a selected few. Less-experienced draftsmenshould experiment with different types of pens andpractice lettering until able to produce acceptablework. Quality of ink work may be improved bytesting a variety of pens, selecting the best, thengently smoothing, rounding, or sharpening the nibswith fine crocus cloth or oilstone as necessary. Aset of pens for each of the various colors should beused to avoid blending of colors.

Erasures on drafting film may be accom-plished by careful use of plain water or a liquid de-tergent into which a cotton swab, soft rubber eras-er (small areas), or an abrasive tissue (large areas)has been immersed. Hard abrasive erasers mustnever be used on any drafting surface.

When a sheet has been completed, a fixativemust be applied to the inked surface to assure a perma-nent bond of the ink to the drafting film and preventloss of hydrographic data. Krylon Workable FixativeSpray Coating, No. 1306 (manufactured by the Bor-den Company, Columbus, Ohio) or equivalent is ap-proved for this purpose. The room must be well venti-lated while spraying the fixative and a protectivemask worn over both mouth and nose. Filter masknumber 3500 (manufactured by the 3M Company, StPaul, Minn.) or equivalent is recommended.

If an erasure must be made after spraying, asmall amount of water or additional fixative appliedlightly with an eraser, then wiped off before drying,usually removes the original coat of fixative to permitcorrections. Ink applied to a fixative-coated surfacemust be protected by additional spraying.

All instruments used to plot, verify, and re-view positions of hydrographic data shall bechecked periodically for accuracy; such instru-ments must be kept clean and in excellent repairand calibration. Poorly maintained or unadjustedinstruments can result in serious inaccuracies of thesmooth plot. Particular care must be given whenusing and checking plastic protractors since theyhave a tendency to warp. (See A.9.1.)

HYDROGRAPHIC MANUAL

Procedures for constructing projections bymanual methods are described in the U.S. Coast andGeodetic Survey (1935) Special Publication No. 5,''Tables for a Polyconic Projection of Maps andLengths of Terrestrial Arcs of Meridians and Paral-lels, Based Upon Clarke's Reference Spheroid of1866.''

Nonrecoverable supplemental stations, lo-cated for temporary use during the survey, aresymbolized by red circles 3.0 mm in diameter; sta-tion numbers and names or designations are shownin red ink.

7.3.2. Electronic Positioning Lattices

Hydrographic control stations located bysextant three-point fixes or intersecting sextant cutsare symbolized by blue circles 3.0 mm in diameterwith the station number in blue.7.3.3. Control Stations

7.3.4. Shoreline and Topographic Details

7.3.3.1. BASIC CONTROL STATIONS. Eachgeodetic control station of second-order or betteraccuracy is symbolized by a red equilateral triangle,4.5 mm on a side, with the base leg parallel to thelines of latitude. Station names, years of establish-

(JUNE 1, 1981) 7-6

ing requirements. Labels for meridians and parallelsare placed in the sheet margins beyond the limits ofhydrography.

When specifically required by NOS Head-quarters, electronic control lattices shall be draftedfor appropriate areas of coverage on the smoothposition overlay that accompanies the smoothsheet. (See 4.2.6 and 6.3.3.) Multiple horizontalcontrol overlays (6.3.2) should be used (1) to showlattices for complex control schemes or (2) whenthe lattice lines cause undue congestion on thesmooth position overlay. Distinctive contrastingcolors should be used. Orange and yellow are to beavoided. Lattice lines are spaced at intervals be-tween 7.5 and 10 cm and are shown by unbrokenlines in ink not more than 0.2 mm wide.

Lattice labels must reference their sourcecontrol station(s) by station number. (See 4.2.6.)Lattice points of origin that lie within sheet limitsshall be symbolized by the appropriate station sym-bol and a 5 mm diameter circle. (See appendix B.)Distance, lane, or time intervals represented byeach arc are shown in ink in their correspondingarc color using numerals about 2.5 to 3.0 mm high.When possible, these intervals are positioned inotherwise blank areas of the sheet.

All horizontal control stations within thesheet limits that were used for the survey shall beplotted and shown by the appropriate symbol usinga line width less than 0.5 mm. Station annotationletters and numerals shall be approximately 3 mmhigh and in the same color as the station symbol.Actual positions of stations are shown as fine inkeddots (penciled dots on manual plots) or small tickmarks centered in the corresponding symbol. Seechapter 3 for control station designations.

ment, and identification numbers are also shown inred ink.

7.3.3.2. SUPPLEMENTAL CONTROL STA-TIONS. Recoverable supplemental control stations(3.1.2) of third-order accuracy, for which descrip-tions have been prepared, are symbolized by a redtriangle and annotated according to section 7.3.3.1.

7.3.3.3. HYDROGRAPHIC CONTROL STA-TIONS. These have been located using less thanthird-order accuracy methods (3.1.3) (e.g., stadiatraverse, identification on aerial photographs, planetable, or unconventional methods). Such stationsare generally temporary and unmarked; they areused only for expedience during the hydrographicsurvey. Photo-hydro stations and other stations lo-cated by less than third-order conventional surveymethods are shown by the same red circle symboland annotation used for unrecoverable supplemen-tal stations as specified in section 7.3.3.2.

Stations may be established during theprogress of hydrography by transferring directly tothe field sheet a point identified on an aerial photo-graph. Unless subsequently located by more accu-rate methods, such points are symbolized by agreen circle 3.0 mm in diameter with the stationidentification number in green ink.

These details in the nearshore and waterareas shall be carefully traced or transferred to thesmooth sheet from the shoreline manuscript for all in-shore hydrographic surveys. Generally, topographyis not shown on offshore sheets, particularly wherescale differences are involved. As a general rule, onlycontemporary photogrammetric or registered plane-table surveys are used for delineation of shoreline.Only class-I manuscripts shall be used when transfer-ring shoreline and topographic details from photo-grammetric compilations. (See 3.2.) Copies ofsmooth sheets are frequently furnished to individualsunaware that the hydrographic survey is not thesource document for shoreline location; therefore,

SMOOTH SHEET

that section is shown in red ink. (See 3.2.5 and4.5.8.) Revised shoreline is shown by a continuousline 0.4 mm wide if located by acceptable field meth-ods. [See National Ocean Survey (1974) ''Provisionalphotogrammetry Instructions for Field Edit Sur-veys.''] Otherwise, shoreline is shown by a dashedline.

the transfer of shoreline from a photogrammetricmanuscript to a smooth sheet must be done accurate-ly.

Generally, shoreline is not shown beyond thelimits of a survey. Although extended or flankingshorelines are sometimes shown for reference, exces-sive work on a large amount of unrelated shoreline isunwarranted; under no circumstances shall featuresbe drafted that are offshore from the shoreline be-yond the limits of the survey.The shoreline is never generalized or

smoothed on hydrographic sheets. Topographic de-tail shall never obscure a control station point. (Seefigure 7–4.) Minor details usually can be omittedwithin the station symbol; when necessary, use an ex-tremely fine line to delineate important features with-in symbols. Shapes of islets must be shown accurate-ly except in areas where slight distortions arepermitted to prevent misinterpretation as zero sound-ings.

7.3.5. Low Water Lines

When a section of the shoreline is revisedduring hydrographic operations and supersedes aprior survey for reasons of natural change or error, A low water line delineated hydrographi-

FIGURE 7–4. — Correct and incorrect shoreline delineation on a smooth sheet

7-7 (JANUARY 1, 1979)

The shoreline, as defined for the project area(1.6.1) shall be shown with a solid black inked lineabout 0.4 mm wide. Apparent shoreline in marsh,swamp, or mangrove areas is shown by black inkedlines 0.2 mm wide. Sections of shoreline shown asdashed or broken lines on class-I shoreline mapsshall be left in pencil until the survey has been veri-fied in its entirety. When verification has been com-pleted, such shorelines are shown in ink by the ap-propriate symbol.

The low water line is the intersection of theland with the water surface when the water is at theelevation of the datum of reference prescribed for thearea. (See 1.6.1.) Low water lines may also be con-sidered as contours of zero depth. In ocean areas,these lines are often determined photogrammetricallyfrom tide-coordinated infrared aerial photography.Low water lines located by this method are inked inblack as dotted lines on smooth sheets.

HYDROGRAPHIC MANUAL

Low water datum lines are shown only whenfeasible on hydrographic surveys of the Great Lakes.

7.3.6. Limit Lines

Do not show zero soundings inside ledge orreef symbols where they may be mistaken for barerocks or islets. Such soundings should be deleted andremoved from the records.

7.3.7.2. CORAL. This feature is found as areef fringing the shore, as an atoll, or as a detachedcoral ''head'' or a pinnacle (usually submerged). Acoral reef awash or uncovering at the soundingdatum is represented by the reef symbol with the leg-end ''coral.'' Where all ledges and reefs are composedof coral, only a general note to that effect need beentered on the sheet. Pinnacles and small patches ofcoral are represented by rock symbols with the ab-breviation ''Co'' or the legend ''coral.''

Similarly, limits of other danger areas dis-covered during the hydrographic survey shall be de-fined by dashed lines and identifying notes; these areto be inked in black. Such areas usually cannot besounded because of high-risk factors. (See 4.3.3.)

7.3.7.3. BARE ROCKS. These extend abovethe datum of mean high water in tidal areas and mayextend above low water datum in the Great Lakeswhere the shoreline is determined by the water levelat the time of the topographic survey. Rocks with el-evations of 1.6 ft or more above mean high water onthe Atlantic Ocean or Gulf of Mexico Coasts, 2.6 ftor more above mean high water on the Pacific OceanCoast, or 4.3 ft or more above low water datum inthe Great Lakes shall be shown as bare rocks. Actualsizes and shapes of rocks should be shown, if possi-ble, at the scale of the survey. If not, small singlerocks are exaggerated in size and shown on thesmooth sheet with an open center. Where clusters ofbare rocks are shown by dots on photogrammetricmanuscripts, use one or more open center symbols asnecessary. The bare rock symbol is never overlappedby rock awash or submerged rock symbols. Barerock elevations in tidal areas are referenced to thedatum of mean high water; in the Great Lakes, suchelevations are referenced to low water datum. (Seefigures B-1 through B-3 in appendix B.)

7.3.7. Hydrographic Features

Appendix B, ''Cartographic Codes and Sym-bols,'' contains the conventional symbols to be usedon smooth sheets to depict the hydrographic featuresdiscussed in the following sections.

Symbols for ledges and reefs transferredfrom shoreline manuscripts are not inked until the

7-8(JANUARY 1, 1979)

cally from sounding values is shown by a continuousorange inked line. When located by estimateddistances from a launch or by other approximatemethods, it is shown by a dashed orange line. Lowwater lines around steep rocky features such asaround ledge outcrops are usually represented by theledge or reef symbol. In some areas, however, anouter ledge limit may be far enough inshore of theactual low water line that the low water line shouldalso be shown. (See figure B-3 in appendix B.)

Dashed lines on photogrammetric manu-scripts that delineate approximate limits of featuressuch as channels, shoals, kelp, or foul areas are in-tended to serve as guides to the hydrographer andusually are superseded by hydrographic information.(See 4.2.7.) After the survey has been smooth plot-ted, such limit lines not superseded by hydrographicinformation are added in black ink as accepted dur-ing office verification. These dashed lines shall be ac-companied by an appropriate notation such as"shoal,'' ''foul,'' ''breakers,'' or ''kelp.''

7.3.7.1. LEDGES AND REEFS. Rock andcoral formations that uncover during some stage ofthe water level or tidal range are classified asledges and reefs. A ledge is a rock formation con-necting and fringing the shore of an island or larg-er landmass; it is generally characterized by a steepshear in the submarine topography. A reef is arocky or coral formation dangerous to surface navi-gation. Reefs may be above or below the datum ofreference. Rocky reefs are always detached from theshore; coral reefs may or may not be connectedwith the shore.

hydrographic survey has been smooth plotted and alldelineation discrepancies resolved. When transferringvery small isolated reef patches, substitute the rockawash symbol for the reef symbol; but where a clus-ter of closely grouped rock awash symbols extendover an appreciable area, use the reef symbol. Lowwater detail is not shown on smooth sheets in areasbeyond the limits of hydrography.

Along continuous stretches of ledge or reef,the ledge symbol shall be substituted for the zerodepth contour. Care should be taken not to extendsuch symbolization through intervening beacheswhere the symbol is not applicable and the zerodepth contour should be shown.

SMOOTH SHEET

7.3.7.4. ROCKS AWASH. In tidal areas, therock awash symbol (*) is used to portray rocks thatbecome exposed, or nearly so, between the datum ofreference (1.6.1) and mean high water. In the GreatLakes, the rock awash symbol is used for rocks thatare awash, or nearly so, at low water datum. Therock awash symbol shall be applied in accordancewith appendix B and the following:

Rock awash symbols are drawn with bold,neat pen strokes and must not be substantially re-duced in size even where there is a congestion ofother rocks or soundings. A symbol need not beshown for each rock in a closely grouped cluster ofrocks. The number of symbols should be reduced toavoid overlapping. When appropriate, use the reef orledge symbol.

7.3.7.7. SUBMERGED OBSTRUCTIONS. Allsubmerged obstructions found during a hydrographicsurvey shall be shown on the smooth sheet using theappropriate symbol listed in appendix B. If leastdepths could not be determined over unnaturalfeatures such as stubs or piles, ruins of piers andother structures, and wreckage of various kinds, thefeature is shown by a 1-mm circle or by a dashedoutline with appropriate annotation. If the nature ofan obstruction was not determined, the note ''obstr''shall be used. Dashed lines are used to indicate anextension below the high water datum of marine rail-ways, groins, breakwaters, sewer outfalls, or otherunnatural features rising above the bottom. All anno-tations shall be in slanted lettering.

7.3.7.5. ROCK ELEVATIONS. Heights ofrocks, coral heads, reefs, and ledges are referenced tolow water or high water datums as specified in sec-tions 7.3.7.3 and 7.3.7.4. Elevations above any datumare shown to the nearest whole foot; 0.5-ft values arerounded down to the lower value (i.e., a 2.5-ft eleva-tion is shown as 2 ft). Elevations are always shownclose to the feature in slanting figures enclosed in pa-rentheses. Elevations referenced to a low waterdatum are underlined as shown in appendix B. Ele-vations of bare rocks transferred from topographicsurveys or shoreline manuscripts are shown by redinked numerals about 2 mm high; elevations of simi-larly transferred rocks awash are shown in black ink.All elevations determined by hydrographic methodsshall be shown in black ink.

7.3.7.8. VISIBLE OBSTRUCTIONS. In waterareas, visible obstructions such as wrecks, piles,breakwaters, groins, fences, duck blinds, and fishhouses are generally located on photogrammetricmanuscripts—then transferred to smooth sheets iffield confirmation has been made. Such obstructionsare depicted by the distinctive symbols shown in ap-pendix B or, if necessary, by outlining the obstruct-

7-9 (JANUARY 1, 1979)

Atlantic Ocean Coast. When rock summitsare in the zone from less than 1.6 ft below mean lowwater to less than 1.6 ft above mean high water.

Gulf of Mexico Coast. When rock sum-mits are in the zone from less than 1.6 ft below GulfCoast Low Water Datum to less than 1.6 ft abovemean high water.

Pacific Ocean Coast. When rock summitsare in the zone from less than 2.6 ft below meanlower low water to less than 2.6 ft above mean highwater.

Great Lakes. When rock summits are inthe zone from 2.7 ft below to less than 4.3 ft abovelow water datum.

Rock elevations are placed within paren-theses beside the symbols as shown in figures B–1through B–3 in appendix B.

An elevation on a rock covered or exposed≤ 0.5 ft at the sounding datum is shown as an under-scored zero (0)—the notation ''awash at (appropriatedatum, MLW, MLLW, GCLWD, or LWD)'' may besubstituted to emphasize the existence of a dangerousisolated rock. The notation ''covered 1 ft MLW (2 ftMLLW on the Pacific Ocean Coast)" should be used ininland waters where such covered rocks are seldom ex-posed by rough water or during low tide. On outercoasts or in areas where a rock is frequently exposed atlow tide, the zero value or awash notation shall be used.

Where rocks are grouped closely, the eleva-tions of lesser importance should be omitted. The im-portant values are at the outermost edges of thegroup and on the highest rocks.

7.3.7.6. SUBMERGED ROCKS. These are cov-ered at the sounding datum and considered to be po-tentially dangerous to navigation. Rocks with summitsbelow the lower limit of the zone specified for rocksawash (7.3.7.4) are represented on the smooth sheet bysymbol only (+) or by soundings accompanied by thelegend ''Rk,'' depending on the information available.(See 4.7.) Where several least depths were obtainedover a submerged reef and the type of bottom was re-corded, the proper notation is the abbreviation ''rky''(indicating a rocky bottom). When a depth was notdetermined and the standard symbol used, the nota-tion ''breakers'' is shown if so noted in the records.

HYDROGRAPHIC MANUAL

less reported by the hydrographer to be visible at thesounding datum.

ing area with dashed lines. Annotations are to be invertical lettering for features rising above the shore-line datum for the area (1.6.1); otherwise, use slantedlettering.

7.3.7.11. BREAKERS, TIDE RIPS, AND ED-DIES. Breakers, whether offshore or alongshore,should be delineated by a dashed line in black inkwith the notation ''breakers.'' The intersection of di-rectional cuts taken to breakers over submergedrocks should be indicated by the appropriate rocksymbol.

7.3.7.9. WRECKS. Stranded wrecks, wherepart of the hull uncovers at the sounding datum,are generally transferred to smooth sheets fromshoreline manuscripts, particularly when a wreck isprominent and close to the shoreline. The small cir-cle of the wreck symbol shown in appendix B isthe actual position of the wreck. Wrecks occurringafter aerial photography was obtained are normallylocated by detached positions or by reference to asounding line; they may be spotted approximatelyon field sheets. Large hulks should be outlined andlabeled accordingly if the scale of the survey per-mits.

Tide rips, which occur in conjunction withstrong currents, are usually encountered near shoalsor uneven bottom. Small areas of tide rips may beshown by legend. Approximate limits of extensivefeatures should be outlined with dashed lines and anappropriate descriptive note added. Tide rips may bequalified as heavy, moderate, or light. Current eddiesare shown by legend.

7.3.7.12. WIRE-DRAG HANGS, GROUND-INGS, AND CLEARANCES. Least depths over shoalsor obstructions determined by wire-drag examin-ations conducted as a part of a hydrographic surveyare shown on smooth sheets in green ink—providedthat the least depth determined by wire drag was lessthan the depth determined hydrographically. Addi-tional descriptive notes are entered on sheets in greenink as necessary with leaders and arrows used to in-dicate the proper area. Areas cleared, hangs, ground-ings, clearance depths, and other wire-drag data areshown on a separate overlay to accompany thesmooth sheet, or are included in the Descriptive Re-port.

7.3.7.10. MARINE GROWTH. Limits of kelpbeds and other forms of marine growth shown onshoreline manuscripts are frequently revised by hy-drographic survey data prior to being smooth plot-ted. If discrepancies between the two sources arise,the hydrographic determination shall take prece-dence. Areas of marine growth are shown in pencilon the smooth sheet until the survey has been veri-fied and the final limits accepted. Extensive areas ofgrowth inshore of the sounding lines are finally de-lineated by dashed lines in black ink and annotatedaccordingly (e.g., ''kelp''). When soundings are in-cluded in the growth area, the delineation line isnot shown; the kelp legend alone is used. Small de-tached areas of kelp, whether inshore or offshore,are shown by symbol only. Grassy areas are identi-fied by the abbreviation ''Grs'' or by the note''grass.''

When contemporary wire-drag surveys havebeen conducted by another survey party, all draghangs and groundings, but not clearances, are trans-ferred to the smooth sheet in green ink following ver-ification of both surveys. In such cases, a note mustbe entered on the sheet that identifies the wire-dragsurvey(s).

7.3.8. Soundings

Masses of free unattached kelp or otherfloating marine growth noted during the survey arenot shown. Marine growth recorded on the analogdepth record is not shown by symbol or legend un-

Sounding numerals shall be between 2.0 and2.5 mm high. At this size, legible photographic repro-ductions can be made at reduced scales. The cen-

7-10(JANUARY 1, 1979)

Sunken wrecks are covered at low water, butthe masts may uncover. In such cases, the notation"masts" accompanies the sunken wreck symbol.When a least depth over a sunken wreck has beenaccurately determined, the depth with the notation''wreck'' is shown instead of using the wreck symbol.Offshore sunken wrecks are normally located bywire-drag surveys—least depths, groundings, andhangs are transferred to the smooth sheet in greenink with appropriate notation after verification ofboth surveys.

These and related hydrographic detail need-ed to compile marine charts are the most importantobservations of a hydrographic survey. It is essentialthat the final corrected soundings plotted on thesmooth sheet be accurately and graphically displayedin a uniform conventional manner. (See figures 7–6and 7–7.)

SMOOTH SHEET

When conversions between fathoms and feetare necessary, use table 4–15. (See 4.9.9.)

Soundings are shown to the nearest 0.5 ft onsmooth sheets for which the soundings are in wholefeet in the following areas:

3. On both sides of the low water line.

Over smooth bottom, soundings can beplotted without congestion at the following intervals.

East-west lines:

North-south lines:

Soundings with decimals generally are spaced atslightly greater intervals on east-west lines.

Multiple-digit soundings should be shown atan angle to sounding lines when necessary to por-tray the bottom configuration adequately. In manycases, angled soundings provide an attractive alter-native to plotting a smooth sheet at a scale largerthan planned or to ''excessing'' an inordinate num-ber of soundings because of overlapping numerals.

The same ranges are applicable when plot-ting soundings in overlap areas between surveysplotted in fathoms that join surveys plotted in feet.In addition, fathoms and decimals are used in otherareas as necessary to define depth contours moreaccurately. When soundings are shown in 0.5-fm in-

7.3.8.3. SELECTION OF SOUNDINGS AND EX-CESSING. Soundings must be selected from the hy-drographic records to plot on smooth sheets. It can-

(JULY 4, 1976)7-11

ter of the sounding numeral, excluding decimals, isthe position of the sounding. Figures for the decimalpart of a depth shall not be larger than three-fourthsthe size of the whole sounding integer. For depths ofless than one whole sounding unit, decimal parts arealways preceded by a zero (e.g.,04).

7.3.8.1. SOUNDING UNITS AND ROUNDING.Smooth sheet sounding units for various areas anddepths are specified in section 1.5.5. Only onesounding unit may be used on a smooth sheet. Frac-tional parts of soundings are shown only in decimalform (e.g., 05).

1. Over critical points on navigablebars.

2. For controlling depths in dredged ornatural channels.

4. As necessary or desirable for betterdefinition of standard depth contours. (See figure7–5.)

When rounding soundings to 0.5-ft incre-ments, reduced decimal values from 0.3 to 0.7 ft areshown as 05-ft both positive and negative sound-ings. When rounding positive soundings to integralfeet, decimals less than 0.8 ft are disregarded; deci-mals of 0.8 to 0.9 ft are increased to the next wholeunit. When rounding minus soundings, decimals lessthan – 0.3 ft are disregarded and decimals from – 0.8 to – 0.9 ft are treated as – 1.0 ft. See table4–15 for a method used to round-off soundings.

When the smooth sheet unit is the fathom,negative soundings and soundings in depths lessthan 20 fm are shown in fathoms and tenths. Indepths greater than 20 fm, soundings are generallyrounded to integral fathoms; but where depths arecharted in feet over smooth bottom and gentleslopes, soundings shall be shown in fathoms andtenths to depths of 31 fm. In such areas, depths be-tween 31 and 101 fm are shown to the nearest 0.5fm.

tervals, decimals from 0.3 to 0.7 fm shall be plottedas 01–fm. When soundings are entered in integralfathoms, decimals less than 0.8 fm shall be disre-garded; 0.8 and 0.9 decimal values increase thesounding to the next whole number.

from 5 mm for single-digit numbers to7 mm for up to four-digit numbers.

Where the bottom is irregular, the spacingof soundings will also be irregular. Soundings mustbe shown at abrupt changes in the bottom slope andover peaks and deeps that characterize the bottomas irregular, undulating, ridged, or channeled.

7.3.8.2. SPACING OF PLOTTED SOUNDINGS.The spacing and density of soundings on smoothsheets shall be such that each depth contour is delin-eated adequately and the configuration of the bot-tom is fully revealed. Soundings should have beenobserved and recorded at intervals appropriate tothe scale of the survey, the configuration of the bot-tom, the speed of the sounding vessel, and the depthof water. (See 1.4.6 and 4.5.6.) Soundings in addi-tion to those taken at regular intervals must often bescaled from the analog depth records to portray allhydrographic features adequately. Smooth sheetsoundings are generally spaced uniformly, except asnoted in section 7.3.8.3.

5 mm for single-digit soundings;7 mm for two-digit soudings;

10 mm for three-digit soundings; and15 mm for four-digit soundings.

HYDROGRAPHIC MANUAL

7-12(JULY 4, 1976)

FIGURE 7–5.—(A) Use of 0.5ft soundings to smooth otherwise unnatural depth contours and to betterdelineate a natural continuous channel and (B) use of dashed contour lines (20 fm) over a flatbottom

SMOOTH SHEET

not be overemphasized that the proper selection ofsoundings is essential for a complete and accurateportrayal of the bottom configuration. Analog depthrecords must be referred to frequently to providethe verifier with a proper conception of the bottomprofile that must be reflected by the plotted sound-ings.

not contribute to the development of the area shallbe omitted.

7.3.9. Depth Curves

Realistically, every irregularity cannot berepresented at the scale of the smooth sheet—minorrelief and insignificant features in very irregular bot-tom generally must be disregarded. That significantpeaks and deeps be shown is, however, essential.Soundings to be inserted at uneven intervals mustnot be shown in small distorted numerals or thosethat run together and fail to identify individualsoundings. Under such conditions, slope soundingsmay be omitted if another sounding can be scaledfrom the analog depth records.

Because smooth sheets should reflect therelative density of hydrography, shoal and channeldevelopments, investigations, and crossline sound-ings should be evident on an initial cursory inspec-tion of the completed sheet.

Noncritical soundings from high-densitydevelopments and examinations and soundings thatwould obscure others (as in the case of line cross-ings) are nonessential and are shown on supplemen-tal overlays for excess soundings. (See section6.3.4.1.2 and figure 7–6.) Least depths and othersneeded to properly delineate depth curves and thebottom configuration must be shown on the smoothsheet.

When routine sounding lines overlap orcross, the shoaler soundings are plotted; however,consideration must be given to retaining the identityof a sounding line when selecting soundings. Thereshould be no hesitation about erasing previouslyplotted soundings as necessary—such deletionsshould not mar the smooth sheet surface or impairthe legibility of adjacent soundings.

Drafting aids such as French curves shallnot be used to ''smooth'' the drawn lines; the depthcurves should delineate a natural bottom configura-tion. From a cartographic viewpoint, minor irregu-larities in soundings should not be overemphasizedwhen drawing the depth curves. The two main rea-sons for overlooking minor irregularities are (1)when soundings are rounded to integral values, atenth of a unit change from 0.7 to 0.8 causes a fullunit change in the plotted sounding value and (2)

7-13 (JUNE 1, 1981)

7.3.9.1. STANDARD DEPTH CURVES. Thoselisted in table 4–5 shall be drawn on each smoothsheet. Depth curves (isobaths or lines of equaldepth) are comparable to topographic contours onland. Principles governing the delineation of topo-graphic contours are equally applicable when draw-ing depth curves. They generally shall be drawn toinclude soundings equal to and less than the curvevalue, but should be broken at soundings as neces-sary to avoid an unnatural bottom configuration.Depth curves are usually transferred to smoothsheets from preliminary sounding overlays (6.3.4)compiled during the verification phase. See section6.3.4.4 for a discussion of the conventions for draw-ing depth curves and see section 7.2.6.1 for the se-lection and use of inks for line work.

Depth curves are shown on smooth sheetsby inked lines approximately 0.4 mm wide in thecolors specified in table 4–5. Curves in congestedareas and on steep slopes should be about half thiswidth. Curve lines must not be drawn verticallyabove and below the numeral 1 or on a 45° align-ment with the left part of the numeral 4. Theyshould never overlap or cross a letter, numeral, orother symbol. Depth curves are broken into longdashes where not adequately defined by the sound-ings (e.g., extremely flat monotonous bottoms wherethe plotted soundings defy the drawing of a mean-ingful curve). See figure 7-5.

In some inshore areas, only short sections ofdepth curves can be drawn because of insufficientsoundings. Where inshore curves can be extendedwith reasonable certainty of position, they should becompleted to the extent determined by the hydrog-raphy. In comparatively shoal depths dangerous tonavigation, the cartographer normally will bias thecurves on the side of safety.

When photobathymetry is used to support ahydrographic survey, soundings and other detailsshall be transferred from photobathymetric overlaysto smooth sheets in red ink—except for depth curvesthat shall retain their prescribed colors. Identify thesource of this data on the smooth sheet with thenote ''Soundings in red from photobathymetry of (month and year) from T - (sheet number). "In areas of overlap, useful and significantsoundings shall be transferred; soundings that do

HYDROGRAPHIC MANUAL

in many areas, this line is a legal seawardboundary. Particular care must be taken whendelineating this line.

continuous minor undulations and irregularitiesalong depth curves detract from the desiredemphasis on more significant irregularities. Thesecriteria are difficult to describe and are best cited byillustration. (See figure 7–5.) On the other hand,generalization is desired to a point, but significantconfigurations of the bottom should not be maskedby injudicious smoothing.

7.3.10. Bottom Characteristics

All recorded bottom characteristics shall beshown on smooth sheets except when an excessivenumber have been recorded on pole or lead linesurveys. (See 4.7.) In the latter case, a selectionshould be made and all isolated rocky or hardbottom characteristics plotted. In important waterssuch as harbors and anchorages, the plottedcharacteristics should be adequate to define theapproximate limits of various types of bottom inthe area. On those surveys where bottom samplingdensity requirements have been reduced, bottomcharacteristics may be transferred (in color) from aprior survey following verification provided thegeneral depths in those areas have not changed.

Standard abbreviations for bottom character-istics have been adopted and are used on smoothsheets. Such abbreviations are entered in black inkusing slanted uppercase and lowercase letters asshown in appendix B. The capital letters should notexceed 2 mm in height. Bottom characteristics shouldbe placed reasonably close to and slightly below and tothe right of the pertinent soundings, provided there isspace. Otherwise, characteristics can be placed in aconvenient place nearby. When displacing a bottomcharacteristic, do not place the lettering where it doesnot represent the nature of the bottom unless thedisplacement is indicated by a leader and arrow. Thedescriptive note ''Rk'' should always adjoin leastdepths on submerged rocks when so identified in thesounding records.

When depth curves become congested onsteep slopes, only the shoalest and deepest curvesneed be shown; intermediate depth curves areomitted. The shoalest curves that emphasize hazardsto navigation and the deepest curves that definelimits of channels or passages are the mostimportant. Where pinnacles, rocks, or steep shoalsrise abruptly from much greater depths, one or moreof the deeper curves should be omitted for clarity.Where islands, shoals, or reefs rise abruptly frommuch greater depths and several of the shoalerdepth curves are very close to shorelines of theislands or edges of the reefs, the shoaler curves areomitted. To preclude redundancy, never draw depthcurves around rock or reef symbols unless thecurves can be justified by adjacent soundings that lieon both sides of the curves. The low water line orzero depth curve is an important foreshore feature;

7.3.11. Aids to Navigation

7.3.11.1. LANDMARKS AND NONFLOATINGAIDS TO NAVIGATION. Most landmarks that havebeen recommended by hydrographers and areapproved for charting (See 5.5) are plotted onsmooth sheets using the symbols listed in appendixB. Source position data may be the shorelinemanuscript, published geodetic position listings, orinclusions in the hydrographic records. Landmarksused to control hydrography or located by geodeticmethods are shown on smooth sheets by the controlstation symbol, not the landmark symbol. To showthat a control station is a landmark, enter theproper landmark name in black ink in parenthesesafter the station identifier. The word ''landmark'' isentered in parentheses below the station name—if

7-14(JUNE 1, 1981)

7.3.9.2. SELECTION OF DEPTH CURVES.Supplemental depth curves listed in table 4–6 shouldbe added as necessary in shallow waters where (1)there is a considerable horizontal distance betweenstandard depth curves or (2) where supplementaldepth curves provide better definition of submarinefeatures such as least depths, tops of shoals, and oth-erwise undefined channels and depressions. Deepersupplemental curves are added only when significantirregular configurations of the bottom warrant theiruse. Such applications are a matter of judgment. Toemphasize an important shoal sounding or other fea-ture that otherwise would not be delineated by thestandard or supplemental depth curves listed in tables4–5 and 4–6, draw additional depth curves as neces-sary using short dashes. Such additional depth curvesare shown in the same color specified for the nextshoaler curves provided that the additional line isonly one unit deeper (e.g., (1) if a shoal rises abruptlyto a least depth of 19 ft, a 19-ft curve is drawn with adashed line in the color specified for the 18-ft depthcurve or (2) a 101 fm depth curve may be drawn witha dashed line using the 10 fm curve color). Otherwise,additional necessary depth curves are inked as a solidbrown line.

SMOOTH SHEET

FIGURE 7–6. — Example one of a completed hydrographic smooth sheet. See also figure 7–7.

(JULY 4, 1976)7-15

SMOOTH SHEET

FIGURE 7–7. — Example two of a completed hydrographic smooth sheet. See also figure 7–6.

(JULY 4, 1976)7-17

SMOOTH SHEET

7.3.12. Miscellaneous Detail

Permanent aids established by individualsor nongovernment organizations that were notused to control hydrography are shown by a 1 mmdiameter circle and described as '' Priv marker,''whether or not maintained. Private semipermanent aids such as stakes, with or without baskets orkegs, along shallow channels are plotted as a 1-mmcircle and described as ''stake.''

The buoy symbol circle is the position of thebuoy. When plotting a mooring buoy, the lower cir-cle indicates its position. Soundings taken at theseaids, if important, are shown slightly lower and outof true position so not to overlap the symbol; suchsoundings may be excessed if they are unnecessaryfor bottom delineation. Each aid shall be identifiedby classification and number (e.g., N ''7 " or Bell "4''as shown in the examples in appendix B). Any dis-crepancy between charted or U.S. Coast Guard

7.3.12.4. DESCRIPTIVE NOTES. A variety ofdescriptive notes is required on each smooth sheet tofully identify, reference, and complete the survey data.(See figure 7-6.) Notes are shown in parentheses whenpreceded by a station name or other similar designa-tion. Notes shall be as brief as possible, sometimes

7-19 (JUNE 1, 1981)

known, the height of the landmark above groundand above high water is also shown in black ink inthese parentheses.

Objects recommended as landmarks but notused as signals, if not plotted on a shoreline manu-script, shall be plotted on the smooth sheet. Suchlandmarks are symbolized by a black circle 2 mmin diameter. Names of these landmarks and re-quired annotations are entered in black ink.

All nonfloating aids to navigation foundwithin the survey limits are shown on the smoothsheet. Most of these aids, which include both lightsand daybeacons , will have been located previouslyby photogrammetric methods or by conventionalground surveys of third-order accuracy or better,and may have been used as control stations for thehydrographic survey. (See 1.6.5.) Because positionsof new or relocated aids are often established duringhydrographic operations, copies of Form 76-40 filedby the hydrographer or field editor must be consult-ed. (See 5.5.) Each fixed aid in the survey area at thetime of the survey shall be shown by the appropriatecontrol station symbol or by the approved carto-graphic symbol (appendix B) when not located bygeodetic methods. If the name or designation of anaid as it appears in the U.S. Coast Guard Light Listis not included in the control station name, enter theLight List name in slanting red characters.

7.3.11.2. FLOATING AIDS TO NAVIGATION.All of these located by the hydrographer shall beshown on the smooth sheet. Floating aids shall beindicated by the appropriate aid symbol in theproper color. (See appendix B.)

Light List information, designation, description, orcharacteristic noted during the survey must be men-tioned in the Descriptive Report.

7.3.12.1. CABLES AND BRIDGES. Locationsand paths of overhead and submerged cables are nottransferred to smooth sheets from photogrammetricmanuscripts; however, terminal points such as tow-ers or signs that were used as signals must be plotted,identified, and described by suitable notes. (See fig-ures 7–6 and 7–7.) Cable and bridge clearances areshown on the smooth sheet only when measured inaccordance with section 4.5.14. When positions fortowers or signs are unavailable, the approximate in-shore ends of cables are shown by black dashed lineswith appropriate notes entered in land areas.

7.3.12.2. TIDE AND CURRENT STATIONS.Locations of tide, water level, and current stationsshall be shown on smooth sheets by blue circles 4mm in diameter, without a center dot, and labeledaccordingly. (See figure 7–6 and appendix B.) Loca-tions of oceanographic stations or plots of currentobservations are not shown.

7.3.12.3. GEOGRAPHIC NAMES. These areentered on smooth sheets lightly in pencil after thesoundings and other hydrographic data have beenverified and plotted. Each name must be placed so asto indicate clearly the feature designated. Geograph-ic names shall not obscure or otherwise confuse plot-ted soundings and related hydrographic data. Gener-ally, all names are placed landward of the shorelineon inshore survey sheets. Where names must be let-tered in water areas, particularly in congested areas,judicious placement and spacing of letters are neces-sary. Final selection, placement, and inking of geo-graphic names are done after review and approval ofthe names list by the NOS Chief Geographer. (See5.3.5(C) and 5.5.)

Since smooth sheets are the authority for thecharted names of all features seaward from the shore-line, extreme care must be used when spelling andplacing geographic names. Instructions for letteringnames are contained in section 7.2.5. Published chartsserve as excellent guides for placement of names andrelative size of lettering for various features.

HYDROGRAPHIC MANUAL

Junctions should be made with contemporarysurveys which comprise surveys of the same year, thepreceding year, or the following year. If no contempo-rary surveys are available in stable bottom areas orareas where no noticeable changes have occurred, ade-quate junctions usually can be completed with recentnoncontemporary surveys. These comprise surveysmore than 1 year older than the survey being pro-cessed.

7.3.12.6. SMOOTH SHEET IDENTIFICATIONBLOCK. Stamp No. 1A (figure 7–8) shall be applied onthe lower right-hand corner of each non-automatedsmooth sheet. Appropriate entries are made for thefield number, registry number, scale, horizontal datumof the sheet, and reference station and its latitude andlongitude. In the event geodetic control does not existfor the survey area and control is established by alter-nate methods, e.g., astronomically, the establishedcontrol (reference control station and geographic po-sition) will be so noted in the non-automated titleblock. It will also be indicated as to whether values areadjusted or unadjusted, and if unadjusted, to what geo-detic datum. An identification block is not required onsmooth sheets produced by automation.

HYDROGRAPHIC SMOOTH SHEETMachine plotted by

No. 1A

Reg no.Field no.

controlScale

Datum

Ref .stn.

m adj.Lat.

m unadj.Long.

FIGURE 7 – 8. — Rubber stamp 1A, smooth sheetidentification block

7-20(JUNE 1, 1981)

preceded by a station name or other similar designa-tion. Notes shall be as brief as possible, sometimesabbreviated, but always clear and specific. Letteringmay be in neat freehand and not larger than 1.8 mmfor most notes, except at landmarks where primarydescriptions are entered in capital letters 2.2 mmhigh. Differentiation between elevated and sub-merged features and the corresponding placement oflettering are discussed in section 7.2.5. Control sta-tions in water areas must be described. (See 4.2.5.)To avoid misinterpretation between bare rocks andpositions, do not place dots over the letter “ i ” or usethem as punctuation in water areas.

7.3.12.5. JUNCTIONS AND ADJOINING SUR-VEYS. A comparison shall be made with adjoiningsurveys to determine the completeness and relativeagreement of hydrography. When necessary, state-ments are entered by the verifier in the appropriateDescriptive Report concerning consistent disagree-ments between soundings, significant displacementsof depth contours, and inadequate survey coverage.Soundings and other hydrographic information gen-erally should not be transferred from adjoining sur-veys to smooth sheets except when needed to revealleast depths, to delineate depth contours, or to bettershow significant bottom configurations. If an adjoin-ing survey has not been completed or verified, pencilnotes are used to indicate junctional surveys untilsuch time as they can be inked.

Critical or significant soundings are trans-ferred from adjoining surveys—even if less importantsoundings plotted on the smooth sheet must be de-leted. Where there are unresolvable differences ingeneral depths in the junctional areas, the less-reliablesoundings are disregarded and a butt junctioneffected. The superseded area should be outlinedwith a dashed colored line and a label SUPERSED-ED BY H- (19 ) should be added. Thelabel on the superseding survey should be the normaljunctional designation.

If verification of the survey shows goodagreement, the notation “JOINS H-_____ (19 ) ” is placed in the junctional areas beyond thelimits of hydrography for that smooth sheet.

Prior surveys are those listed in the Verifier'sReport for comparison with the survey being pro-cessed. Usually overlapping surveys need be consid-ered under only one section of the Verifier's Report,either under JUNCTIONS or COMPARISONWITH PRIOR SURVEYS.

der. Blue and green should be avoided because theyphotograph poorly. In wire-drag areas, the colorgreen is reserved for transferring wire-drag soundings.Depth curves shall be drawn so there is a definite conti-nuity and agreement in overlap areas. Supplementaldepth curves shown on adjoining surveys, however,should not be transferred unless needed to delineatethe bottom configuration adequately.

Lettering for junctional notes shall be me-chanically drafted, approximately 2.5 mm high,slanted, and in colored ink. (See figure 7–6.) Differ-ent colors should be used to show junctional notesand critical soundings transferred from each consec-utive adjoining survey. Preferred ink colors are car-mine red, red violet, orange, and brown — in that or-

SMOOTH SHEET

NATIONAL OCEAN SURVEY

A. L. POWELL, Director

HYDROGRAPHIC SURVEY No. 9316

ALASKA

GLACIER BAY

TARR INLET

Date of Survey. . . July-August 1972

Scale . . . . . . . . . . . . . 1 : 20,000

Chief of Party. . . . George M. Poor

Surveyed by . . . . . Ship's Officers

SOUNDINGS IN FATHOMS AND TENTHSat Mean Lower Low Water

• FIGURE 7–9. — Title block of a non-automated hydrographic smooth sheet •

7-21 (JUNE 1, 1981)

HYDROGRAPHIC MANUAL

Titles for wire-drag surveys are similar, ex-cept that the words ''WIRE DRAG'' replace theword ''HYDROGRAPHIC'' in the third line of thetitle. (See figure 7–9.)

7.3.12.7. TITLE BLOCK. The information tobe entered in the title of a hydrographic smoothsheet is extracted from the Title Sheet in the De-scriptive Report. (See 5.3.2.) Approximate dimen-sions for the title block are a height of 6 in and awidth of 8 in. Survey data or notes shall not, underany circumstances, be shown inside the block. Onmost inshore surveys, there is adequate title space inland areas or in unsounded water areas. Offshoresheets must be laid out so there is sufficient space forthe title. No particular portion of a sheet is favoredover another for the title block.

SPECIAL PROJECTS AND FIELDEXAMINATIONS

7.4.

The primary purpose of special projects andfield examinations is to effect specific investigationsof reported shoals, wrecks, or obstructions whichconstitute a potential danger to navigation. Specialprojects may also include equipment evaluation, orother special investigations unrelated to the chartingprogram. Requirements for processing special proj-ect data will be spelled out in the project instruc-tions. Field examinations are conducted using thesame field procedures and office processing requiredfor conventional hydrographic or wire drag surveys.A brief Descriptive Report or Descriptive Letterthat provides the necessary details for the surveymust be prepared to accompany the sheet. Surveysheets of field examinations shall be cut or folded to8½ X 11 in. size and inserted into the DescriptiveReport.

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATIONNATIONAL OCEAN SURVEY RADM ALLEN L. POWELL , DIRECTOR

HYDROGRAPHIC SURVEY H-9810CALIFORNIA, SAN FRANCISCO BAY

OAKLAND TO RICHMONDFIELD SHEET: DA-10-1-79 PROJECT: OPR-L123

DATUM: HOR. NORTH AMERICAN DATUM OF 1927MEAN LOWER LOW WATERSNDG.

PROJECTION POLYCONIC W122 ° 19 'CENTRAL LONGITUDE 30",

SCALE 1 : 10000 SOUNDINGS IN FEET

SURVEYED BY NOAA SHIP DAVIDSONCDR C. W. HAYES CMDG.

MAR-APR 1979

VERIFIED BY S. H. OTSUBORADM C. K. TOWNSEND APPROVED BY Feb 12 1981

• FIGURE 7-10 — Title Block of Automated Hydrographic Smooth Sheet •

7-22(JUNE 1, 1981)

All titles manually drafted shall be in blackink— letter sizes and line widths are illustrated in fig-ure 7–9. Title lettering for automated smooth sheetsshall be as illustrated in figure 7–10. Titles shall beoriented with the bases parallel to the latitudinalprojection lines. The proper entry for the Director isthe name of the individual holding office at the timefield work was completed. Each Chief of Party in-volved in the sounding operations shall be listed. En-ter only months and years for the date of the survey.Use the general term ''Ship's Officers'' rather thannames of the individual hydrographers.

DIRECTOR PACIFIClCMARINE CENTER

8. FINAL INSPECTION AND APPROVAL

FINAL INSPECTION8.1.

Each Marine Center Director shall selectand maintain a hydrographic survey inspection team(HIT) to conduct a critical inspection of each com-pleted verified survey with regard to survey cover-age, delineation of depth contours, development ofcritical depths, cartographic symbolization, and veri-fication or disproval of charted data. The Verifica-tion Report is examined to ensure that all facts havebeen accurately and properly presented, that signifi-cant actions taken and procedures used during thesurvey verification were appropriate, and that rec-ommendations made by the verifier are logical andjustifiable. Survey records must be inspected forcompleteness and compliance with NOS require-ments. An Inspection Report shall be prepared thatexpresses the team's concurrence or disagreementwith the verifier's findings, actions, and recommen-dations. In addition, discrepancies and deficiencies inthe survey or survey data that were previouslyundetected must be included in the report. Adversefindings of the inspection team concerning verifica-tion procedures are sufficient justification to requireadditional processing before submitting a survey forfinal administrative approval.

Additional field work needed on a surveystated as deficient shall be scheduled by the Hydro-graphic Surveys Division in NOS Headquarters at theearliest opportunity — preferably before the projecthas been completed and the field unit leaves the area.

8.3. SHIPMENT OF RECORDS

The following records shall be transmittedwith each approved survey:

Although the members of a hydrographicsurvey inspection team may vary from time to timedepending on local circumstances, each team couldtypically include the chief of the processing unit, aseasoned verifier, and a person experienced in theoperational phases of hydrography. The team shouldneither be involved with the actual processing of asurvey nor be expected to do any further processing.Each member of an inspection team must sign the fi-nal Inspection Report.

2. Preliminary overlays used duringverification of the survey.

8.2 ADMINISTRATIVE APPROVAL

Following satisfactory final inspection, eachsmooth sheet and its accompanying overlays and re-ports shall be submitted to the appropriate MarineCenter Director for final approval of the survey. Thefinal approval statement and Marine Center Direc-tor's signature are placed on a separate sheet and in-serted as the last page of the Descriptive Report. TheMarine Center Director's signature is also requiredon the title block as shown in figure 7–10.

5. Smooth position and sounding listings.Raw hydrographic field data listings.Data listings corrected in the field.

6.7.

8-1 (JUNE 1, 1981)

Copies of the approved Verification Reportand Inspection Report will be furnished to the fieldsurvey unit, the Chief of Party, and other key per-sonnel who participated in the survey.

Following final approval of a survey at theMarine Center, all survey records, the smoothsheet, and the accompanying overlays and reportsshall be sent by registered mail to the Hydrograph-ic Surveys Division, OA/C353. Certified mailshould not be used when forwarding survey re-cords. Original records must be packaged andmailed on a staggered schedule as a safeguardagainst losing an entire survey. Mailing proceduresshould be established that will provide a capacityfor survey reconstruction if a shipment is lost inthe mails. Computations and processed data listingsshould not be packaged with original field records.

1. The smooth sheet, smooth positionoverlay, and other overlays as necessary — these areto be sent only in the special containers providedfor this purpose.

3. The original copy of the DescriptiveReport and appended Verification Report, Inspec-tion Report, and statement of final approval.

4. The field sheet(s) and accompanyingoverlays.

8. Sounding Volumes or equivalent doc-uments used to record field observations.

9. Analog position and depth records (tobe filed and identified by day in accordion type fold-ers).

HYDROGRAPHIC MANUAL

11. Magnetic tapes containing the sur-vey data in prescribed transmittal digital formats

8-2(JUNE 1, 1981)

10. A stable base copy of the shorelinemanuscript used to locate hydrographic signals anddelineate shoreline and the reference datum line.

12. Other information or documentsneeded for a thorough understanding of the survey,such as the contemporary nautical chart that wasused for chart comparison.

PART THREE

Appendixes

A. EQUIPMENT AND INSTRUMENTS

A.1. INTRODUCTION

This appendix, however, contains a morecomplete description of hydrographic equipmentand instrumentation not described adequately else-where. In addition, special NOS requirements oncalibration, maintenance, and operation that maynot be specified in the manufacturers' literature areincluded herein. Readers and users of the equip-ment described in the following sections are ur-gently requested to submit information on new pro-cedures of interest to the field at large, updatedinformation, and any corrections needed to keepthis appendix current.

A-1 (JUNE 1, 1981)

A complete description of the physicalcharacteristics, theory, operation, and maintenanceof each piece of modern equipment and instrumen-tation used by NOS for hydrographic surveying isconsiderably beyond the scope of this manual. Mostof the information contained herein has been con-densed and capsulized from various manufacturers'manuals, other publications, and in-house knowl-edge. References have been freely made to thesource material used, and proper credit has beengiven where appropriate. This information is, hope-fully, channeled toward the immediate needs of thehydrographer. It is the final responsibility of eachchief of party to acquire and maintain a complete

up-to-date set of the manufacturers' manuals neededfor a given survey. The Marine Centers and the Of-fice of Marine Operations are prepared to provideall necessary assistance in securing this information.

EQUIPMENT AND INSTRUMENTS

FIGURE AA–1.—NOAA Ship Davidson, a class-III hydrographic survey vessel

AA. HYDROGRAPHIC SURVEY VESSELS AA.2. Coastal Survey Vessels

AA.1. Major Survey Vessels

The complement of the ship is approxi-mately 70 officers and crew. Each major surveyvessel normally carries a variety of skiffs and smallboats for inshore hydrography and three or foursurvey launches. The Fairweather and similarNOAA survey ships are fully equipped to carryout automated surveys.

AA.3. Auxiliary and Minor Survey VesselsA wide variety of launches and small boats

AA-1 (JUNE 1, 1981)

Major survey ships operated by NOS arecapable of conducting detailed hydrographic sur-veys virtually anywhere in the world. For exam-ple, the NOAA Ship Fairweather (figure 1-1) gen-erally operates in the North Pacific Ocean. Theship has a length of 231 ft, a cruising speed of 13kn, a range of 7,000 nmi, and an endurance of 20days. The Fairweather is also capable of performinga limited range of oceanographic and meteorologi-cal operations.

These ships are smaller than the major ves-sels and are generally used for conducting hydro-graphic surveys in the coastal waters of the UnitedStates and possessions. Coastal ships such as theNOAA ship Davidson (figure AA-1) are also capa-ble of carrying out limited oceanographic and me-teorological observations. The Davidson has alength of 175 ft, a cruising speed of 12 kn, a rangeof 6,000 nmi, and an endurance of 17 days.

The complement of the Davidson and othercoastal survey ships is about 40 officers and crew.These vessels normally carry two survey launchesand several smaller boats for inshore hydrographyand other activities. All NOS operated coastal sur-vey vessels used for hydrographic surveys are fullyautomated for data acquisition and processing.

HYDROGRAPHIC MANUAL

FIGURE AA- 2.— NOAA launch 1257, a high-speed (20-kt) hydrographic survey vessel.

FIGURE AA- 3 - NOAA (Jensen) 29-ft hydrographic surveylaunch

are used to perform the field work necessary fornautical charting in inshore and shoal water re-gions. These vessels range from 59-ft high-speedlaunches (figure AA-2), 29-ft aluminum hull (Jen-sen) launch (figure AA-3), to 18-ft skiffs rigged forshoal water surveying (figure AA-4). Data acquisi-tion and processing capabilities vary from full auto-mation aboard 59-ft launches to fully manualrecording methods aboard the skiffs.FIGURE AA–4.— Skiff outfitted for shoal water surveying

AA-2(JUNE 1, 1981)

EQUIPMENT AND INSTRUMENTS

Although nominal accuracies of 1 nmi dur-ing daylight and 2 nmi at night have been claimed,recent NOS evaluations show that errors of 4 to 5nmi are not uncommon if published skywave cor-rections are used without adding additional correc-tions based on in-port readings in the operatingareas. Omega, therefore, is used only when andwhere more precise position fixing equipment isnot available. Special Omega corrections are fre-quently included in the weekly U.S. Coast GuardLocal Notice to Mariners.

LONG RANGE NAVIGATION SYSTEMS AB.1. Omega Navigation System

AB.

This system is an electronic position-fixingsystem developed by the U.S. Navy to meet the gen-eral requirements for continuous vessel and aircraftglobal navigation capability. Omega operates in thevery low frequency (vlf) range (10.2 kHz) and is ba-sically a phase difference measuring system; as such,it provides line-of-position information in terms oflanes. Although Omega is primarily used in the hy-perbolic mode, range-range operation is possibleprovided the proper calibration adjustments aremade. A cesium beam frequency standard is used foraccurate timing in the range-range mode. At Omegaoperating frequencies, the lanes on the base line areapproximately 8 nmi wide.

For a more thorough technical discussionof the Omega navigation system, the reader is re-ferred to Dutton's Navigation and Piloting (Dunlapand Shufeldt 1969) and Navigation Systems, a Sur-vey of Modern Electronic Aids (G. E. Beck 1971).

In addition to the basic 10.2 kHz frequen-cy transmission, Omega stations transmit signals at11.33 and 13.6 kHz. A third frequency, 3.4 kHz,can be derived by taking the difference between13.6- and 10.2-kHz observations. This frequencydifference generates an additional family of hyper-bolic lanes that are about 24 nmi wide along thebase line.

Although six Omega stations locatedthroughout the world will provide complete globalnavigation coverage, eight stations have beenestablished to generate check position lines and tomaintain full coverage in the event of a base stationfailure or erratic operation.

A number of electronic firms currentlymanufacture Omega receiving systems. Dependingupon the manufacturer, certain of these compo-nents may be integrated. The hydrographer mustrefer to the manufacturer's manual for specific de-tails concerning his receiver— its use, calibration,and troubleshooting procedures.

A minimum of two lines of position are re-quired for a position fix. Wherever possible, one ormore additional lines of position should be plotted asa check. When possible, the use of transmission pathsalong which sunrise is occurring should be avoidedas these are the times for which the predicted propa-gation (skywave) corrections are least accurate.

AB-1 (JUNE 1, 1981)

Omega's very low frequency long-wavetransmissions reflect off the ionosphere and, there-fore, can be received by vessels at much greaterdistances from the base stations than signals ofshorter wave lengths. This capability is Omega'sprincipal advantage over most other electroniccontrol systems; however, in Omega's strength alsolies its weakness. Since skywaves (reflected fromthe ionosphere) rather than groundwaves provideline-of-position data, corrections must be applied tothe observed electronic values. Published skywavecorrections are predictions based on known proper-ties of the ionosphere. Because meteorological con-ditions and solar activities cause significant distur-bances in the normal behavior of the ionosphere,the predicted correction values can be inaccurate.Real-time methods of determining skywave correc-tion values are being developed, as are similar sys-tems such as Differential Omega and Micro Omegain an effort to enhance the navigational accuracy.

AB.1.1. EQUIPMENT. Another advantage ofOmega navigation is the comparatively low cost ofthe receiving and peripheral shipboard equipment. Atypical Omega installation (figure AB-2) is com-posed of the following basic components: receiverand synthesizer, gating unit and comparator, lanecounter, chart recorder (graphic record of lanechanges), whip antenna, power supply with batterypack, and cesium beam frequency standard forrange-range (rho-rho) operations.

AB.1.2. OPERATION. The Defense MappingAgency/Hydrographic/Topographic Center, Wash-ington, D.C. 20315, publishes charts showing Omegahyperbolic line-of-position lattices and skywave cor-rection tables for most areas. Use and application ofthe published charts and skywave correction tablesare straightforward. Ocean survey sheets (OSS se-ries, section 4.13. 1.) showing Omega lattices are pre-pared at NOS Headquarters for surveys controlledby this system.

HYDROGRAPHIC MANUAL

FIG

UR

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B-1

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OR

AN

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nav

igat

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cove

rage

dia

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the

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map

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Age

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S.D

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Was

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AB-2(JUNE 1, 1981)

EQUIPMENT AND INSTRUMENTS

FIGURE AB–2. — Omega shipboard navigation unit (courtesyof Tracor, Inc., Austin, Texas)

LORAN-C uses 8 chains (31 transmitters)with base lines varying from 500 to 800 nmi inlength. Although the system is usually operated inthe hyperbolic mode, range-range positioning canbe available provided that a frequency standard isused as the basic timing unit. (See U.S. CoastGuard (1974) ''LORAN-C User Handbook,'' Publi-cation CG-462.)

AB.2. LORAN Navigation System

AB-3 (JUNE 1, 1981)

Line-of-position readout may also be noisy whenelectrical storms are occurring near the vessel. Toobserve a line of position, assuming the equipment isoperating properly and the switches are properly setfor the appropriate hyperbolic or range-range mode,the hydrographer simply reads the lanes and frac-tional lanes from the lane counter and applies theskywave correction values for the readings observed,the time of observation, and the dead-reckoned posi-tion of the vessel. The corrected line of position isthen plotted directly on the hydrographic chart.

Time synchronization is essential for properperformance of an Omega shipboard receiver. If thegating unit is set and adjusted properly, it shouldmaintain synchronization indefinitely. A batterypack should accompany each Omega power supplyto avoid losing time synchronization during inter-mittent power fluctuations aboard ship. A system isin synchronization when the beginning of the trans-mitted aural tone from each station and keying ofthe gating unit light occur at the same time. Shouldsynchronization be lost, it must be restored by fol-lowing the procedures recommended in the manu-facturer's manuals. After a loss in synchronization,lane counters may also require resetting.

Values on Omega lane counters must beverified at frequent intervals. Lane values are veri-fied by monitoring the chart recorder and annotat-ing the graphic record–a relatively simple task be-cause the lanes are approximately 8 nmi wide.Hydrographers must be continually aware of thestrength of the fix–a function of line-of-positionintersection angle and lane expansion effects whenreceivers are operated in the hyperbolic mode. (See4.4.3.) Switching base station arrays is easily doneon the Omega comparator; however, the wholelane count values for new stations must be knownto reset the lane counter properly.

Every opportunity should be taken tocheck Omega position fixes independently. Fixesby satellite navigation systems or by other similarmethods are useful for determining systematic biasin Omega positions. Land ties shall always be madewhen possible. (See 4.13.1.) When offshore (weath-er permitting), take astronomic sights in the morn-ing and in the evening. (See 4.13.1.1.) Accuratedead-reckoning records shall be maintained(4.13.1.2) for all surveys controlled by Omega.

This long-range (LORAN) hyperbolic nav-igation system is usable during favorable conditions

at ranges up to 3,000 nmi from transmitting basestations. LORAN-C has a far greater navigationrange and higher positional accuracy than its pre-decessor LORAN-A. LORAN-C effective naviga-tion coverage is not yet worldwide, but continuesto expand. (See figure AB-1.) LORAN-C simulta-neously employs the principles of both time differ-ence measurements and phase comparison measure-ments to enhance the accuracy of an observed lineof position.

HYDROGRAPHIC MANUAL

LORAN-C operates in the low frequencyrange (100 kHz), thus enabling a navigator or hy-drographer to determine line-of-position informa-tion from the reception of either groundwavestraveling along the surface of Earth or skywavesreflected from the ionosphere. Nominal accuracyclaims for LORAN-C are:

2. Skywave, from 3 to 5 nmi.

FIGURE AB-3. - LORAN-C shipboard navigation unit (courtesyof The International Navigation Co., Inc., Bedford,

Massachusetts)

bility to machine draft LORAN-C lattices on hydro-graphic sheets or on ocean survey sheets for use onoffshore surveys. If tabular data are used, the hydrog-rapher merely interpolates between listed rates andgeographic values to determine the line of positioncorresponding to the readings observed aboard thevessel. Corrections and additions to charted and tabu-lated LORAN-C data are issued regularly in the U.S.Coast Guard Local Notice to Mariners. Skywave cor-rection values are included with the tabulated data.

AB.2.1. EQUIPMENT. A number of electron-ics manufacturing companies are currently produc-ing a wide variety of LORAN-C navigation equip-ment. Available equipment varies from simplereceivers and indicators to fully automated receiverswith self-rate tracking capabilities that can beinterfaced with shipboard computing systems. Oneof the more typical units is shown in figure AB-3.

National Ocean Survey publishes nauticalcharts with LORAN-C line-of-position latticessuperimposed. The U.S. Navy prints LORAN-C ta-bles for computing latitudes and longitudes of LO-RAN-C observations if charts are not available. NOSHeadquarters in Rockville, Maryland, has the capa-

AB-4(JUNE 1, 1981)

1. Groundwave, from 0.25 to 1 nmiover short distances and 0.1% of the distance thewave traveled for greater ranges.

See section AB.1. and the references in ap-pendix D for more detailed technical discussions ofthe characteristics of LORAN and the uncertaintyand inaccuracies of predicted skywave correctionvalues. Lines of position based on skywaves shallnot be used if the survey vessel is 350 nmi or lessfrom transmitting stations. Groundwave coveragenormally extends to approximately 2,000 nmi fromthe base stations under relatively stable atmospher-ic conditions, but can be expected to decreasesharply during periods of high electrical noise andexternal interference.

To simplify operating procedures, mostmanufacturers have mechanized receivers so thatonly the first part of each transmitted pulse orgroundwave signal is used. Although such measureseliminate skywave contamination of fix data,skywave positioning at longer distances is curtailed.

AB.2.2. OPERATION. Operational usage andconstraints for LORAN-C are generally similar tothose of other low frequency long-range hyperbolicpositioning systems (See 4.4 3 and AB.1) where thebasic accuracy and strength of the fix is a function ofthe line-of-position intersection angle and divergenceof equivalent rates with distance from the base line.

As with any navigation or position-fixingsystem, the hydrographer must select lines of posi-tion that will provide the strongest fix. (See 4.4.3.)Lines of position determined from groundwave ob-servations are inherently more accurate thanskywave determinations and shall be used wheneverpossible. A minimum of three lines of position is de-sirable for a hydrographic fix, although four are pref-erable. LORAN-C groundwave position determina-tions are preferable to Omega observations.

When LORAN-C positioning is used forhydrographic surveys, every opportunity shall betaken to check the system accuracy by making shoreties. (See 4.10.1.) If skywave observations must beused for positioning the vessel, morning and eveningastronomic sights are taken in an effort to improvepositional accuracy. (See 4.13.1.1.) Accurate dead-reckoning records must be maintained. (See4.10.1.2.)

EQUIPMENT AND INSTRUMENTS

MEDIUM RANGE POSITION-FIXINGSYSTEMS

AC. Figure AC-1 shows a typical shipboard installationof Sea-Fix positioning equipment and data display;figure AC-2 shows a shore station installation. Seethe appropriate Decca manual for more compre-hensive descriptions of the equipment required tooperate a position-fixing chain.

AC.1. Decca Hi-Fix and Sea-Fix Systems

These medium range electronic position-fixing systems are designed for hydrographic sur-veys. Much of the following discussion has beenextracted from the Hi-Fix and Sea-Fix manualspublished by Decca Survey Systems, 8204Westglen, Houston, Texas 77042. These manualsand another publication entitled Hydrographic Sur-vey With Hi-Fix should be referred to as necessaryby each hydrographic field unit using either con-trol system.

The basic operating principle of the Hi-Fixand Sea-Fix systems is the generation and phase dif-ference measurement of a pair of stationary wavepatterns. An array of wave patterns is commonlycalled a ''lattice.'' Receivers carried by hydrographicvessels give a continuous indication of positionswith respect to the transmitting stations. If the posi-tions of the shore stations are known, data given bythe receiver can be transformed into geographic co-ordinates by computation or by reference to a mapor chart on which Hi-Fix or Sea-Fix lattice patternshave been plotted.

The systems are essentially the same; Sea-Fix is a newer modified version of Hi-Fix. Sea-Fixis generally considered more reliable under actualfield conditions because of the use of solid-statecomponents, and can be modified to operate atranges equal or greater than Hi-Fix capability.

Hyperbolic or circular patterns may begenerated depending upon which mode was

AC-1 (JUNE 1, 1981)

* FIGURE AC-1.-Decca Sea-Fix positioning system shipboard installation ( courtesy of Decca Survey Systems, Inc; *Houston, Texas)

HYDROGRAPHIC MANUAL

• FIGURE AC–2. — Decca Hi-Fix shore station (courtesy of Decca Survey Systems, Inc., Houston, Texas) •

is the ''base line extension.'' In hyperbolic lattices,the lines of position diverge with distance from thebase line causing an increase in lane widths and acorresponding reduction in positional accuracy.

AC.1.1. HI-FIX AND SEA-FIX CHAINS. BothHi-Fix and Sea-Fix chains require a minimum of threetransmitting stations to provide a unique position fix— one master station and two slave stations.

AC-2(JUNE 1, 1981)

selected to control the hydrographic survey. Thehyperbolic mode permits multivessel operationswhere many receivers can work on a time-sharingbasis from one set of shore stations; the range-range mode allows only one receiver to be used.

With the systems operating in a hyperbolicmode, each set of hyperbolas consists of lines repre-senting equal phase difference between the signalsreceived from two transmitting stations. These hy-perbolas form navigational position lines called''lanes.'' The intersection of a line of position fromone pattern with a line from the other at the ves-sel's receiver fixes the position. A hyperbolic lat-tice, therefore, needs at least two pairs oftransmitting stations to provide a fix. In practice,the one station common to both pairs is called the''master'' station; the other two stations are called"slaves.'' An imaginary line between the master andeach slave is the ''base line''; the extension of which

Where greater accuracies are required andline width expansion cannot be tolerated, Hi-Fixand similar position-fixing systems should be oper-ated in the range-range mode. When in the range-range mode, two patterns are generated as before—but the master station is aboard the vessel ratherthan ashore. The resulting lattice patterns becomeconcentric circles centered on each of the twoslave stations rather than hyperbolic.

EQUIPMENT AND INSTRUMENTS

Nominal transmission frequency ranges for Hi-Fixand Sea-Fix operations lie in the 1600- to 2100-kHzband.

When used in the hyperbolic mode, a masterdrive unit (MDU) signals a transmitter at the masterstation with trigger and master pulses. Each slavestation and vessel also receive these pulses. The ini-tial pulse activates the timing circuitry, and the sec-ond pulse locks each receiver to the phase and fre-quency of the master signal. When locked, a receiverstores the datum used for measurement of phase dif-ferences. Locking signals are transmitted about fivetimes each second to maintain phase lock with themaster station. The trigger pulse is relayed througheach slave station to the vessel receivers

In a two-range (range-range) system, themaster station is installed aboard the vessel togetherwith the receiver. The complement of equipment isidentical to that required when operating in the hy-perbolic mode. As a vessel maneuvers, the two

TABLE AC–1.— Characteristics of Hi-Fix and Sea-Fix Positioning Systems

Hi-Fix Sea-FixCharacteristic

Mode of operation Hyperbolic or range-range

1605-2000 kHz

Same

Pattern transmission 1600-2000 kHzfrequency

SameType of transmission Interrupted continuous wave, timemultiplex

Radiated power Approximately 40 W from 9.5-mvertical antenna

Approximately 100 W from9.5-m vertical antenna

Maximum operating Same160-320 km in temperate latitudesranges over water

paths

In tropical latitudes, this distance Samemay be reduced by 50% by ambientnoise levels.

Maximum receiver speed One lane per second Same

Power supply 22-28 V d.c.24 V d.c., positive ground;receiver requires 12-V centertap.

Readout accuracy 0.01 lane Same

• Claimed positional Hyperbolic: standard deviation of0.015 lane (i.e., approx 1 m)

Better than 1 m on theaccuracy base line under optimum

conditions

These figures represent long-term andshort-term repeatability over waterat the 65% probability level.

Over land, ground conductivity may beaffected by factors such as weather—a reading taken at any given timemay not be repeatable within theabove limits if significant groundconductivity changes occur.

• These accuracy figures do not rcflect the unknown, uncompensated systematic errors that maybe present in the observed line-of-position values

AC-3 (JUNE 1, 1981)

where phase differences between the signals are re-solved and displayed on lane counters for bothbase lines (pattern 1 and pattern 2). A series of con-stant phase differences results in a family of hyper-bolas—a value displayed aboard a vessel identifiesthe hyperbola on which the vessel lies. At any giv-en instant, a position fix can be determined by ob-serving the readings on both lane counters. Valuesare displayed to the nearest hundredth of a lane ona five-digit counter.

HYDROGRAPHIC MANUAL

base lines vary in length—phase differencesdisplayed aboard the vessel are now patterns of cir-cular lines of position radiating from each slave sta-tion. Fixes are displayed on the lane counters as be-fore. In range-range operation, however, lanecount increases with vessel distance from a slave;in the hyperbolic mode, lane numbers increasealong any azimuth with distance from the base line.

AC.1.2. SYSTEM CHARACTERISTICS. TableAC-1 contains a listing of various characteristics ofHi-Fix and Sea-Fix positioning systems as cited byDecca Survey Systems, Inc., Houston, Texas.

AC.2. Raydist System Raydist is designed so that frequency errors(and resulting ranging errors) caused by oscillatordrift are cancelled, provided that the frequency er-rors are small and the frequencies are centered on thenarrow band-pass curve of the NAVIGATOR unitreceiver filters. The filter band-pass is approximately20 Hz wide.

The Raydist DR-S Positioning System isa medium range all-weather radio location systemcapable of operating at distances greater than lineof sight between transmitting and receiving anten-nas. Basic principles of the theory of operation,usage, and geometric considerations for Raydist

AC-4(JUNE 1, 1981)

AC. 1.3. LANE INTEGRATION AND IDEN-TIFICATION. Hi-Fix and Sea-Fix receivers automati-cally provide the hydrographer with fractional lanereadings as the result of the phase difference mea-surement. Determination of the whole lane numberor count is not automatic. The geographic positionof the receiver antenna must be determined indepen-dently, then transformed analytically or graphicallyto lane system coordinates. Calibration proceduresand methods to resolve whole lane count are dis-cussed in section 4.4.3.3. Once the whole lane valuehas been determined and set manually in the patternlane counter, the equipment automatically countswhole lanes as they are crossed. If equipment mal-functions or other occurrences cause a lengthy lossof signal, the hydrographer may have to return to aknown reference point or otherwise determine hisposition to reset the whole lane value. ''Saw-toothrecorders'' should always be used because they pro-vide an analog record (See 4.8.6) of lane changes thatcan often be used to accurately reconstruct thewhole lane count when brief signal losses occur. Sig-nal stability is generally better with Sea-Fix thanwith Hi-Fix, provided that the receiver is properlyphase locked into the chain.

positioning are similar to those of Decca Hi-Fix asdescribed in the preceding sections. Much of thefollowing discussion was extracted from Raydistsystem manuals published by Teledyne Hastings-Raydist, Hampton, Virginia 23361. Technical man-uals that completely describe the system operationmust be aboard any vessel using Raydist.

The Raydist DR-S system operates in thehigh frequency radio band and is comparable inrange and accuracy with Hi-Fix and Sea-Fix. Theequipment is transistorized and reasonably porta-ble. Unlike Hi-Fix and Sea-Fix, Raydist can oper-ate with up to four-party users in the range-rangemode. Range-range operation is favored over hy-perbolic because of increased accuracy over abroader area of coverage. The Raydist ''T'' net,which uses two master stations and two relay sta-tions at crossed base lines to increase the area ofstrong geometric intersections, is not presentlyused by NOS survey vessels. Many of the varia-tions of these operational modes described in themanufacturer's manuals are seldom used by NOS.Raydist integrates well with the HYDROPLOTsystem and provides continuous encoded data tothe navigation interface.

As is the case with most other mediumrange positioning systems, the basic concept of theRaydist operating principle is measurement ofphase differences between the antennas at the fixedshore stations and aboard the hydrographic vessel.Raydist operates on continuous wave rather thanpulsed signals. Using the formulas cited in sections4.4.3.1 and 4.4.3.2, one can construct a lattice ofconcentric circles or hyperbolic lines of position(depending on the mode of operation) for locatingthe vessel. The discussion on lane widths and sta-tion geometry included in section AC.1 is also ap-plicable to the Raydist system.

EQUIPMENT AND INSTRUMENTS

Raydist lane integration and identificationprocedures are identical to those discussed forDecca Hi-Fix in section AC.1.3.

TABLE AC–2.— Ganeral characteristics of the RaydistDR–S Electronic Positioning System

DescriptionCharacteristic

AC.2.1. SYSTEM CHARACTERISTICS. Thegeneral characteristics of the Raydist DR–S Elec-tronic Positioning System are listed in table AC-2.

Range-range or hyperbolicMode of operation

1600-4000 kHz. (NOS fre-Operating frequenciesquencies are approx3300 kHz, resultinglane widths of 45 m.)

Range 200 nmi day, 150 nmi night

Continuous waveWave transmission

Radiated power 50 W from vertical antennaheight of one-quarter wavelength or less

25.5 V d.cPower supply

Readout resolution 0.01 lane

* 10 ft (3m)Positional accuracy

FIGURE AC–3.— Raydist positioning system vessel components, (left) navigator with position indicator and (right) track plotter(courtesy of Teledyne Hastings-Raydist, Hampton, Virginia)

AC-5 (JUNE 1, 1981)

AC.2.2. SYSTEM COMPONENTS. See figureAC-3 for a typical Raydist shipboard installation. TheNAVIGATOR, which is normally installed aboardthe survey vessel, continually measures and displaysthe position of the receiving antenna in terms of systemcoordinates. When Raydist is operated in the range-range mode, these coordinates are the ranges, in lanes,from the antenna to each of the fixed slave or relay sta-tions normally located ashore. Teledyne Hastings-Raydist literature designates the slave stations as ''red''and ''green'' for convenient reference. When operat-ing in the hyperbolic mode, the mobile transmitter islocated at the master or reference station ashore, andthe NAVIGATOR provides hyperbolic coordinates.Line-of-position data can be read from the phase me-ters to the nearest hundredth of a lane. In addition to di-rect readout capability, encoded signals can be made

• The 10-ft positional accuracy is cited for range-range operation by Hastings andComstock (1969). "Pinpoint Positioning of Surface Vessels Beyond Line-of-Sight"This value is a minimum theoretical limit probably not achievable on offshore surveyswhere it is impractical to calibrate with sufficient frequency to remove unknown sys-tematic errors in line of-position data

HYDROGRAPHIC MANUAL

available to a navigation interface unit for HYDRO-PLOT automated operations. Outputs are also pro-vided for driving a dual channel sawtooth recorderfor analog position data.

The mobile transmitter contains the refer-ence oscillator. The transmitter frequency is used tocalculate lane widths. The mobile transmitter gener-ates the reference that is relayed through the slave orrelay stations back to the NAVIGATOR. At theNAVIGATOR, the phase of the returning signals iscompared with the phase of the transmitted signal todetermine the relative position of the vessel antennawith respect to the shore stations.

FIGURE AC-4. - Raydist shore station installation, (courtesy ofTeledyne Hastings-Raydist, Hampton, Virginia)

Elaborate shielding methods must be resorted tofor protecting all electronic equipment from strayradio frequency fields. For these reasons, range-range operation should be limited to metal hulls ifpossible. Hyperbolic operations present no prob-lems in this area because only a receiver is usedaboard the vessel.

Power supplies must be selected carefullyfor the satisfactory operation of Raydist. Voltagerequirements for all system components is nominal-ly 25.5 V d.c. Standard procedures, when com-mercial power is available, are to use a regulatedpower supply capable of recharging the batteriesshould an extended power failure occur. The pow-er supply must be fully shielded from radio fre-quency interference that may be generated by theequipment. Such a shielding is especially importantat the shore relay stations where harmonics of thetransmitted signal are generated by the rectifiers inan unshielded power supply. These harmonics liewithin the band pass of the station receiver and

AC-6(JUNE 1, 1981)

Ideally, the antennas at each of the relay sta-tions and at the mobile transmitter must be one-quar-ter of a wavelength high (approximately 43 m) whenoperated in the range-range mode. As a practicalmatter during surveys at nominal ranges, antennas20-25 m high can be used ashore and a 12-m fiber-glass whip antenna used aboard the vessel. Antennasas low as 13 m have been used successfully at theshore stations for very short range operations. WhenRaydist is operated in the hyperbolic mode, a small"voltage probe'' type of antenna about 55 cm highcan be used aboard the vessel, although a 12-m fiber-glass whip antenna, if already aboard, will suffice.Antenna heights at the master station and two slavestations vary from 13 to 43 m depending on the oper-ational ranges. A ground plane of 24 radials, equal inlength to the antenna height, must be constructed ateach shore station.

Raydist slave or relay stations are compactportable units, each housed in a single weatherproofaluminum casing, (See figure AC-4.) Each relay sta-tion receives the signal from the mobile transmitter,then relays the phase information to the NAVIGA-TOR receiver aboard the vessel. Power require-ments for the stations are approximately 2.6 A at 24V d.c. for 50-W output. Operation at reduced outputis possible for short ranges with a reduction in cur-rent requirements to 2 A or less. A fully charged pairof 12 V, 90 A-hr automobile batteries will operate avessel or shore station satisfactorily for 24 hr shoulda power failure occur.

An antenna coupler (model QB-52B) per-mits the mobile transmitter to be installed in any con-venient location aboard the hydrographic surveyvessel. Without an antenna coupler, the transmitter

would have to be mounted very close to the antennawhen the system is operated in the range-rangemode. Such connections are undesirable—a ''hot''antenna wire would be needed inside the vessel thatcould cause radio frequency interference to echo-sounding equipment and computer systems. Antennacouplers should be mounted very close to the base ofthe antenna and be grounded securely. When usedaboard fiberglass or wooden vessels, grounding canoften be satisfactorily accomplished by installinglarge copper bottom plates and heavy ground cables.

EQUIPMENT AND INSTRUMENTS

Where shore power is not available, propanegas-powered thermal generators should be used. Al-though the energy conversion efficiency of theseunits is low (less than 5%), they are more economi-cal to operate and maintain than gasoline or dieselgenerators because they can be run unattended forlong periods of time. Gas-powered generators nor-mally consume about 0.68 lb of propane per hour.

Each system component must be securelygrounded through a common ''bus'' to the hull ofthe vessel. (A 0.75-in flat copper braid works well.)Cable connections and power supply voltage mustbe checked. Accurate operating frequencies of thechain are critical and should be checked beforestarting a new operation. Although the oscillatorsin the various components generally are stable, oc-casional spot checks should be made. The systemshould be allowed to stabilize, preferably over-night, before a final check is made following a fre-quency adjustment.

5. Be sure that the navigation interfacetracks with the phase meter dials.

Shore stations. Relay stations should bechecked only during non-operational periods of thesurvey. To simplify the checks, activate only onemobile transmitter; switch all others to the standbymode.

The antenna system at each relay stationshould receive the same careful attention given tothe mobile station. Clean tight connections are es-sential at all joints of the antenna tower, at thelead-in wire, and at each ground connection.

A quick operational check of each mobilestation should be made before beginning daily op-erations:

AC-7 (JUNE 1, 1981)

will override the desired signal from the mobilestation. Only power supplies manufactured by Has-tings-Raydist or custom-made units designed byNOS for this system meet the requirements for lineload regulation, radio frequency interferenceshielding, and operational reliability. When thesepower supplies are used, batteries are not needed;however, when batteries are not used, there is nopower backup if a power failure occurs.

AC.2.3. CHECKOUT PROCEDURES. The fol-lowing system checkout procedures are a combina-tion of those recommended by Teledyne Hastings-Raydist and those learned from in-house experience.

Mobile station. As with any phase differ-ence measuring system, one of the key elements tosuccessful operation is a good antenna system. In-termittent connections cause phase shifts that aretranslated into positional errors. Extreme precau-tions must be taken to ensure that all electrical con-nections are clean and tight, including each joint ina sectional antenna, feed line attachments to the an-tenna and coupler, and each ground connection.

1. Check the reflected and forward pow-er levels on the front panel meter of the mobiletransmitter. Reflected power should be near zerowith a near full scale indication of forward power. Ifhigh reflected power readings are observed, adjustthe antenna coupler according to instructions in themanufacturer's manual. Adjustments made to theequipment during survey operations at any stationrequire that the system be recalibrated.

2. Each of the four audio tone levelsshould be clear and steady. Tones can be moni-tored using the speaker in the NAVIGATOR unit.

3. Phase meter amplifier levels shouldbe steady and read approximately 0.4 on the meter(100 to 110 on the meter for the later model ZA-67).

4. Torque of the phase meters shouldbe checked by slewing each meter plus or minusless than half a lane and observing how quickly thedial returns to its original reading.

HYDROGRAPHIC MANUAL

A recommendation is that each shore relaystation be checked at 2-week intervals. Items tocheck include:

a double log reciprocal relationship to the signalstrength. A value of 150 represents a lack of signalor a very weak signal; 50 represents a very strongsignal. A good norm is between 70 and 90.

1. Proper tower guy tension and sandanchor exposure. 10. With the sideband switch ON and

the meter switch on AGC, momentarily turningthe FINAL switch to OFF, then back to ON.There should be no change in the AGC level. Ifthe AGC level moves down the scale, internal ad-justments to the equipment are required.

2. Water level in batteries.

11. Turning the meter switch to OFF.Special caution, the station will not operate with themeter switch in the REF or FWD positions. Har-monics will be generated by the diodes in the SWRbridge that will totally block the receiver. As a finalcheck before closing the cover, be sure all toggleswitches are UP and the meter switch is OFF.

4. Metal objects not allowed to touchany part of the grounding system.

12. Potentially dangerous radio frequen-cy voltages are present on Raydist antennas.Though not lethal, small painful burns could beinflicted. Radio frequency burns tend to heal slow-ly because of their depth. Shore stations, when lo-cated near public access areas, must be fenced offand warning signs displayed. Do not allow metalparts of the fence to touch the ground plane.

AC.3. Hydrotrac System

If the master station is installed in the ship,the system operates in range-range mode; but if the

AC-8(JUNE 1, 1981)

3. General condition of antenna andground plane wires with special attention given toall connections. Weeds must not be allowed togrow around a tower base insulator. Wet weedstapping against the tower can generate electricalnoise and instability at the phase meters.

5. Importance of good shelter ventila-tion. A small fan should be aimed at the station alu-minum housing during warm weather.

6. Opening the relay station cover andusing the high impedance head phones suppliedwith the system to monitor the tone quality. Thetone should be clear and steady. While listeningwith the phones, jar the antenna tower using a dryinsulated object. Loose or dirty connections willshow up as static in the tone.

7. Turning the sideband ''SB'' switch toOFF. Move the meter selector switch to ''BattTest.'' The normal reading is about 125.

8. Using the meter selector switch tocheck the forward ''FWD'' and reflected ''REF''power levels. Normal forward reading lies between50 and 90. The reflected reading should be nearzero. Refer to the manufacturer's manual if tuningis required.

9. Turning the meter switch to auto-matic gain control ''AGC'' position, then turningthe sideband switch to the ON position. The AGClevel should read between 50 and 150. The AGClevel represents the strength of the received signalfrom the mobile transmitter and has approximately

Hydrotrac is a medium-range positioningsystem operating in the 2-MHz frequency band andwas designed and developed by Odom Offshore Sur-veys, Inc., Baton Rouge, Louisiana. It utilizes a sin-gle radio frequency by sequential transmissions froma master and two or three slaves, with synchroniza-tion between the stations achieved by use of a triggersignal 60 Hz below the pattern frequency. Within thereceiver, three internal frequencies are generatedwhich correspond in phase and frequency to the sig-nals received from the master and two of the slaves;these internal signals are used for phase comparisonso that position data are available continuously eventhough the transmissions are intermittent.

EQUIPMENT AND INSTRUMENTS

master is sited ashore, the mode will be hyperbolic.The range-range mode offers greater geometricalaccuracy than hyperbolic but the effect of an errorin the assumed velocity of propagation may beconsiderably greater—and in range-range, any vari-ations in velocity cannot be detected. Since onlyone vessel may use the system in a range-rangemode, this will often be the deciding factor be-tween multivessel operations with hyperbolic orsingle vessel with range-range. Where a choice ex-ists it is normally better to use hyperbolic on a con- cave coastline and range-range where the coastlineis convex. Offlying islands can be used to over-come problems caused by coastline irregularities.Whichever mode is used, greater operational flexi-bility and a considerably greater area of cover maybe achieved by establishing a third slave station.

Ideally the transmitting antennas should be

TABLE AC–3. — General Characteristics of theHvdrotrac System(courtesy of Odom Offshore Surveys, Inc., Baton Rouge, Louisiana)

Characteristic Description

Range-range or HyperbolicMode of operation

Operating Frequency 1.6 to 2.0 MHz in steps of 10 Hz

60 Hz below operating frequencyTrigger Frequency

Transmission Cycle Two Slave-1.0 secondsThree Slave-1.3 seconds

I. F. Band Width 120 Hz at 3 dB points

R. F. Sensitivity 1 µν from 50 Ω source

Day - 250 nm in areas of high electricalnoise, such as the Gulf of Mexico.

Range

Night - Unpredictable. In the Gulf of Mexico125 nm is attainable 80% of nights.

Wave Transmission 0.1 AO Time-shared continuous wave.

Radiated Power 0-150 watts Peak Envelope Power,continuously variable.

22-30 V d.c. (negative ground)Power Supply

Readout Resolution 0.01 lane

Positional Accuracy 2–40 meters, depending on geometry,stability of the velocity of propaga-tion, and the accuracy with whichthe system is calibrated.

AC-9 (JUNE 1, 1981)

The mathematical and cartographic treat-ment of Hydrotrac is similar to that of other sys-tems in the 2-MHz band.

Hydrotrac is designed so that mistriggeringduring electrical storms—a frequent cause of laneloss in earlier single frequency systems—is eliminat-ed. Each receiver and each control unit contains aprecise time source that allows it to operate withoutupdate for several hours, and before it is updated,256 consecutive good triggers, each 1,000 millisec-onds apart, must be received. Another feature pre-vents the uncontrolled loss of lanes when skywavecauses signal cancellation, by restricting the maxi-mum rate of change of the display readings to thatwhich would be caused by a vessel traveling at 25knots along the baseline. Thus, if cancellation shouldoccur, lane loss is minimized and the number of laneslost may easily be counted on a sawtooth recorder.

The transmitted frequencies are generatedby a synthesizer which allows any frequency withinthe range 1.6 to 2.0 MHz to be selected by thumb-wheel switches, in steps of 10 Hz. Harmonics andsidebands are at least 65 dB down from the funda-mental so that the system is acceptable in regionswith stringent frequency licensing regulations.

Data outputs are available at a selectablerate, between 1 and 12 times per second, and in eachcase the output is of the current raw data, no filteringor smoothing being applied within the receiver. Thestandard outputs are serial BCD, serial ASCII, and0-10 V d.c. analog for a sawtooth recorder. NOSuses a separate interface box which receives the seri-al BCD and converts it to both analog and paral-

lel BCD and converts it to both analog and parallelBCD for input to the HYDROPLOT navigation in-terface. The cable length between the NOS interfacebox and the HYDROPLOT navigation interfaceshould not exceed 20 feet but the interface box maybe as much as 500 feet from the Hydrotrac receiver.Much of the following discussion on outputs andother details has been extracted from the Odom Off-shore Surveys, Inc. (Hydrocarta/Hydrotrac), systemmanuals, 1979.

AC.3.1. SYSTEM CHARACTERISTICS. Thegeneral characteristics of the Hydrotrac system arelisted in table AC–3.

AC.3.2. SYSTEM COMPONENTS. The com-ponents of the transmitting stations are a MasterDrive Unit (MDU) or Slave Drive Unit (SDU), asappropriate, a Power Amplifier (PA), and an An-tenna Coupler. The PA serves also as a power dis-tribution unit. In the hyperbolic mode, the ship-board installation consists only of a receiver and areceiving antenna, but in range-range mode theMDU, PA, and coupler will also be on board. Inthe latter case a solid state transmit/receiver switchwithin the PA allows use of a single antenna.

HYDROGRAPHIC MANUAL

Another source of error that should be re-moved by calibration is the reflection of the signalfrom the ship's structure. This error will vary withthe relative bearing of the slave station from the shipand may be measured by taking a series of calibra-tion comparisons while the ship turns through 360°at rest, so that the bearing from the slave remainsconstant. By plotting C-O against relative bearing,the position of the ''electrical center'', or apparentpositioning from which the ranges may be assumedto be measured, may be determined. It should not benecessary to repeat this part of the calibration until

The procedure is to measure the position ofthe ship's Hydrotrac antenna by an independent po-sitioning system simultaneously with reading theHydrotrac dials. The independent system values areconverted to x-y and thence to Hydrotrac readings,described as the computed values. From these aresubtracted the observed values to give a C-O cor-rection.

AC-10(JUNE 1, 1981)

¼ wavelength in height. This is often difficult toachieve in practice and may be reduced when lessthan maximum range is required; they should notbe less than 30 ft.

All units except the Antenna Coupler arehoused in watertight (when closed) transit/operating cases, measuring 22 in X 93 in X 16 inThey may also be rackmounted, in which case eachunit occupies 7 in of rack height.

AC.3.3. INSTALLATION. Site Selection:Transmitting station sites should be sought in areaswhich minimize the amount of landpath between thestation and the ship and, for hyperbolic mode, be-tween the master and each slave. In particular theyshould be located so that the length of landpathfrom each station will not vary as the ship movesthrough the survey area. The antennas themselvesshould be on ground of good electrical conductivi-ty, have a clear view of seaward, and be sited so thattall objects are at least six times their own heightdistant. (Double this if they are metallic or liable tomove.) Meeting these conditions will help toachieve a stable radiated pattern, but each must beweighed against the need for good geometry, as inany other positioning system.

Station Setup: The methods of interconnec-ting the units, tuning the transmitters, and initiatingoperation are covered in the Technical Manual. Par-ticular care should be taken to ensure that all electri-cal connections are clean and tight. A ground planeof 36 (72 when conductivity is poor) radial wires,equal in length to the antenna height, should be laidout (and preferably buried) symmetrically round theantenna, a ground rod should be driven to refusal,and the electronic units connected to it. Precautionsshould be taken to keep vehicles, people, and ani-mals off the ground plane.

Calibration: Although the Hydrotrac re-ceiver is self-referencing, there is an NOS require-ment for daily testing for instrumental accuracy.There is also a requirement to measure the systemat-ic errors whenever a chain is established or a changeis made in any of the shore station components.

With a hyperbolic chain it is desirable tocarry these comparisons through the survey area,reducing random errors by meaning sets of three tofive comparisons in each location. Advantageshould be taken of the hyperbolic mode by record-ing readings at a monitor station throughout thecalibration and whenever the chain is used subse-quently, since these will indicate any further cor-rections necessary to eliminate diurnal changes inpropagation conditions.

Calibration of a range-range chain is bestperformed in a different manner, taking each patternseparately. Since the pattern values represent ranges,the comparison is most easily effected by placing theremote station of a microwave system close to theslave antenna (but outside the ground plane) andcomparing ranges directly. The ship's heading andthe bearing of the slave should be recorded at eachcomparison so that the small distance corrections ateach end may be applied to the microwave ranges.These ranges are then converted to Hydrotracranges directly and the C-O computed.

Every Hydrotrac range will contain a con-stant error and a variable error, where the vari-able error is caused by an incorrect assumption ofthe velocity of propagation and will vary directlywith the range, while the ''constant'' error con-tains both a constant systematic element and an el-ement caused by the different velocity of propaga-tion along the land path from the antenna to theshoreline. This latter element may be assumed tobe a constant on any one bearing but is likely tochange with change of bearing, as the length andnature of the landpath will vary. It is thereforenecessary to carry out the calibration by steamingthe ship across the full range of bearings to thesurvey area at a distance of 2 to 4 miles from theslave station so that the effect of a velocity erroris minimized.

EQUIPMENT AND INSTRUMENTS

pective whole lane count one lane at a time. Forease in recording, the Display Hold button may bedepressed at each fix to freeze the display.

AC.4. ARGO System

The ARGO DM-54 positioning system is aprecision radiolocation system designed to provideaccurate, long-range, positional information for amobile station with respect to two, three, or fourfixed location stations. The ARGO system operatesin the medium-frequency (MF) band (1600 to 2000kHz), utilizing the ground wave component of theradiated signal. The DM-54 will provide some po-sitional information at ranges up to 400 miles,depending on atmospheric conditions, antennaheight, and power output. Tests conducted in April1979 by the Office of Marine Technology revealeddaytime observations were usable for at least 253km (134 nmi) and much less than that for nighttimeuse. A small mobile antenna was in use during thetests.

Where a survey is carried out at extremerange, the effects of changes in atmospheric condi-tions become significant and it is desirable that tem-perature, barometric pressure, and vapor pressure bemeasured during the calibration and subsequentlywhenever the optimum accuracy is desired.

AC.3.4. RECEIVER OPERATION.

3. Check frequency thumbwheels.4. Select required slave pair.

The basic ARGO DM-54 utilizes a multi-plexing sequence and a shortened RF pulse to ser-vice up to seven mobile stations interrogating fourfixed responders with 2-second update capability.

A typical multiplexing sequence is shownin figure AC-5. All RF pulses are 36 milliseconds,in overall length and are contained within a 44-mil-lisecond time allotment except for the system tim-ing pulse. The timing pulse occupies 70 millisec-onds of a 120-millisecond allotment and istransmitted by a single network station designatedthe master. All other stations identify the timingpulse by its unique width and adjust their timing tocoincide with the network before transmitting.

The receiver is then ready for use. In Op-erate mode the Frequency, Slave Select, and Dis-play Slew controls are disabled. Operation of theWhole Lane toggle switches will change the res-

AC-11 (JUNE 1, 1981)

there is a change in the ship's superstructure or theantenna location.

It should be noted that the range-range cali-bration procedure removes only the constant ele-ment of the systematic errors. Any error in the as-sumed velocity of propagation will cause an error inthe range which is directly proportional to the mea-sured distance. Furthermore, in the range-rangemode it is not possible to use a monitor station to re-cord the diurnal changes in velocity caused bychanges in atmospheric conditions. In a hyperbolicmode, on the other hand, a change in the velocity ofpropagation will have no effect along the base linebisector, since the error will affect master and slavetransmissions equally and one is subtracted from theother, while the maximum error, occurring on thetwo base line extensions, will be the same as that on arange-range chain at 30 miles range.

1. Switch power on. Observe a.c. andd.c. lights and allow a 20-minute warmup before pro-ceeding beyond step 5.

2. Select SET mode. Switch audio alarmoff.

5. Set C-O correction appropriate tothe area of operation.

6. After warmup, all alarms (decimalpoints in the displays) should be out. Select 7 onthe Monitor Select; a reading of about 0.7 indicatesreception of good trigger signals. Select 4, 5, and 6successively on the Monitor Select; center scale in-dicates that master, slave 1 and slave 2, respective-ly, are locked.

7. At a point when lane count is down,set the whole lane value on each pattern. SelectOperate mode.

8. Switch on audio alarm and adjust dis-play intensity as necessary.

AC.4.1. PRINCIPLES OF OPERATION. TheARGO DM-54 operates on the principle that an MFradio signal traveling along the earth's surface in the"ground wave" mode experiences a time (and hencephase) delay proportional to the distance traveled.For short to moderate distances, the ground wavepredominates at all hours over the ''skywave'' signalreflected by the ionosphere. Daytime absorption bythe D-layer of the ionosphere attenuates skywavesignals so that the ground wave predominates up toseveral hundred kilometers in distance. At night,due to changes in the ionosphere, the skywave maycontaminate the ground wave. Since only theground wave is useful for positioning, the range atnight is reduced depending on the amount ofskywave contamination.

HYDROGRAPHIC MANUAL

FIGURE AC–5. — Typical 4 Range Transmission Sequence (courtesy of Cubic Western Data, San Diego, Califomia).

Within each timeslot one RF pulse is gen-erated by a designated mobile station as an inter-rogation. This signal is received by all the fixedresponders which measure the carrier phase withrespect to their locally synthesized references.Each fixed station replies with a comparable pulsehaving its phase adjusted to replicate the receivedphase. The mobile station receives the replies fromeach fixed responder and compares the receivedphases with the transmitted phase to determine theround trip phase delay to each fixed responder.The process is repeated with each timeslot havingits own assigned mobile station.

Each station, fixed or mobile, includes aRange Processing Unit (RPU) and an AntennaLoading Unit (ALU). Each mobile station also hasa Control and Display Unit (CDU). Figures AC-6and AC-7 show the equipment interconnection.(See also figure AC-8.)

In figure AC-5 the eighth timeslot is re-served for the sector Lane Identification feature.During the timeslot, all units of the system switch toan alternate frequency approximately 10% higherthan the ranging frequency. One mobile station at atime may thus interrogate in its regular timeslot andfrequency concurrently with an offset frequency. Acomparison of the phase data on two frequencies isthe basis of sector Lane Identification.

AC.4.2. DESCRIPTION OF EQUIPMENT. Thestandard ARGO DM-54 as configured for NOS,consists of four land-based fixed stations and up tofour mobile stations. Two- and three-range opera-tions are also possible, with up to twelve and nine

AC-12(JUNE 1, 1981)

mobile stations, respectively. ARGO also allowsunlimited user capacity in the hyperbolic mode ofoperation, while retaining three range-range users.

1. Range Processing Unit (RPU). TheRPU contains the electronic components necessaryto generate, transmit, receive, and process all sig-nals for range measurement. The RPU also con-tains operator controls and associated circuits forremotely controlling the ALU.

2. Antenna Loading Unit (ALU). TheALU contains the electronic circuits and compo-nents necessary to match the RPU transmitter out-put to the antenna.

3. Control and Display Unit (CDU).The CDU contains the electronic components andoperator interface necessary to perform all opera-tional control, range displays, and interface func-tions between it and the RPU. In addition, theCDU provides output data for such peripherals asstrip chart recorders, digital printers, andcomputer/calculators.

EQUIPMENT AND INSTRUMENTS

AC.4.4.2. Range Quality Indications. EachARGO range is accompanied with two indicationsof signal quality. One is an indication of low ampli-tude. The second is an indication of poor data quali-ty, occurring if the measured range has deviatedmore than a safe margin from the predicted range;i.e., the data were edited by the smoothing algo-rithms. These quality indicators are visually present-ed to the operator and available at the rear dataoutput connectors. This provides a real time andpermanent record of the quality of individualARGO ranges at all times.

AC.4.4.3. Data Smoothing. Data smoothingconsists of nonlinear (editing) and linear (filtering)processes . Smoothing is basically an exponentiallyweighted average with a selectable time constant.An ARGO operator may select 10 differentsmoothing codes from the front panel to theARGO Control and Display Unit. Smoothing 0 isthe lightest smoothing, being essentially raw data.Smoothing 1 through 9 are increasingly longertime constants with 9 being suitable only for slowmoving operations such as a wire-drag survey. Theoperator may select or change smoothing duringoperation to compensate for varying signal condi-tions and ship dynamics. Note: HYDROPLOTshould not be used with smoothing code 0, asmoothing code is recommended in Table AC-5.

Smoothing provides the potential for opera-tion through impulse noise such as lightning storms,and during periods of moderate skywave activity, in-creases the number of hours per day or miles ofrange through which ARGO can operate.

TABLE AC–4. — General Characteristics of the ARGO ElectronicPositioning System

Characteristic Description

Mode of operation Range-range or hyperbolic AC.4.4.1. Multiple Ranges. The ARGO

DM-54 can be used in two-range, three-range, orfour-range format. The capability of multipleranges adds a new dimension to network flexibili-ty with ARGO. In a conventional two-range sys-tem it is common to have two ranges deployedalong the coastline, and a third station maintainedon shore as backup. With ARGO, this third sta-tion would actually be installed at another loca-tion and on the air. If any one station of thethree fails in this configuration, no downtime re-sults to the mobile stations because two rangesare still available for positioning.

Frequency band 1600-2000 kHz. Lane identification(when used) requires a second fre-quency 9% to 10.5% higher thanthe range frequency. (Lane width74 to 94 meters) Band width 80 Hz

Range At least 253 km (134 nmi) by dayLess than 253 km by night–qualityof data obtained during either dayor night operations depends on an-tenna height, atmospheric condi-lions, and power output.

100 watts peakRadiated power

Range accuracy 0.02 lane instrumental, 0.05 laneachieveable field accuracy-4.7 mif lane width is 94 m

AC-13 (JUNE 1, 1981)

FIGURE AC–6. —Standard ARGO Fixed Station Inter-connecting Cabling Diagram (courtesy of Cubic WesternData, San Diego, California)

FIGURE AC–7. — Standard ARGO Mobile Station Interconnec-ting Cabling Diagram (courtesy of Cubic Western Data, SanDiego, California)

AC.4.3. SYSTEM CHARACTERISTICS. Seetable A–4 for the physical and operational charac-teristic of the ARGO DM-54 system.

AC.4.4. OPERATIONAL FEATURES. TheARGO DM-54 has numerous features rangingfrom packaging to operating interface to networkflexibility. The main features are discussed below.

HYDROGRAPHIC MANUAL

of the front panel and does not require the use of testequipment. The built-in test is designed to do threethings: First, increase a user's confidence that theequipment will perform when deployed to the field;second, to reduce the downtime in case of failure;and third, to partially eliminate the need of expen-sive test equipment at maintenance facilities. Withthe use of standard test equipment, a technician cantroubleshoot down to the component level.

TABLE AC–5.— ARGO Smoothing Codes

TIMESMOOTHING CONSTANT

APPLICATION(SECONDS)CODE

Raw Data Computer ProcessingHigh speed-survey (launch)High speed-surveyModerate speed - survcyModerate speed-seismicLow speed-seismicVery low speed-seismicLarge ship. No maneuvers.Large ship. No maneuvers.Wire-drag survey. At anchor.

AC.4.4.8. Remote Antenna Tuning. TheARGO DM-54 is unique in that its Antenna Load-ing Unit is remotely controlled from the RangeProcessing Unit. Since an antenna may be tunedfrom the location of the Range Processing Unit, anoperator need never go to the Antenna LoadingUnit once installed. For this reason, ARGO anten-nas may be located for best performance, and notfor ease of operator access for tuning.

AC.4.4.9. Selectable Frequencies. ARGODM-54 may be preprogramed at the factory for upto 16 fequency pairs, each pair having one fre-quency for ranging and one for lane identificationfeatures. Once programed, the operator may selectany frequency pair desired by the use of a protect-ed rotary switch on the Range Processing Unitfront panel. Within a band of 200 kHz, no return-ing of any internal circuitry is required to selectbetween the 16 preprogramed frequency pairs . Useof this feature allows ARGO stations to be pro-gramed for a wide choice of network frequencies.Stations may then be transferred between netswithout the need for modifications, retuning, or be-ing returned to a maintenance facility.

AC.4.4.5. Hyperbolic Operations. The DM-54may be used in a range-range only operation, in a hy-perbolic only operation, or simultaneously with bothmodes on the same net. The shipboard operator se-lects the mode of operation he desires for his partic-ular vessel by front panel commands to the Controland Display Unit. Once selected by the operator, therest of the net will automatically respond to the sig-nals from that ship. This feature allows multiplerange-range users on a net, unlimited hyperbolicusers on a net, and individual users to switch backand forth between modes as their needs change.

In a net with hyperbolic operation, onetimeslot is reserved for that function. A fixed station(the master) generates the interrogation for thattimeslot, and the other fixed stations reply just as toa mobile interrogator. The master station may beone of the range-range responders, or it may be anadded station. Therefore, a five-station net yieldingfour hyperbolic lines of position is possible.

AC.4.4.10. Transmitter Protection. TheDM-54 transmitter design was improved to increasepower output from 60 watts to 100 watts, and to al-low DM-54 stations to continue to transmit in spiteof severely detuned antennas. The DM-54 transmit-ter will continue to operate into a dead short or openload. The transmitter is protected from damage by acircuit that monitors the reflected power and re-duces the transmitter output below destructive lev-els. This feature is a significant advantage for us onnonmetallic vessels such as small launches that havea very unstable antenna platform.

AC.4.4.6. Aircraft Operation. Aircraft oper-ation utilizes the hyperbolic mode at increased datarates. ARGO has been tested in aircraft travelingon the order of 100 knots, and the ARGO softwarecan be modified for speeds in excess of 200 knots.

AC.4.4.11. Data Outputs and Formats. Mod-el DM-54 has a number of different data outputsmaking it possible to interface to a wide range of pe-ripheral equipment. It provides analog output

AC.4.4.7. Built-In Test. Both the ARGORange Processing Unit and the Control and DisplayUnit contain built-in test software. The operator'sbuilt-in test always results in a go/no-go indication

AC-14(JUNE 1, 1981)

AC.4.4.4. Lane Identification. Another op-erational advantage is the incorporation of the laneidentification feature. By intermittently makingrange measurements on an offset frequency, theDM-54 can generate a lane count error over a sec-tor of ±5 lanes. An operator may, if he suspects hehas had a lane addition or subtraction due to thenoise or interference, initiate lane identificationwhich will then display the error in lanes.

0123456789

N/A2.83.03.95.69.013192639

EQUIPMENT AND INSTRUMENTS

portional to each range suitable for use with stripchart recorders. On the GPIB output, these data in-clude such information as 24-hour time formats,quality data for each range (including edits and lowamplitude), and all operator commands to the frontpanel of the Control and Display Unit. In addition,the operator may command range data with time an-notation and quality annotation to be output periodi-cally at fixed intervals determined by the operator.

AC-15 (JUNE 1, 1981)

The HYDROPLOT system is interfaced toARGO through the GPIB, which does not includethe range quality data. Synchronization with theARGO update is provided at the GPIB interface.

AC.4.5. INSTALLATION AND OPERATION.The details of ARGO station installations are de-scribed in the operator's manual. Both mobile andshore stations must have vertical antennas between25 and 100 feet in height, and a stable efficient groundplane. On shore, this ground plane is normally ac-complished by the installation of 32 radial wires, each100 feet long. On board metallic ships, the groundplane consists of the ships' superstructure and hull; oron nonmetallic vessels, ground straps and groundingplates under the water line can often be sufficient.Quality in antenna installations is always essential forthe best ARGO performance and accuracy.

Operation of individual units is described asfollows:

1. Antenna Loading Unit. The AntennaLoading Unit requires no operation or adjustment.Once securely installed, the lead to the antenna andthe lead to the ground plane and ground rods mustbe as short as possible and rigid so that they willnot move in the wind.

2. Range Processing Unit. Operation ofthe Range Processing Unit begins at the left of thepanel and proceeds to the right. Begin by turningthe power switch on. Adjust the frequency selec-tion knob to the desired frequency pair (which hasbeen preprogramed at the factory). Verify that theVoltage Normal light is on and that the No Carrierlight is not on. Move to the station configurationblock and put the switch in the Antenna Tune po-sition, press execute, and using the inductor and ca-

FIGURE AC–8. — ARGO Control and Display Unit, and RangeProcessing Unit (courtesy of Cubic Western Data, SanDiego, California)

pacitor controls in the antenna tune block, tunefor a peak reading for both the range and laneidentification frequencies. Once tuned, put the sta-tion configuration switch in the desired station op-eration (mobile or fixed) and select the desiredtiming (master, slave, or relay). Press the executebutton and the station will assume the desired op-eration.

3. Control and Display Unit. Whenmobile station operation is desired, connect theControl and Display Unit to the Range ProcessingUnit with the Unit Interconnect Cable. Set therear panel power switch to the remote position.Once on, go to the Control and Display Unitfront panel. Beginning with the Clock positionand proceeding in a clockwise direction, enter thedesired information. First, set 24-hour time inhours, minutes, and seconds. Second, setSmoothing from 1 through 9 Third, select the de-sired timeslot. In the Range position, enter orstore the desired lane count and fractional lane foreach of the ranges in use. If at some future date itis desirable to add or subtract lanes or fractionallanes from any range, use the Delta Range posi-tion. The Lane Identification position may be usedat the operator's discretion to enable the laneidentification function. Any performance optionsavailable in ARGO software are accessed in thefinal Option Code position.

EQUIPMENT AND INSTRUMENTS

SHORT RANGE POSITION-FIXINGAD.SYSTEMS

AD.1. Del Norte Trisponder System

The Del Norte Trisponder System, manu-factured by Del Norte Technology, is a short-range, line of sight, electronic positioning systemdesigned for use aboard vessels, aircraft, and landvehicles. Most of the material container herein wascondensed from Trisponder, Electronic PositioningSystem, Basic Operation Manual, published by DelNorte Technology, Inc. (1974), 1100 Pamela Drive,P 0 Box 696, Euless, Texas 76039.

The basic Trisponder system is composedof a distance-measuring unit (DMU), a master sta-tion, and two remote stations. Each station is acombined transmitter and receiver. The master sta-tion has an omnidirectional antenna, and each re-mote station has a directional antenna. With the re-mote units placed over stations of knowngeographic positions, ranges are observed at theDMU. These values may be plotted manually on ahydrographic survey sheet or converted bytrilateration methods to position values.

For obtaining accurate range values, the sig-nal is transmitted and received 10 times or 100 times,at the operator's option, and the sum averaged. Eachvalue is checked; spurious data are rejected internal-ly. Final averaged values may be transmitted to the

AD-1 (JUNE 1, 1981)

AD.1.1 DESCRIPTION OF EQUIPMENT.

The Del Norte Trisponder system components arecompact, portable, and weatherproof. Each masterand each remote station consist of a transponderand an antenna. The DMU is installed aboard thevessel. See figures AD-1 through AD-3.

Coded bursts of microwave frequency (X-band) energy are transmitted from the master unitto each remote unit for a determination of rangedistances. These signals are received and decodedby each remote unit, but only the unit with theparticular code is triggered to send back an iden-tical burst of energy to the base unit. The timethe signal takes to make the round trip minuselectronic delays for decoding is converted to dis-tance using the velocity of X-band energy in theatmosphere. Round trip distances are divided by 2to obtain the displayed range distances. At micro-wave frequencies, the system is limited to line-of-sight distance measurements.

FIGURE AD–1.— Del Norte trisponder positioning system compo-nents, (top left) master trisponder with omni antenna, (topright) remote trisponder with sector antenna, and (bottom) dis-tance-measuring unit (courtesy of Del Norte Technology, Inc.,Euless, Texas)

HYDROGRAPHIC MANUAL

TABLE AD–1.—Del Norte Trisponder system characteristics

Characteristic Description

Range-rangeMode of operation

AD.1.2 SYSTEM CHARACTERISTICS. Seetable AD-1 for the physical and operational char-acteristics of the trisponder system as cited by DelNorte.

WeightAD.1.3 INSTALLATION AND OPERATION.

In addition to following the proceduresrecommended in the Del Norte Technical manuals,see section 3.1.2 for shore station control accuracyrequirements and section 4.4.3.2.2 on the generalcharacteristics of range-range distance-measuringsystems. The Del Norte Trisponder system oper-ates at microwave frequencies and, thus, is limitedto line-of-sight distance measurements. Also in sec-tion 4.4.3.2.2. is a discussion of line-of-sight condi-tions and computations.

Weight

0.5 in

Range error

Time-sharing option formultivessel, operation

FIGURE AD–2. — Del Norte trisponder shore station installation(courtesy of Del Norte Technology, Inc., Euless, Texas) Voltage monitoring

Waterproof rugged hous-ing; floating units

Packaging

AD-2(JUNE 1, 1981)

HYDROPLOT controller (See AJ) through avail-able interface units. If the required number of''good'' observations cannot be obtained by theDMU, a red warning light, near the digital displayfor that range, goes on and the display is notupdated. The averaging process improves substan-tially the measurement stability characteristics.

Results from tests conducted by NOS in-dicate that electronic drift over a period of timemay cause variations in the measurements. Tomaintain a ± 3 m range measurement accuracy,each unit must be calibrated over a measured baseline at least once every 200 hr of operation. Tomaintain a ± 6 m range accuracy, a calibration atleast once every 500 hr of operation will suffice.

Remote transponder(shore unit)Input voltagePower consumptionReceiver frequencyTransmitter frequencyTransmitter powerAntenna beam width

23 to 32 V d.c.17 W9480 MHz9325 MHz1000 W87º horizontal, 5º vertical

or 180º horizontal, 5ºvertical

15 lb

Receiver-transmitter(vessel unit)Input voltagePower consumptionReceiver frequencyTransmitter frequencyTransmitter powerAntenna beam widthWeight

23 to 32 V d.c.17 W9325 MHz9480 MHz1000 W360º horizontal, 30º vertical15 lb

Distance-measuring unit(DMU, vessel unit)Input voltagePower consumptionRangeChannels (displays)Code selectionUpdate interval

23 to 32 V d.c.40 W80 km24 codes available1 s, 2 s (jumpered internal-ly)25 lb

Other featuresRange readout resolution

± 3 in under good fieldconditions

Permits four vessels totime share position datafrom a common set oftransponders

Transponder standbycircuitry

Automatically switchesmagnetron filamentcircuit off to reducecurrent drain frombatteries approx 40 minafter interrogations cease

Automatically shuts downremote stations when in-put voltage drops below21 V d.c.

Transponderinterchangeability

Master and remote trans-ponders identical exceptfor respective transmit-ting and receiving fre-quencies

EQUIPMENT AND INSTRUMENTS

Although calibrations over a measured base lineare unnecessary each time a unit is moved, the sys-tem must be calibrated whenever the DMU, themaster station, or the slave stations are replaced orhave had parts replaced.

cuitry prevents signal overlap and interference.Each vessel, therefore, must wait the maximumtime that could be needed for the previous vesselto complete its interrogation and summing process(88 ms for a summation of 10 measurements and354 ms for a summation of 100 measurements forcodes 72 through 88).

To conduct an acceptable base line calibra-tion, lay out a short measured range (Third-order,Class II accuracy) with a known distance of about2000 m (1800 to 2500 m). Set the master stationand DMU at the zero reference point. Place eachremote station over the other point. Adjust theRANGE CALIBRATION screws on the frontpanel of the DMU so the correct distance isdisplayed for each remote unit.

Thus when planning a time-shared opera-tion, a hydrographer is limited by the total numberof vessels that can be used by the updating option ofthe system. Table AD-2 indicates these constraints.

TABLE AD–2. — Trisponder time-sharing constraints

100 sum10 sumUpdating time

(Vessels)(Vessels)(s)0.25

FIGURE AD–3.— Del Norte trisponder vessel installation (cour-tesy of Del Norte Technology, Inc., Euless, Texas)Trisponder systems using the time-sharing

option allow four vessels to operate from the sameremote units without signal interference. Such sys-tems must designate one of the vessel units as themaster (Base 1) and designate the remaining units asslaves (Base 2, 3, or 4). The master station first in-terrogates the remote units, then the slaves interro-gate each remote station sequentially. If a slave de-tects loss of synchronization with Base 1, a frontpanel light indicates fail-safe operation, Internal cir-

When operating in the time-sharing mode,n–1 of the vessels must be equipped with the nec-essary time-sharing hardware – the nonequippedvessel acts as master (Base 1) and has the highestinterrogation priority. Because fixes may not beobtained at precisely the right times when using

AD-3 (JUNE 1, 1981)

The initial equipment warmup and checkoutprocedures specified by the manufacturer must beadhered to rigorously. Del Norte transponders emitlow-powered radar waves so there is no radiationhazard if nominal care is exercised whenever anyunit is operating. However, high levels of radio fre-quency radiation can seriously affect the eyes of per-sonnel standing near and in line with the antennas.Do not look down the antenna while the transmittersare operating. Distances greater than 1 m from theantennas are considered to be safe operating areas.

All radio communications equipment mustbe kept at least 3 m from the stations to avoid falserange data. Each unit must be separated from anyequipment that may emit radio frequency energy.

Position-fixing data may be recorded eithermanually or automatically depending upon the oper-ational needs. For manual recordings, ranging data issimply observed from the numerical display for theappropriate channel. For automated recording, theposition data are transmitted to the display indica-tors and transferred to an interface to the computerthrough an interconnecting cable. Any two of fourranges are available and can be furnished to the com-puter and be displayed on the DMU.

431

441

21

HYDROGRAPHIC MANUAL

any ''summing'' system, special care must be takenwhen working at high vessel speeds – particularlyspeeds in excess of 20 kn. Range values displayedon indicators and at the computer interface maynot be correct at the instant observed.

AD.2. Motorola Mini-Ranger III System

The MRS III, manufactured by Motorola,Inc., is a short range position-fixing systemdesigned for vessels, aircraft, or land vehicles. Ma-terial in this section has been condensed from the''Operation and Installation Manual for Mini-Rang-er III System (MRS III),'' published by Motorola,Inc. (1974), Government Electronics Division,Scottsdale, Arizona 85252.

A unique coding system is used in theMRS III system to minimize false range readingscaused by radar interference and to provide selec-tive transponder interrogation. MRS III is alsocapable of interrogating transponders with a singlepulse if desired. Operating frequencies of theMRS III can be set, at the factory, above or be-low the operating frequencies of onboard radarsystems to eliminate possible interference withnormal radar operation. Because MRS III oper-ates at C-band frequencies and most marine radarsradiate at X-band, the possibility of mutual inter-ference is minimal.

AD.2.1. DESCRIPTION OF EQUIPMENT. TheMRS III is a compact, light, highly mobile distance-measuring system consisting of a receiver-transmit-ter assembly with antenna, a range console, and ra-dar transponders with antennas. (See figure AD–4.)

AD-4(JUNE 1, 1981)

There are two possibilities that can cause thedistance measurements to be ''old'' at the momentthe computer fetches the data. The first and mostsignificant is the update timing. Data that have beenwaiting in the navigation buffer for as much as oneupdate period may be used for a position. At a speedof 20 kn, a vessel moves 10 m/s. Thus at these higherspeeds, special consideration must be given to theupdate rate to determine if the maximum update er-ror can be tolerated at the scale of the survey. If theupdate error is significant, a faster update rate can beobtained by changing the update printed circuitboards. To obtain faster rates, however, one mayfind it necessary to reduce from a 100-sum mode to a10-sum mode or to reduce the number of time- shar-ing vessels, or both.

The second possibility of position error isnon-simultaneous range data. The position-fixingsystem first calculates a range (distance) for onechannel, then calculates a range (distance) for thesecond channel. The computer, however, usesthese two range values as if taken simultaneously.The time difference between the two measuredranges depends on how long it takes for the sum-ming process for each channel. For a 10-summa-tion system, time differences can range from 19ms under ideal atmospheric conditions to 44 msunder poor conditions when a maximum of 50 at-tempts must be made for each channel to obtain10 good readings to average.

In the 100–sum mode, time differences canrange from 140 to 314 ms. This error can be con-verted from time to distance by multiplying by thespeed of the survey vessel in meters per second. Athigh speeds on large-scale surveys, this sequentialrange error may be large enough to be of concern.In such cases, switch the DMU MODE switch to10-sum operation, which will degrade the stabilityof the readouts slightly but will not reduce the±3-m accuracy, and slow down the sounding ves-sel until the error magnitude becomes tolerable.

The MRS III, operating on the basic princi-ple of pulse radar, uses a transmitter aboard the sur-vey vessel to interrogate radar transponder refer-ence stations located over geographically knownpoints. (See 1.3.) Elapsed time between transmittedinterrogations produced by the MRS III transmitterand the reply received from each transponder is usedas the basis for determining the range to each trans-ponder. This range information, displayed by theMRS III together with the known location of eachtransponder, can be trilaterated to provide a positionof the vessel. The standard MRS III operates at line-of-sight ranges up to 37 km. With appropriate cali-bration, the probable range measurement accuracy,stated by Motorola, Inc., is 3 m. Ranges may bedisplayed in meters, yards, or feet. Time sharing ofcommon transponders by more than one unit permitsmultivessel operation from a single control array.

EQUIPMENT AND INSTRUMENTS

The basic operating principles of these units are de-scribed in the following paragraphs.

FIGURE AD–5. — MRS III schematic diagram (courtesy ofMotorola, Inc., Scottsdale, Arizona). See also figure AD-4.

a signal that serves as the start pulse for therange counters is developed. Received transpon-der signals are routed from the antenna throughthe circulator to the receiver. The output of thereceiver is decoded to provide a stop pulse to therange counters. Receiver-transmitter units oper-ate on +28 V d.c. power supplied by the rangeconsole.

transponder (depending on the pulse spacings of theinterrogation), and the transponder generates a re-ply.

AD.2.2. SYSTEM CHARACTERISTICS. Thephysical and operating characteristics of the stan-dard MRS III package, as cited by Motorola, Inc., in1974, are shown in table AD-3.

AD.2.3. INSTALLATION AND OPERATION.In addition to observing the following proceduresrecommended by Motorola, see section 3.1.2 forshore station control accuracy requirements and sec-tion 4.4.3.2.2 on the general characteristics of range-range distance-measuring systems.

When a start signal transmitted by the re-ceiver-transmitter is received, the range counterbegins to count. After five sequential interrogationsand reception of five replies from a transponder,

AD-5 (JUNE 1, 1981)

The receiver-transmitter unit consists of aradar receiver and transmitter. Transponder interro-gation signals from the transmitter are passedthrough a circulator to the antenna. Simultaneously,

FIGURE AD–4.— Mini-Ranger III System. The range console isflanked by a radar transponder and is topped by another tran-sponder and a receiver-transmitter assembly (courtesy ofMotorola, Inc., Scottsdale, Arizona). See also figure AD-5.

The range console consists of a coder, a de-coder, a range counter control, a numerical read-out (range display), and a power supply that pro-vides the necessary direct current (d.c.) operatingvoltages. The power supply also provides +28 Vd.c. for the operation of the receiver-transmitter.(See figure AD-5.)

the count is displayed on the range console frontpanel as range to the transponder. This range to-gether with channel and code information are alsotransmitted in parallel binary coded decimal (BCD)format from a rear-panel connector to peripheralprinters and computers. Channel A and channel Brange data are gathered and displayed within 10 msduring each sample period of operation.

Solid-state radar transponders are installedat known locations and serve as reference points forthe MRS III. The transponders receive pulse-cod-ed interrogations from the receiver-transmitter.The interrogations are decoded by the applicable

HYDROGRAPHIC MANUAL

TABLE AD–3.— MRS III package operating characteristics

DescriptionCharacteristic

Radar transpondersReceiver

5570 MHz C-bandFrequency9410 MHz X-band (optional)18 MHz maximumBand width-70 dBSensitivity

Maximum signal input +20 dBTransmitter

5480 MHz C-bandFrequency9310 MHz X-band (optional)

Peak power output 400 WSingle or codedReply pulse

Reply pulse width 0.5 µµs maximumAntenna

5400 to 5600 MHz C-bandFrequency range9200 to 9500 MHz X-band

(optional)HorizontalPolarization13 dB nominalGain

3-dB beam width80°Azimuth15°Elevation-54°C to +71°C (-65°F toOperating temperature

+160°F)

Typical radiation patterns for shore basedtransponder fixed antennas and for rotating antennasaboard survey vessels are shown in figure AD-6.

Receiver-transmitterReceiver

5480 MHz C-bandFrequency9310 MHz X-band (optional)-70 dBSensitivity

Maximum signal input +20 dBTransmitter

5570 MHz C-bandFrequency9410 MHz X-band (optional)

Power 400 W peakPulse width

875 pulse groups per secondPRFOmnidirectional antenna

Frequency range 5400 to 5600 MHz C-band9200 to 9500 MHz X-band

(optional)Gain 6 dB nominal

3-dB beam widthOmnidirectionalAzimuth25°Elevation-40°C to +60°C (-40°F toOperating temperature

140°F)

Range console100 m minimumRange20 nmi maximum

(approx 37 km)2Range channels

Code selection Pulse coded (4 codesavailable), singlepulse

0°C to +50°C (32°F toOperating temperature

Power consumption+122°F)

a.c.-60, d.c.-40 W nominal(excluding receiver-trans-mitter power consumption)

Update interval May be selected by switchon front panel at variousintervals from 1/s to 10/s

AD-6(JUNE 1, 1981)

0.5 µµs maximum

Because the Mini-Ranger System III oper-ates at microwave frequencies, the range of the sys-tem is limited to line-of-sight distances. To obtain themaximum usable range, install the radar transpon-ders at the highest possible elevation. (See 4.4.3.2.2for slant range considerations.) When locating eachtransponder at the selected site, maintain a minimumseparation of 7 ft between the transponder and othermagnetic sensing devices, such as compasses, and besure that the transponder is positioned at least 2 infrom all iron, steel, or other magnetic material. Ade-quate ventilation must be provided. During tran-sponder operation, the case temperature of the unitmust not exceed 71°C (158°F). Transponder unitsand antennas must be installed vertically.

The receiver-transmitter and omnidirection-al antenna are installed as a unit using these sameprecautions. Each unit should be mounted at thehighest possible point aboard the vessel where nopart of the superstructure will shield the antenna.

EQUIPMENT AND INSTRUMENTS

FIGURE AD–6.—Transponder antenna and typical radiation patterns (courtesy of Motorola.)

AD-7 (JUNE 1, 1981)

EQUIPMENT AND INSTRUMENTS

AE. SEXTANTS

AE. 1. Navigating Sextant

FIGURE AE–1. — Hydrographic sextant with telescope

Next, adjust the horizon mirror to be per-pendicular to the plane of the arc. With the indexmirror in adjustment, set the index arm near zero.Hold the sextant so that its plane is vertical; sightthe sea horizon. Bring the horizon and its imageinto coincidence using the tangent screw. Rotatethe sextant slowly and observe whether the hori-zon and its image remain in coincidence. If not, ad-just the position of the mirror with the screws atthe back of the frame until coincidence is obtained.

Sextants are adjusted as follows: the indexmirror (large mirror on the index arm) must first bemade perpendicular to the plane of the instrument.To make this adjustment, set the index arm atabout 10º and hold the sextant with the eye closeto the index mirror and as nearly as possible in theplane of the sextant. Observe the graduated arc di-rectly and its reflection in the index mirror, mov-ing the arm back and forth slowly. The arc and itsreflection should form an apparently continuousunbroken arc if the mirror is perpendicular to theplane of the arc. If the arc is discontinuous, correctthe position of the mirror by adjusting the screw atthe back of the frame.

AE.1.2. INDEX ERROR OF SEXTANT. Theseerrors in sextants are caused by nonparallelism ofthe reflecting surfaces of the mirrors when the in-dex arm is set at zero. Index error magnitude canbe determined by one of these three methods:

AE-1 (JUNE 1, 198 1)

A sextant is a hand-held instrument used tomeasure angles between two points up to a maximumof about 140º. Navigating sextants, which can be readto 10 s or 0.1 min of arc, depending on the design, areclassified as vernier or micrometer drum accordingto the method used to obtain final readings. See chap-ter 15 of the ''American Practical Navigator, an Epit-ome of Navigation'' (Bowditch 1962) for a completediscussion of various types of sextants in use.

To use a clamp screw sextant, wet the in-dex arm at the approximate angle, then clamp thearm firmly to the frame. Bring the two objects intoexact coincidence using the tangent screw. Modernvernier sextants have a worm gear attached to thearm that functions as an ''endless'' tangent screw.

Micrometer drum sextants (figure AE-1)also have an endless tangent screw, but the finalreading is made on a graduated drum rather thanon a vernier scale. Drums are graduated to 10 s,0.1 min, or 1 min of arc. Drum-type sextants arepreferred by most observers; however, it may bedifficult to measure angles accurately when theyare changing very rapidly.

AE.1.1. ADJUSTMENT OF SEXTANT. Eachsextant used for hydrographic surveying must beadjusted as necessary before beginning a day'swork. Sextant adjustments must be verified eachnight at the close of the day's work and amounts ofindex correction found entered in the sounding re-cords. (See 4.8.3.) Proper adjustment should bechecked periodically throughout the day and indexerrors, if present, noted.

Finally, the two mirrors must be parallel toeach other when the index arm is set at zero. Aftermaking the two adjustments described above, setthe index arm exactly at zero; then hold the sextantin a vertical position and sight at the horizon. Theobserved and reflected horizons should coincide. Ifnot, adjust the mirror with the screws at the side ofthe mirror until the observed and reflected hori-zons coincide. This adjustment may disturb thevertical adjustment. Repeat each until the horizonmirror is adjusted for all positions of the sextant.

1. Hold the sextant vertically and ob-serve the sea horizon. Bring the direct and reflect-ed images into coincidence and read the setting ofthe index arm. Repeat the process several times, al-ternately bringing the reflected horizon down to

3. Measure the apparent diameter of theSun by holding the sextant vertically. Bring the up-per limb of the reflected image to touch the lowerlimb of the direct image. Read the angle. Then bringthe lower limb of the reflected image to touch theupper limb of the direct image and read the settingoff the arc. Half the difference of the two readings isthe index correction. The correction is positive if thelarger of the two values is off the arc. For example,if the diameter measures 33'50'' (on the arc) and 32'40'' (off the arc), the index correction would be ½(33'50''-32'40'') = 35'' (minus). Several such obser-vations should be taken and the average used. Obser-vational accuracy may be verified by comparing theSun's semidiameter for the date of observation fromthe Nautical Almanac with one-quarter of the sumof the two readings (regardless of the sign).

HYDROGRAPHIC MANUAL

As a general rule, after measuring and read-ing an angle, an observer should not move the indexarm until the position has been plotted, so the read-ing can be verified if necessary. Sextant anglesshould always be verified before the arm is moved.

The two angles of a three-point fix must bemeasured simultaneously on signal. If one of the ob-jects cannot actually be seen or if they are not in co-incidence at that instant, the angle must be recordedas a ''miss.''

AE.1.4. ANGLES TO FAINT OBJECTS. Whensignals are faint, it may be difficult to reflect right-hand objects although they can be seen fairly wellwhen looking directly at them. In such cases, thesextant should be set to the expected angle at thenext position so the reflected image of the right-handobject will be in the field of view of the telescope.There are several methods of determining approxi-mate angles:

AE.1.3. USE OF SEXTANT. To measure ahorizontal angle between two objects with a sextant,sight the left object over the top of the horizon mir-ror. Unclamp and move the index arm until the re-flection of the right object can be seen (by double re-flection) in the horizon mirror directly under theleft-hand object. Bring both objects into exact coin-cidence using the index arm tangent screw.

When objects are definite and readily visi-ble, many observers use the sextant without a tele-scope, especially when angles change rapidly or ifthe sounding vessel is unsteady. When objects aredistant, indistinct, or indefinite and angles arechanging slowly, a sighting telescope should al-ways be used on the sextant—particularly when asmall error in an angle will significantly affect theposition.

If the center object is difficult to reflect, ob-servers can measure the right angle and the totalangle between right and left objects, then subtractthe former from the latter to obtain the left angle. Ifthe right-hand object is difficult to reflect and theleft object is very distinct, the sextant may be heldupside down to look directly at the right-hand ob-ject and reflect the left-hand one.

Little experience is required to measure sex-tant angles between prominent objects when an an-gle is changing slowly and the observer's platform issteady. In hydrographic surveying, the circumstanc-

AE-2(JUNE 1, 1981)

coincidence and up to coincidence. Average the re-sults. If the zero of the vernier is to the right of thezero of the are, or ''off the arc,'' the correction ispositive and is added to the measured angles. If tothe left or ''on the arc,'' the correction is negativeand is subtracted from measured angles.

2. At night, substitute a star for the seahorizon. Point the sextant at the star and bring thedirect and reflected images into coincidence andread the setting of the index arm. Repeat severaltimes and use the average of the results as described.

es are often reversed— angles change rapidly, ob-jects are indistinct, and the survey vessel is far fromsteady. Under such conditions, a great deal of prac-tice is required to enable an observer to measure sex-tant angles quickly and accurately.

1. Angles may be scaled from field sheetswith a protractor at the approximate location of thenext position.

2. If an angle is not changing too rapidly,the rate of change between the two preceding anglesmay be applied to determine the approximate angleat the next fix.

3. The relation between the faint signaland a conspicuous object near the signal may be not-ed and that object reflected initially. A slight move-ment of the sextant brings the correct signal withinthe field of view.

4. If the observer first determines the an-gle subtended between the ends of thumb and littlefinger with the arm outstretched, he can roughly ap-proximate an angle by sighting over his hand and vi-sually stepping off the angle along the horizon.

AE

-3

FIGURE AE–2.— Corrections to inclined sextant angles when one object is elevated appreciably above the second object

CORRECTION

(JUN

E 1, 1981)

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HYDROGRAPHIC MANUAL

AE.1.5. INCLINED ANGLES. Sextant anglesfor hydrographic control must be measured be-tween objects that lie approximately in the samehorizontal plane as the observer. If an angle be-tween two objects of considerable difference in ele-vation must be measured, the observed value iscorrected according to the graph in figure AE-2;this graph is based on

standard arc values; and electronic interpolation isused to determine drum vernier readings. Thecurved scale is attached to the sextant base, and theelectro-optical encoder head is mounted on the ra-dial arm that pivots with the sextant mirror shaft.

The encoder scale is a vacuum depositedchrome ruling on an optical glass arc segment. Thereading head uses phototransistors as sensing ele-ments and light-emitting diodes as illumination ele-ments. All components are extremely durable andare highly resistant to rough handling, vibration, saltwater, and corrosion. A reticle of vacuum depositedchrome on glass with a minimum clearance of 0.003in from the encoder scale is used to ensure zerowear, striction, or drag in the encoder readout as-sembly. The conventional sextant bearing is replacedby a high accuracy, preloaded ball bearing pair to in-crease the rigidity of the pivot arm and achieve er-ror-free digitizing under all conditions. A large

cos O - sin (h¹) sin (h²)--Cos Ccos (h¹) cos (h²)

where C is the horizontal or computed angle, O isthe observed inclined angle, and h ¹ and h ² are theangular elevations of the elevated objects from thepoint of observation. This formula reduces to

Cos OCos C -- cos h

if only one signal is elevated (h¹ or h² = 0).

AE.2. Electronic Digital Sextant

In electronic sextant operation, a curvedglass scale replaces the conventional graduated arc;an electro-optical reading head is used to extract FIGURE AE-3. Electronic digital sextant

AE-4(JUNE 1, 1981)

To find the correction to an observed an-gle, enter the graph at the left-hand margin withthe altitude angle as the ordinate. From this point,extend a line horizontally until it intersects thecurve representing the observed inclined angle–in-terpolate between the curves if necessary. The ab-scissa value at the point of intersection on the hori-zontal scale at the bottom of the graph is thecorrection to be applied. Corrections for observedangles from 0º to 90º are negative; corrections forobserved angles from 90º to 180º will be positive.

This sextant, manufactured by Teledyne-Gurley, Troy, New York, is designed to provideaccurate angular data to the HYDROPLOT systemfor automatic recording and machine-plotted posi-tions. The digital sextant is a modified U.S. NavyMark III sextant–lightness (4 lb), durability, andcorrosion resistant characteristics of the standardsextant have been retained. (See figure AE–3.) Theinstrument is used and operates in a manner similarto that of a conventional sextant, except that theobserver does not read the arc drum and verniervalues–all angular data are transmitted by cabledirectly to the processor.

EQUIPMENT AND INSTRUMENTS

by a grounding pin on the connector. Digital sex-tants are designed to operate without accuracydegradation or loss of repeatability in temperaturesfrom 35° to 120°F (approximately 2° to 49°C) andin a relative humidity range of 10 to 90%. Low tomoderate vibrations normally encountered aboardships or smaller survey vessels will not affect theinstrument. Each electronic digital sextant must bestored and carried in the specially designed carry-ing case provided with the instrument—the case af-fords reasonable protection against vibration andimpact damage and also provides storage space forthe telescope, special adjusting instruments, and theconnecting electrical cable. When in use, the sex-tant can be rested in the ''optics down, handle up''position on the three legs mounted for this purpose.

0.25-in-diameter movable mirror shaft is used forthe same reason. The entire assembly is sealed in aremovable lightweight fiberglass enclosure towhich a contoured balanced observer's handle isattached. The entire electronics assembly is on asingle printed circuit board mounted on the insideof the fiberglass enclosure. Reading head outputsare electronically amplified by a factor of 4 to per-mit a less dense ruling and increase the quality ofscale readouts.

A special wrench for making optical adjust-ments is included in the instrument carrying case.When adjusting or operating the instrument, use thedigital values only. Direct readings from the arc,drum, and vernier are not accurate and are intendedonly for use when making approximate angle set-tings to the nearest degree. Optical adjustment pro-cedures for electronic sextants are identical to thosedescribed in section AE.1.2 for conventional sex-tants. The need to make frequent optical adjustmentsis an indication that the instrument is defective or isbeing mishandled. The rear lens housing of the tele-scope must be adjusted by each individual observerfor the sharpest and clearest image possible. Remem-ber the reading on the diopter scale for use whenmaking future settings.

When using the telescope attachment, diffi-culty in bringing two objects into coincidence indi-cates that the telescope line of sight is not parallel tothe plane of the sextant frame. Unfortunately, thereare no adjustments that can be made in the field toremedy the situation. Adjustments can be made onlyby the manufacturer. Telescope alignment can bechecked by:

Observer safety was a primary consider-ation in the design of the instrument. Probability ofelectric shock is nil. Power supply buses are com-pletely isolated from all metallic parts. The cableconnecting the sextant to the navigation interfaceprovides a ground path between the two systemsubassemblies. The ground lead on the digital sex-tant frame terminates at the other end of the cable

AE-5 (JUNE 1, 1981)

Conventional sextant configuration waspreserved in the design of the electronic digitalversion. Electronic sextants are easy to handle andoperate and are safe to use under all environmentalconditions. The rapid coarse angle setting and fineadjustment features are identical to those of a stan-dard sextant—observer's ''feel'' is not affected. Theelectronic sextant is well balanced when held bythe handle, which is located beneath the center ofgravity and is canted slightly forward to reducearm strain to a minimum. A push-button switchthat causes an interrupt to the computer is locatedin the handle where it can be easily depressed bythe index finger. The function of this push button iscontrolled by the computer software and may beused to reject fixes, record fixes, or take checkfixes depending upon the particular program beingused. In general use, a fix is taken automatically ona programmed schedule rather than at the push ofa button. The observer's left hand is free to per-form the same adjustments necessary for conven-tional sextant operation. The conductor cable leadsfrom the bottom of the handle for minimum inter-ference to the observer. The connecting cable ismechanically strain relieved at the instrument han-dle so the seals will not be damaged by stress orstrain. Special materials such as titanium and fiber-glass are used to keep the weight of the electronicdigital sextant to an absolute minimum (4 lb with-out telescope, 4.5 lb with telescope attached). Ap-proximate dimensions are 11.5 in x 11 in x 10.5 in.

AE.2.1. ADJUSTMENT AND CALIBRATION.The electronic digital sextant is a factory calibratedinstrument. Electrical or electronic adjustments shallnot be attempted in the field. Basic settings arelocked by epoxy bonding or pinning of components.

1. Holding the sextant horizontally in theleft hand with the horizon glass nearest to the ob-server.

2. When the ''mark'' signal for the fix issounded, the value of the angle is instantaneouslytransmitted from the sextant to the computer for re-cording and machine plotting of the fix. Observersdo not have the luxury of being able to make another''crank'' on the tangent drum to "touch up" the an-gle after the signal. The fix, however, can be reject-ed by pressing the button on the sextant angle.

HYDROGRAPHIC MANUAL

3. Aligning the centerline of the horizonmirror with its image in the index mirror.

4. Seeing in the index mirror the imageof the entire telescope tube back to the eyepiece.

AE.2.2. OPERATION. Procedures for ob-serving an angle with an electronic digital sextantare nearly the same as those when using a conven-tional sextant, but there are two important differ-ences:

AE-6(JUNE 1, 1981)

2. Setting the index arm at approximate-ly 0°.

1. After the instrument has been adjust-ed to an angle of 0°, set the angular digital displayvalues on the navigation interface to 0 and set themode switch to the ENCODER position. (Remem-ber that values read from the graduated marks areinaccurate.)

EQUIPMENT AND INSTRUMENTS

SOUNDING EQUIPMENT

AF.1. Manual Depth-Measuring Devices

AF.

AF.1.1. LEAD LINE. All field units en-gaged in hydrographic surveys where generaldepths are less than 20 fm shall have one or morelead lines marked and calibrated. Lead lines are re-quired for the following purposes:

Standard lead-line material is mahogany-col-ored tiller rope with a phosphor-bronze wire center.The center consists of six strands of seven 33-B (S-gage) wires each. The wire core is flexible and shouldnot break after continual use and coiling. The rope issize 8 (about 0.24 in. in diameter), and is made of water-proofed, solid braided, long-staple cotton. The braidshould be tight enough so that broken wire strandswill not protrude through the covering and injure aleadsman's hands. Material for lead lines may either berequisitioned from the Marine Centers or be pur-chased from a well-equipped marine supply dealer.

AF.1.1.1. Marking lead lines. Depending onthe depths in which they will be used and on thesize of the vessel, lead lines should be 15 to 30 fmlong. Each lead line is identified by a consecutivenumber stamped on a metal disk attached at the in-board end of the line. Identification is made when aline is initially graduated. This number is to be re-tained throughout the life of the lead line or untilre-marking is necessary.

Two units of measurement, the fathom andthe foot, have traditionally been used to mark leadlines for hydrographic surveys in the United States.Only one unit is to be marked on a lead line. Hy-drographic parties surveying in both depth unitsshould be equipped with at least one lead line grad-uated in each unit.

The braided covering of an unseasoned leadline tends to shrink when wet causing the wire coreto buckle and the strands to break. Broken strandsare likely to protrude through the covering andcause hand injuries. To prevent rupturing the core

Intermediate marks are placed between thefathom marks to permit readings to the nearesttenth of a fathom. Each half of a fathom is marked

AF-1 (JUNE 1, 1981)

1. To search for or to confirm leastdepths over shoals and sunken rocks.

2. To confirm echo soundings in kelp orgrass areas.

3. To obtain bottom samples (whensampling device is attached).

4. To obtain vertical cast comparisonswith echo soundings.

5. Occasionally to suspend instrumentsfor temperature and salinity observations from asmall vessel.

with repeated use, preseason each lead line as fol-lows:

1. Prepare the lead line by soaking it insalt water for 24 hr. Then, while the line is stillwet, work the cotton covering along the wire byhand until the wire protrudes from the covering.The wire should protrude about 1 ft for each 10fm of line. This is a tedious procedure requiringthe cooperative efforts of several people. Thecovering can be pushed back and slackened onlya few inches at a time; this length of slack mustbe pushed nearly the full length of the line beforethe next few inches can be started. The excessprotruding wire is cut off. The covering must notbe worked back too far, or it will form bulgesalong the wire. Lead lines so prepared will main-tain an almost constant length for future use.

2. Next, the line is dried under tension(about 50 lb) and then soaked again for 24 hr.Never boil a lead line as this destroys the water-proofing of the cover.

3. After attaching a lead to the line, theline should be wetted down again and placed undera tension equal to the weight of the lead; this ten-sion is maintained while the line is being graduated.Temporary marks made at this time can be usedfor later permanent marking. Graduation marks ona new lead line may be laid off with a steel tape.The best method, however, is to mark the distancespermanently on a suitable surface such as on thedeck of a ship or on a wharf if the survey party isshore based. Permanent markings are convenientwhen verifying the graduations in the future.

Traditional markings for lead lines graduat-ed in fathoms are shown in Table AF-1.

HYDROGRAPHIC MANUAL

TABLE AF–2.— Markings for lead lines graduated in feet

MarksFeet

Each fathom mark should extend 2 in fromthe lead line. Leather marks are made in one piece

TABLE AF–1. — Markings for lead lines graduated in fathoms

MarksFathoms

ipated, a metric lead line should be prepared. Eachmeter and half meter is marked using an identifica-tion system convenient to the observers. A markingsimilar to that of a lead line graduated in feet isrecommended (such as red, white, blue, yellow,and leather).

On occasional surveys for which the depthunit is the meter, soundings may be taken with leadlines graduated in feet, provided that the measure-ments are converted to meters prior to plotting. Insuch cases, the hydrographic records must clearlyand unmistakably identify which soundings are infeet. When extensive soundings in meters are antic-

AF.1.1.3. Sounding leads. These in standardweights of 5, 7, 9, 14, and 25 lb are requisitionedfrom the Marine Centers. Each survey unit shouldhave one or more leads with a snapper-type bot-tom-sampling device attached. (See AK.2.7.) Vari-ous methods may be used to attach the lead to the

AF-2(JUNE 1, 1981)

by a seizing of black thread; each even tenth of afathom (0.2, 0.4, 0.6, and 0.8) is marked by a seizingof white thread. Odd tenth readings are estimated.

1, 11, 212, 12, 223, 13, 234, 14, 24

5, 15, 256, 167, 178, 189,191020

One strip of leatherTwo strips of leatherBlue buntingTwo strips of leather secured in the

middle so that two ends pointupward and two downward

White buntingWhite cord with one knotRed buntingThree strips of leatherYellow buntingLeather with one holeLeather with two holes

with strips (about ¼ in in width) that are slit inthe free end of the mark. Bunting marks are madeby folding a small piece of bunting to about 5/8 inwide by 5 in long; this length of folded bunting isthen folded once again in the middle then securedto the lead line so the folded end is free.

Waxed linen thread should be used to se-cure marks to the lead line in such a manner thatthere can be no possibility of slippage. Do not in-sert the thread through the braided covering of theline. All marks except 4-, 14-, and 24-fm marksshould be secured so that their free ends are upwhen sounding. Marks so secured will tend tostand out more from the line when vertical.

Traditional markings for lead lines graduat-ed in feet are shown in table AF-2.

Intermediate odd feet (1, 3, 5, 7,...) aremarked by white seizings. Leather markings at the10-ft multiples should be the same size as the fath-om marks on lines graduated in fathoms. Buntingmarks that identify intermediate even feet shouldbe slightly smaller in size.

2, 12, 22, ...4, 14, 24, ...6, 16, 26, ...8, 18, 28, ...10, 60,11020, 70, 12030, 80, 13040,90, 14050100

Red buntingWhite buntingBlue buntingYellow buntingOne strip of leatherTwo strips of leatherLeather with two holesLeather with one holeStar-shaped leatherStar-shaped leather with one hole

AF.1.1.2. Verification of lead lines. Leadlines used for sounding are compared with a stan-dard at the beginning of a season and at frequentintervals thereafter, depending on usage. When thechecks are made, lead lines must be wet and undera tension equal to the weight of the attached leadin water. The testing standard should be a good re-cently calibrated steel tape or premeasured gradua-tion marks on deck or ashore.

Stamp 5 (figure 4-29, section 4.8.3.6), Lead-Line Comparison, is used to record comparison re-suits in sounding records. A comparison should bemade either at the beginning or at the end of eachday a lead line is used. (See 4.8.3.6.) If a lead line isfound to be correct, a statement to that effect is suf-ficient. When incorrect, comparison results are en-tered for each fathom or for each 5 ft to the extentof the depths measured. True lengths of the gradua-tion marks as determined by comparison against thestandard are entered on stamp 5 in the column head-ed ''D''; corresponding graduation mark values areentered under the column headed ''M." Correctionsto lead-line soundings are obtained by subtractingcolumn M from column D. Replace or re-mark leadlines if the errors exceed 0.5 ft or 0.2 fm.

EQUIPMENT AND INSTRUMENTS

lead line. The preferred method is to have a galva-nized thimble at the lower end of the lead line towhich the lead can be attached by a shackle. Thesounding lead and the snapper sampling lead canthen be interchanged on the same line.

sections of thin walled tubing, such as condensertubes. The ends of the tubes are plugged and madewatertight. The tubes are placed about 0.25 in apartand clamped in position with three sections of strapiron. A hinged yoke secures each end of the bar.Additional weights are added as necessary to over-come the buoyancy of the trapped air and to keepthe suspension lines taut where the bar is lowered.The overall length of the bar should be about thesame as the beam of the sounding vessel. Bars usedin depths greater than 30 ft should be at least 9 inwide.

AF.1.2. SOUNDING POLE. Shallow depthsover extensive flat areas in protected waters can bemeasured more easily and more accurately with asounding pole than with a lead line. Sounding polesshall be used in areas too shoal for echo soundings,but restricted to depths less than 12 ft. Soundingpoles are generally not used in depths greater than 6ft except to provide supplemental soundings neededto interpret analog depth records, Pole soundingsare read and recorded to the nearest half foot.

Flexible wire or line with a wire core is usedto suspend the bar below the sounding transducer.Bar check lines are marked and verified by the samemethods prescribed for lead lines. (See AF.1.1.)

A sounding pole is made from a 15-ft lengthof 1.5-in round lumber capped with a weighted met-at shoe at each end to hasten sinking. Shorter polesmay be used depending on the depth conditions.Any convenient system of marking that is symmetri-cal toward both ends and will minimize reading er-rors may be used. The following marking system isrecommended:

The bar apparatus must be a sound-reflect-ing surface that can be lowered to a known depthbelow the transducer. Various types of bars can beused, such as a section of 2- to 3-in pipe that issealed at both ends, a section of sheet steel about 9in wide and 3 ft long, or a weighted board. One ofthe more effective bars is constructed of six to eight

A similar trawl sweep suspended betweentwo vessels can be used advantageously in areaswhere the bottom is foul with oyster clumps, rocks, orother debris too insignificant to locate individually.

AF-3 (JUNE 1, 1981)

Mark each foot and half-foot graduationpermanently by cutting a small notch in the pole.Paint the entire pole white; then paint the spacesbetween the 2- and 3-ft, the 7- and 8-ft, and the 12-and 13-ft marks black. Other foot marks are indicat-ed by 0.5-in colored bands—red at the 5- and 10-ftmarks and black at the 1-, 4-, 6-, 9-, 11-, and 14-ftmarks. Half-foot marks are 0.25-in bands, whitewhere the pole is black and black where the pole iswhite.

AF.1.3. BAR CHECK APPARATUS. A barcheck is one method used to verify the accuracy ofan echo sounder and to determine corrections forinstrument error and velocity error. When accuratebar checks can be obtained throughout the fullrange of depths in the project area, velocity correc-tions can be determined without making oceano-graphic observations. (See 4.9.)

AF.1.4. MODIFIED TRAWL SWEEP. This canbe used to search for and locate submerged snagsand obstructions when only one vessel is available.The sweep is made of two small or miniature trawlboards or doors identical to those used by commer-cial shrimp or fish trawlers. Completely finished andoutfitted trawl boards (also called trawl doors or ot-ter boards) are available at most of the larger com-mercial fishing outlets. The trawl boards are con-nected by 150 to 200 ft of 3/16- or 1/4-in oval linkchain as illustrated in figures AF-1 and AF-2. Thesweep is bridled and towed so that the connectingchain is dragged along the bottom approximately200 ft astern of the towing vessel. Chain is easier tohandle than steel cable and does not kink and fray,although chain will ''mud up' faster than cable.Towlines of 1/2-in nylon or 5/8-in manila line areadequate for most small modified trawl sweeps.

A small buoy should be anchored in the im-mediate search area to provide a visual reference dur-ing the sweep operaton. Radial or closely spacedsweep lines are run with about one-third overlap overthe adjacent swept area. Fixes along and at the ends ofthe sweep lines are plotted to show the area coveredby each run. When an object is snagged, the trawlboard towlines converge gradually and allow suffi-cient time for the coxswain to stop the vessel. Thetowlines are then hauled aboard and the vessel ma-neuvered until the snagged object is close enough tofix its position and take a pole or lead-line sounding.

HYDROGRAPHIC MANUAL

FIGURE AF-2. — Modified trawl sweepFIGURE AF– l.— Trawl board construction

LAUNCH WIRE – DRAG GEAR

END BOUY [ metal sphere, approx. 3. ft. dia. ]

UPRIGHT [¼ in. dia. line, graduated to allow fordifferent depth sailings]

vK-rLEAD WEIGHT [ approx. 50 lbs ] /

TTOM WIRE [Five, 50-ft sections of 3/10 cable]

TOGGLLES [ attached to the bottom wire at 50-ft intervals]

NOTE all connections between adjoining sections of bottom wire, bottom wire and towline,

upright and bottom wire, load weights and bottom wire. and toggle to bottom wire should

be made with shackles and swivels.

FIGURE AF–3. — A simple technique for launch wire-drag

AF-4(JUNE 1, 1991)

EQUIPMENT AND INSTRUMENTS

Suspended sweeps are made up of 200 ft of 3/16-instainless steel cable in 50-ft lengths. Half-gallon''Clorox'' type plastic containers spaced at intervals ofabout 16 ft support the cable during a sweep. Weightsof 50 lb are placed at each end of the bottom wire to re-sist the lift of the sweep as it is being towed. Theseweights are supported by larger floats with uprightsset an appropriate distance off the bottom. Such sys-tems must be towed slowly to minimize lift. Normally,there will be 1 ft of lift at 2 or 3 kn.

rent permits greater speed over the ground.

AF.1.6. LAUNCH WIRE DRAG. This is asystem of locating submerged items and in some in-stances is a variation of standard wire drag proce-dures. Launch wire drag has been used for severalyears especially in Alaska and to some extent alongthe U.S. east coast for item investigation and areaclearance. For areas in Alaska, standard wire dragequipment— including bottom wire, buoys, weightsand bridles—has been used with continued success.In recent years along the U.S. east coast a modifiedwire drag procedure has been used aboardlaunches for item investigation. The equipment andlayout are shown in fig. AF-3. This modified wiredrag is recommended for shallow water (less than20 feet) and then only when other efficient tech-niques would not be more effective in locatingitems. Divers are highly recommended for obstruc-tion identification and for accurate determinationof least depth over the obstruction. See Special Re-port-Launch Wire Drag (Ethridge 1979).

AF-5 (JUNE 1, 1981)

AF.1.5. PIPE DRAG. This is often more ef-fective and easier to handle than a trawl sweepfrom very small boats. Construction is simple. Thepipe is a standard length (21 ft) of approximately1.5-in pipe. Each end of the pipe is packed withlead to provide more weight and reduce lift whenunderway. The pipe is suspended below the vesselby graduated lines over each gunwale. Pipe weightis the major factor in allowable vessel speed. Trialand error variations are usually necessary to deter-mine the best combination. Dragging with the cur-

AG.1.2. ECHO-SOUNDING TRANSDUCERS.These convert electrical energy pulses to acousticalenergy, then reconvert returning echoes back toelectrical energy. Returned energy pulses are ampli-fied and used to determine and record depths.Transducers are normally designed to operate atspecific frequencies (AG.1.3) depending on the ap-plication and depth range. Transducer frequenciesare divided into three groups: (1) low frequency—below 15 kHz, (2) medium frequency—from 15 to50 kHz, and (3) high frequency—above 50 kHz.

EQUIPMENT AND INSTRUMENTS

ECHO SOUNDINGAG.

AG.1. Introduction

Echo sounders measure the time requiredfor a sound wave to travel from its point of origin tothe bottom and return, then convert this time to dis-tance or depth. Various instruments and methodshave been devised to generate the sound, then re-ceive and record its echo. The transmission of soundused in echo sounding is dependent on certain prop-erties of the water and on the reflecting surface. If asound wave is to travel at a constant velocity fromsurface to bottom, the water must have the samephysical characteristics throughout the entire depth—there should be no attenuation of sound, and thereshould be total reflection from a bottom parallel tothe surface. Such conditions are nonexistent.

Velocity corrections usually are determinedfor all hydrographic surveys; however, correctionsof less than 0.5% of the depth may be ignored.

Electrical energy pulses are converted toacoustical energy by a transducer mounted in thehull. Transducers with various frequencies are usedfor different ranges of depth and for specific pur-poses. Low-frequency pulses are used for soundingin deep water because high-frequency signals aresubject to greater absorption and require greater ini-tial power.

Pulses transmitted by an echo sounder arein the form of sound or compression waves, andmay be varied in frequency, duration, and shape.The sound wave may be dispersed in all directionsor may be contained and concentrated into a nar-row beam by a reflector. The suitability of any echosounder for a given requirement depends upon howthese variables are combined. The repetition rate ofthe pulse may also be varied to suit a particularsounding requirement.

Echo-sounding equipment is designed togenerate the sound wave, receive and amplify theecho, measure the intervening time interval, thenconvert the time interval into units of depth and re-cord the results graphically, digitally, or both. It isimportant to remember that an echo sounder doesnot and cannot measure depth directly. An echosounder measures time (i.e., the time it takes for asound pulse to travel from the transmitter to thebottom or other reflecting surface and back again).The time interval is converted mechanically orelectronically to depth by multiplying by the veloci-ty of sound in water:

1- —-

-Depth ννt2

AG.1.3. ECHO PULSE FREQUENCY. Varia-tion of pulse frequency causes great changes in echo-sounder capabilities. Most instruments used for gen-eral navigation lie in the audible frequency range.Because audible frequency echoes have a low ab-sorption rate, their high penetrating power makesthem useful for deep soundings. Audible frequencies,however, have certain limitations. They cannot beused to measure extremely shoal depths with a highdegree of accuracy. Because most of the noise in thewater generated by the sounding vessel and other

Sound travels through water at a fairly con-stant velocity; however, velocity varies with densi-ty, which is a function of temperature, salinity, and

AG-1 (JUNE 1, 1981)

AG.1.1. GENERAL PRINCIPLES. Nearly allsoundings for hydrographic surveys are measured byecho sounders that record a nearly continuous pro-file of the bottom below the survey vessel. All echosounders operate on the basic principle that a soundproduced near the surface of the water travels to thebottom and reflects back to the surface as an echo.

where ν is the velocity of sound in water and t is thetime for the pulse to travel to the bottom and back.Conversion to the proper sounding unit is a functionof the recording equipment.

If depths indicated by echo sounders are tobe correct, then (in theory) the measurement of tmust be correct. The value of ν used in the calcula-tion must equal the average velocity of sound in thewater through which the pulse has traveled.

depth. Echo-sounding instruments convert time todepth using a preset or an assumed velocity ofsound—the ''calibration velocity.'' Measured sound-ings will be in error by an amount directly propor-tional to the variation of the actual velocity fromthe assumed or calibrated value.

HYDROGRAPHIC MANUAL

sources is in the audible frequency range, soundingsare more susceptible to interference from straysources; and because of their long wavelengths,low-frequency pulses cannot be beameddirectionally without using transmitting and receiv-ing units of a prohibitive size.

column. The higher frequencies are ineffective indeep water.

Ultrasonic frequencies overcome, to a largeextent, most of the disadvantages of audible frequen-cies. Advantages of ultrasonic frequency pulses are:

Figure AG–2 shows an undamped transmis-sion pulse. With a long pulse of this type, a trans-ducer is energized over a longer period of time,which prevents the transducer oscillations from di-minishing, and results in a more powerful transmit-ted pulse. Deep water echo-sounder pulses varyfrom about 0.001 s to 0.04 s. Under good conditions,initial pulses with these durations assure bottomecho reception in waters over 5000 fm deep; howev-

5. Reduced side echoes (AG.1.5).

With ultrasonic frequencies, however, thesound pulse suffers greater attenuation, and straysare often recorded when sounding in turbulent wa-ter or when in areas where rapid changes in watertemperature or density occur throughout the water

FIGURE AG–2.— Long acoustical pulseFIGURE AG–1.— Short acoustical pulse

AG-2(JUNE 1, 1981)

1. High directivity and concentration ofacoustical energy achieved with small transmittingand receiving units.

2. Less recorded interference from vesseland water noises.

3. Shoal depths measured more accurate-ly.

4. A more detailed profile of an irregularbottom.

AG.1.4. PULSE DURATION AND SHAPE.Shapes of acoustical pulses through water vary con-siderably. General purpose echo sounders usuallytransmit a short pulse similar to that shown in figureAG–1. When a transducer is energized, it oscillatesat its design frequency and transmits a sound pulseinto the water. The damped oscillations diminishrapidly until they cease to be effective at a point ap-proximately half the original amplitude. The effec-tive pulse length for this type of transmission is ap-proximately 0.2 ms. Although pulses of this type arerelatively easy to produce, they generally do notcontain very much power. Under good conditions,however, this type of pulse does provide good bot-tom definition in waters as deep as 1000 fm.

EQUIPMENT AND INSTRUMENTS

er, as a result of pulse length, the return echoesprovide a relatively poor definition of the bottombecause in 0.04 s a sound wave travels about 33 fm.

Unfortunately, the energy of a beam cannotbe confined entirely within the limits of the mainlobe. Outside the main lobe, the strength of thepulse diminishes rapidly, except in the two sidelobes where the power increases again and is cen-tered about the axes approximately 30° to eitherside of the main axis. Side lobes serve no usefulpurpose and often cause false echoes that couldmislead the hydrographer. Some transducers gener-ate more than one pair of side lobes; but if the unitis well designed, most of the acoustical energy isconfined to the main lobe. Reflectors cannot con-fine all of the transmitted energy within the mainlobe.

Transducer beam width has an importanteffect on the accuracy and appearance of a record-ed echo. Energy directed toward the bottom willincrease as the width of beam is decreased and, atthe same frequency, the energy in the echo will in-crease. Smaller beams also reduce the adverse ef-fects of noise arriving from directions other thanthe bottom. For obtaining the greatest accuracy inecho sounding, a beam should be extremely nar-row. Under this condition, the echo comes from avery small bottom area, and side echoes fromslopes and other irregularities are reduced to aminimum. Certain other practical aspects, however,govern the selection of beam width.

FIGURE AG–3.— Shape of a general-purpose echo sounder

acoustical beam

AG-3 (JUNE 1, 1981)

AG.1.5. TRANSDUCER BEAM WIDTHS. Atransducer is generally mounted in the hull of avessel and has its radiating face directed towardthe bottom. Transmitting units are equipped withreflectors that concentrate the acoustical energyinto a beam. The shape of the beam depends uponthe diameter of the reflector and the pulse frequen-cy. The greater the diameter of the reflector andthe higher the pulse frequency, the narrower andmore concentrated the beam will be. Echo sounderbeam widths generally vary from 2° to more than50° depending on the purpose for which the instru-ment was designed. A transmitted beam may besymmetrical about its main axis or be wider in onedirection than in another. The shape of a beamtransmitted by a general purpose echo sounder isshown in figure AG-3. Most of the acoustical ener-gy is concentrated in the main lobe, which for allpractical purposes may be considered a cone.

HYDROGRAPHIC MANUAL

For example, low-frequency sound wavesmust be used in deep water; however, it is imprac-tical to install a transducer large enough to pro-duce a narrow beam at low frequencies. (OnNOAA vessels, frame spacing varies from about 20in to 27 in.) More accurate delineation of bottomslopes will be attained by partial elimination of re-corded side echoes when wide beam transducersare used.

sounders use damped pulses—unless sheer power forextremely deep soundings is a basic requirement.Undamped pulses are generally necessary for sound-ings deeper than 2500 fm. Long pulses transmit moreenergy than short pulses, making it more likely thatsome energy will be directed vertically to the bot-tom from a rolling and pitching ship. Long pulses,however, impair definition of the bottom profile andare used only when absolutely necessary.

Unless a stabilizing system is used, narrowbeaming is ineffective when sounding in deep waterand rough seas— as a vessel rolls, the beam is transmit-ted along a nonvertical path. Although an echo maynot be lost, it will not represent a true depth.

Deep water echo sounders almost universal-ly use low frequencies (less than 15 kHz). Absorptionlosses are least at these frequencies. Beams are wide—often as much as 25° on each side of the main axisof the lobe. Such wide beams decrease sounding ac-curacy over steep slopes and irregular bottom. Sideechoes from slopes may overlap or mask echoesfrom the bottom of a valley or trench. Higher fre-quencies with narrower beams are desirable, but can-not be used in great depths because of the high rateof attenuation. Increased power to the transducer toovercome attenuation is not a solution because thereis a limit to transducer driving power. If the limit isexceeded, cavitation occurs, and the power of thegenerated sound is decreased.

AG.1.6. ATTENUATION OF ACOUSTICALSIGNALS. After a sound wave is transmitted by thetransducer, it is continuously subjected to losses instrength, and the echo returning to the transducer isoften quite weak. Sound waves spread out or radiateas they make the round trip to the bottom and back,causing a gradual and continuous loss of energy.Some of the energy is absorbed in the water by con-version to heat. Absorption losses increase with sig-nal frequency. Such losses are significant with high-frequency echo sounders, but have little effect atlower frequencies. Scattering losses occur whensound waves are diverted from their original direc-tion of travel. Discontinuities in the water columncaused by turbulence, aeration, changes in waterdensity, or by solid matter in suspension contributeto scattering loss.

Medium frequencies (15 to 20 kHz) are usedfor most medium depth echo sounders designed tooperate. in depths less than 300 fm. In this range,transducers are quite small— the maximum dimen-sion does not exceed 8 in; however, the higher fre-quency generates a comparatively narrow beam thatresults in a more accurate definition of the bottom.

When a sound wave reaches the bottom,only part of the sound is reflected as an echo and re-turns to the transducer. If the bottom is rough and ir-regular or if the sound wave strikes at an angle, aportion of the wave is reflected away from a directline to the transducer and becomes lost. Part of thesound energy penetrates the bottom and is absorbedby or reflected from deeper layers of the bottom ma-terial.

High-frequency echo sounders are charac-terized by small transducers and narrow beamwidths. Short wavelengths and narrow beams resultin excellent detailed bottom definition; however,high absorption losses restrict their application tomaximum depths of about 300 ft. Most of the high-frequency sound will be reflected from the top of thesea bottom; there will be very little reflection fromlower formations.

Because all of the desirable features cannotbe combined for optimum performance, the design ofmost general purpose echo sounders is a compro-mise.

AG.1.7. FREQUENCY, PULSE LENGTH ANDSHAPE AND BEAM WIDTH. Because damped pulses(figure AG–1) are considerably easier to producethan undamped pulses (figure AG–2), most echo

AG-4(JUNE 1, 1981)

EQUIPMENT AND INSTRUMENTS

ECHO SOUNDERSAH.AH.1. Introduction

The following discussions are limited to gen-eral descriptions of echo-sounding systems currentlyused by the National Ocean Survey for hydrograph-ic and bathymetric surveying. Technical manualspublished by the appropriate manufacturer are a ne-cessity for satisfactory operation and maintenance ofeach system.

The basic depth range of the recorder is 1ft to 250 fm. Soundings can be recorded either infeet or in fathoms—a toggle switch on the recorderpermits rapid and easy changing of the soundingunit. Six sounding ranges or phases can be selected

AH.1.1. RAYTHEON ANALOG AND DIGI-TAL DEPTH SOUNDERS. Raytheon portable preci-sion recording fathometer produces a nearly contin-uous analog chart record of water depths. DE-723Dsystems provide, in addition, a remote digital displayof depth values. These digital depth data are trans-mitted in standard binary coded decimal (BCD) for-mat to external equipment such as the HYDRO-PLOT system or to peripheral data loggers.

Most of the following discussion has beenextracted from the Raytheon Co. (1974a, 1974b) DE-723B and DE-723D systems manuals. The Ray-theon Marine Co. (1975) Bathymetric Systems Hand-book is an excellent detailed technical reference forthe specification, installation, and operation ofRaytheon systems. Their address is Raytheon Ma-rine Company, Ocean Systems Center, P.O Box360, Portsmouth, Rhode Island 02871. The hand-book also provides general theoretical consider-ations, system selection guidance, and a performanceprediction system that are applicable to most echosounders.

FIGURE AH-1. Raytheon DE-723 echo sounder recorder unit(courtesy of Raytheon Marine Co.)

on the ''RANGE'' switch. These phases are:

AH.1.1.1. DE-723 depth recorders. Analogdepth recorders for the Raytheon DE-723B andDE-723D echo sounders are essentially the same. Toallow for portability or permanent mounting, thedepth recorders are housed in separate cast-alumi-num cases. Each opening surface is gasketed to en-sure that the unit is splashproof when operated in anunprotected environment. (See figure AH-1.)

A 10-unit overlap in each range permits thehydrographer to change ranges without missingsoundings and provides the means to determinephase corrections to soundings. Because thepreprinted chart paper is not graduated for phasesE and F, interpolation is necessary when scaling inthose depth ranges. Chart paper is calibrated acrossa width of 6.25 in. Paper speed can be set at either1 in/min or 2 in/min—use the lower speed if itgives adequate bottom definition.

To obtain the best depth profile, keep theSENSITIVITY setting at the minimum positionthat produces a good easy-to-read record. Hardbottoms reflect echoes stronger than do soft bot-toms. A flat bottom composed of rock, sand, orpacked mud should produce a sharp, clear, dark

AH-1 (JUNE 1, 1981)

The analog recorder registers depths bymeans of a mark made on a dry electrosensitive cali-brated paper by a stylus on a rotating arm that passesover the chart paper at a constant speed (600 rpmwhen sounding in feet and 100 rpm when soundingin fathoms). Sound energy is transmitted from thetransducer when the stylus passes zero on the chart.During the round trip of the sound energy to thebottom and back, the stylus travels across the chartpaper and makes a mark at the zero (or initial) point

–then when the echo is received from the bottomand converted to electrical energy, additional marksare made that show a depth profile of the bottom.

A, 1 to 50 ft or fm;B, 40 to 90 ft or fm;

C, 80 to 130 ft or fm;D, 120 to 170 ft or fm;E, 160 to 210 ft or fm; and

F, 200 to 250 ft or fm.

HYDROGRAPHIC MANUAL

AH.1.1.2. Electronics cabinet unit. This con-tains the transmitter, receiver, keyer, and a 12- and24-V d.c. power inverter. (See figure AH-2.) Unitsfor both the DE-723B and the DE-723D systemscan also be operated on 120-V a.c. power — regard-less of type of power, the accuracy of recordeddepths depends primarily on the frequency stabilityof the 60 Hz power input because a synchronoustype motor drives the stylus arm.

FIGURE AH–2. — Raytheon DE-723 echo sounder electronicscabinet unit (courtesy of Raytheon Marine Co.)

figure AH-3.) Both of these controls shall be set atzero while conducting hydrographic surveys. Digi-tal depth values are shown in a four-digit segmenteddisplay to the nearest tenth of a unit.

Additional characteristics of the electronicscabinet unit are described in table AH-1.

AH.1.1.3. Digital depth monitor. This is aseparate cabinet containing the digital display cir-cuitry and the tide and draft preset controls. (Seeecho pulse at a depth selected by the operator. The

TABLE AH–1. — Some characteristics of the Raytheon sounders

DE-723B DE-723DCharacteristic

21 kHzOperating frequency 90 kHz

Transmitted pulse length 50 Same

Sounding rate In ft: 10/s SameIn fm: 1 2/3/s Same

Accuracy*To depths of 100 ft 0.25% of depth± 0.25 ft

± 0.1 ft or fm100 ft to 240 fm Same± 0.25% of indicated

Minimum sounding 5 ft2 ft

Phase position shift error Zero± 0.1 ft

Environmental specificationst†Operating temperature rangeStorage temperatureMaximum relative humidity

Digital logic output Four bytes in 0.1Noneunit increments

AH-2(JUNE 1, 1981)

trace. Hard bottoms often create multiple echoes inshallow water because the sound waves reverber-ate between the bottom and the water surface.Such echoes are recorded as multiples of the actualdepth — the actual depth is always the shoalestreading. Multiple echoes usually can be eliminatedby reducing the SENSITIVITY setting. Soft mud-dy bottoms produce broad echoes of lighter inten-sity because the signal is reflected from both thetop and bottom of mud surfaces. Mud thicknesscan often be determined from the characteristics ofthe recorded echo.

0º to 50ºC-55º to 100ºC95%

SameSameSame

*Accuracy figures are based on a velocity of sound in water of exactly 4,800 ft/s and a line frequency of exactly 60 Hz.†When in the Tropics, never allow direct sunlight to fall on the electronics cabinet because the resulting internal temperature may

exceed safe limits. Do not operate this equipment below freezing temperatures as this may cause damage to the components.

AH.1.1.4. Digital phase checkers. Thesecheckers, designed at the Pacific Marine Center (Se-attle, Washington), are used to check the mechani-cal functions of Raytheon DE-723 systems analogdepth recorders (Raytheon Marine Co., Manchester,New Hampshire). The phase checker simulates

EQUIPMENT AND INSTRUMENTS

Soundings can be recorded in feet, fath-oms, or meters. Chart paper graduated to incre-ments of 100 units is used to record soundings infeet, 50 units for soundings in fathoms and 50 or100 units for metric soundings. Four recorderranges can be selected: (1) 0 to 100 ft or 0 to 50fm, (2) 100 to 200 ft or 50 to 100 fm, (3) 200 to300 ft or 100 to 150 fm, and (4) 300 to 400 ft or150 to 200 fm. A slight overlap between range set-tings is printed on the chart paper to reduce the

FIGURE AH–3.— Raytheon DE-723D digital depth monitor(courtesy of Raytheon Marine Co.)

an echo pulse at a depth selected by the operator.The simulated pulse is recorded on the analog re-cord. Comparison of exact simulated depths withthe corresponding values scaled from the recordpermits an accurate determination of phase errors.Recorded values of the simulated pulses are basedon a velocity of sound of exactly 4,800 ft/s.

chance of missed soundings when changing scalesover rapidly changing bottom.

AH.1.2.1. Ross depth recorder. This depthrecorder displays soundings on electrosensitiveNDK-type chart paper (Ross Laboratories, Inc.,Seattle, Washington). An endless rubber beltmoves a stylus across the chart paper. As the sty-lus makes contact with a trolley rail, the signalfrom the transmitter-receiver is transferred throughthe stylus to the chart paper. These signals are''burned'' on the chart paper to provide the graph-ic record of the bottom profile.

The recorder initiates all signal timing bygenerating a key pulse with a magnet that isriveted to the rubber belt and passes the pickupcoils. The key pulse is delayed electronically toaccommodate the various sounding ranges.

Chart paper speeds of 15, 30, 60, or 120in/hr may be selected. Choice of paper speed is

AH-3 (JUNE 1, 1981)

AH.1.2. ROSS DEPTH–SOUNDING SYSTEM.The basic Ross depth-sounding system consists ofseveral units, including a transducer, a transmitter-receiver, and a chart recorder. (See figure AH-4.)In addition to the basic units, a digitizer is used toacquire depth data in digital form for the NOS auto-mated system. Under ideal conditions, Ross systemscan sound in depths up to slightly greater than 150fm. For a more detailed technical discussion of theRoss depth sounder than is contained in the follow-ing sections, see the Ross Laboratories (1975) Auto-mated Hydrographic Survey System Operating andMaintenance Manual and the Ross Laboratories(1972) Technical Bulletin, System 1 package. Theiraddress is Ross Laboratories, Inc., 3138 FairviewAvenue East, Seattle, Washington 98102.

FIGURE AH–4. — Ross depth sounding system components, (left)analog recorder and (right) power supply topped by a digitizer(courtesy of Ross Laboratories, Inc., Seattle, Washington)

The endless belt is driven by a dual speedsynchronous motor, which causes the recordeddepth to be directly proportional to the powersupply frequency. Thus, 115-V a.c. constant-fre-quency 60-Hz power must be used if the recorderis to operate at the proper calibrated speed ofsound through water (4,800 ft./s). If the soundingvessel is not equipped with a constant-frequencypower supply, an accurate d.c. to a.c. invertermust be used.

HYDROGRAPHIC MANUAL

dictated by the bottom detail desired. Select theslowest speed that provides the necessary detail. Asensitivity switch on the recorder permits variationof the bottom trace density at different depths, anda fine line control switch can be used to produce ashort dark mark at the leading edge of the echo formaximum definition of a soft bottom profile. Apulse length (AG.1.4) switch for use in varyingdepths is also available.

The Ross analog recording system issubject to three instrumental errors:

AH.1.2.2. Ross Transceiver. The echo-sound-er transceiver, when keyed by a delayed pulse forthe selected depth range, transmits electrical energyto the transducer. The transducer converts theelectrical energy into acoustical energy at afrequency of 100 to 105 kHz. The transmitted echobeam is narrow and has distinct side lobes. Long orshort pulse widths can be selected by the chartrecorder operator. Short pulses (approximately 0.1ms) are normally selected for shallower depthsdown to about 400 ft and for the necessity tointerpret traces of fish or other small spurioustargets. Long pulses (approximately 0.5 ms) are usedto increase power as necessary to obtain strongerechoes when sounding in deeper waters. Longpulses cannot be used in depths less than 5 ft.

Calibration phase checks are performed onRoss analog depth recorders as follows:

1. Prior to beginning a new project.

The transducer also functions as a receiverfor return acoustical pulses that have been reflectedby the bottom or by other objects; returningacoustical energy is reconverted into electricalenergy by the transducer. The transceiver amplifiesthe returned electrical energy by the magnitude ofthe SENSITIVITY setting, then keys the chartrecorder where depth is indicated.

6. Following completion of a project orfield season.

AH-4(JUNE 1, 1981)

1. Initial where the leading edge of theoutgoing pulse is not coincident with the zero lineon the chart paper. This error is generallycompletely eliminated by operator adjustments; buton some models, the initial may record about 0.2units high following the calibration phase checksubsequently described.

2. Stylus belt length where calibrationmarks are recorded correctly at the top but not atthe bottom of the graphic record. Hydrographersmust be continually alert for the presence of thiserror by making frequent checks. When sucherrors are detected, belt lengths shall be adjusted assoon as possible.

3. Phase where disagreement existsbetween soundings on adjacent overlapping rangeswhen switching occurs between those ranges. Thiserror is due to improper internal adjustments in therecorder and can be corrected only by a qualifiedelectronics technician.

2. At least once a day or if operationsare conducted on a 24-hr basis, once each 4-hrwatch.

3. Before and after changing recordingpaper.

4. Following a recorder malfunctionand repair or adjustment.

5. At any time analog and digital depthvalues disagree by more than 0.5 ft, 0.2 fm, or by1% of the depth, whichever is greater.

To perform a calibration phase check,1. Set the digitizer function switch to

''CAL.''2. Dial in the calibration depths, then

scale the corresponding recorded depths asfollows:

a. If survey depths lie entirely onone scale such as 0 to 100 and 100 to 200, dial indepth increments of 10 units throughout the entirescale.

b. If survey depths range over twoor more scales, calibrate at three depths spacedequally throughout each scale; the greatest depthon each scale should be the least depth checked oneach succeeding scale.

3. If an analog trace is not constant ateach depth or varies by more than 0.5 ft, 0.2 fm, orby 1% of the depth, whichever is greater, surveyoperations should be suspended until a qualifiedelectronics technician calibrates or checks theinstrument.

4. Each calibration check shall berecorded on the graphic record and be filed as apermanent part of the survey records.

EQUIPMENT AND INSTRUMENTS

AH.1.3. RAYTHEON PORTABLE ECHOSOUNDER. This echo sounder, model DE-719 (figureAH-5), is a portable, precision, survey-type soundinginstrument manufactured by Raytheon Marine Com-pany, 676 Island Pond Road, Manchester, NewHampshire 03103.

Because the shape of the return signalpulse depends on the nature of the reflecting bot-tom, the analog signal level may be reached eitherslightly before or slightly after the digital signallevel. Differences in these signal levels can resultin the value of a digital depth varying from that ofan analog depth. Such conditions become particu-larly apparent when sounding over soft bottoms,bottoms covered with a layer of silt, or steeplysloped bottoms.

FIGURE AH–5. — Raytheon Echo Sounder Model DE-719(courtesy of Raytheon Marine Co.)

Depths from 2 ft to 410 ft are recordedanalogically on electrosensitive straight-line chartpaper by a flexible belt-mounted stylus. The re-cording rate is 534 soundings per minute. The op-erating range of the instrument through fouroverlapping depth phases (0-55, 50-105, 100-155,and 150-205 ft) is controlled by a selector switch.In addition, the ''X2'' range control switch dou-bles all range scales. Four paper speeds of 1through 4 in/min may be selected.

The digitizer can also be used to make a nar-row dark mark on the analog depth record at thedepth actually digitized. Such marks confirm properdigitizer operation and can be used to provide a clearprofile of the bottom. The model DE-719 is designed to operate

AH-5 (JUNE 1, 1981)

AH.1.2.3. Ross digitizer. This provides depthvalues in the format necessary for automatic logging.Depth measuring by digital methods is an electronicprocess whereby the time it takes a sound pulse totravel to the bottom and return is measured by an ac-curate electronic clock. This time is divided by twoand multiplied by the sound velocity (800 fm/s) todetermine depth. Depth measurements by this pro-cess are inherently more accurate than thoseobtained from analog recording methods — mechani-cal instrument errors and human scaling errors areeliminated. In addition, digital depths are free of ini-tial error. Both the Ross analog and digital recordersrequire a pulse to have a certain signal level before itwill be recognized as a possible bottom return. Thelevels are, however, slightly different for the analogrecorder and the digitizer.

Digitizers used by NOS are equipped with afour-digit readout that displays depths either in feetor in fathoms to the nearest tenth of a unit. (See figureAH-4.) Digital depth data is also transmitted in paral-lel binary coded decimal (BCD) form through an ex-ternal connector for use as input to the HYDRO-PLOT system. The manufacturer's statement of ac-curacy of the digital readout and the BCD output is0.01% ± 0.1 ft or fm, assuming a constant velocity ofsound of 4,800 ft/s.

Ross digitizers feature a range gate that caus-es the unit to ignore echoes that are received outside apreset depth range. These digitizers also provide cali-bration pulses to permit precise adjustment of thechart recorder. Calibration pulses are derived by dig-ital techniques from an internal crystal-controlledtime base.

A missed soundings counter is used to resetthe readout to zero after n consecutive soundings.Until n misses occur, the readout continues to displaythe last digital depth measurement. On each update ofthe readout, the decimal point flashes.

HYDROGRAPHIC MANUAL

from a 12-V d.c source; however, it can befurnished with a built-in power converter to operatefrom a 115/230 V a.c. 50-60 Hz power source. (SeeRaytheon Marine Co. 1976.) This conversion doesnot affect the ability to operate from a 12-V d.c.power source. The power requirement is 30 W.

The second mark (calibrated) will beinterrupted periodically to indicate the phase onwhich the recording was made. For example, twointerruptions with one solid mark indicates operationon phase 1 (0-55 ft), and three interruptions withtwo solid marks indicates operation on phase 2. Thecalibrate lines (at 0-50 ft) are not present when oper-ating on the X2 range. No adjustments shall be madeto compensate for variations in the temperature andsalinity content of the water or to force agreementbetween recorded soundings and bar check results.

AH-6(JUNE 1, 1981)

A barium titanate transducer that is fur-nished as standard equipment can be installed per-manently or temporarily. The transmitting beamwidth is 8º at the half power points and will notexceed 18º at the – 10 dB points at an operatingfrequency of 208 kHz. An optional narrow beamtransducer with the following characteristics is alsoavailable; operating frequency of 204 to 210 kHzand a beam width of 2.75º at – 3 dB points, 3.5º at– 6 dB points, and 4º at – 10 dB points. Minor sidelobes for both transducers are at least 11 dB downfrom maximum acoustic level. These narrow beamcharacteristics combined with the operating fre-quency make this instrument particularly wellsuited to record small depth changes and accurate-ly define rates of change in steeply sloped and ir-regular bottoms.

When operating the depth sounder withstandard chart paper, fixed reference marks aregenerated by a stable time base circuit that pro-duces two sharp pulses spaced exactly 20.833 msapart. These pulses are electrically superimposedon the analog output to the recording stylus andwill fall exactly 50 ft apart on the chart paperwhen the stylus drive motor speed is adjusted tothe speed of sound in water of 4,800 ft/s. Thesharp line inscribed on the chart by the transmit-ted pulse is adjustable to the zero depth calibra-tion on the chart by the CAL ZERO control, andthe line initiated by the second pulse will fall onthe 50-ft chart ''calibrate'' line.

FIGURE AH–6. — Raytheon Echo Sounder Model DE-719 alu-minum housing with rear storage area (courtesy of RaytheonMarine Co.)

The FIX-MARK switch when pressed tothe right will inscribe a mark on the chart paperfor time and/or position reference. Annotations canbe made adjacent to the fix mark by opening thehinged window in the front of the recorder. Aguard prevents accidental contact with the rotatingstylus and belt assembly.

The Raytheon DE-719 depth recorder uti-lizes completely solid-state circuitry, magnetic key-ing, and electronically controlled chart speed. Theequipment is housed in a splash-proof aluminum caseto assure maximum protection when operated underadverse conditions. For optional 115/230 V a.c. op-eration, the power supply is designed to mount onthe main chassis below the platen assembly. Space isalso provided in the rear half of the case for storingthe transducer, rigging, and power cable (figureAH-6). The entire package weighing 47 lb is provid-ed with a zippered canvas cover for protection dur-ing handling and transportation. Claimed accuracyof the sounder is ± 0.5% ± 1 unit of indicated depth.

AI.2.1. GENERAL PRINCIPLES. As withmost other underwater sonar devices, side scan so-nar derives its information from reflected acousticenergy. In operation, however, it bears a markedsimilarity to radar, in that it produces a continuous,coherent plan view of a relatively broad scannedarea. A set of transducers mounted in a compacttowfish generate the high-power, short durationacoustic pulses required for the extremely high res-olution of the system. The pulses are emitted in afan-shaped pattern that spreads downward to eitherside of the fish in a plane perpendicular to its path.As the Fish follows the tow vessel's track, the beamscans a bottom segment ranging from the point di-rectly beneath the fish outward as far as 500 metersto each side depending on the towed depth and fre-quency. Acoustic energy reflected from bottom(and waterborne) discontinuities is received by aset of transducers, amplified, and transmitted aselectric energy to the towing vessel. There it isamplified, processed, and converted to hard copyby the side scan recorder. The resulting output isessentially a detailed representation of ocean floorfeatures and characteristics. Good acoustic reflec-tors—rocks, ledges, metal objects, and sand ripples—are represented by darkened areas on the record.Depressions and other features scanned from theacoustic beam are indicated by light areas. An ex-perienced observer can interpret most records at aglance, recognizing not only significant featuresand objects, but often more subtle data such as thecomposition and relative hardness of the bottomand the shape and condition of submerged objects.

EQUIPMENT AND INSTRUMENTS

AI. Side Scan Sonar Equipment

AI.1. Introduction

Two basic acoustic approaches are used todistinguish topographic features of the sea floor andobjects on or above the sea floor. The conventionalmethod of echo sounding employs a vertical axisacoustic beam. The alternate methods, called sidelooking or side scanning sonar, requires an acousticbeam whose main axis is slightly below horizontal.

AI.2.2. SIDE SCAN SONAR APPLICATIONS.Side scan sonar is used in a wide variety of appli-cations in many phases of undersea endeavor.Those of interest to the National Ocean Survey in-clude:

The towfish is towed by one of a choice ofseveral cable lengths. The tow cable is connected tothe recorder by a second covered cable. Short rub-ber-covered tow cables (in the range of 50 m to 100

AI-1 (JUNE 1, 1981)

1. General searching. Because it high-lights objects which protrude above the surroundingocean floor, side scan sonar has proven to be a mosteffective means for bottom search. The fine resolu-tion in the system recordings enables users to identifyaircraft parts, small vessels, well heads, shipwrecks,and numerous other submerged objects.

2. Bathymetry and hydrography. The so-nar can be used to give detailed topography of thebottom not only below the towfish, but out to bothsides as well. This gives a much more rapid coveragethan a standard depth sounder and it helps prevent''holidays'' or skips of important targets betweensounding lines. The system can also provide the veryhigh probability of detection required in channelclearance surveys.

3. Sea floor geology. By comparing theintensity and shape of recorded echoes, the side scanoperator can differentiate between various bottommaterials. In most cases, sand, mud, rock outcrops,shell beds, gravel, coral, and other materials can bereadily differentiated from each other.

AI.2.3. SYSTEM DESCRIPTION. The basiccomponents of a side scan sonar system are a dualchannel graphic recorder, a transducer towfish, andassociated cables. Most units are capable of a.c. ord.c. (battery) operation.

Side scan sonar systems employ a stable,towed transducer (as opposed to a hull-mountedtransducer) to minimize distortion of recorded databy allowing the transducer to be used below the ther-mocline. Also, the towed transducer is not attachedto the hull, thus reducing distortion caused by vesselroll, pitch, and yaw. The towfish is usually towed toone side or astern of a vessel and can be launched orretrieved by one person. It contains two sets of trans-ducers which aim fan-shaped beams to either side ofthe towfish perpendicular to the direction of fish mo-tion. In addition, the towfish contains the transducerdriver and preamplifiers for received signals. Break-away tail fins are provided to minimize the possibilityof snagging the fish on an obstruction. The towfish isusually operated at a distance above the sea floorequal to 10% to 20% of the range scale in use.

HYDROGRAPHIC MANUAL

Depth of the transducer towfish is controlledby the length of cable deployed, vessel towing speed,and vessel course. Tow depths can be increased bythe use of a depressor or suitable weights.

The graphic recorder contains most of theelectronics for the system as well as the graphicmechanism. Most recorders are designed to operatefrom 24 V d.c. or 110 to 220 V a.c. power supply.(See figure AI-1.)

AI.3. Side Scan Sonar

1. Dual Channel Hydroscan Recorder2. 50-kHz Dual Channel Towfish.

3. 100-kHz Dual Channel Towfish.4. Lightweight Tow Cable - 300 feet.5. Lightweight Tow Cable - 600 feet.

6. Armored Tow Cable - 2,000 feet.7. Towfish Stablizer Depressor.

The Klein side scan system can be operatedfrom both small and large ships. The system is imper-vious to marine environments including temper-atures of 0°C to 50°C. The equipment will operatefrom both 24 V d.c. ±10% and 120 V a.c. 60 Hz ±10%. The service manual (Klein Associates, Inc.-1977) includes all necessary instructions, schematics,parts lists, troubleshooting, and general maintenanceinstructions. This manual is available as Klein PartNo. 521-01 from Klein Associates, Inc., Route 111,RFD 2, Salem, New Hampshire 03079.

AI-2(JUNE 1, 1981)

m) are useful in shallow waters and where mechani-cal cable handling equipment is not available. Longertow cables (200 m to 10,000 m) are steel armored,high-density cables designed to achieve maximumtow depth and minimum noise interference at giventow speeds.

The following discussion is limited to a de-scription of the side scan sonar system currently usedby the National Ocean Survey for hydrographic andbathymetric surveying. The technical manual pub-lished by the manufacturer is a necessity for satisfac-tory operation and maintenance of the system.

A1.3.1. KLEIN ASSOCIATES, INC., SIDESCAN SONAR SYSTEM. The Klein side scan sonarsystem consists of the following components:

8. Operation and Maintenance Manual,Recording Paper, Breakaway Tail Assemblers, andSpare Parts.

FIGURE AI–l.— Klein Hydroscan Dual Channel Side Scan SonarRecorder (courtesy of Klein Associates, Inc., Salem, NewHampshire)

AI.3.1.1. Side Scan Recorder. The Klein re-corder contains the patented Hands-Off-Tuningfeature which provides automatic adjustment, mak-ing uniform results across the sonar chart. Switchesare provided for each channel to additionally permitmanual selective tuning. Three event mark featuresare included: an internally generated 2-minute mark,a pushbutton on the recorder control panel, and aremote event mark pushbutton.

Both recording channels print simultaneous-ly, reading outward from the center of the record intrue left/right perspective. The range of the systemusing the 100-kHz towfish is at least 1,500 feet portand starboard at speeds up to 6 knots. At a 5-knottow speed the 50-kHz towfish range is at least 2,000feet. The range of the side scan system is also depen-dent on the operational environment, target, and thetow speed.

AI.3.1.2. Side Scan Transducers. The towfishconsists of individual modular port and starboardtransducers whose vertical beam may be varied in10° ± 2° increments from 0° to 20° by means of mi-nor external mechanical adjustments to the trans-ducer modules. (See figure AI-2.) The tail finassembly consists of two individual breakaway tailfins, separating when they strike a submerged ob-ject. The towfish parts are capable of operation inwater depths to 7,500 feet. Separate identical leftand right channel plug-in circuit boards are housedin the nose of the towfish.

EQUIPMENT AND INSTRUMENTS

AI.3.1.3 Tow Cable Assemblies. Lightweighttow cable assemblies consisting of a polyurethanejacket and a Kevlar strength member are provided.The minimum breaking strength is 6,000 pounds.The core consists of four conductors, two of whichare individually shielded and used for the right andleft channel signal returns, while the other two arefor power and trigger pulses. The entire core is ad-ditionally shielded. A 300-foot and a 600-foot light-weight cable are provided. The 2,000-foot cablehas the same core as the lightweight cable and usesa dual-armored steel jacket providing a breakingstrength in excess of 15,000 pounds.

speed. Both of these decrease the area which can besearched in a given period of time. It should bepointed out that speed over the ground is very im-portant in side scan operations. Slow, constant speedcan often be maintained by moving into the current.

Another environmental factor limiting useof side scan is sea state. This factor is most influen-tial in water under 40 feet, but decreases withdepth. Sea surface return is so strong with wavesof only 2 and 3 feet in less than 40 feet, that it can-not be completely tuned out. As a result, targets onthe bottom may be lost. One recourse is to lowerthe towfish below the interference. This would, ofcourse, endanger the towfish in shallow water. An-other means is by use of a recently developedtowfish with a variable vertical beam (20° or 40°).The 20° setting is useful to minimize sea clutter.

AI.3.1.4. Operations Considerations. Al-though automatic tuning is available in the controlcircuitry manual tuning is superior when employedby a trained operator. Experience has shown thatproperly adjusted, manual controls strongly print aknown target which might have been entirelyoverlooked among other returns on automatic tun-ing. Herein lies a problem, for if the manual tuning isnot properly adjusted, it is worse than the automatictuning for search. Manual tuning requires constant at-tention, and some skill to know, or feel, when propertuning has been achieved. It is important to developskill in hand tuning by working near a known targetfor a short period of time. This known target may beattached to an implanted buoy anchor line.

Environmental conditions limit the use ofthe sonar. The pulse repetition frequency is limitedby the time required for the acoustic signal to reachthe limit of the search band and return to the towfish.This physical limitation is in direct conflict with thedesire to gain resolution on a target by getting asmany separate pulses as possible to bounce off thetarget. There are two solutions to this problem: First,limit search path width; second, move at very slow

FIGURE AI–2.— Klein Side Scan Sonar Towfish (courtesy ofKlein Associates, Inc., Salem, New Hampshire)

AI-3 (JUNE 1, 1981)

EQUIPMENT AND INSTRUMENTS

NOS HYDROPLOT SYSTEMAJ

The computer is a DEC PD(–8/E with 12K,12-bit words of memory (Digital Equipment Cor-

FIGURE AJ-2.—HYDROPLOT installation aboard the NOAA

ship Mt Mitchell

FIGURE AJ–1—HYDROPLOT system block diagram

(JUNE 1, 1981)AJ-1

This is NOS's hydrographic survey auto-mated data acquisition and processing system.Figure AJ-1 is a block diagram of the system.HYDROLOG is a slight variation of the HYDRO-PLOT acquisition program in that an incrementalplotter is not used. The HYDROPLOT system is ca-pable of plotting hydrographic data on an on-line ba-sis as the data are acquired and on an off-line basisafter the data have been adjusted and corrected. Seealso figures AJ-2 and AJ-3.

HYDROGRAPHIC MANUAL

poration, Maynard, Massachusetts). System periph-erals, all of which share a common input-outputbus, include:

The interrupt system, which includes sevenhand-operated momentary contacts on the controllerfront panel and five electrical connections on therear panel, provides the means by which a hydrogra-pher and the sensing equipment can communicatewith the computer. Interrupts are used for suchevents as time synchronization, periodic inputs fromsensors, and system starts and stops. Four relay clo-sures are used to generate visual or audible alarm sig-nals and to put timing marks on analog records suchas graphic depth profiles.

The HYDROPLOT Controller, a specialpurpose input-output interface, is the nucleus of thesystem hardware. This unit, manufactured by DECto NOS specifications, provides these functions:

3. Four relay closures.

5. Two pulse outputs.All data from the echo sounder, positioning

equipment, and 49 controller panel thumbwheelswitches enter the system under program controlthrough the 32-word multiplexer. Hydrographerscan select either of two echo sounders, one of severalpositioning systems, and various survey parameters;enter data using the panel switches. The operation of

Approximately 55 computer programs areavailable for use with the HYDROPLOT system.Most are in assembly language. These programs canbe categorized into three basic groups: (1) prelimi-nary and utility programs, (2) data-acquisition pro-grams, and (3) off-line data editing and plotting pro-grams.

The first group of programs are used for thefollowing purposes: (a) to construct the modifiedtransverse Mercator (MTM) grid (in both plane andgeographic coordinates); (b) to construct range-rangeand hyperbolic lattice plots for the positioning systemin use; (c) to convert electronic line-of-position valuesto plane and geographic coordinates, and vice

FIGURE AJ-3. — Complete HYDROPLOT system launchinstallation

AJ-2(JUNE 1, 1981)

1. An eight-channel paper tape readand punch unit (reads 300 characters per secondand punches 50 characters per second).

2 Two model ASR-33 teletypewritersthat provide additional keyboard and paper tape in-put as well as paper tape and hard copy output.

3. A crystal controlled frequency inter-rupt clock located within the computer.

4. A Houston Instrument Company(Austin, Texas) COMPLOT DP-3 incremental rollplotter. The plotter has a 22-in-wide plotting surfaceand, in effect, an unlimited plotting surface length.The maximum plotting speed is 300 increments persecond at 0.005-in increments.

1. A digital multiplexer for up to 32 datainput words, each 12 bits long.

2. An interrupt system for 12 inputsources.

4. Analog output to activate a left/rightsteering indicator.

the system and software applications are thoroughlydocumented in NOS Technical Manual No. 2,''HYDROPLOT/HYDROLOG Systems Manual''(Wallace 1971).

The controller also contains a digital to ana-log coverter. Computer-controlled output of theconverter activates a meter-type left/right steeringindicator. Helmsmen keep the sounding vessel on apredefined line by following the steering indicator.The two pulse outputs from the controller inhibitchanging of depth and position data while being sam-pled by the computer.

An echo sounder used with a HYDRO-PLOT system is a complete subsystem that providesan analog depth record, a visual digital depth dis-play, and parallel binary coded decimal (BCD) depthinput to the computer. Echo sounders used by NOSare discussed in section AH.

The navigation interface converts the out-puts of an electronic positioning system (AC andAD) or the digital sextant (AE.2.) to parallel BCDinformation that is acceptable to the system. Anynavigational or positional device to which an incre-mental encoder can be attached can be used as an in-put to the navigation interface.

EQUIPMENT AND INSTRUMENTS

NOAA vessels to manually or automatically sampleand log sounding information onto punched papertape and provide a hard-copy listing. Time, position,and depth information from peripheral equipment,thumbwheel switches, or keyboard is logged inASCII code in fixed formats. Data can be logged inreal time or from manually kept sounding recordsafter the hydrography has been run.

The logger operates in any of three modesselected by the operator — automatic electronic, au-tomatic visual, or manual. In the automatic mode,position and depth are taken from a digital source,such as a Ross digitizer and navigation interface,then logged automatically at preselected time inter-vals. Intervals are selected with a front panelthumbwheel and vary from 6 s to 99 min 59 s. Theword length is set at medium for all data logged in

Off-line plotting programs of the HYDRO-PLOT system will also accept as input format-modi-fied output of hydrographic data loggers. Hydro-graphic data loggers (figure AJ-4) are used aboard

Hydrographic data logger aboard the NOAAship Davidson

FIGURE AJ–4. —

AJ-3 (JUNE 1, 1981)

versa; (d) to convert three-point sextant fixes toplane and geographic coordinates; (e) to generatepredicted and actual tidal reduction values; (f) tocalculate direct and inverse position computations;(g) to compile parameter inputs (based on theMTM projection) for real-time data acquisition;and (h) other utility programs designed to savetime and labor from the preliminary phases of asurvey to final data processing.

The second group encompasses HYDRO-PLOT data-acquisition programs. These programspermit either manual or automated real-time inputsof depth, position, and predicted tide or water lev-el correction information. Acceptable positionaldata modes are range-range or hyperbolic electron-ic positioning values and three-point sextant fixes.Each program permits the input of actual tidal orwater level stages by digital radio telemetry linkwhen available. Echo sounder transducer draft,electronic position corrections, position fix interval,sounding interval, and other similar variables areentered manually on the controller thumbwheels.Velocity corrections to soundings are not appliedon a real-time basis, but are compiled in digital for-mat for application in a subsequent processingphase. Other data, such as sounding line spacing,coordinates of the starting point for the first line,heading of the first line, and orientation of thesounding numeral, are entered through the tele-typewriter keyboard. System outputs include anon-line plot of positions and depths, analogleft/right steering directions to the helmsman, digi-tal hydrographic: data file on both punched papertape and hard copy, and a listing of operator mes-sages to the system. Positional information is ac-quired and listed for each sounding. Skewed pro-jections may be used for both on-line and off-lineplots.

The third group of programs permits a hy-drographer to edit raw survey data, to computeand compile final corrections to positions andsoundings, and to prepare final field sheets that areneeded to evaluate the work prior to leaving thearea. Off-line plotting programs will accommodatehybrid control systems, such as the combination ofa sextant angle with a circular or hyperbolic line ofposition. (See 4.4.4.)

The semiautomatic hydrographic data log-gers now in use were designed by NOS and aremanufactured by Aircraft Standards, Inc. (ASI),Seattle, Washington.

ASI logger electronics are entirely solidstate consisting of integrated circuits on interchange-able modules. A memory unit stores input data be-fore it is printed on a model ASR-33 teletype. Foroperator convenience, a keyboard is used to enterdata in the manual mode. A real-time clock with vi-sual display is available for automatic logging.

HYDROGRAPHIC MANUAL

this mode. In the automatic visual mode, positionand depth data are taken from a source such as aRoss depth digitizer and a digital sextant (RossLaboratories, Inc., Seattle, Washington). The wordlength varies between short and long, with a long

word printed for every position update.

AJ-4(JUNE 1, 1981)

When in the manual mode, the operatorkeys in all depth and position data; time and positionare automatically updated by the increment set inthe time and position thumbwheels.

EQUIPMENT AND INSTRUMENTS

TIDE AND WATER LEVEL GAGESAK.

AK.l. Automatic Gages

FIGURE AK–1. — Standard tide gage

(JUNE 1, 1981)AK-1

Tidal and water level gages are used to mea-sure water surface heights and the times at which theheigths occur. These measurements are used to reduceobserved soundings, taken at various tidal or waterlevel stages, to the appropriate reference datum for thearea. (See 1.5.4 1.) In areas where charted depths arereferenced to tidal datums, the tidal datums are also de-termined from the water surface measurements.

Gages used exclusively to support hydro-graphic surveys shall conform to the requirements ofthis manual; however, gages to be used for both theNOS water levels program and hydrographic surveysshall conform to section 3.2 of the ''Standing ProjectInstructions: Great Lakes Water Levels'' (NationalOcean Survey 1977b).

Gages that automatically record tidal or wa-ter level variations and corresponding time referencesare used for most NOS operations. Such data are re-corded either graphically (marigram) or on punchedpaper tape. The gages most frequently used include (1)the analog to digital recording (ADR) gage (AK.1.2),(2) the gas-purging pressure gage, commonly called a''bubbler'' gage (AK.1.3), and (3) the analog electric,weight, or spring-driven gage (AK.1.4).

Tide gages and water level recorders are simi-lar instruments in that both rely on a float, float cable orfloat tape, and a float wheel as the basic measuring de-vice. Because greater fluctuations of the water surfaceoccur over shorter periods of time in tidal areas than inlakes, tide gages use a counterbalance spring in themeasuring system. The spring takes up float-cableslack that is caused by sudden surges. Water level re-corders are generally designed to measure more grad-ual changes in water surface heights.

Nonrecording gages include the simple staff(AK.2.1) and the electric tape gage (AK.2.2). Becauseobservers are needed to record water heights andtimes, nonrecording gages are used only for short-term observations and as reference standards for auto-matic gages. Additional information on gages can befound in the Integrated Logistics Support Plan avail-able from the Office of Oceanography, OA/C231.

AK.1.1. STANDARD GAGES. These automat-ic gages used by the National Ocean Survey measureand record water levels by means of a float that iscontained inside a stilling well. Use of a stilling

well diminishes the effects of horizontal water move-ment and, by using a small intake opening, greatly re-duces the effects of rapid changes in water level, suchas surges generated by wind waves. A line attachedto the float operates a worm screw on the gage—theworm screw drives a recording stylus across a stripof paper, and the paper is advanced at a uniform rateby a clock motor. The combined motion of the stylusand the paper produces a graphic or analog record(marigram) of the rise and fall of the tide or of varia-tions in water level. (See figures AK-1 and AK-2.)

Standard automatic gages usually are in-stalled only at control tide stations or at water levelgaging control stations (i.e., stations that aremaintained over a period of many years). Standardautomatic gages are being phased out of use by NOSand few gages are now in operation. Because the re-cords from control stations provide basic tidal andwater level data of such importance, installation andmaintenance procedures must meet rigorous stan-dards to ensure the highest degree of reliability andprecision of data. Essential equipment for a controlstation includes an automatic gage, a stilling well, ashelter, and a graduated staff or reference gage. Asystem of bench marks (AK.4) is established at eachstation. See U.S. Coast and Geodetic Survey (1965a)Publication 30—1, ''Manual of Tide Observations.''

AK.1.2. FISCHER AND PORTER ANALOG TODIGITAL RECORDING (ADR) GAGE. The followinginformation was extracted from the Fischer andPorter Co. (1972) Instruction Bulletin for Type 1550and 1551 Punched Tape Level Recorder (SpringCounter Balance Type), Design Level ''C.'' Theircomplete address is Fischer and Porter Company,Warminster, Pennsylvania 18974.

Standard tide gage installationFIGURE AK–2.—

FIGURE AK–4. — Side view of a Fischer and Porter waterlevel recorder (courtesy of Fischer and Porter,

Warminster, Pennsylvania)

The type 1550 recorder is contained in aweatherproof housing and is mounted on a 4-inpipe. The type 1551 recorder is flat, surface mount-ed in a dust-tight housing. Both instruments use a7.5-V d.c. battery for power. A push button on thefront plate initiates a tape punch on demand.

Fischer and Porter ADR gages have a maxi-mum operating range of 50 ft. Water level heightsare measured to the nearest hundredth of a foot.Ocean tides are recorded at 6-min intervals—GreatLakes water levels are recorded at 5-, 6-, and 15-minintervals.

The punched tape recorder mechanism is se-quentially and mechanically interlocked, thus mak-ing it impossible for a function or action to be outof phase with the others. The operation of a

FIGURE AK–3. — Front view of a Fischer and Porter waterlevel recorder (courtesy of Fischer and Porter,

Warminster, Pennsylvania)

AK-2(JUNE 1, 1981)

Fischer and Porter (ADR) water level re-corders, figures AK–3 and AK–4, mechanicallyconvert angular positions of a rotating shaft intocoded digital output, then punch these digital val-ues on paper tape at selected time intervals. Theseinstruments are designed specifically to measureliquid level by means of a cable, drum, and floatassembly. This measurement source can be gearedto the instrument to obtain any convenient ratio be-tween rotation of the recorder input shaft and rota-tion of the primary actuating unit shaft.

The measuring device consists of a float in avertical stilling well or pipe, a float cable, a floatwheel, and a spring counterbalance. Use of thespring counterbalance eliminates the need for coun-terweights, thus permitting a smaller well; however,on the Great Lakes, the Fischer and Porter Model1542 is often used (counterweight vice spring coun-terbalance).

Although the punched tape record is intend-ed to be processed by high-speed mechanical scan-ning methods, time and height values can be decodedeasily. (See figure AK-5.) Each horizontal row ofpunched holes represents, in digital form, the totalamount of shaft rotation. The row is divided intofour sections that represent, in binary coded decimalform, the tens, units, tenths, and hundredths digits ofthe value — a quick mental summation of the bit val-ues provides the digital value. Each gage is alsoequipped with graduated disks for direct reading oftimes and heights. A combination of electrical con-nections are available to permit data telemetry.

EQUIPMENT AND INSTRUMENTS

proof cases that make tape changing and routinemaintenance easy.

punched tape recorder is best described as an inter-related function of two separate mechanisms — theinput gearing-count memory system and the punchprogramming cycle system. The input system de-tects shaft rotation, then converts the amount of ro-tation to successive positions of the memory codedisks. By means of a timing device, the punch-pro-gramming system initiates the punch demand, thentriggers the proper punching and reset operationsrequired to record the measured values on tape.

Fischer and Porter recording gages are rug-design and are mounted in weather-

AK-3 (JUNE 1, 1981)

FIGURE AK–5. — Fischer and Porter punched tape record(courtesy of Fischer and Porter, Warminster,

Pennsylvania)

AK.1.3. GAS-PURGED PRESSURE GAGE.These pressure-recording gages (commonly called''bubbler'' gages) are used to obtain tidal or waterlevel data in areas where the installation of struc-ture-supported gages would be impractical. (See fig-ure AK-6.) Detailed procedures for installation, op-eration, and maintenance are contained in the''User's Guide for the Gas-Purged Pressure Record-ing Bubbler Tide Gage'' (Young 1976).

Bubbler gages are portable pressure-record-ing instruments that produce a continuous strip chartrecord of water level changes. (See figure AK-7.) The underwater part of the gage consists of asmall bubbler orifice chamber attached to a gas sup-ply tube. The shore end of the tubing is connectedto the gas system (pressure-regulating mechanismand gas storage tank) and to the transducer (temper-ature-compensated pressure bellows) of a strip chart

FIGURE AK–6.— Gas-purged pressure (bubbler) gage compo-nents 1, nitrogen tank; 2, high-pressure valve; 3, pressure-re-ducing valve; 4, high-pressure gage; 5, low-feed pressuregage; 6, supply hose; 7, pressure differential regulator; 8,transparent bubble chamber; 9, adjustable needle valve; 10,shut-off valve; 11, orifice supply line; 12, orifice; 13, dampen-ing valve; and 14 recorder

HYDROGRAPHIC MANUAL

The operating principles of a bubbler gagesystem are simple and straightforward. When gasis bubbled freely into a liquid from the fixed endof a tube, the pressure in the entire length of thetube is approximately equal to the the pressurehead of the liquid over the bubble orifice. Anychange in the hydrostatic pressure, such as thatcaused by a change of water level, is transmittedby gas pressure through the tubing to the trans-ducer bellows of the recorder where pressure vari-ations are recorded. Use of a specially designedbubbler orifice chamber at the underwater end ofthe tube prevents rapid expulsion of gas and riseof water level in the tube, which would resultfrom large waves if only a tube of fixed open endwere used. Thus, errors caused by wave action arereduced to within practical limits of accuracy. Therequired rate of gas supply is determined by themaximum rate of water height increase and thevolume of the system, including the orifice cham-ber, supply lines, and bellows. The rate of supplycan be measured by counting the bubbles as the

FIGURE AK–7.— Bubbler gage strip chart recorder (cover re-moved)

FIGURE AK–8.— Bubbler gage gas flow system components 1, constant differential pressure regulator; 2, oil-filled sight jar flow me-ter; 3, flow-regulating needle valve; and 4, shut-off valve

AK-4(JUNE 1, 1981)

recorder. Nitrogen gas is used because it is inert,dry, inexpensive, and readily available. Gas cylin-ders are available in three sizes. The smallest cylin-der, 35 ft³, supplies the system for about 3 mo of nor-mal use. Figure AK–8 shows the gas flow system

EQUIPMENT AND INSTRUMENTS

other purposes. The following description of the sys-tern was extracted from Leupold and Stevens (1976)Bulletin 12, 24th Edition. Their address is Leupold &Stevens, Inc., P.O. Box 688, Beaverton, Oregon97005.

gas is released through oil in a transparent bubblechamber and can be regulated by an adjustableneedle valve.

The pressure sensing and recording ele-ments of the bubbler gage are designed and cali-brated to register depth with an error less than1% of the full-scale values. Temperature-inducedwater density changes are not measurable. Errorscaused by variations in salinity are usually sosmall that they may be ignored, but in extremecases may become significant. Changes in atmo-spheric pressure do not affect water level recordsbecause the atmospheric effects on the bellowsand on the surface of the water are equal. Pres-sure errors caused by friction of flowing nitrogenin the orifice tubing can be great. Such errors oc-cur when high purging rates or excessive lengthsof tubing are used. Pressure errors are minimizedby maintaining recommended purge rates and lim-iting orifice tubing lengths to 800 m.

Water level sensing is accomplished by afloat, enclosed in a stilling well, and a beaded floatline or float tape passing over a spined float pulley. Acounterweight keeps the float line or float tape taut.As water levels change, the pulley rotates. By me-chanical gearing, pulley rotation is translated to hori-zontal movement of a recording stylus. The stylusrecords the water levels on a strip chart that movesat a predetermined rate controlled by a clock move-ment. A 12-lb weight on a cable drives the clock.

The recording mechanism is precision madeand ball bearing equipped and will respond to a0.01-ft change in water level on a 1:6 recording ratiowith a 10-in float. Interchangeable gears and pulleyspermit easy changes to strip chart advancement rateand vertical motion scale. The instruments can bequickly converted in the field from English to metricmeasurements and vice versa. Strip charts graduatedin metric units are available.

The gas-purging pressure-recording gagedoes not require a supporting structure. It can beused on open beaches, on shoals, at sites where it isimpractical to install or use other types of tide gages,and where distances up to 800 m separate the orificechamber and the recorder. The recorder can beplaced in a buoy, on an offshore platform, or ashore.It also can be adapted to telemetering from remoteand inaccessible areas. When installing a gage, theorifice chamber should be secured to a pipe that isdriven into the ocean bottom or be embedded in ablock of concrete. The tubing from the orifice cham-ber to the recorder may be lashed to a weighted ca-ble, must be securely fastened at the inshore end. Ifthe installation of a staff is impractical, datums forthe observations may be established by referencingthe elevation of the orifice chamber to the top of thepipe, which in turn is referenced to the elevation ofbench marks.

AK.2. Nonrecording Gages

These gages, such as the tide or water levelstaff and the electric tape gage, are used for (1) short-term tidal or water level observations for hydro-graphic surveys and (2) as a reference standard forcomparative observations at automatic gage sites.

AK.2.1. TIDE STAFF. The simplest tide orwater level gage is a plain staff or board, 1 or 2 inthick, 4 to 6 in wide, and graduated in feet andtenths. Staffs are normally secured vertically to pil-ings or other suitable supports and must be longenough to permit observations throughout the fullrange of tides or water levels. Because painted grad-uations on boards become illegible after short peri-ods in salt water, NOS uses scales that are made bybaking a vitrified coating onto wrought iron strips.The strips are about 2.5 in wide and 3 ft long andwhen placed end to end form a continuous scale.(See figure AK–10.) Each strip is secured to a wood-en staff, using brass screws and lead washers. Gradu-ated aluminum staffs are generally used at GreatLakes hydrographic water-gaging stations.

AK.1.4. STEVENS WATER LEVEL RECORD-ER. The Stevens Type A, Model 71, Water Level Re-corder (figure AK-9), currently in use at manyGreat Lakes water level gaging stations, providesdata essential for hydrographic surveys and provideshydrologic and hydraulic information needed for en-gineering studies, water resources development re-search, publication of water levels data, and many

AK-5 (JUNE 1, 1981)

HYDROGRAPHIC MANUAL

FIGURE AK–10. — Tide or water level staff installation

For obtaining accurate values for reducingsoundings to the datum of reference, temporary staffsmust be installed as near as possible to the soundedarea. In tidal waters, observations are recorded contin-uously throughout the portion of the day that sound-ings are taken, and are extended each day as necessaryto include at least one high water and one low watervalue on the staff. In nontidal waters, observationsneed be recorded only during sounding operations.Staff observations are entered at 15-min intervals inNOAA Form 77-53, ''Tides — Location of TideStaff.''

AK-6(JUNE 1, 1981)

FIGURE AK–9. — (Top) Stevens water level recorder and (bot-tom) digital recorder (courtesy of Leupold and Stevens, Inc.,Beaverton, Oregon)

Observations of tides or water levels on simplestaffs are often used by hydrographers in small areaswhere anomalies caused by meteorological conditionsor landmass configuration are suspected and when thelength of observations will not be more than a fewdays.

EQUIPMENT AND INSTRUMENTS

The electric tape gage (ETG) (figure AK-11) consists of a Monel metal tape conductor at-tached to a metal drum and supporting frame, avoltmeter, and a 4.5- or 6-V battery. The tape,which is graduated in hundredths of feet, is con-nected through the frame to one of the terminals ofthe battery. The other terminal is grounded to thewater in the stilling well by a connecting wire thatleads either to the metal wall of the well or directlyto the water in the well if the well is made ofnonconducting material. The electric circuit is com-pleted when the weight at the free end of the tapestrikes the water surface. Contact is indicated by amovement of the needle on the voltmeter dial. Atthat instant, the graduated tape is read at the read-ing mark (zero electric tape gage) of the gage togive the distance of the water surface below thereading mark. The reading mark is referenced in el-evation by differential levels to local bench marks.

Accurate staff observations are difficult toobtain when the water is rough. One satisfactoryand proven solution is to attach a clear glass orplastic tube (about 0.5 in in diameter) next to thestaff graduations using spring clips or other suit-able fasteners. Partially close the lower end of thetube with a notched cork or rubber plug to dampwave surges. Leave the upper end of the tubeopen. Water level heights in the tube are readfrom the graduated scale.

When a staff remains in the water forlong periods, particularly in harbors where refuseand oil contaminants are present, graduation mark-ings rapidly become illegible. In such cases, a por-table staff, which is easily removed from a perma-nent support, is often used. Such staffs may behinged in sections for convenient storage. Thepermanent staff support must be rigidly secured sothat zero on the graduated scale will always be atthe same elevation when placed in the water foruse. Staff supports are usually planks, 2 in wideand nearly as long as the staff. Protect the woodfrom teredos and other marine borers by a coverof copper sheathing. The staff is held to the sup-port in a vertical position by metal guides at in-tervals along the support. To keep the zero pointof the staff at a fixed elevation, mount a metalplate shoulder at the top of the support. Whenthe staff is inserted in the metal guides, the metalstop that is secured to the back of the staff restsfirmly on the metal shoulder of the support.

Five comparative observations per weekare needed to obtain a statistically significant num-ber of staff readings that will precisely relate the

AK-7 (JUNE 1, 1981)

Tidal staff observations are correlated to thesounding datum by one of the following methods: (1)an automatic recording gage is nearby and operatingsimultaneously—the automatic gage must have beenoperating continuously or is scheduled to operate forat least 30 days; or (2) levels are run between the staffand nearby existing bench marks—elevations of thebench marks with respect to the sounding datummust be known. Water level gages or staffs must al-ways be tied to a reference datum by leveling.

For detecting lifting or settling of a tempo-rary staff, levels are run between the staff and threenearby recoverable points prior to beginning obser-vations, then again after all observations have beencompleted. These recoverable points need not bemarked by survey disks but should be described. Theleveling data can also be used to reestablish thesounding datum should the staff site be reactivatedafter discontinuance. See AK.4 for specificationsand guidance on leveling procedures.

AK.2.2. TAPE GAGES. These are oftenused in place of staffs at exposed locations wherestaff cannot be read conveniently or if the water istoo rough for accurate readings.

AK.2.3. COMPARATIVE OBSERVATIONS.These are required to determine the relationship be-tween the staff or tape gage and the height datumof the gage continuous record. This relationshipshould remain stable throughout the operation of atide or water level station. If a new staff or tapegage is installed during the series, the original indexsetting of the automatic recording gage should nei-ther be altered nor be reset to new staff values.Corrections to the data are applied by using the dif-ference in elevation between the old staff and thenew staff as determined by differential levels. If arecording gage is replaced, the index of the newgage shall be reset to a value which will make thegage-to-staff difference approximately 5 feet greateror less than the previous gage-to-staff difference.Any disturbance of an electric tape gage will neces-sitate releveling to determine the new zero electrictape gage elevation. Tidal analog to digital record-ers should be set to read 10 ft above the staff read-ing to avoid negative values. At the time of level-ing, concluding establishment of a gage, or beforedismantling any gage or station, careful simulta-neous water level readings shall be taken on allgages and staffs.

HYDROGRAPHIC MANUAL

AK.4. Bench Marks and Leveling

Five recoverable bench marks shall beestablished within a 1-mi (1.6-km) radius of eachcontinuous recording tide station or water levelreference gage. Each of the bench marks must beconnected to the gage staff (or measuring mark)by third-order leveling. These marks are estab-ished to: (1) protect against the loss of the verti-cal datum, once determined, (2) provide a refer-ence to which tide and water level observationsare ulimately correlated, and (3) detect settlementor lift of the gage and staff.

FIGURE AK–11.— Tide or water level electric tape gage

gage datum to the staff. Fewer readings reduce thedegree of accuracy of datum determination. SeeU.S. Coast and Geodetic Survey (1965a) Pub-fication 30-1 for detailed instructions on compara-tive observations.

AK-8(JUNE 1, 1981)

A bench mark is a marked vertical controlpoint on a relatively permanent object, natural orcultural; its elevation with respect to a datum isknown. Bench marks established in the vicinity of atide station for the reasons stated above are called"tidal bench marks''—those in the vicinity of aGreat Lakes water level gaging station are simplycalled ''bench marks.''

Tidal bench marks shall be connected bylevels to any other bench marks within 1 mi (1.6 km)of the tide station that have been adjusted into theNational Geodetic Vertical Network (formerly theSea Level Datum of 1929). To determine whetherthere are any such bench marks in the vicinity, con-sult the appropriate NOS State Map for ControlLeveling or the Geodetic Control Diagram for thearea. (Horizontal control stations are often includedin the vertical network as well.) A network benchmark or horizontal control station that is included ina tidal bench mark level circuit is considered to beone of the required five marks. Include bench marksestablished by other organizations, if practical. Tidalbench mark elevations are referenced to MLLW. Inthe Great Lakes, lake levels are referred to benchmarks on the International Great Lakes Datum(IGLD) of 1955.

Standard National Ocean Survey disks areused to identify bench marks established at tide sta-tions or gage sites. Each disk has a long shank forcementing the mark into a structure, concrete sur-face, or survey monument. Bench mark identifica-tion numbers are assigned by the Office of Ocean-ography, NOS, and included in the projectinstructions; tidal bench mark numbers are assignedby the Tidal Requirements and Acqui-sition Branch (OA/C231) and Great Lakes benchmark numbers are assigned by the Water LevelsBranch (OA/C234). Tidal bench marks are iden-

EQUIPMENT AND INSTRUMENTS

The principal qualities of a good benchmark are permanence, stability, and recoverability.In settled areas, substantial building foundations areexcellent bench mark sites. In undeveloped areas,rock ledges or partially buried masses of concreteare suitable foundations for bench mark disks. Per-manent bench marks should not be located on hy-drants, trees, curbstones, or structures vulnerable tochange. Such objects may, however, be used astemporary bench marks for expedience during aleveling run. Coast and Geodetic Survey Special Pub-lication No. 239, ''Manual of Geodetic Leveling''(Rappleye 1949) and U.S. Coast and Geodetic Sur-vey (1965a) Publication 30–1, ''Manual of Tide Ob-servations,'' and ''Users Guide for the Establish-ment of Tidal Bench Marks and LevelingRequirements for Tide Stations'' (1977) contain de-tailed guidance and standards for bench markplacement and leveling.

Distance between bench marks Maximum error allowed

(feet) (foot)

One setup 0.006

500 .011

.0151,000

.0212,000

.0273,000

.0304,000

.0345,000

AK-9 (JUNE 1, 1981)

tified by a four-digit number and letter with thenumber representing the tide station and the letterindicating the established sequence of the benchmark. This identification number and the year thebench mark was established is stamped with a dieset on each disk. Duplication of numbers and let-ters must always be avoided. For example, fivenew tidal bench marks set at tide station 924–1234would be identified and stamped 1234A, 1234B,1234C, 1234D, and 1234E, along with the yearestablished. If a new mark is set, this identificationsequence would be retained (i.e., 1234F, even ifthis new mark was set to replace a previouslyestablished and numbered mark).

A complete description for each benchmark established must be prepared to accompanyNOAA Form 76–77, ''Leveling Record—Tide Sta-tion,'' each time differential levels are run for a tideor water level gage station. Descriptions must beclear, distinct, and detailed enough to permit easyrecovery and identification. If a disk is used, thedescription must state whether the number and es-tablishment year are stamped on the mark. If abench mark is located on a building, give the streetand number—otherwise, indicate the owner's name.When a bench mark is not on a prominent struc-ture, reference it by distance and direction to sev-eral prominent nearby objects. Draw a sketch tohelp future location and identification of the mark.

Third–order levels must be run between thegage staff and the bench marks whenever a tide orwater level gaging station is established. Levels are

run again when station observations are terminated.Gages scheduled to continue operating after a hy-drographic party leaves an area are leveled prior todeparture. Before using data from such a gage at alater date, levels must be run to detect any changein the elevation of the staff.

The graduated lines on vitrified staffs areabout 0.01 ft wide. The middle of each line is thereference for heights. If a portable staff is used, theleveling rod should be held on the flat top of thestaff support (i.e., the lower staff stop). The staffreading at the staff support must be entered in therecord. This value is easily determined from theposition of the upper metal stop attached to theback of the staff. Be sure to place the staff in itssupport to ensure that the upper staff stop comes inactual contact with the lower staff stop on the sup-port without interference. When a tape gage isused, third-order levels are run from the readingmark of the gage to the bench marks. The relationof the reading mark to the tape-gage datum is de-termined from the value of the plane of flotation.

Levels between marks must be checked bya forward and a backward run. The closing error,in feet, must not exceed ± 0.035 ± M where M isthe distance in statute miles over which levels wererun between adjacent bench marks. Table AK-1based on the formula,

maximum error = ± 0.035 √√M,gives the maximum allowable closures for selecteddistances in feet between bench marks.

If the difference between the results fromthe forward and backward lines between any twobench marks exceeds the allowable error, the sec-tion shall be rerun until a forward and backwarddifference falls within the allowable error limits.Questionable values from previous runs should notbe used with new levels to obtain agreement.TABLE AK–1.— Maximum allowable leveling error between bench

marks

EQUIPMENT AND INSTRUMENTS

a straight line on stable-base drafting film; then care-fully construct a perpendicular to that line. (See fig-ure AL-2.) From point A, measure off 50 cm topoint B. From the same point, measure 18.2 cm (50cm x tan 20°) along each perpendicular to points Cand C'. Center the protractor over point B and alinethe fixed arm through point A. The angles throughC and C' should read exactly 20°. Any differencesare applied to scaled angles as index corrections.Plastic protractors used for smooth plotting shouldbe compared daily against a standard.

AL. MISCELLANEOUS EQUIPMENT

AL.1. Protractors

AL.1.1. PLASTIC THREE-ARM PROTRAC-TORS. Three-point sextant fixes can be plotted us-ing a plastic three-arm protractor. Although auto-mation has nearly eliminated the drudgery of handplotting every position taken during a survey, thethree-arm protractor remains a versatile and indis-pensable tool of the hydrographer. Plastic protrac-tors are transparent and are available in severalarm lengths for plotting convenience.

Plastic protractors used during verificationto plot final positions are calibrated as follows: draw

Each protractor is especially constructed forthe scale of the plotting sheet and measuring units

--AC and AC' tan 20° x 50 cm

18.2 cm 18.2 cm\ /C C'

FIGURE AL–1.— Plastic three-arm protractors Calibration of a three-arm protractorFIGURE AL-2.—

AL-1 (JUNE 1, 1981)

One fixed arm and two movable arms eachcontain an etched line that is radial with the center ofthe protractor. Each movable arm has a vernier grad-uated in 2-min intervals—angles can be estimated tothe nearest minute. Plastic protractors are availablewith arms either 13.5 or 24 in long. (See figure AL–1.)

Plastic protractors cannot be adjusted, butmust be tested for index correction and warping.The radial lines on the arms are checked forstraightness by superimposing them over a steelstraightedge. To determine index correction, placethe protractor on a test plate, match the etched lineswith the lines on the test plate at 30%, 60%, and 90%,then read the angles on the protractor. Differences,if any, represent index corrections.

AL.1.2. ODESSEY PROTRACTORS. Positionsdetermined from electronic ranging systems can bequickly and accurately hand plotted using anOdessey protractor (figure AL–3) provided that lat-tice lines have been drawn on the survey sheet. (See4.5.5.) The protractor is simply a series of graduatedclosely spaced concentric circles etched on clearplastic. The circles represent distances from the tem-plate center in the output units of the electronic po-sitioning system used. The protractor is maneuvereduntil the difference in distance between each ob-served range value and the plotted lattice line clos-est to that value is in register with the concentricdistance circles. A small hole in the center of the,protractor permits a pinhole to be pricked at theplotted position.

HYDROGRAPHIC MANUAL

FIGURE AL–4. — Engineer's drafting machine

FIGURE AL–3. — Odessey protractor

of the electronic positioning system. The largestdistance circle on the protractor is usually made tobe twice the interval of the lattice lines on thesurvey sheet.

After the control stations have been plottedand the azimuthal orientations of the theodolites areestablished on a hydrographic sheet, the machine isclamped to the plotting board.

Engineers' drafting machines are light-weight portable instruments that can also be used tomanually plot and verify plotted control stations,landmarks, and aids to navigation.

AL.2. Oceanographic Equipment

AL-2(JUNE 1, 1981)

AL.1.3. DRAFTING MACHINE. Mechanicaldrafting machines are used to hand plot vesselpositions and soundings on surveys controlled bythe theodolite intersection method. (See 4.4.2.2.)When properly used with geometrically strongcontrol, positions can be rapidly and accuratelyplotted with the instrument. The engineer'sdrafting machine is a refinement of the parallelmotion protractor. (See figure AL-4.)

The two basic components of a draftingmachine are an azimuth circle or protractor and anazimuth-measuring arm. The azimuth circle is 10 to12 cm in diameter, is graduated to the nearest 0.5°of arc from 0° to 360°, and can be set and locked inany azimuthal orientation. The azimuth-measuringarm has a double vernier graduated to the nearestminute of arc and can be locked to permit an angleor azimuth to be moved across the plotting surfacewhile maintaining positive directional orientation ofthe instrument. A variety of plain or graduatedstraightedges 15 to 36 cm long can be rigidlyattached to the arm for projecting directionalmeasurements.

The azimuth circle and arm are mounted onthe working end of a jointed arm or carrier. Thereversible joint or elbow at the midpoint of the armprovides lateral folding and corresponding extensioncapability of the instrument. The stationary end ofthe arm pivots laterally on a vise clamp that isattached to the plotting board or drafting table.

The azimuth circle is then properly orientedand locked. An orientation reference line is drawnon the sheet for occasional checks to guard againstslippage. Observed theodolite or transit directionsare duplicated on the azimuth circle by setting andlocking the values on the measuring arm of theprotractor. The inner end of the protractorstraightedge is aligned over the proper ''cutoff''stations and the line of position indicated by a shortpencil line drawn across the approximate track of thesounding vessel. Intersecting lines or "cuts"observed simultaneously establish the position.

AL.2.1. NANSEN BOTTLE. This bottle (figureAL-5) is the senior member of a rapidly growing familyof devices used to obtain water samples from variousdepths for the measurement of their physicalproperties. Although many more modern and versatiledevices are available, the Nansen bottle remains

EQUIPMENT AND INSTRUMENTS

Nansen bottles must be carefully checkedbefore use to ensure that all moving parts are lu-bricated and move freely. Close the air vent anddraincock; then secure the bottle to the wire withthe clamp and fulcrum assembly at the bottom. Amessenger is attached to all but the lowest bottleon the cast. Before lowering a bottle, be sure thatthe mercury in each thermometer has draineddown to the main reservoir.

Always use the oceanographic winch cau-tiously and give consideration to the sea state—never begin paying out or brake rapidly. Suddenjolts or excessive strain can part the cable or causethe string of bottles to be tripped before the prop-er time.

When the cast is hauled aboard, each Nan-sen bottle is detached from the cable as it reachesthe surface and is placed in a specially constructedFIGURE AL–5.— Nansen bottle

AL-3 (JUNE 1, 1981)

the classical standby for gathering temperatureand salinity data needed to determine sound ve-locity corrections and for field checking the accu-racy of more sophisticated electronic sensors.

The Nansen bottle is a cylindrical metalreversing water sampler with a 1.25 L (2.25-pint)capacity. Each end of the bottle is fitted with a slitvalve. The slit valves are joined by a connectingrod that controls the opening and closing mecha-nism. The bottom of each bottle is clamped firmlyto the lowering cable; the top of each bottle is con-nected to the cable by a mechanical tripping de-vice. When a bottle is lowered to the desireddepth, the valves are opened, permitting contami-nants to be flushed out and an in situ sample toflow through the bottle. A mechanical messengerdevice slides down the cable, releases the trippingdevice at the top of the bottle, and causes the bot-tle to become upended or reversed. When re-versed, the bottle is suspended from the cable bythe bottom clamp. When the bottle is tripped, twoother events occur: (1) the connecting rod shifts

and closes the end valves causing the in situ sam-ple to be trapped in the bottle and (2) a messengerattached to the bottom of the bottle is releasedand begins its travel down the cable to trip thenext bottle.

Each bottle is equipped with a frame de-signed to hold two protected and one unprotecteddeep sea reversing thermometers. (See AL.2.2.)Brass tubes in the frame are slotted for easy read-ing of thermometer scales. One end of the tube isperforated to permit water circulation around thethermometer. The large reservoir end of the ther-mometer is placed at this end of the tube. Rubberpads backed by helical springs are fitted in eachend of the tube to hold the thermometer securelyin place and to protect it against shock.

Not more than 12 Nansen bottles should beused on a cast with 5/32-in wire; not more than 5should be used with standard bathythermographwinch cable. As the bottles are lowered, a flushingaction of their contents occurs; however, flushing isincomplete when the bottles reach the samplingdepths. Before releasing a messenger down the cable,let the bottles stand open at the sampling depths forat least 6 min to ensure complete flushing of theircontents and registration of correct thermometertemperatures. The wire angle is measured and re-corded immediately before or after releasing themessenger. Messengers fall at rates from 150 to 200m/min, depending on the angle of the wire. Do nothaul in the cast until the bottom bottle has been re-versed. On shallower casts, the release of each bottlecan be detected by a slight vibration of the cable.

HYDROGRAPHIC MANUAL

ments and must be handled with extreme care at alltimes, A protected reversing thermometer and itsauxiliary thermometer are enclosed in a heavy glasscase that is sealed at both ends for protectionagainst pressure at the depths at which they areused. The special features of a reversing thermome-ter include a knife edge in the capillary tube that ismade by an appendage in the tube, a gooseneck(which may be a U-turn, S-turn, or a complete cir-cle), and a supplemental mercury reservoir at theopposite end from the main reservoir.

salinity = 0.03 + 1.805 x chlorinity %o.

Reversing thermometers are delicate instru-

An unprotected reversing thermometer,similar to the protected type in most respects, isopen at one end of the glass jacket. This openingpermits the thermometer to come in direct contactwith the water and be subjected to hydrostaticpressure. The unprotected reversing thermometerhas no mercury surrounding the reservoir as doesthe protected thermometer. Such instruments donot give true temperature readings. Registeredtemperatures increase with depth. By lowering aprotected and an unprotected thermometer togeth-er, the depth at which the thermometers were re-versed can be determined by the difference inthermometer readings.

AL.2.2.1. Care of reversing thermometers.Deep-sea reversing thermometers are expensivedelicate instruments. Each thermometer is carefullycalibrated at considerable expense. Unless they areproperly handled, the mercury column can be sepa-rated by gas bubbles in the capillary tube with a re-sultant loss of calibration. Observe the followingprecautions when using these instruments:FIGURE AL–6.— Reversing thermometers

AL-4(JUNE 1, 1981)

rack. Water samples are drawn into glass bottles,and the thermometer temperatures are recorded.Water samples may be analyzed for such proper-ties as salinity, dissolved oxygen content, or vari-ous nutrients. Detailed instructions for drawingand preserving water samples are contained in theU.S. Naval Oceanographic Office (1968) Publica-tion No. 607. When sample analysis is limited todetermining salinity for echo-sounding corrections,each sample may be drawn in a hydrometer jarfor a measurement of specific gravity (AL.2.4).Salinometers are usually used aboard larger ves-sels for salinity determinations. (See AL.2.3.)When samples are titrated to determine chlorinity,salinity values may be determined by using table16 in U.S. Naval Oceanographic Office (1968)Publication No. 607 or by the formula,

AL.2.2. REVERSING THERMOMETERS. Pre-cision reversing thermometers used for Nansen bot-tle casts are graduated to 0.1°C and are accurate to afew hundredths of a degree. (See figure AL-6.)

When the protected thermometer is reversedor inverted, the extra weight of the mercury in theenlarged section of the capillary tube in the goose-neck breaks the mercury column at the knife edge.Mercury flows into the supplemental reservoir, theninto the graduated stem where the temperature isread when the instrument is held in an inverted posi-tion. Thus when the thermometer is reversed, thetemperature at the depth of reversal is obtained. Be-cause the jacket protects the thermometer from hy-drostatic pressure, a true temperature is registered. Ifthere is no auxiliary thermometer, the protected re-versing thermometer is allowed to come to thermalequilibrium in an enclosed thermally stable location.Use a good-quality laboratory thermometer to deter-mine ambient air temperature when reading valuesfrom reversing thermometers. Air temperature is re-corded as the auxiliary temperature.

EQUIPMENT AND INSTRUMENTS

ature accuracy requirements for oceanographic re-search projects are generally much more rigorous(often to the nearest 0.02°C) than for hydrographicapplications, reversing thermometers shall be as-signed and calibrated as follows:

AL.2.3. SALINOMETERS. Portable laborato-ry salinometers are frequently used aboard NOS ves-sels to determine salinity percentages of acquiredwater samples. (See figure AL–7.) Most instrumentsof this type use an inductive coupling to sense andmeasure the conductivity ratio between an unknownsample and a standard sea water sample such as Co-penhagen Standard Sea Water. Modern instrumentsof this type automatically compensate for tempera-ture differences between the known and the un-known sample. Conductivity ratios are recordedfrom an instrument meter, then converted to salinityfrom standard tables. Some salinometers have cir-cuitry that permits salinity values to be read directly.Salinometer data are of sufficient accuracy for hy-drographic applications and for most oceanographicobservations.

A glass hydrometer has a small graduatedstem and a bulb counterweighted for the graduationrange. It is a very fragile instrument and must be han-dled carefully. Hydrometers are furnished in sets ofthree and are graduated for the following ranges ofspecific gravity: 0.9960 to 1.0110, 1.0100 to 1.0210,and 1.0200 to 1.0310. Only hydrometers for which acalibration table is available are to be used for specif-ic gravity measurements.

New reversing thermometers generally ex-hibit a greater drift in calibration values than doolder thermometers because of the aging process thatthe glass undergoes. As the glass is exercised and cy-cled through general usage, it eventually stabilizes toan acceptable level of change. Because temper-

AL-5 (JUNE 1, 1981)

1. Never lay a reversing thermometer ina horizontal position.

2. When a thermometer is not beingused, put it in its protective cylindrical container;store the container in a padded carrying case withthe large mercury reservoir in a down position;and stow the carrying case in an upright position.

3. All thermometers should be washedin fresh water and dried before being stored.

4. Handle the thermometers gently. Ifthe mercury fails to return from the supplementalreservoir, a light tap with the finger will usuallybring it down.

5. Never store thermometers in Nansenbottle frames for long periods. If thermometers areleft in Nansen bottle frames during a brief run be-tween stations, place the bottles in a storage rackwith the large mercury reservoirs down.

AL.2.2.2. Corrections to observed tem-peratures. A calibration certificate is furnished witheach reversing thermometer; from the calibrationdata, graphs are drawn from which corrections canbe scaled as needed. Although temperatures ofmaximum precision are not required for computingcorrections to echo soundings, corrected tempera-tures must be accurate to ± 0.1°C.

Observed temperatures often contain smallerrors. One is caused by minor irregularities in thecapillary tube and slight errors in the graduationmarkings. When this condition exists, the calibra-tion curve retains its shape; but over a period oftime, shifts slightly with respect to the freezingpoint. Corrections for this error can be determinedonly by recalibrating the thermometer.

Another error is caused by a change in thevolume of mercury in the capillary tube and in thesmall reservoir. Volume changes occur with tem-perature changes when a thermometer is broughtto the surface. The magnitude of this error can becomputed from auxiliary thermometer readings.Detailed discussions on methods to compute andapply temperature corrections are contained in H.O.Pub. No. 614, ''Processing Oceanographic Data''(LaFond 1951).

1. New reversing thermometers, after aninitial calibration, shall be assigned to vessels en-gaged in hydrography— recalibrate after 1 yr and ev-ery 5 yrs thereafter unless the instrument has beendamaged or obviously is in error.

2. Seasoned reversing thermometers withwell-documented stable calibration histories shall beassigned to vessels engaged in oceanographic investi-gations—calibrate once each year and at other timesthat the instrument is suspect.

AL.2.4. HYDROMETERS. When in situ sen-sors or salinometers are not available, salinity deter-minations can be made by measuring the specificgravity of a water sample with a hydrometer. Watersample temperature and specific gravity are mea-sured using a hydrometer set (i.e., a hydrometer jar,an accurate laboratory thermometer graduated in °C,and a set of three hydrometers for various ranges ofspecific gravity). (See figure AL-8.)

HYDROGRAPHIC MANUAL

Samples to be preserved for subsequentlaboratory analysis are stored in properly labeledand identified citrate bottles. Observed densitiesand temperatures can be converted to salinities byusing figure AL-9.

FIGURE AL–7.— Induction-type salinometer (courtesy ofPlessey Environmental Systems, San Diego, California)

Hydrometers are calibrated and graduatedto register specific gravity when the sample is atthe temperature of 15°C. (The specific gravity offresh water at 4°C is unity.) Salinity tables arecomputed on this basis.

When this type of instrument is used, theconductor cable should be graduated at intervals tohelp the observer. Periodic field checks must bemade by comparing velocity and depth dataobtained by the instrument with data determinedby a classical method, such as a Nansen cast. Un-der no circumstances shall these instruments beused in depths greater than the recommended max-imum.

An instrument of this type frequently usedaboard NOS vessels is the Martek Model TDC Me-FIGURE AL–8.— NOS hydrometer set

AL-6(JUNE 1, 1981)

A sufficient quantity of a water sample ispoured in a hydrometer jar so the hydrometerfloats without touching bottom. Place the jar on alevel bench or shelf—hold it in your hand if thevessel is rolling. Float the hydrometer and rotate itslowly; then insert the thermometer and wait untilthe mercury column comes to rest. To obtain accu-rate values, the hydrometer must float freely with-out touching the sides of the jar. Read the specificgravity of the water sample with the eye slightlybelow the water level in the jar. From this posi-tion, the water surface should appear as a straightline intersecting the graduations on the hydrometerstem. Observe and record the water temperature assoon as possible after reading the specific gravity.Disturb the hydrometer and repeat the observa-tions as soon as it comes to rest.

AL.2.5. TEMPERATURE, DEPTH, CON-DUCTIVITY (TDC) SENSORS. Relatively inexpen-sive electronic sensors are available commerciallythat provide a more economic and efficient meansof determining the velocity of sound through waterfor computing corrections to echo soundings. (See4.9.) A number of firms manufacture light portablesensors for use aboard small hydrographic vesselsthat work in the lesser depth ranges. The sensorand conductor cables can be easily manhandledoverboard in depths less than 100 fm, and observa-tions can be easily read on data display moduleswith sufficient accuracy for hydrographic survey-ing. Tables and graphs to convert meter readingsto sound velocities for various depth layers are in-cluded with the instruments.

APPARENT SPECIFIC GRAVITY

SAL

INIT

Y ‰

EQ

UIP

ME

NT

AN

D IN

STR

UM

EN

TS

APPARENT SPECIFIC GRAVITY

FIGURE AL–9.— Conversion of apparent specific gravity to salinity

AL

-7 (JU

NE

1, 1981)

SAL

INIT

Y ‰

HYDROGRAPHIC MANUAL

tering System. (See figure AL–10.) Advertised ca-pabilities of this instrument are:

3. Conductivity range of 0 to 40 ppt sa-linity with an accuracy of ± 2%.

Small clamshell snappers similar to those

(JUNE 1, 1981) AL-8

1. Depth range of 0 to 100 m or 0 to150 lb/in² with an accuracy of ± 1.5%.

2. Temperature range of 0°C to 40°Cwith an accuracy of ± 0.5°C.

AL.2.6. SALINITY, TEMPERATURE, DEPTH(STD) SENSORS. Modern sophisticated oceano-graphic instruments are available for in situ mea-surements of the parameters needed to computevelocity of sound corrections for surveys in deepwaters. Most of these systems are unduly expensiveif purchased only for routine hydrographic sur-veys. Deep ocean casts require heavy oceano-graphic winches; whether the data are obtained byclassical methods or by an electronic sensor, costsare high in terms of vessel operating time; howev-er, such equipment should be used when available.

FIGURE AL–10.— Temperature, depth, and conductivity (TDC)metering system (courtesy of Martek Instruments, Inc., New-port Beach, California)

Deep ocean velocity corrections can bedetermined efficiently and economically by usingan expendable salinity, temperature, depth(XSTD) system. Plessey Environmental SystemsModel 9090 XSTD System (figure AL–11) has astandard depth range of 750 m. The system con-sists of an expendable probe or sensor that mea-sures conductivity, temperature, and depth. Thedata are transmitted through a fine-wire link thatconnects the sensing probe to the shipboard re-cording and processing equipment. The probe isdeployed through a simple deck- or hull-mountedlauncher and has a drop rate of 6.1 m/s (20 ft/s).Measurement accuracies exceed those required forhydrographic survey sound velocity corrections.

When working in waters deeper than themaximum range of a sensor, historical oceano-graphic data for the area and time of year can beused to extend the observed data to the requireddepths.

AL.2.7. BOTTOM SAMPLERS. Equipmentfor bottom sampling used by NOS vessels to de-termine bottom characteristics for nautical chart-ing are basically ''snapper'' type devices.Sampling devices must be capable of obtainingsamples of sufficient volume to enable a hydrog-rapher to readily determine the bottom charac-teristics of the surface layer and to provide agood representative sample of the bottom forsubmission to the Smithsonian Institution, Wash-ington, D.C (See 4.7.1.)

One such device, frequently used aboardlarger vessels, is the Shipek Sediment Sampler.(See figure AL–12.) This sampler is designed toobtain samples of unconsolidated sediment, fromsoft ooze to hard-packed sand and sizable rocks,from any depth. The sample size is approximate-ly 400 cm² in surface area, and about 10 cm deepat the center.

Basically, the sampler is composed of twoconcentric half cylinders. The inner semicylinderor sample bucket is rotated at high torque to twohelically wound external springs. A winch is need-ed to lower and hoist this sampler. Upon contactwith the bottom, it is automatically triggered bythe inertia of a self-contained weight upon a searmechanism. At the end of its travel, the samplebucket is stopped and held in its closed position byresidual spring torque.

EQUIPMENT AND INSTRUMENTS

FIGURE AL–12.— Shipek sediment sampler (courtesy of HydroProducts, San Diego, California)

AL-9 (JUNE 1, 1981)

FIGURE AL–11. — Expendable salinity, temperature, and depth(XSTD) system (courtesy of Plessey Environmental Systems,San Diego, California)

FIGURE AL–13.— Clamshell snappers for bottom sampling(Ballauf Mfg. Co., Inc., 619 H Street, N.W., Washington,D.C.)

HYDROGRAPHIC MANUAL

Clocks used for hydrographic survey tim-ing shall be compared to a reliable standard at thebeginning and at the end of each workday andmust be adjusted to keep the best time possible.Clocks that cannot maintain time accurate to with-in ± 5 min a day shall not be used.

FIGURE AL .– 14 .— Hydrographic clock

AL-10(JUNE 1, 1981)

shown in figure AL-13 are used for bottom sam-pling from smaller vessels.

Accurate clocks are essential to correlatethe various events of a hydrographic survey, par-ticularly when the tidal ranges are large. For skiffhydrography and use on launches not equippedwith a controlled frequency power source, an8-day mechanical clock with a 6-in dial is used fortiming. (See figure AL-14.) The clock must besturdy and shock resistant; it must be housed in awaterproof casing and equipped with a battery-ac-tivated buzzer or bell that can be set to sound atintervals of 10, 15, 20, 30, or 60 s.

AL.3. Hydrographic Clock

B. CARTOGRAPHIC CODES AND SYMBOLS

TABLE B–1.— Control stations*

Symbols and examplesDescriptionsCartographic codes

139

250 Basic or supplemental control station (recoverable) used aselectronic positioning system antenna site

243

254 Undescribed, nonrecoverable station used as electronic posi-tioning system antenna site

252 Hydrographic station located by sextant fixes or cuts

253

* Station names and numbers of tanks, gables. chimneys, piles, rocks, and similar recoverable objects used as signals shall he accompanied bya brief description in black ink in parentheses, unless described in the control station name. Signals in water areas always shall be described fully;temporary signal descriptions are accompanied by the note ''(temp).''

TABLE B–2— Low water line and associated features*

DescriptionsCartographic codes Symbols and examples

013 Contour of zero depth drawn from corrected soundings

Contour of zero depth estimated and sketched from hydro-graphic data

188

008 Contour of zero depth from photogrammetric shorelinemaps or topographic surveys

009 Ledge†

009 Reef

None Grass

* See also section 1.6.1.†See also figure B-4 for more detailed ways to depict ledges and reefs.

B-1 (JULY 4, 1976)

The cartographic codes and symbols shown in tables B-1 through B-9 shall be used to identifyhydrographic information on final master data tapes and to represent features and data on surveysheets. Control station codes are entered by hydrographers in the field; the rest of the codes areentered during verification. Code entry methods and formats are specified in the''HYDROPLOT/HYDROLOG Systems Manual'' (WALLACE 1971) and in ''Specifications for AutomatedHydrographic Survey Magnetic Tapes and Listings" (Office of Marine Technology 1973). For themeanings of most abbreviations in the tables, see Chart No. 1, United States of America NauticalChart Symbols and Abbreviations (National Ocean Survey and Hydrographic Center 1975); and forthe conversion of measurements, see appendix C.

Basic or supplemental control station. Use of this symbolshall be limited to described, marked, recoverable sta-tions, and intersection stations of third-order class-II orhigher accuracy. (See sections 3. 1.1 and 3.1.2.)

101MORTON, 1959

102SANDY, 1973

213TRAV-1, 1975

117AA - 74, 1974

319 (chy)

327 (cup)

Hydrographic station located by traverse, plane table, orphotogrammetric methods—or undescribed, non-recoverable stations of third-order or lower accuracy.(See 3.1.3.)

Hydrographic station located by unconventional methods(e.g., by spotting its position on a topographic map oraerial photograph for transfer to the hydrographic sheet)

HYDROGRAPHIC MANUAL

TABLE B–3.— Dangers to navigation

Symbols and examplesCartographic codes Descriptions

056* Oil or gas well

094 Rock awash

099 Wreck, mast(s) visible

Wreck100

104† Rock (no depth)

107 Ruins

108 Crib

233 Dolphin

234 Pile

235 Pipe

236 Stake

237 Stump

238 Snag

287 Obstruction

094‡ Rock awash (no elevation determined)

Wreck098

278 Dolphin

279 Pile

Pipe280

Stake281

282 Stump

283 Snag

284 Obstruction

Ruins285

286 Crib

291† Rock awash (elevation in feet above datum)

010§ Dolphin

Obstruction085

097 Islet (if impractical at survey scale, actual size and shapeneed not be shown)

Wreck098

B-2(JULY 4, 1976)

CARTOGRAPHIC CODES AND SYMBOLS

TABLE B-3.– Concluded

Symbols and examplesDescriptionsCartographic codes

Pipe105 pipe

stakeStake106

crib109 Crib

pilePile110

platformPlatform (oil or gas)111

stump230 Stump

Snag231 Snag

deadhead232 Deadhead (usually one end afloat)

Duck blind duck blind241

duck blind ruins242 Duck blind ruins

248 survey platformPlatform, survey

platform (lighted)249 Platform, lighted

ruins260 Ruins

103¶ Kelp (symbol not to be used for bottom characteristic butto indicate small isolated patches visible on the surface)

599 Kelp (limit lines not shown-used to indicate extensive kelpbeds visible on the surface) kelp

146 Tide rips (limit lines not shown) tide rips

spoil533 Spoil area (limit lines not shown)

walerfall534 Waterfall

535 Rapids rapids

eddies536 Eddies

shoal537 Shoal (limit lines not shown)

538 Foul (limit lines not shown) foul

539 Breakers (limit lines not shown) breakers

B-3 (JULY 4,1976)

* Features in the 14 codes 056 through 287 do not uncover at the sounding datum prescribed for the area. (See section 1.5 4.1.)†See figures B-1 through B-3 for additional information on rock symbolization.‡Features in the 12 codes 094 through 291 uncover at the sounding datum but are covered at mean high water (not applicable to surveys of

the Great Lakes).§Features in the 17 codes 010 through 260 are visible at mean high water for surveys in tidal waters or are visible at shoreline datum in the

Great Lakes.¶Symbols in the 10 codes 103 through 539 are used to depict miscellaneous dangers that do not fall into any of the preceding categories.

HYDROGRAPHIC MANUAL

TABLE B-4.–Soundings

Symbols and examplesDescriptions

129 Sounding (whole fathoms)

Sounding (fathoms and tenths)

Sounding (fathoms and fraction)

Minus sounding (whole fathoms)

Minus sounding (fathoms and tenths)

Minus sounding (fathoms and fraction)

Sounding on rock (whole fathoms)

Sounding on rock (fathoms and tenths)

Sounding on wreck (whole fathoms)

Sounding on wreck (fathoms and tenths)

Sounding on obstruction (whole fathoms)

Sounding on obstruction (fathoms and tenths)

130

131

148

137

142

265

262

270

267

274

275

126 Sounding (whole feet)

Sounding (feet and tenths)

Sounding (feet and fraction)

Minus sounding (whole feet)

Minus sounding (feet and tenths)

Minus sounding (feet and fraction)

Sounding on rock (whole feet)

Sounding on rock (feet and tenths)

Sounding on wreck (whole feet)

Sounding on wreck (feet and tenths)

Sounding on obstruction (whole feet)

Sounding on obstruction (feet and tenths)

127

128

135

141

136

290

264

101

269

272

273

B-4(JULY 4, 1976)

CARTOGRAPHIC CODES AND SYMBOLS

TABLE B-4.— Concluded

Symbols and examplesDescriptionsCartographic codes

47Sounding (whole meters)

Sounding (meters and tenths)

Minus sounding (whole meters)

Minus sounding (meters and tenths)

Sounding on rock (whole meters)

Sounding on rock (meters and tenths)

Sounding on wreck (whole meters)

Sounding on wreck (meters and tenths)

Sounding on obstruction (whole meters)

Sounding on obstruction (meters and tenths)

132

13²133

-2149

138

2 Rk266

Rk263

2 wk271

wk268

2 obstr276

obstr277

134 Unqualified sounding (final corrections will not be applied,plot in whole units) 31

251 (No symbol)

42 wk - cleared by 40 ft090

18 Rk - cleared by 15 ft091

18 obstr - cleared by 18 ft092

16 Co-cleared by 14 ft095

12 cleared by 9 ft239

25 hrd-cleared by 23 ft240

TABLE B-5-Shoreline and alongshore features

Cartographic codes Symbols and examplesDescriptions

007* Fast solid land (0.4 mm)

Marsh, swamp, and mangrove (0.2 mm)003

Approximate shoreline (HWL)001

None Piers and waterfront areas (0.4 mm and 0.2 mm)

144† Fast solid land (0.4 mm)

Marsh, swamp. and mangrove (0.2 mm)190

Fast solid land (0.4 mm)

Marsh, swamp. and mangrove (0.2 mm)

145‡

189

JULY 4, 1976)B-5

* Features in codes 007, 003, 001, and none are from photogrammetric shoreline maps and topographic surveys or other method of equivalentaccuracy Measurements in parentheses are line widths

†Features in codes 144 and 190 are shoreline revisions sketched bv the hydrographer using fixes or other methods of equivalent accuracv.‡Features in codes 145 and 189 are shoreline revisions sketched by the hydrographer using estimated positions.

Miss (no sounding)

Wreck (wire drag clearance)

Rock (wire drag clearance)

Obstruction (wire drag clearance)

Coral (wire drag clearance)

Shoal (wire drag clearance)

Hard (wire drag clearance)

HYDROGRAPHIC MANUAL

TABLE B–6.—Buoys*

Symbols and examplesDescriptionsCartographic codes

255 Red buoy (e.g., red nun buoy, number 32)

Black buoy (e.g., black can buoy, number 33)

Red buoy (lighted – e.g., bell buoy, number 4)

Black buoy (lighted – e.g., bell buoy, number 5)

256

257

258

214 Vertically striped buoy (e.g., black and white mid-channelcan buoy, unnumbered)

216 Horizontally banded buoy (e.g., red and black junction canbuoy, unnumbered)

217 Checkered buoy (Enter appropriate

descriptions for218 Diagonally banded buoy all other buoy

Symbols.)212 Open buoy symbol (color to be added by hand)

259 Open buoy symbol (lighted – color and/or striping to beadded by hand)

Mooring buoy215

* For buoys not shown, use symbols prescribed in Chart No. 1 . United State of America Nautical Chart Symbols and Abbreviations (National OceanSurvey and Hydrographic Center 1975).

TABLE B–7.— Bottom characteristics

Carto-Carto-Carto-Colors Symbols andNouns graphicSymbols andgraphic Adjectives Symbols andgraphic

examplesexamples codescodescodes examples

Black550 569545Ooze Gritty

White570548551 Clay Rocky

Silt552 555 571Fine Gray

Mud553 Brown577Coarse557

Sand558 RedSoft572 581

YellowGravel 582Hard573559

574560 Shingle 584Sticky Blue

576Coral head562 Broken Orange586

578Pebbles566 Speckled Green587

Violet579567 589Stones Light

Dark583Boulders568

597 Small575 Shells

598Coral580 Large

Seaweed594

Grass595

(JULY 4, 1976) B-6

B. CARTOGRAPHIC CODES AND SYMBOLS

TABLE B-8.— Nonfloating aids to navigation and landmarks

Descriptions Symbols and examplesCartographic codes

Day beacon "33" A '32*219

F Range BnDay beacon, front range223

R Range Bn224 Day beacon, rear range

priv markerMarker (privately maintained)261

marker (mile)Marker, front mile*221

marker (mile)222 Marker, rear mile

marker (dredging range)

marker (dredging range)

246 Marker, front dredging range

Marker, rear dredging range247

108139

SAND POINT LIGHTHOUSE, 1887(Bay Shaft Light)

117

BIRD ISLAND LIGHTHOUSE, 1857139 Structure, † third-order accuracy, no longer in

service, used as a signal(abandoned)

070

Bald Pt Lt

112 Landmark, ‡ less than third-order accuracy(not used as a signal) 0

139 Radio tower, § located previously by third-orderintersection methods, not used during thesurvey, but suitable for use as a landmark

RADIO TOWER, WNOR, 1972(landmark: 620 ft above ground,

705 ft above MHW)243

187(B Bn "33")

TABLE B-9.— Miscellaneous features

Descriptions Symbol& and examples

Tide or water level gaging station244

Current StationCurrent station245

011 Limit lines

078(No symbol)

(JULY 4, 1976)B-7

* All mileages are in nautical miles unless otheriser specified

†If structures of this type were not used to control the surve). omit the signal number (e.g., cartographic code 070)

‡Landmarks of third order or better accuracy that were not used to control the survey are shown using the control station symbol and the land

mark description (e.g., cartographic code 139).

§If an aid to navigation or landmark was located by less than third-order methods for use as a signal during the survey, the appropriate control

station symbol takes precedence (e.g. cartographic code 243).

Structure, of third-order or better accuracy,used as a signal. Give station name andyear, and U.S. Coast Guard (1976) LightList name, if different.

Lighted structure, not used as a signal andlocated by less than third-order methods.Give U.S. Coast Guard Light List name.

Black day beacon, number 33, locatedphotogrammetrically and used as ahydrographic signal

Feature for which an individual cartographic code has notbeen assigned. Code 078 also may be utilized fordetached positions used to delineate features.

TANK, ELEVATED (Country Club Hills)(landmark: 60 ft obove ground.

245 ft above MHW

Tide Station

CARTOGRAPHIC CODES AND SYMBOLS

- x

(JULY 4, 1976)B-9

FIGURE B–2.—Rock symbols and elevation references for the Pacific Coast. Although based on a 2-ft range of tide, the zonevalues are valid for any tide range. See also "Photogrammetric Instruction No. 70, Rocks, Reefs, and Ledges Shown onPhotogrammetric Maps'' (National Ocean Survey 1975).

HYDROGRAPHIC MANUAL

FIGURE B-3.— Rock symbols and elevation references for the Great Lakes. See also ''Photogrammetric; Instruction No. 70,Rocks, Reefs, and Ledges Shown on Photogrammetric Maps'' (National Ocean Survey 1975).

B-10(JULY 4, 1976)

CARTOGRAPHIC CODES AND SYMBOLS

Reef uncovers at roundingdatum.

Reef uncovers 3 ft atsounding datum.(3)

Rocks (high points) top reef.

Elevations of bare rocks fromtopographic source are shownin red on hydrographic survey

Elevations of rocks and reefare known.

(7)

Ledge uncovers at soundingdatum.

Ledge indicates foreshorecharacteristic only;dotted line is lowwater line.

Rocks (high points) top ledge.

Bare rocks from hydrographicsources are shown in red onhydrographic survey

Elevations of rocks are known.

Add this abbreviation if thefeatures are coral.

Reef is smallerthan 1.5 x 1.5 mm.

FIGURE B–4.— Symbols and elevation references for reefs and ledges

(JULY 4, 1976)B-11

(4)

(3)

surveys within the United States would continue tobe based upon the old standard (1 ft = 1200/3937m). This foot is named the ''U.S. Survey Foot.''

MISCELLANEOUS CONVERSIONS, TABLES, AND GRAPHSC.

As a result, all land measurements in theUnited States will relate to the meter by the oldstandard. The U.S. Survey Foot is also the unitadopted by the National Ocean Survey for its map-ping and charting measurements; hence, linear andareal conversion factors in this appendix are basedon the U.S. Survey Foot rather than the Interna-tional Foot. See tables C-1 through C-7 and figureC-1.At the same time, it was decided that data

derived from and published as a result of geodetic

TABLE C–1.— Conversion Factors (U.S. Survey Foot)

Area Length1 square inch (in²) 1 inch (in) = 25.4000508 millimeters (mm)

= 2.54000508 centimeters (cm)1 square foot (ft²)

1 foot (ft)1 square statute mile (mi²)

1 square centimeter (cm² ) 1 yard (yd)

1 square meter (m² )

1 square kilometer (km²)1 fathom (fm)

1 hectare (ha)

1 statute mile (mi)Mass

1 ounce(oz)

1 pound (lb)1 nautical mile (nmi)

1 short ton

= 100 centimeters (cm)= 39.37 inches (in)= 3.28083333 feet (ft)= 0.54680556 fathom (fm)= 0.00062137 statute mile (mi)= 0.00053996 nautical mile

(nmi)

1 meter (m)1 kilogram (kg)

Mathematicsπ1 radian (rad)

1 kilometer (km)1 degree (1°)

360 degrees (360°)

C-1 (JULY 4, 1976)

Since 1893, the basis of length measurementthroughout the United States has been derived frommetric standards. In 1959, a small refinement wasmade in the definition of the yard to resolve discrep-ancies both in this country and abroad. This refine-ment changed the length of 1 yd from 3600/3937 m(approximately 0.914402 m) to 0.9144 m, exactly.The new value became shorter than the old by twoparts in a million. The foot defined by this neweryard is equal to 0.3048 m, exactly. and is called the''International Foot.''

=6.45162581 squarecentimeters (cm²)

=0.09290341 squaremeter (m²)

=2.58999847 squarekilometers (km²)

=0.15499969 squareinch (in²)

= 10.76386736 squarefeet (ft² )

=0.38610061 squarestatute mile (mi²)

=0.29155335 squarenautical mile (nmi² )

= 10,000 square meters (m² )=2.471 acres

=28.34952673 grams (g)=0.02834953 kilogram (kg)=0.0625 pound (lb)=453.59242768 grams (g)=0.45359243 kilogram (kg)=2,000 pounds (lb)=907.1848554 kilograms

(kg)=0.90718486 metric ton=0.89285714 long ton=2.20462234 pounds (lb)=1000 grams

=3.1415926535897932=206,264."80625=57°17'44."80625=0.0174532925199433

radian (rad)= 2 π radians (rad)=400 grads

=3,280.83333333 feet (ft)=1000 meters (m)=0.62136995 statute mile (mi)=0.53995680 nautical mile

(nmi)

= 6,076.10333333 feet (ft)= 2,025.36777777 yards (yd)= 1852 meters (m)= 1.15077715 statute miles (mi)

= 5,280 feet (ft)= 1,760 yards (yd)= 1609,34721869 meters (m)= 0.86897798 nautical mile

(nmi)

= 6 feet (ft)= 2 yards (yd)= 1.82880366 meters (m)= 182.890366 centimeters (cm)

= 36 inches (in)= 3 feet (ft)= 0.91440183 meter (m)= 91.4401829 centimeters (cm)

= 12 inches (in)= 0.30480061 meter (m)

=16.38716233 cubiccentimeters (cm³)

=0.01638670 liter (1)=0.00432900 gallon (gal)

HYDROGRAPHIC MANUAL

TABLE C-1.— Continued

VolumeSpeed1 cubic inch (in³)1 Knot (kn)

1 cubic foot (ft³)

1 cubic centimeter (cm³)

1 cubic meter (m³)

= 57.75 cubic inches (in³)= 0.94633213 liter (l)

1 quart (qt, U.S.)

1 gallon (gal, U.S.)

1 liter (l)Temperature°F = (9/5 X °C) + 32°°C = 5/9(°F–32°)

Celsius to FahrenheitFahrenheit to Celsius

TABLE C-2.— Linear distance conversion (fathoms, meters, feet, and yards)

Fathoms to Meters to Feet to Yards tofeet meters fathoms feet metersyards fathoms meters

12345

6789

(JULY 4, 1976) C-2

36424854

10.9728212.8016314.6304316.45923

3.280833.827644.374444.92125

6.561677.655288.748899.84250

19.6850022.9658326.2466729.52750

1.828802.133602.438402.74321

1.000001.166671.333331.50000

5.486416.400817.315218.22962

612182430

1.828803.657615.486417.315219.14402

0.546811.093611.640422.187222.73403

1.093612.187223.280834.374445.46806

3.28083 6.56167 9.8425013.1233316.40417

0.304800.609600.914401.219201.52400

0.166670.333330.500000.666670.83333

0.914401.828802.743213.657614.57201

= 1 nautical mile per hour(nmi/hr)

= 101.26838879 feetper minute (ft/min)

= 30.87666667 meters perminute (m/min)

= 1.852 kilometers per hour(km/hr)

=1.15077715 statute milesper hour (mi/hr)

=0.51444444 meter persecond (m/s)

= 1,728 cubic inches (in³)= 28.31622363 liters (l)= 7.48051948 U.S.

gallons (gal)= 0.02831702 cubic

meter (m³)

= 0.06102338 cubic inch(in³)

= 0.00026417 U.S.gallon (gal)

= 264.17046733 U.S.gallons (gal)

=35.31445483 cubicfeet (ft³)

= 3785.43449592 cubiccentimeters (cm³)

= 231 cubic inches (in³)= 0.13368056 cubic foot

(ft³)= 3.78532851 liters (l)

= 1000.028 cubiccentimeters (cm³)

= 61.02508662 cubic inches(in³)

= 1.05671146 quarts (qt)= 0.26417786 gallon (gal)

MISCELLANEOUS CONVERSIONS, TABLES, AND GRAPHS

TABLE C–3.— Linear distance conversion (nautical miles, statute miles, and kilometers)

Kilometers toStatute miles toNautical miles tostatute nauticalkilometersnauticalstatute kilometers

miles milesmilesmiles

12345

6789

TABLE C–4.—Temperature conyersion (Celsius to Fahrenheit and Fahrenheit to Celsius)

Celsius to Fahrenheit

°F

Fahrenheit to Celsius

C-3 (JULY 4, 1976)

1.150782.301553.452334.603115.75389

6.90466 8.05544 9.2062210.35699

1.852003.704005.556007.408009.26000

11.1120012.9640014.8160016.66800

0.868981.737962.606933.475914.34489

5.213876.082856.951827.82080

1.609353.218694.828046.437398.04674

9.6560811.2654312.8747814.48412

0.621371.242741.864112.485483.10685

3.728224.349594.970965.59233

0.539961.079911.619872.159832.69978

3.239743.779704.319654.85961

°C°F°C°F°C°F°C °F°C

-2-101234

28.430.232.033.835.637.439.2

56789

1011

41.042.844.646.448.250.051.8

12131415161718

53.655.457.259.060.862.664.4

19202122232425

66.268.069.871.673.475.277.0

26272829303132

78.880.682.484.286.087.889.6

°F °C °F °C °F °C °F °C °F °C

26.727.227.828.328.929.430.030.631.131.732.232.833.3

80818283848586878889909192

67686970717273747576777879

19.420.020.621.121.722.222.823.323.924.425.025.626.1

12.212.813.313.914.415.015.616.116.717.217.818.318.9

54555657585960616263646566

5.0 5.6 6.1 6.7 7.2 7.8 8.3 8.9 9.410.010.611.111.7

41424344454647484950515253

- 2.2- 1.7- 1.1- 0.6 0.0+0.6 1.1 1.7 2.2 2.8 3.3 3.9 4.4

28293031323334353637383940

HYDROGRAPHIC MANUAL

TABLE C–6.— Microwave horizondistance, range versus antenna height

(nautical miles and statute mile). See also table C–5.(Courtesy of Del Norte Technology, Inc, Euless, Texas.)

Kilometers Statute MinimumMinimum Nautical MinimumKilometers Minimumnecessaryrange necessary necessary milesnecessaryrange miles

height (ft) height (ft)rangeheight (m) height (m)

123456789

*This table shows the distance to the radar horizon for various antenna heightsEnter the table with the master station antenna height and note the range to the radarhorizon; then repeat using the remote station height. Add the two ranges justdetermined to find the maximum range possible for the given combination of antennaheight [e.g. an antenna height of 16 m at a master station would result in a horizonrange of 16 km—while an antenna height of 1.5 m at a remote station would result in aborizon range of 5 km; the theoretical maximum range of this antenna combinationwould be 21 km].

C-4(JULY 4, 1976)

TABLE C–5.— Microwave horizon distance,range versus antenna height (kilometers). *

See also table C–6.(Courtesy of Del Norte Technology, Inc. Euless, Texas.)

0.72.14.78.3

13.018.725.533.342.152.063.074.987.9

102.0117.0133.2150.4168.6187.8208.1229.4251.8275.2299.7325.2351.7379.3407.9437.6468.3500.0532.8566.6601.5637.46743712.3751.3791.4832.5874.6917.8962.0

1,007.31,053.61,100.91,149.31,198.71,249.21.300.7

1011121314151617181920212223242526272829303132333435363738394041424344454647484950

123456789

1011121314151617181920212223242526272829303132333435363738394041424344454647484950

0.72.76.0

10.716.824.232.943.054.467.281.396.7

113.5131.7151.2172.0194.2217.7242.5268.7296.3325.2355.4387.0420.0454.2489.8526.7565.0604.7645.7688.0731.7776.7823.0870.7919.8970.2

1,021.91,075.01,129.41,185.21,242.31,300.71,360.51,421.71,494.11,548.11,613.11,679.7

103108113119124130135141147153159166172179185192199206213220228235243251259267275283292300309317326335344354363373382392

41424344454647484950515253545556575859606162636465666768697071727374757677787980

0.06.27.55.98

1.52.23.03.95.06.17.48.8

10121416182022252730323538414548515559636771757984889398

123456789

10111213141516171819202122232425262728293031323334353637383940

MISCELLANEOUS CONVERSIONS, TABLES, AND GRAPHS

TABLE C–7.— Velocity correction factors for a calibration velocity of 800 fm/ s

FactorsFactors Actual velocityActual velocity(m/ s) (m/ s )

1,4601,501

1,5101,470

1,480 1,520

1,490 1,530

1,540

(JULY 4, 1976)C-5

6162636465

66676869

7172737475

76777879

8182838485

86878889

9192939495

1,500

96979899

– 0.00205– .00137– .00068

.00000+ .00068+ .00137

+ 0.00205+ .00273+ .00342+ .00410+ .00478

+ 0.00547+ .00615+ .00684+ .00752+ .00820

+ 0.00889+ .00957+ .01025+ .01094+ .01162

+ 0.01230+ .01299+ .01367+ .01435+ .01504

+ 0.01572+ .01640+ .01709+ .01777+ .01846

+ 0.01914+ .01982+ .02051+ .02119+ .02187

+ 0.02256+ .02324+ .02392+ .02461+ .02529

02030405

06070809

1112131415

16171819

2122232425

26272829

3132333435

36373839

+ 0.04990+ .05058+ .05126+ .05195+ .05263

+ 0.04648+ .04716+ .04785+ .04853+ .04921

+ 0.04306+ .04375+ .04443+ .04511+ .04580

+ 0.03964+ .04033+ .04101+ .04170+ .04238

+ 0.03623+ .03691+ .03759+ .03828+ .03896

+ 0.03281+ .03349+ .03418+ .03486+ .03554

+ 0.02939+ .03008+ .03076+ .03144+ .03213

+ 0.02597+ .02666+ .02734+ .02802+ .02971

HYDROGRAPHIC MANUAL

ht = R= hr = RPS ANTENNA RANGE IN TRANSPONDER

NAUTICAL MILESHEIGHT IN FEET HEIGHT IN FEET

FIGURE C–1.— Line-of-sight nomograph (courtesy of Motorola, Inc., Scottsdale, Arizona)

(JULY 4, 1976) C-6

q q q

EXAMPLE: HEIGHT OF MRS (TRANSMITTING) ANTENNA 60 FEET; HEIGHT OFTRANSPONDER (RECEIVING) ANTENNA 500 FEET: MAXIMUM,FREE-SPACE LINE-OF-SIGHT TRANSMISSION IS APPROXIMATELY37 NAUTICAL MILES.

D. BIBLIOGRAPHY

This manual is one of a series of NOAApublications designed to state the requirements forvarious survey operations and to describe the meth-ods and equipment used. This manual emphasizesproper or recommended techniques and proceduresfor conducting hydrographic surveys. The hydrogra-pher should consult the following technical publica-tions, for they may be needed during combined oper-ations projects. Note that the dates of publication ofthe references cited in the text appear in boldfacetype.

Burger, Thomas C., and Tomlinson,Raymond W., American Congress on Surveying andMapping (ACSM), Electronic Distance Measuring In-struments, Technical Monograph No. CS-2, FirstEdition, March 1971, 60 pp.

Commander, Third Coast Guard District,U.S. Coast Guard Local Notice to Mariners, U.S. De-partment of Transportation, Governors Island, NewYork, N.Y, Jan. 21, 1976, 18 pp.

Cubic Western Data, Maintenance Manualfor DM-54 Positioning System, San Diego, California,1977, 384 pp.

Cubic Western Data, Operator's Manual,DM-54 Positioning System, San Diego, California,1977, 140 pp.

Decca Survey Systems, Inc., HydrographicSurvey With Hi-Fix, Houston, Tex., 1972, 108 pp.plus appendixes A and B.

Deetz, Charles H., and Adams, Oscar S.,''Elements of Map Projection With Application toMap and Chart Construction,'' Coast and GeodeticSurvey Special Publication No. 68, Fifth Edition, re-vised, U.S. Department of Commerce, Washington,D.C, 1945, 226 pp.Beito, Edwin A. (revised by), Dutton's Navi-

gation and Nautical Astronomy, U.S. Naval Institute,Annapolis, Md., 1957, 561 pp.

Defense Mapping Agency HydrographicCenter, ''Numerical Listing of Charts and Publica-tions,'' Catalog of Nautical Charts, Eighth Edition,U.S. Department of Defense, Washington, D.C., cor-rected to Mar. 1, 1976, 96 pp. (See LORAN tables,p. 88.)

Berry, Ralph M., ''Steel Tape Measurements:Tables and Charts for Correction,'' Coast and Geo-detic Survey Special Publication No. 307, U.S. De-partment of Commerce, Washington, D.C. 1954, 27PP. Defense Mapping Agency Hydrographic

Center (U.S. Department of Defense), NationalOcean Survey (U.S. Department of Commerce),and U.S. Coast Guard (U.S. Department of Trans-portation), 1976 Notice to Mariners, Washington,D.C., May 1, 1976, Sections 1-III (publishedweekly).

Bowditch, Nathaniel, ''American PracticalNavigator, an Epitome of Navigation,'' H.O. Pub.

D-1 (JANUARY 1, 1980)

Adams, Oscar S., and Claire, Charles N.,''Manual of Plane-Coordinate Computation,'' Coastand Geodetic Survey Special Publication No. 193,U.S. Department of Commerce, Washington, D.C.,1935, 271 pp.

Atlantic Marine Center, Manual, NationalOcean Survey, National Oceanic and AtmosphericAdministration, U.S. Department of Commerce,Norfolk, Va., 1970 – 1975 (includes chapters, sections,and looseleaf inserts).

Baker, Leonard S., ''Specifications for Hori-zontal Control Marks,'' ESSA Technical Memoran-dum C&GSTM–4, Geodesy Division, Coast andGeodetic Survey, Environmental Science Services Ad-ministration, U.S. Department of Commerce, Rock-ville, Md., Apr. 1968, 14 pp.

Beck, G.E. (Editor), Navigation Systems, aSurvey of Modern Electronic Aids, Van NostrandReinhold, London, England, 1971, 383 pp.

Bialek, Eugene L. (Compiler), ''Handbook ofOceanographic Tables — 1966,'' U.S. Naval Oceano-graphic Office Special Publication No. 68, Washing-ton, D.C, 1967, 427 pp.

No. 9, U.S. Navy Hydrographic Office, Washington,D.C, 1962, 1524 pp.

Bruder, Wallace A. (Editor), ''NauticalChart Manual,'' Sixth Edition, Coast and GeodeticSurvey Publication 83-1, U.S. Department of Com-merce, Washington, D.C., 1963, 213 pp.

LaFond, E.C., ''Processing OceanographicData," H.O. Pub. No. 614, Hydrographic Office, U.S. Navy, Washington, D.C., 1951, 114 pp.

HYDROGRAPHIC MANUAL

Gossett, F.R., ''Manual of Geodetic Trian-gulation,'' Coast and Geodetic Survey Special Publi-cation No. 247, U.S. Department of Commerce,Washington, D.C., 1959, 344 pp.

Del Norte Technology, Inc., Trisponder,Electronic Positioning System, Basic Operation Manu-al, Euless, Tex., 1974, 49 pp.

Dracup, Joseph F., and Kelly, Carl F.,Horizontal Control as Applied to Local SurveyingNeeds, Control Surveys Division, AmericanCongress on Surveying and Mapping, Washington,D.C., 1973, 127 pp.

Jeffers, Karl B., ''Hydrographic Manual,Third Edition,'' Coast and Geodetic Survey Publica-tion 20-2, U.S. Department of Commerce, Wash-ington, D.C., 1960, 283 pp.

Klein Associates, Inc., Operations andMaintenance Manual-Hydroscan Side Scan SonarSystem Model 520, Salem, N.H., 1977, 14 sections.

Lambert, Walter D., and Swick, ClarenceH., ''Formulas and Tables for the Computation ofGeodetic Positions on the International Ellipsoid,''Coast and Geodetic Survey Special Publication No.200, U.S. Department of Commerce, Washington,D.C., 1935, 120 pp.

Federal Geodetic Control Committee, Speci-fications to Support Classification, Standards of Ac-curacy, and General Specifications of Geodetic Con-trol Surveys, National Ocean Survey, NationalOceanic and Atmospheric Administration, Rock-ville, Md., July 1975 (Reprinted 1977), 30 pp.

Maul, George A., ''Precise Echo Sounding inDeep Waters,'' ESSA Technical Report No. 37, Coastand Geodetic Survey, Environmental Science ServicesAdministration, U.S. Department of Commerce,Rockville, Md., January 1969, 9 pp.

Fischer and Porter Co., Instruction Bulletinfor Type 1550 and 1551 Punched Tape Level Re-corder (Spring Counterbalance Type), Design Level''C'' Warminster, Pa., Sept. 1972, 18 pp.

D-2(JANUARY 1, 1980)

Dracup, Joseph F., ''Suggested Specificationsfor Local Horizontal Control Surveys," TechnicalMonograph No. CS-1, First Edition, revised, Con-trol Surveys Division, American Congress on Survey-ing and Mapping, Washington, D.C, Apr. 1973, 24pp.

Dracup, Joseph F. (Editor), Surveying In-strumentation and Coordinate Computation WorkshopLecture Notes, American Congress on Surveying andMapping, Washington, D.C., 1973, 208 pp.

Dunlap, G.D., and Shufeldt, H.H. (Edi-tors), Dutton's Navigation and Piloting, Twelfth Edi-tion, U.S. Naval Institute, Annapolis, Md., 1969,715 pp.

Edwards, Bobby D., ''ESSA Coast andGeodetic Survey Coast Pilot Manual,'' C&GS Tech-nical Manual No. 1 (EM 75-01), Third Edition,Environmental Science Services Administration, U.S.Department of Commerce, Washington, D.C, 1969,50 pp.

Federal Geodetic Control Committee, Clas-sification, Standards of Accuracy, and General Speci-fications of Geodetic Control Surveys, NationalOcean Survey, National Oceanic and AtmosphericAdministration, U.S. Department of Commerce,Rockville, Md., May 1974, (Reprinted 1977) 12 pp.

Ferrara, Angelo A., ''Electronic PositioningSystems for Surveyors,'' ESSA Technical Memoran-dum C&GSTM–3, Engineering Division, Coast andGeodetic Survey, Environmental Science ServicesAdministration,. U.S. Department of Commerce,Rockville, Md., May 1967, 98 pp.

Hastings, Charles E., and Comstock, AllenL. (Teledyne Hastings-Raydist, Hampton, Va.),''Pinpoint Positioning of Surface Vessels BeyondLine-of-Sight,'' paper presented at National MarineNavigation Meeting of The Institute of Navigation,San Diego, Calif., Nov. 4, 1969, 8 pp.

International Hydrographic Bureau, ''RadioAids to Maritime Navigation and Hydrography,''Special Publication No. 39, Monaco, 1965 (includeslooseleaf inserts).

International Hydrographic Bureau, ''Accu-racy Standards Recommended for HydrographicSurveys," Special Publication 44, Monaco, Jan.1968, 11 pp.

International Hydrographic Bureau, ''Hy-drographic Dictionary, Part 1," Special Publication32,, Third Edition, Monaco, 1974, 370 pp.

Leupold and Stevens, Inc., ''Stevens TypeA Model 71 Water-Level Recorder,'' Bulletin 12,24th Edition, Beaverton, Oreg., 1976?, 5 pp.

Marmer, H.A., ''Tidal Datum Planes,'' Coastand Geodetic Survey Special Publication No. 135, re-vised, U.S. Department of Commerce, Washington, D.C, 1951, 142 pp.

BIBLIOGRAPHY

Mussetter, William, ''Manual of Reconnais-sance for Triangulation,'' Coast and Geodetic SurveySpecial Publication No. 225, revised, U.S. Depart-ment of Commerce, Washington, D.C., 1959, 100PP.

National Ocean Survey, ''Atlantic CoastCape Cod to Sandy Hook,'' United States Coast Pilot2, Eleventh Edition, National Oceanic and Atmo-spheric Administration, U.S. Department of Com-merce, Washington, D.C., Jan. 1976a, 259 pp. plustables and index (published annually).

National Ocean Survey, ''Operations Manu-al," NOS Manual No. 1 [NDM (NOAA DirectivesManual) 75–01], National Oceanic and AtmosphericAdministration, U.S. Department of Commerce,Rockville, Md., 1971a? (Includes looseleaf inserts;chapter 76, section 27, contains a current list of Pho-togrammetric Instructions; see also National OceanSurvey 1971b? 1974, and 1975.)

Nautical Almanac Office, The Nautical Al-manac for the Year 1976, United States Naval Ob-servatory, U.S. Department of Defense, Washington,D.C., 1974, 276 pp. plus 35 pp. of tables.

Odom Offshore Surveys, Inc., HydrotracMk-2 Circuit Description and Schematic Drawing,Baton Rouge, Louisiana, 1979, 150 pp.

Office of Marine Technology, ''Specificationsfor Automated Hydrographic Survey Magnetic TapesNational Ocean Survey, ''Photogrammetric

D-3 (JANUARY 1, 1980)

Motorola, Inc., ''Operation and InstallationManual for Mini-Ranger III System (MRS III),''Document No. 68 – PO4883F, Sections I and II, Gov-ernment Electronics Division, Scottsdale, Ariz., Apr.30, 1974, 29 pp.

National Oceanic and Atmospheric Ad-ministration, ''NOAA Circular 72-134,'' NOAADirectives Manual, Chapter 17, Section 17, U.S. De-partment of Commerce, Rockville, Md., Nov. 8,1972, 9 pp.

National Ocean Survey, ''Gulf Coast LowWater Datum,'' National Oceanic and AtmosphericAdministration, U.S. Department of Commerce,Rockville, Md., Jan 1977a, 70 pp.

National Ocean Survey, "PhotogrammetryInstructions No. 64, Requirements and Proceduresfor Collecting, Processing and Routing Landmarksand Aids to Navigation Data — PhotogrammetricOperations,'' National Oceanic and Atmospheric Ad-ministration, U.S. Department of Commerce, Rock-ville, Md., 1971b, 15 pp. plus appendixes 1– 3. (In-house memorandum; see also National Ocean Survey1971a and 1974.)

National Ocean Survey, Tide Tables Highand Low Water Predictions 1974 East Coast of Northand South America Including Greenland, NationalOceanic and Atmospheric Administration, U.S. De-partment of Commerce, Rockville, Md., 1973, 288 pp.

National Ocean Survey, ''Provisional Photo-grammetry Instructions for Field Edit Surveys,'' Na-tional Oceanic and Atmospheric Administration, U.S.Department of Commerce, Rockville, Md., Mar. 13,1974, 37 pp. (In-house memorandum including Photo-grammetry Instructions 27, 54, 56, 63, 64, and 70; seealso U.S. Coast and Geodetic Survey 1965b and 1969band National Ocean Survey 1971a, 1971b, and 1975.)

Instruction No. 70, Rocks, Reefs, and Ledges Shownon Photogrammetric Maps,'' National Oceanic andAtmospheric Administration, U.S. Department ofCommerce, Rockville, Md., Mar. 10, 1975, 7 pp. (In-house memorandum; see also National Ocean Survey1971a and 1974.)

National Ocean Survey, ''Standing ProjectInstructions: Great Lakes Water Levels,'' NationalOceanic and Atmospheric Administration, U.S. De-partment of Commerce, Rockville, Md., May 31,1977b, 9 pp., appendixes A and B, 3 tables, and 12figures (in-house memorandum).

National Ocean Survey (National Oceanicand Atmospheric Administration, U.S. Department ofCommerce) and Hydrographic Center (Defense Map-ping Agency, U.S. Department of Defense), Chart No.1, United States of America Nautical Chart Symbolsand Abbreviations, Sixth Edition, U.S. Department ofCommerce, Washington, D.C, July 1975, 25 pp.

Nautical Almanac Office, The AmericanEphemeris and Nautical Almanac for the Year 1975,United States Naval Observatory, U.S. Department ofDefense, Washington, D.C, 1973, 568 pp.

Odom Offshore Surveys, Inc., HydrotracMk-2 Theory of Operation, Baton Rouge, Louisiana,1979, 200 pp.

Odom Offshore Surveys, Inc., The HydrotracSystem, Baton Rouge, Louisiana, 1977, 6 pp.

Office of Marine Surveys and Maps (dissemi-nation of instructions), ''Directions for Using a Tran-sit Magnetometer,'' revised, Letter Instructions FileDO–T–3/2 National Ocean Survey, National Oce-anic and Atmospheric Administration, U.S. Depart-ment of Commerce, Rockville, Md., Feb. 19, 1959, 3pp. (unpublished manuscript).

HYDROGRAPHIC MANUAL

and Listings,'' Marine Data Systems Project, NationalOcean Survey, National Oceanic and AtmosphericAdministration, U.S. Department of Commerce,Rockville, Md., Dec. 1973, 21 pp. plus 6 appendixes(includes looseleaf inserts).

Swanson, L.W., ''Topographic Manual, PartII, Photogrammetry,'' Coast and Geodetic Survey Spe-cial Publication No. 249, U.S. Department of Com-merce, Washington, D.C., 1949, 570 pp.

Peters, Jean, Eight-Place Tables of Trigono-metric Functions for Every Second of Arc (with an ap-pendix on the computation to 20 places), SecondPrinting, Chelsea Printing Co., Bronx, N.Y., 1965,954 pp.

Thompson, Morris M. (Editor), Manual ofPhotogrammetry, Vols. I and II, American Society ofPhotogrammetry, Falls Church, Va., 1966, 1199 pp.

Ulm, Kenneth S., ''Wire Drag Manual,''Coast and Geodetic Survey Publication No. 20–1,U.S. Department of Commerce, Washington, D.C.,1959, 103 pp.

Rappleye, Howard S., ''Manual of GeodeticLeveling,'' Coast and Geodetic Survey Special Publica-tion No. 239, U.S. Department of Commerce, Wash-ington, D.C., 1948, 94 pp.

U.S. Coast and Geodetic Survey, "Formulasand Tables for the Computation of Geodetic Posi-tions,'' Special Publication No. 8, Seventh Edition, U.S. Department of Commerce, Washington, D.C.,1929, 101 pp.

U.S. Coast and Geodetic Survey, ''Tables fora Polyconic Projection of Maps and Lengths of Ter-restrial Arcs of Meridians and Parallels, Based UponClarke's Reference Spheroid of 1866,'' Special Publi-cation No. 5, U.S. Department of Commerce, Wash-ington, D.C., 1935, 189 pp.

Shortrede, Robert, Logarithms of Sines andTangents for Every Second, revised, Charles andEdwin Layton, Ltd., London, England, 1948, 602PP.

Swainson, O.W., ''Topographic Manual,''

D-4(JANUARY 1, 1980)

Pacific Marine Center, OPORDER, NationalOcean Survey, National Oceanic and AtmosphericAdministration, U.S. Department of Commerce, Seat-tle, Wash., Apr. 11, 1974 (latest update), 4 chaptersand appendixes A–M (includes looseleaf inserts).

Raytheon Co., DE–723 A1/B1/C1 SystemsPrecision Survey Fathometer Echo Depth Recorders,Marine Products Operation, South San Francisco,Calif., 1974a, sections 1-IX.

Raytheon Co., DE–723D System PrecisionSurvey Fathometer Echo Depth Recorder, MarineProducts Operation, South San Francisco, Calif.,1974b? sections 1-IX.

Raytheon Marine Co., Bathymetric SystemsHandbook, 7 sections, Ocean Systems Center, Ports-mouth, R.1., Apr. 25, 1975, 81 pp.

Raytheon Marine Co., DE–719B Fathome-ter Precision Survey Depth Recorder Operator's Man-ual, Manchester, N.H., Mar. 1976, 38 pp.

Reynolds, Walter F., ''Manual of Triangu-lation Computation and Adjustment,'' Coast andGeodetic Survey Special Publication No. 138,U.S. Department of Commerce, Washington, D.C.,1934, 242 pp.

Ross Laboratories, Inc., Ross Automated Hy-drographic Survey System Technical Bulletin, Seattle,Wash., Apr. 1972, 15 pp.

Ross Laboratories, Inc., Automated Hydro-graphic Survey System Operating and .MaintenanceManual. Seattle, Wash., Apr. 1975, 217 pp.

Coast and Geodetic Survey Special Publication No.144, U.S. Department of Commerce, Washington, D.C, 1928, 121 pp.

Teledyne Hastings-Raydist, Raydist TypeDRS–H Radiolocation System Familiarizaiion Bro-chure, Hampton, Va., June 1972, 81 pp.

U.S. Board on Geographic Names, UnderseaFeatures, Official Standard Names, Second Edition,Geographic Names Division, U.S. Army Topograph-ic Command, U.S. Department of Defense, Washing-ton, D.C., 1971, 182 pp.

U.S. Coast and Geodetic Survey, "GeneralTheory of Polyconic Projections,'' Special PublicationNo. 57, U.S. Department of Commerce, Washington,D.C., 1919, 174 pp.

U.S. Coast and Geodetic Survey, ''Manual ofSecond- and Third-Order Triangulation and Tra-verse,'' Special Publication No. 145, revised, U.S. De-partment of Commerce, Washington, D.C., 1935, 226PP.

U.S. Coast and Geodetic Survey, ''NaturalSines and Cosines to Eight Decimal Places,'' SpecialPublication No. 231, U.S. Department of Commerce,Washington, D.C, 1942, 541 pp.

U.S. Coast and Geodetic Survey, ''Defini-tions of Terms Used in Geodetic and Other Sur-veys,'' Special Publication No. 242, U.S. Depart-

BIBLIOGRAPHY

ment of Commerce, Washington, D.C., 1948, 87 pp.

U.S. Navy Hydrographic Office, ''Tables ofComputed Altitude and Azimuth,'' H.O. PublicationNo. 214, 9 vols., Washington, D.C., 1939, 1940,1941, and 1946.

Vega, Georg, Vega Seven Place LogarithmicTables of Numbers and Trigonometrical Functions,Hafner Publishing Co., New York, N.Y., 1960, 575pp.

Westbrook, D.E., ''Tables of Meters to Fath-oms for Selected Intervals,'' ESSA Technical Memo-randum C&GSTM–2, Coast and Geodetic Survey,Environmental Science Services Administration, U.S.Department of Commerce, Rockville, Md., 1966, 9pp.U.S. Coast Guard, ''LORAN-C User Hand-

book,'' Publication CG–462, U.S. Department ofTransportation, Washington, D.C., Aug. 1974, 25pp.

Wilson, W.D., ''Equation for the Speed ofSound in Sea Water,'' The Journal of the AcousticalSociety of America, Vol. 32, No. 10, Oct. 1960, p.1357.

Wraight, A. Joseph, and Roberts, Elliott B.,United States Coast and Geodetic Survey 1807 to1957, 150 Years of History, U.S. Department of Com-merce, Washington, D.C., 1957, 89 pp.

U.S. Lake Survey, ''Standing Operation Pro-cedures'' (for Hydrographic Surveys), Inshore Sec-tion, Hydrographic Branch, Engineering Division,U.S. Army Engineer District, Corps of Engineers,Detroit, Mich., 1968, 12 pp. (unpublished manu-script).

Young, Stephen A., ''User's Guide for theGas-Purged Pressure Recording (Bubbler) TideGage,'' Printing Section, Publication Services Branch,Administrative Operation Division, National Oceanicand Atmospheric Administration, U.S. Departmentof Commerce, Rockville, Md., 1976 (to bepublished).

U.S. Naval Oceanographic Office, ''Tables ofSound Speed in Sea Water,'' Special Publication 58,Washington, D.C., 1962, 47 pp.

D-5 (JANUARY 1, 1980)

U.S. Coast and Geodetic Survey, ''NaturalTables for the Computation of Geodetic Positions,Clarke's Spheriod of 1866,'' Special Publication No.241, U.S. Department of Commerce, Washington,D.C., 1949, 86 pp.

U.S. Coast and Geodetic Survey, ''Manual ofTide Observations,'' Publication 30–1, U.S. Depart-ment of Commerce, Washington, D.C, 1965a, 72 pp.

U.S. Coast and Geodetic Survey, ''Photo-grammetry Instructions No. 22, Field Recovery andIdentification of Horizontal and Vertical Control,''Revision 2, Environmental Science Services Adminis-tration, U.S. Department of Commerce, Washington,D.C, Sept. 30, 1965b, 16 pp. plus plates I throughVI. (In-house memorandum; see also National OceanSurvey 1971a and 1974.)

U.S. Coast and Geodetic Survey, Coast PilotManual, Third Edition, Environmental Science Ser-vices Administration, U.S. Department of Com-merce, Rockville, Md., 1969a, 50 pp.

U.S. Coast and Geodetic Survey, ''Photo-grammetry Instructions No. 63, Instructions—Geographic Names and Object Names for Photo-grammetric Maps—Field and Office,'' Environmen-tal Science Services Administration, U.S. Departmentof Commerce, Rockville, Md., Apr. 28, 1969b, 13pp. plus charts. (In-house memorandum; see alsoNational Ocean Survey 1971a and 1974.)

U.S. Coast Guard, Light List, 5 vols., U.S.Department of Transportation, Washington, D.C.,1976 (published annually).

U.S. Naval Oceanographic Office, ''Instruc-tion Manual for Oceanographic Observations,'' H.O.Publication No. 607, Third. Edition, Washington,D.C., 1968 (looseleaf).

U.S. Naval Oceangraphic Office, ''Sight Re-duction Tables for Marine Navigation,'' H.O. Pub.No. 229, 6 vols., Washington, D.C, 1970.

U.S. Navy Hydrographic Office, ''LORANLattice Tables, Latitudes 0°–23°,'' H.O. Pub. No.245, Volume One, Washington, D.C, 1953, 279 pp.

Wallace, Jack L, ''HYDROPLOT/HY-DROLOG Systems Manual,'' NOS Technical Man-ual No. 2, 3 vols., National Ocean Survey, NationalOceanic and Atmospheric Administration, U.S. De-partment of Commerce, Rockville, Md., Sept. 1971(looseleaf).

E. GLOSSARY OF ABBREVIATIONS AND ACRONYMS

The abbreviations in table B–7 in appendixB shall be used to record data obtained by bottomsampling. See also Chart No. 1, United States ofAmerica Nautical Chart Symbols and Abbreviations(National Ocean Survey and Hydrographic Center1975). Table E–1 below is a listing of most abbrevia-tions and acronyms used in this manual. Some, such

E-1 (JANUARY 1, 1980)

as in-house usage and trademarks, have not been in-cluded—if the interested reader desires this informa-tion, write to Requirements Branch (OA/C351);Hydrographic Surveys Division, Office of MarineSurveys and Maps, 6001 Executive Boulevard, Rock-ville, Maryland 20852. This branch will also welcomewritten matter to correct and update the manual.

HYDROGRAPHIC MANUAL

TABLE E–1.— Abbreviations and acronyms used in this manual*

Julian dateJD

* Continued on next 2 pages; see also table B-5 in appendix B

E-2(JANUARY 1, 1980)

Aa.c.ASCII

adjADR

AGCahdAMCASIARGOassyavg

battBCBCDbldg(s)BnBSBT

C° CC&GScalC/CCFchanchyCLcmcomplotcon.contcorcorrcovC/ScscCSSCTRLCUP

DdBd.c.DECdecdirdistDivdm'sDMUdolDPdp'sDR

ECCEDEDMEDPelevFSSAETG

ampere(s)alternating currentAmerican National Standard Code

for Information InterchangeadjustedAnalog to Digital Recording;

Automatic Digital RecordingAutomatic Gain ControlaheadAtlantic Marine CenterAircraft Standards, Inc.Automatic Ranging Grid Overlayassemblyaverage

batteryBathymetric ChartBinary Coded Decimalbuilding(s)beaconBottom Samplebathythermograph

can; center; coreCelsius (degrees)Coast and Geodetic Surveycalibrationchange courseConstant Frequencychannelchimneychecklistcentimeters(s)computer plottedcontinuedcontrolcorner; correctioncorrectioncoveredchange speedcosecantCoastal Survey Shipcontrolcupola

depth; dredgedecibel(s)direct currentDigital Equipment Corporationdecreasedirectiondistancedivisiondifferences along meridiansDistance Measuring UnitdolphinDetached Positionsdifferences along parallelsDead Reckoning

eccentricExistence DoubtfulElectronic Distance MeasuringElectronic Data ProcessingelevationEnvironmental Science Services Administrationelectric tape gage

F• FFMfmfm/sF/Sftft/fmFWD

field; frequencyFahrenheit (degrees)Frequency Modulationfathom(s)fathom(s) per secondFull Speedfoot (feet)feet or fathomsforward

GCLWDGMTG.P.O.grpgyro

Gulf Coast Low Water DatumGreenwich Mean TimeGovernment Printing Officegroupgyroscope; gyroscopic

HH.O.horizhrH/ShtH/VhydhydroHYDROPLOTHydrotracHYPHYPLOTHz

HydrographicHydrographic Officehorizontalhour(s)Half Speedheighthyperbolic-visualhydrographyhydrographicHydrographic data systemHydrographic trackinghyperbolicHYDROPLOThertz

I(s)IDIGLDininfoinstrI/S

island(s)identificationInternational Great Lakes Datuminch(es)informationinstrumentIncreased Speed

kHzkmkm/skn

kilohertzkilometer(s)kilometer(s) per secondknot(s)

LlLAJLat.LBlbLBDBlb/in²LBLLBRL BrksLELEDELJLLJRLLLNMlong.LORANLRLSCLt

lane; left; locationliter(s)Lane JumplatitudeLine Beginspounds(s)Line Begins, Day Beginspound(s) per square inchLine Bends LeftLine Bends RightLine BreaksLine EndsLine Ends, Day EndsLine Jogs LeftLine Jogs RightLead LineLineal Nautical MiWs)LongitudeLong Range Aid to NavigationLine ResumesLake Survey Centerlight

GLOSSARY OF ABBREVIATIONS AND ACRONYMS

TABLE E–1.— Continued

Per Steering CompassLTL Line Turns Left PSCPT partLine Turns Left AboutLTLAPt.LTR pointLine Turns Right

publicationpubLine Turns Right AboutLTRALWD Low Water Datum

rejected; report; rightRMm

receivedRCVDmark; middle; missedrdg readingmeter(s)

recorderrecMaster Drive UnitMDUrecov recoveredmeridianmer

reductionRedMHz megahertzREFMHW reflectedMean High Water

referencerefmi Mile(s) statutereg registry; regulationmin minute(s)rev(s)miscellaneousmisc revolution(s)

root mean square errorMean Lower Low WaterMLLW rmserevolutions per minuterpmMLW Mean Low WaterRange-RangeR/Rmillimeter(s)mm

R/Smo Reduced Speedmonth(s)R/V Range-VisualMRV Middle Reed Vibrating

ms millisecond(s)same (fix)MSS Medium Survey Ship

MountMt salinity; snapper; south; speedMTM Modified Transverse Mercator

microsecond(s)Special Projectsecond(s)µsSettlement and SquatS&SSide Bandnitrates; north; nunNsounderNA North America sdrsextantna not applicable sext

North American Datum scoopfishNADNational Geodetic SurveyNGS See Field SheetSFS

nmi shorelineSLnautical mile(s)Serial NumberS/Nnumber(s)No(s).

National Oceanic and Atmos-NOAA soundingsndgpheric Administration station 1S1

National Ocean SurveyNOS spd speedNot PlottedNP squaresq

S/S Slow Speed; Standard Speedoxygen Side Scan SonarSSS0

obj stationstaobjectobstructionobstr starboardstbdon courseO/C STD Salinity, Temperature, and DepthOcean Data EnvironmentalODESSA subm submerged

Science Services Acquisitionopr Toperator; operational TICUS (System)ortho-photo true (azimuth, bearing)T(A,B)OSS Ocean Survey Sheets; Ocean Time and CourseT+C

Survey Ship TDCtemperature; temporarytemp

P pattern; phosphate TG Tide Gagep(p). TICUS Tidal and Current Surveypage(s)PA Technical Manual; Technical MemorandumPosition Approximate TMP/C Partly Cloudy transducerTRA

Position DoubtfulPD traverseTRAVPDR Precision Depth Recorder triangulationtriang

per gyro compasspgephoto photogrammeric; photograph unadj unadjustedphoto-hydro uncov uncovered

Pacific Marine CenterPMCV volt(s)per magnetic compasspmc

PN Vertical CastPosition Number VCvery high frequencypositionpos vhf

parts per millionppm vicinityvicvisparts per thousandppt (‰) visualvlfpresc very low frequencyprescribed

priv vol(s).private volume(s)V-VIS Verified VisuallyPS Pole Sounding

(JANUARY 1, 1990)E-3

photogrammetric- photographic

orthographic-photographic

Temperature, Depth, and Conductivity

SF

sSSS

SB

GLOSSARY OF ABBREVIATIONS AND ACRONYMS

TABLE E-1. — Continued

watt(s); west XSTD expendable, Salinity, Temperature,WWire DragWD Depth

Wk wreck yr year(s)Water LevelWL

Z GMTzero electric tape gageZETGtransponderXpndr

E-4(JANUARY 1, 1980)

INDEX

A 4-109bisectrics in4-108, 4-109errors in

E-1Abbreviations, glossary of 4-109probable position, and the4-35Abnormal depth curves and inaccuracies 4-110sun, on the

Abstract of corrections to 4-108time of, important4-96, 5-7, 5-13, 6-7echo-soundings 4-108—4-106track line surveys, on

4-96, 5-7Descriptive Report, in the Astronomic position fixes and the6-7Accuracy of analog depth records AB-1 AB-3Omega navigation system

4-107Accuracy of astronomic observations Astronomical azimuth stations 3-4,3-5Accuracy Standards for Atlantic Ocean, the

Hydrographic Surveys, International 1-3, 4-85 1-15depth unit forAG-4, AH-1Acoustical signals, attenuation of 1-15hydrographic reference datum for

Acronyms, glossary of E-1 Atmospheric conditions, unusual,Adjectives for bottom listed in Descriptive Report 5-8

B-6characteristics, symbols for Atmospheric noise and electronicAerial photography 4-30positioning systems

advance use of 3-13 Automated data processing,1-10tide-coordinated 5-10Descriptive Report, a section of the

Aerotriangulation stations selected Automated hydrographic survey3-12, 3-13prior to aerial photography systems 1-6, AJ-1—AJ-4

Agencies, contact with other, prior Automated techniques in verification 6-13-2, 4-43, 4-95to survey Automatic digital recording

Aids to navigation 1-15, AK-1—AK-3(ADR) gages5-9Descriptive Report, listed in Azimuth

7-19floating, smooth sheet, on beacon ranges, of 4-421-4, 1-18, 4-1, 4-41,locating 1-18determination, responsibility for

4-84, 7-14, 7-19Azimuth and astronomic observations 3-5

7-4names and designations of, smooth sheet, on 4-18Azimuth array sheets, preconstructed4-42nonfederal, Descriptive Report, listed in Azimuths in use with electronic

7-14, 7-19nonfloating, smooth sheet, on positioning systems 4-311-4, 1-18, 4-1, 4-41,surveys and Azimuth marks at control stations 3-27-14, 7-14

Azimuth orientation in theodoliteAlongshore detail intersection method of positioning 4-18

1-17-1-18bottom characteristics 4-31Azimuth, polaris or solar observations for1-17verification of Azimuth stations, selection of 3-44-94"Altitude and Azimuth, Tables of Computed''

AG-4—AH-6Analog depth recorders BAnalog depth records

4-86 Bar check(s) 1-13, 4-71, 4-72interpretingAF-3apparatus for4-84—4-90scanning

4-62 4-74data, corrections to soundings fromAnalog position data4-80errors and the velocity correction curveAnalog records, supplementary 4-62

AK-1, AK-3 Bare rocksAnalog to digital recording (ADR) gage(see Rocks, bare)Anchorage holding characteristics, bottom

1-18 4-4Basic control stations on field sheetsdescriptions showing4-44 Basic hydrographic survey, theAnchorages, bottom characteristics and 1-5, 4-1

4-105Bathymetric mapping surveysAngulation instruments 3-5AC-6 Beaches and soundings 4-9Antenna couplers, note on

Beacon ranges, azimuths of 4-42Antenna height versus range,Beam compass used for plottingC-4microwave horizon distance, table of

control stations 4-58-1Approval of surveys, final6-18 Bench marksApproval sheet and verification

AK-9maximum allowable leveling error betweenArcsAK-9line-of-position plane of flotation, and the1-12,4-4, 4-5, 4-11

4-28, 4-31 AK-9principal qualities ofBench marks and tide and waterlocus 4-11—4-13

AK-8, AK-9level gages, leveling between4-5plotting ofBibliography D-1ARGO, a long-rangeBottomposition-fixing system

4-54, 7-13configuration of, sounding selection, and(see also Position-fixing systems)AC-11—AC-15 consideration of nature of 1-11ARGO Survey Systems

4-11contours and sounding line systemsAstronomic observations4-108 materials classificationaccuracy of, factors affecting 4-46

I-1

HYDROGRAPHIC MANUAL

charts available for 4-47 Calibration procedure for electronic positioningdescription of 4-46—4-47 equipment and stations 1-8, 1-9, 4-25—4-29

4-3—4-4profiles of Calibration sheets1-13importance of 4-1 Calibration standard for echo sounders1-17interpreting kelp and 4-86, 4-87, 4-88 Caribbean Sea, shoreline detail

sounding lines, and 4-7 B-1Cartographic codes and symbolssample spacing, guidance on 2-2 Cartographic standards for smooth sheet 1-5, 7-1

AL-8—AL-10 C-band positioning equipmentsamplers 4-28samples Celestial bodies and astronomic observations 4-109

5-13Descriptive Report, listed in Channelsfield survey, in dredged, maintenance of4-1 4-13storage of 4-44 shoal indications in 1-11

sampling 1-4 sounding lines in 4-131-17, 1-18, 4-45, 4-93frequency of 5-9, 6-13—6-14Chart comparison and verification

4-45 Chart Evaluation Surveyssediment samples to Smithsonian Institution 2-1, 2-7, 4-1, 4-93—4-105Chart depths, term definedslopes 4-65

1-19, 5-24—5-25Chart inspection reportabrupt changes in 7-11sand and mud, in 4-9 Chart(s), nautical

accuracy of 4-44 1-3surface layer sampling 1-10 data for compilation of 1-3topography of

Bottom characteristics 1-17, 1-18, 4-44, 4-46, 7-14, B-6 Omega navigation system, forabbreviations used on smooth sheet 7-14, B-6

Chief of Partyadjectives and symbols for B-61-17—1-18 changes in operation plans by 2-7along shore detail, and

7-22 to be named on smooth sheetdescriptions of 5-221-18 Chimney as a landmarklimits for

1-18 4-90Choppy seas and irregular profilesuses ofCircles, drawing, on hydrographic sheets 4-6nouns and symbols for B-6

7-14 Circular pattern generation ofsmooth sheet, and the AC-1, AC-2 position fixing systemssurvey scales, and 1-5

Clamshell bottom snappers in bottom sampling 4-44symbols, cartographic B-6Classification of bottom materials 4-46Breakers

4-1—4-24-41 Classification of surveysdetached, seen during soundings4-46Clay, definition ofsymbol for B-3

4-54, AL-10Clocks used on hydrographic surveysBreakwaters on the smooth sheet 7-9Cloth in the construction ofBridges

3-11—3-12hydrographic signals4-42cable crossings in surveys, and1-19, 4-93—4-95, 5-24Coast Pilot reports4-42field sheets, shown on

3-11—3-13Coastal mapping in shoreline surveys5-22Building as a landmark4-35Coastal shelves, depth curves onAF-1—AF-2Bunting used with lead lines

1-3Coastal zone managementBuoys3-11Coastal zone maps to support nautical charting(see also Aids to navigation)

B-1Codes and symbols, cartographic4-28radar reflectors andB-6Codes, bottom characteristics, for4-70settlement and squat, used in measuring

Colors and symbols, bottom characteristics, for B-64-28U.S. Coast Guard to be informed of use of4-37, 4-38Colors of depth curves4-27—4-28used in phase comparison systems6-15, 6-18Comparison with prior surveys

Comparisons, direct, for determiningCvelocity corrections 4-71

Cable(s) Compass4-42 4-5cable crossings and bridges in surveys beam, used for plotting control stations4-42 4-55field sheets, shown on type to be part of records

3-14sensor conductor, marking of 4-75 Compilation photography in shoreline surveysCalibrating positioning systems, Computer programs for use with

AJ-1, AJ-24-27,4-28 HYDROPLOT systembuoys used inAL-6, AL-84-1Calibration data in field survey Conductivity sensors

4-2—4-3Calibration of electronic Construction of field sheets4-25—4-29 Contemporary nautical chart andpositioning stations

8-2Calibration of instruments 1-8, 4-25—4-29, AB-1 field survey records4-46Continental Shelf, bottom materials of theCalibration phase checks on Ross4-29AH-4analog depth recorders Control chain's geometric strength

I-2

LORAN navigation system, for use with AB-2, AB-4AB-1, AB-3

1-10, 1-11

INDEX

Current measurement methods3-12, 3-13Control identification in shoreline surveys1-7, 2-2 defined on Progress Sketch 5-2Control instructions

Currents instructions 2-65-8Control listings with Descriptive Report1-4Currents, observations ofControl station(s),

1-16Curve lines, supplemental, on field sheetshydrographic 1-9, 3-7—3-10, 4-4—4-62-6 Curve(s), depthbeyond limits of sheet

(see Depth curve(s))5-7Descriptive Report, listed in4-4field sheets, on7-6horizontal, smooth sheet, on D3-2newly established, recording of

Daily journal during survey 5-44-4numbering of

1-18Dangers to navigation1-9—1-10photogrammetrically located

B-2cartographic codes and symbols for, tabulated4-4plotting on field sheetsDescriptive Report, in the 5-9recoverable, and the Season'sfield survey, in 4-15-4Progress Report

4-1importance of discovery ofsmooth sheet, and the 7-2, 7-6indications of 4-393-1spacing

1-19, 5-24report on7-6supplemental, smooth sheet, onshoals and 4-39—4-41weak signals of, discussed in

7-8—7-10smooth sheet, shown on5-8Descriptive Reportsubmerged, awareness of 4-403-4Control, supplementaltransfer to field sheet 4-74-33Control, visual

DataConversion tablesdata-acquisition programs,

C-1area measurementsHYDROPLOT AJ-3, AJ-4C-3Celsius to Fahrenheit

data listings and printouts,C-3Fahrenheit to Celsiusverification of 6-8C-1length measurements

data sheets, forwardingC-2linear distance1-14requirementsC-1mass measurements

defective, causes of 4-86C-1mathematics1-14faulty, correction ofmicrowave horizon distance, range

historical oceanographic, toC-4versus antenna heightcorrect echo soundings 2-6C-2speed measurements

hydrographictemperature measurements C-2, C-3

4-3field sheet, and theC-5velocity correction factors1-14problems during processing ofAL-5Copenhagen Standard Sea Water

4-32, 4-57identification, Julian dates andCoral3-14photobathymetric, described7-8description of

photogrammetric support, in7-8smooth sheet, and the3-14shoreline surveys, list ofCorrections

4-7prior survey, transfer to field sheet of4-1data in field survey, in4-2, 4-93, 4-95processing of, and the field sheet4-68—4-70dynamic draft

7-10wire-drag, on smooth sheet overlay4-67echo sounding, standard practices concerning

1-15, 4-6, 7-8, AK-8Datum lines, low water4-27in calibration of positioning equipment4-67Datum reduction, definition of1-14, 4-65, 4-74in sounding records6-13Datum ticksAB-1Omega

Datum, United States Standard 6-12, 6-134-67units ofDead reckoningversus applicable depths in

4-110corrections for known factors in4-76velocity Correction procedurescurrent drift allowances and 4-1104-55Course changes to be noted in records

4-109definition ofCoxswain's duties in tag line survey 4-1114-109—4-110vessel engine speeds inB-3Crib, symbol for

4-88Debris, echoes fromCrosslinesDecca Hi-Fix Manuals 4-184-13—4-14bottom profiles, andDecca Hi-Fix, a medium-range1-11,4-43discrepancies, and

1-10—1-11 position-fixing system

(see Position-fixing systems)framework of

1-10—1-11soundings by4-18, AC-1, AC-2Decca survey systems6-8—6-9verification of

5-22 Deep water echo sounders 1-13Cupola as a landmark4-35Current drift allowances in dead Deep waters and depth curves6-144-109—4-110 Deficiencies of verified surveys, list ofreckoning procedures

I-3

HYDROGRAPHIC MANUAL

4-93 5-24Deficiency investigations dangers to navigation report in4-18Del Norte Operations Manual Descriptive Report text 5-54-18Del Norte Technology 4-32detached positions in

Del Norte Trisponder, a short-range 5-7echo sounding corrections listed inAD-1—AD-4 5-10position-fixing system electronic control parameters, detailed in

(see also Position-fixing systems) electronic position control detailed in1-17 5-13abstract of corrections toDelimiting of alngshore areas1-16 entries inDepth curves 5-4, 5-5

5-10abnormal 4-35 field tide or water level note in4-35 5-13, 5-24coastal shelves, on geographic names in

4-37, 4-38colors of hydrographic position control listed in 5-87-14congestion on steep slopes hydrographic sheets in 5-74-13 index of sheets ofdisplacement on steep slopes 5-5

4-35—4-37 6-10field sheets, on inspection for verification purposes4-37 7-20group numbers, and junctions and adjoining surveys, and

4-35, 4-37intermediate junctions detailed in 5-84-37intervals of landmarks for charts filed with 5-151-16nonstandard list of stations in 5-13

7-13, 7-14smooth sheet, and the miscellaneous information to be5-104-37standard, list of included with5-104-37, 4-38, 7-14supplemental order of inserts with

4-37topographic experience and 5-8photogrammetric problems listed in3-15verification plane table surveys, and6-9

Depth measurements in hydrographic position verification, and 6-31-5 2-6Presurvey Review, and thesurveying, allowable errors in

4-7—4-8Depth-measuring 6-2preverification, andAF-1—AF-5Depth-measuring devices, manual prior survey comparisons in 5-8

Depth recorders project number included in 5-7AH-I recommendations for additionalanalog

5-104-67calibration of work to be riled with5-104-45errors listed referral list of separate reports in

4-52 5-10Precision sheet projection, and the4-48 shoreline details in 5-8Depth records

1-14,4-86 54,7-1smooth sheet, and theanalog, interpreting1-13, 4-57 5-7graphic sounding equipment listed in

AL-6, AL-8 5-7Depth sensors sounding vessel(s) listed in5-4, 7-22Depth-sounding equipment

(see Equipment, sounding)special project, for a

7-22survey details5-91-15—1-16, 4-35Depth units statistics summary to be included in

3-10Depth(s) subjects for inclusion in4-75 title sheet forchecking measurements of 5-5, 7-221-14 5-7digital and graphic, differences between unconventional survey methods listed in4-84 verification review ofrecorded, checking of 6-84-74 4-53Deviations from standard value, notation ofstandard observation, oceanographic7-20 AB-1Descriptive notes on smooth sheets Differential Omega

1-19, 5-4—5-15 4-62Descriptive Report Digital depth readings4-66abstract of corrections to echo Digital depths, note on4-88soundings to be filed with Digital echo sounders, side echoes and5-7, 5-13, 6-7

5-13abstract of positions reported in Digital electronic sextant(see Sextants)adequacy of survey reported in 5-9

4-42, 5-9 8-2aids to navigation in Digital records on magnetic tapes1-13anomalies in the control adjustment listed in Digital sounding(s)5-74-845-15approval sheet to be filed with considered primary data

area surveyed entry in 5-7 4-34equipment and sounding intervals5-10 4-86automated data processing reported in spurious5-13bottom samples reported in Direct comparison log for recording4-27 bar check data 4-72calibration of equipment differences, and

5-9, 6-13, 6-14comparison with area chart and the Direct comparisons combined with4-79control stations shown in, 5-7 oceanographic determinations

"Directions for Using a Transit Magnetometer''cover sheet for 5-4 2-64-43—4-44crosslines detailed in 5-8 Discrepancies, hydrography, in

I-4

INDEX

4-43 4-70crossings, at salinity and temperature observations and4-43 4-69,4-70settlement and squat, andDescriptive Report, and the4-44 side echoes injunctions and overlaps, at 4-8

4-44, 4-45, 6-7sources of error, and standard nomenclature in 4-65—4-676-20unresolved verification and stray echoes, and 4-863-14 4-83Discrepancy prints in shoreline surveys stylus arm length errors in

4-841-7Disks, National Ocean Survey stylus belt length errors in3-2 transducer correction inDisks, reference, uses of 4-84

4-14 velocity correction computations,Distance, estimated, and vessel positioning4-56 4-76—4-79examples ofDistance estimates to be noted in records

Distance-measuring instruments 4-71,4-76velocity corrections, and, table of3-5Distance-measuring systems, electronic 4-24 Echoes

4-4 side 4-88Distortion between meridians and parallels4-104-4Dividers, the use of desirability of

hyperbolically-shapedDocks and piers' soundings shown 4-887-2on smooth sheet subplans or insets 4-90slant distance to shoal, and

4-864-110 Docks and tag line surveys stray4-41 1-13Docks and wharves, soundings along Echogram

Dog-ears Eddies7-10instructions on smooth sheet, shown on2-10

symbol for7-1smooth sheets, avoidance on B-3use on smooth sheets Editor, field, and alongshore detail7-2

verificationB-2Dolphin, symbol for 1-175-22Dome as a landmark EDM equipment 3-3, 3-5

Draft copies of Project for measuring distances 3-8Instructions 2-2 periodical testing of 3-3

4-66 Edmonston Beam HolderDraft, dynamic 4-54-66, 4-69Draft, static 5-10, AK-7Electric tape gage

Drafting instruments and the smooth sheet 7-5 Electronic control systems aboardAL-2Drafting machine nonautomated vessels 4-32

4-5—4-6Drawing circles, methods of Electronic dataDuck blinds processing in verification procedures 6-1

4-55smooth sheets, on the 7-9 recorded in recordssymbol for Electronic depth digitizersB-3 1-14

Duplicate field sheets 4-3 Electronic digital sextant(see Sextants)4-68Dynamic draft correction

4-66Dynamic draft, term defined Electronic lattices indicated on arcs 4-4,4-54-18—4-31Electronic position control

E corrections in the Descriptive Report 5-8 5-134-20-4-23hyperbolic positioning systems

Echo sounding(s) Electronic positioning lattices on(see also Soundings)abstract of corrections to,

smooth sheets 7-6Electronic positioning systems

5-13, 6-7Descriptive Report, and the (see Position-fixing systems)Electronic positions, erroneous,comparisons with depths measured by lead line 1-13

5-7corrections shown in Descriptive Report 6-6—6-7resolution ofdirect comparison method for 4-74—4-75Electronic sensors, precision of

4-71determining velocity corrections AG-1—Al-3Equipment, soundingequipment 4-53comparison of

(see Equipment, sounding) echo soundingfish echoes and 4-88

acoustical signal attenuation, and AG-4historical oceanographic data, and 2-6 4-66adjustment of

4-80, 4-83initial errors inAF-3bar check apparatus

instrumental errors in velocityAG-3beam width, and

4-80correction procedures 4-56changes in types of, to be noted in records4-72lead-line depth comparisons, and 4-52, AG-4deep-water

oceanographic and limnologic AG-1description of4-74—4-79determinations, and faulty operation of 1-11

4-83phase errors in fix marker on 4-614-34records produced by AG-1frequencies of pulses of

reduction of field soundings 4-90 frequencies used with AG-4

I-5

HYDROGRAPHIC MANUAL

4-55 1-14lead-lines, interspersed with erroneously scaled values in soundings4-66maintenance of 4-7 heave, correction of

4-62, AH-1National Ocean Survey, used by human and sextant errors 6-6AG-1 4-80principles of initial, in setting echo sounding pulseAG-2 AH-4pulse duration and shape instrumentalAG-4pulse length and shape in velocity correction procedures 4-80-4-84AG-1pulses of phase, explained 4-83AH-1Raytheon analog and digital depth sounders 4-21propagation contours, illustrated

4-51—4-53record-keeping, and sources of 4-44,4-454-52, AG-2shoal water 4-11survey, in, vessel speed variations and

1-16smooth plotting, and update, of the Del NorteAG-4 AD-3stabilizing system, and trisponder position-fixing system

4-134-111tag line survey, in Estuaries, sounding line system forAG-3transducer beam widths Exceptions to third-order control procedures 3-8AG-1transducers of

FAG-2undamped transmission pulse, illustratedAJ-1HYDROPLOT system

False color photographs 3-11(see also HYDROPLOT system)lead line(s) Fathogram 1-13

FathomsAF-1description ofas depth units 1-15AF-1marking of

AF-1lead lines marked inAF-1purposes of4-56Feature investigations to be noted in recordsAF-2sounding leads of

Federal Geodetic Control Committee 1974 3-1AF-3sounding pole alternative toFeetAF-1—AF-2units of measurement, and

1-15as depth unitsAF-2verification ofAF-2lead lines marked in4-80—4 84malfunction of

Field and calibration sheets from Marine Centers 1-9AF-1manual depth-measuring devicesField editAF-3modified trawl sweep

1-19, 3-13, 5-15reportAF-5pipe drag3-13—3-15shoreline survey manuscripts inAF-5construction of

surveys 4-38AF-5use ofField editor, responsibilities of 3-13, 4-37Raytheon analog and digital depthField investigations, surveys classified as 4-2AH-1soundersField numbers, instructions on 2-6AH-2accuracy ofField reports 5-1AH-2characteristics ofField operation of survey party 2-1AH-2digital depth monitor ofField sheet(s)AH-2digital logic output of

4-3—4-4calibration sheetsAH-2digital phase checkers of4-2compilation ofAH-1electronics cabinet unit of

4-2—4-3construction ofAH-2environmental specifications of4-4—4-6control lattices constructed onAH-2error, phase position shift

control stations on 4-4,4-5AH-2operating frequency of4-7dangers to navigation transferred toAH-2transmitted pulse length of

data processing, and 4-2AH-1use ofdefinition 4-2, 4-37AH-5Raytheon portable echo sounder

4-35, 4-37depth contours onAH-3—AH-5Ross depth sounding systemdog ears on 2-6AH-4calibration phase checks onduplicate sheets 4-3AH-5digitizer

1-19examination for clarityAH-4initial error, and4-2explanatory notes required onAH-4instrumental errors subject to

features of the 4-2AH-4phase error, and1-19—1-20forwarding ofAH-4stylus belt length error, and

importance of 1-5,4-2AH-4transceiverinspection by Chief of Party 1-19,4-43Error(s)labeling of 4-34-108astronomic observations, in

AK-9 1-6, 2-7, 4-3margin requirements ofbench markmaterial 1-6erroneous electronic positions,

6-6—6-7 method of making duplicates 4-3resolution ofnumbers 2-9erroneous positions recognized at verification 6-3

6-5—6-6erroneous visual positions, resolution of overlays, transparent, and 4-7

I-6

INDEX

4-85projection line intervals for 4-3 secondary, uses ofuses of1-6projections 1-13

signal descriptions on 4-4 Graphs, miscellaneous C-1size of Grass (kelp) a problem in1-6, 4-2

4-86, 4-87—4-881-16, 4-35soundings interpreting bottom profiles4-6—4-7transfer of topographic detail to Great Lakes, the

4-90—4-91 1-15Field soundings, reduced depth unit for4-1 hydrography reference datum for 1-15Field survey(s), hydrographic6-1data, verification of 3-13photogrammetry used in shoreline surveys of

1-16Final inspection and approval of survey 8-1 shoreline detail on field sheets ofFinal inspection team 8-1 surveys of, low water datum line not shown on 4-6

4-84 AK-5water level recorder in use inFine arc errors in echo soundingAK-1Fischer and Porter water level gage 1-15Greenwich Mean Time (GMT)

4-54(see also Tide and water level gages) used in records4-88Fish, echoes from 7-9Groins on the smooth sheet

7-9Fish houses on the smooth sheets Growth, marineFishing areas, bottom descriptions showing 1-18 (see also Kelp; Grass)

7-10Fix marker on echo sounder 4-61 smooth sheet, on5-22 1-15Flagpole as a landmark Gulf of Mexico, the depth unit for5-22 4-75Flagstaff as a landmark Gulf Stream, temperature variations and the5-22 4-28Flagtower as a landmark Gyroscope repeater and pelorus

Floating aids to navigation1-4, 1-18hydrographic surveys, in H

recommendation procedures regarding 1-18Harbors1-18reporting procedures when off station

4-10line spacing inFoot, U.S. Survey, conversion factors based on C-1shoal indications in 1-113-12Form letter to property owners

Hastings-Raydist, Inc 4-291-17, 7-8Foul areas in shoreline plottingHazards to navigation

(see Dangers to navigation)Foul, symbol for B-3Frequencies of positions along

Heave correction, term defined 4-664-32sounding lines, factors influencing1-14Heave error in soundings4-84Frequency errors in echo sounding

Horizontal control 1-6—1-7angulation instruments 3-5Gazimuths and astronomic observations 3-5

Gages basic control 3-1—3-44-67monitoring of connections to existing control 3-5

tide and water levels connections to geodetic control1-15, 5-10, AK-1, AK-7observations established by other organizations 3-2

5-22Gas or oil tank as a landmark control station spacing in 3-1AK-3—AK-5Gas-purged water level gage density of main scheme control, and 3-1

(see also Tide and water level gages)General instructions for

design of traverse in 3-6distance measurements in 3-5

hydrographic survey 2-2 geodetic control reference system 3-1Geodetic control diagrams 2-2, AK-8 horizontal angles in 3-5Geodetic control established by instruments, distance-measuring 3-5

other organizations, connections to 3-2 main scheme control station spacing 3-11-19, 5-25Geodetic report monumentation 3-4

Geodetic triangulation manual National Ocean Survey instructions1-7, 5-4Geodimeters on location of photo-hydro stations 3-9

models of position checks on spur points 3-63-3, 3-53-6readings with recovery of existing stations 3-1—3-2

6-12 second-order directions and azimuthsGeographic datums and verification procedures 3-31-19, 5-13, 5-23Geographic Names Report second-order traverse in 3-2—3-3

7-19Geographic names on smooth sheets 3-1—3-16shoreline surveys4-47Geophysical Instruments and Supply Co. slope correction procedures 3-6

Glossary of abbreviations and acronyms E-1 station marks and descriptions 3-21-13, 1-14, 4-57, 4-62Graphic depth record station spacing 3-4

Graphic depth recording equipment, stations1-14compensation for errors in (see also Control stations, horizontal)1-13Graphic record of sounding profiles 3-4, 3-14supplemental control

I-7

HYDROGRAPHIC MANUAL

third-order control data submission 3-7—3-8 basic 1-5, 2-1, 4-13-4 bottom characteristicsthird-order control specifications

1-17—1-18third-order measurements with alongshoremicrowave instruments 3-5 14sampling in

3-6—3-7 cartographic standards intraverse design procedure 1-52-1, 2-7, 4-1, 4-93—4-105verification of 6-2 Chart Evaluation Surveys

1-19Horizontal positioning errors in a Chief of Party's inspection responsibilities4-1—4-24-45hydrographic survey, list of classification of surveys

Horizontal traverse angles, control instructions in 2-21-10—1-11observation methods crosslines in3-3—3-4

5-22House as a landmark current observations in 1-4AJ-3data-acquisition programs andHumidity

3-3electro-optical measurements, effects on data to start surveys 2-61-14—1-15datums of reference inmicrowave measurements, effects on 3-3

4-31 definitionHybrid positioning systems 1-3Hydrographer delimiting of alongshore areas 1-17

1-164-38cooperation with field editor depth curves in1-14 1-15—1-16depth units forjudgment exercised by3-14 1-14electronic depth digitizers inresponsibilities of

Hydrographer-field editor coordination, electronic positioning system in 1-7, 1-8, 1-103-14essentiality of equipment used in 1-12, 1-13

AL-10 field edit surveys inHydrographic clock 1-171-19—1-20field reports inHydrographic control stations

(see Control stations, hydrographic) field sheet in 4-24-1Hydrographic field survey, list of requirements for (see also Field sheet)

4-2Hydrographic records(see Records, hydrographic)

importance of1-16soundings on

Hydrographic sheet(s) 1-4floating aids in1-5, 1-6field sheet Gulf Coast Low Water Datum (GCLWD), a1-5, 4-2, 4-3

1-15, 1-172-7 reference datum inlayoutgeneral instructions formaterial 2-11-6, 7-1

1-3—1-4numbers general standards2-9, 2-101-6rubber stamping of 3-1geodetic control inadequate for

scale of survey 1-5—1-6 1-11hazards to navigation in, discovery ofsheet projections horizontal control 14—1-5, 1-71-6,4-3sizes of sheets 1-6, 7-1, 7-2 shoreline surveys 3-1—3-16smooth sheet 1-9hybrid control systems in1-5, 7-1

2-7—2-101-4, 3-10—3-12Hydrographic signals hydrographic sheet planning4-4brief descriptions of, helpful on field sheet hydrographic sheets in 1-5

3-11—3-12 importance of region of survey to navigation 1-11building materials forinclement weather, andcalibration of electronic 4-2

4-28,4-29 inshore surveys inpositioning system using 1-53-10—3-11construction of inspection team 8-1

3-10 1-16junctions, adequacy ofdefinition ofline-of-sight measurements in3-11 1-8entrance on private property, and

3-10 AJ-3logger electronics, andexamples of acceptable4-4field sheet, on the Low Water Datum (LWD), a

1-153-11 reference datum inform letter to property owners regardinghorizontal control, in 3-9 Mean Low Water (MLW), a

3-10—3-11 1-15reference datum innatural and cultural objects as3-11publicly-owned areas, in Mean Lower Low Water (MLLW),3-13 1-15a reference datum inratio prints in location of3-12selection of meteorological data in 3-33-10spacing of microwave instruments in 3-3

Hydrographic Survey Inspection Team(HIT) 8-1 modern definition of 1-3Hydrographic stations, location by sextant angles 3-9 Navigable Area Surveys 1-5, 2-1, 4-1, 4-92, 4-93

1-18Hydrographic surveying(see also Running hydrography)

navigation aids in1-18navigation dangers in1-121-3 numbering of positions inaccuracy, degrees of

aids to navigation in 1-4 ocean surveys 1-62-2—2-10automated systems in 1-6, AJ-1—AJ-4 office planning

I-8

INDEX

AJ-3 AL-5off-line plotting programs in Hydrometersoffshore installations and 1-4—1-5 HYDROPLOT

2-10 AJ-2adjunct equipment selection andoperations planningAJ-1operations relative to computer4-2AJ-21-11—1-12overlap at junctions computer programs for use withAJ-21-7 controllerphotogrammetric surveys

2-10plan of operation 4-32, 4-34data acquisition and processing systemplane table in 4-57, 4-58, 4-59, 4-62, 6-4, AJ-2

Del Norte Trisponder position-fixing3-9—3-15

planning for, note on 1-3AD-22-1—2-10plans and preparations for system, and the

1-9—1-10 AJ-2plotting control echo sounders andAE-4polyconic projection in 1-6 electronic digital sextant, and the

1-4position fixes in manual 4-75—4-76, B-1AJ-2position fixes spacing in 1-4 multiplexerAJ-1position frequency intervals 1-12 plotter

1-12position numbering example Raydist DR-S positioning systempositioning control 1-7—1-8 integrates with AC-4

1-12positions Raytheon analog and digital depthAH-1Presurvey Review in 2-6 sounders, and

priorities for 2-1 Hydrotrac, a medium-range positionproject numbers 2-1—2-5 system

(see also Position-fixing systems)purpose of 1-3, 4-1AC-8—AC-11reconnaissance 4-1 Hydrotrac Survey Systems

1-14—1-15reduction of soundings Hyperbolic lattices should be machine drafted 4-31-19—1-20 AC- 1report and records Hyperbolic mode of position-fixing systems1-19—1-20report evaluation by Marine Center Hyperbolic positioning systems

4-201-17rocks in shoreline plotting in considerations for, tabulated1-14salinity measurements in 4-20description of

scale of survey 1-3—1-6 error propagation contours in 4-21scale selection in 1-5 lane expansion factor, and the 4-21

4-211-8sextant angles in measurement of fractional lane reading insextant-controlled hydrography in 4-20range-range systems, versus1-7, 1-8sextant three-point fix in restriction of use of1-7, 1-8 4-23shore stations in 4-211-8 shore station configurations inshoreline surveys in 3-11—3-15 4-20slave and master stations insmooth sheet in, the 1-5 4-21whole lane value, and thesounding lines in 1-4,1-10—1-12 Hypervisual positioning method 4-30

1-14sounding records correctionssoundings, plotted, and 1-4 Ispecial 4-1

7-20Identification block on smooth sheetspecial reports in 1-19Information sought from those usingspecific standards in 1-4—1-5

1-14 local waters 4-40spurious traces reconciliation in3-121-14 Infrared photography, tide-coordinatedtemperature measurements in4-80Initial errors in echo soundingtide and water levels observations in 1-15

Insets to sheetstransfer of topographic and 2-9, 7-21-16—1-19 Inshore preliminary positionplanimetric detail in

overlays and verification 6-4ultimate purpose of 4-2Inshore surveysvertical control in 1-51-5

electronic positioning systems invertical datum and reference of sounding 1-91-51-19vessels in Inspection procedures relative to field sheets

Inspection report(see Vessels, survey) 8-1Inspection team, hydrographic survey 8-1visual position control in 1-7—1-8Instruction manual for obtainingwire sweeps in 1-10, 1-11

wrecks, obstructions, and shoals in oceanographic data 2-61-5Instructions in hydrographic surveysHydrographic title sheet 5-5

4-1—4-111 control instructionsHydrography 2-2AB-1 currents instructionsinstruments and equipment for 2-4

general instructionsrunning 2-2(see Running hydrography) hydrographic instructions 2-2

visually-controlled 3-8 magnetics instructions 2-6

I-9

HYDROGRAPHIC MANUAL

method for making2-6 2-7—2-9miscellaneous instructions2-6oceanographic or limnological instructions tracing to be sent to NOS headquarters 2-7

1-13photogrammetric instructions Lead line and echo soundings comparisons1-7, 2-21-13Project Instructions Lead lines2-1—2-6,2-10

tides or water levels instructions 2-2 (see also Equipment, sounding)Instrument errors correction and echo sounders, used with 4-55

AF-14-79,4-80velocity correction procedures purposes ofAA-1 recording soundings of 4-53Instruments and equipment

4-72International Accuracy Standards for vertical cast procedures, and1-10Least depths over pinnacles, determination of1-3Hydrographic Surveys

International Association of Physical Ledges and reefs, smooth sheet, on the 7-84-74 Lettering on smooth sheets 7-3Oceanography, standard observation depths of

AK-8International Great Lakes Datum Leveling instrument placed ashore 4-70AK-8International Hydrographic Bureau Leveling, state maps for1-3, 4-105

1-3, 4-85 Light List, the (U.S. Coastaccuracy standards of4-41, 5-9, 5-21, 7-194-74,4-75International Standard Depths, use of Guard)

4-17—4-18 Limit lines and the smooth sheetIntersection, theodolite 7-81-12, 1-13Intervals, sounding, Limitations in using third-order

4-34 traverse methods 3-8guidelines regardingB-2Islet, symbol for Limnological instructions 2-6

Line-of-sight measurements inhydrographic surveyingJ 1-8

4-10Line spacing in harbors and restricted areas4-32Julian dates and data identification Lines4-48in records closely-spaced 1-11

Junctions 1-12consecutive numbered positions on7-20adjoining surveys smooth sheet, and the 1-11split

4-8and overlap soundings Location of photo-hydro stations1-12between survey sheets pricked on to photographs 3-9

4-11—4-13Locus arcsK 4-5field sheets, on

4-74Log sheet-AKelpLong-range hyperbolic navigation system

(see LORAN navigation system)4-86, 4-87, 4-88echo sounding, and

7-10smooth sheet, on5-22Lookout tower as a landmarkB-3symbol for

LORAN long-range navigation system(see Navigation systems)

AI-2Klein Side Scan Sonar

Low Water Datum 1-15, 4-6LLow water lines on smooth sheet 7-7, 7-8

7-14, 7-19, 4-92, 4-94Landmarks5-22—5-23classifications of, listed M

5-15for charts, Descriptive Report, listed in4-7Magic marker pen used on field sheet3-11importance of4-2Magnetic observations5-18, 5-21nomenclature standardization, and2-6Magnetics instructions5-18preparation of reports on

1-19Magnetics report5-25reports on4-41 Maintenance of echo soundingrunning hydrography, in

4-7equipment, importance of5-18supporting chart sections onMangrove and swamps and unconventionalLandmarks and nonfloating aids to

survey methods 3-91-19navigation reportManually plotted surveys, duplicate4-23Lane counters in range-range systems

field sheets for 4-34-62, 4-65Lane gains and losses in records1-20Marine Center evaluation of reports4-56Latitudes and longitudes, recording of

Marine Center processing divisions,Lattice labels on smooth sheets 7-6smooth plotting by 7-14-5Lattices, usefulness of

1-10 Marine Centers' requirements 1-9Launch hydrography6-12MEADES RANCH stationsextant-controlled 3-8

4-34 Meridianssoundings in4-76 4-4adjacentLayer corrections and velocity readings4-75 7-6labels for, on smooth sheetsLayer selection for velocity determination

3-3Meteorological data and distance measurementsLayout, sheet

I-10

INDEX

5-21AB-1 report on nonfloating aids toMicro OmegaNavigation systemsMicrowave horizon distance, range

AC- 1Decca Hi-Fix systemC-4versus antenna height, tables ofAB-1long-rangeMicrowave instrumentsAB-33-5 LORAN navigation systemthird-order measurements withAB-4charts for use with3-3used to measure survey lineAB-43-3 equipment forMicrowave measurements, humidity affectingAB-4LORAN C data correctionsMicrowave line-of-sight distanceAB-44-25 operation ofcomputation formulaAB-3Mini-Ranger position-fixing system phasing out of LORAN AAB-4position fixes for use in(Motorola)AB-3range of(see Position-fixing systems)

4-55-4-56 AB-3Miscellaneous entries in record of survey range-range positioning, andskywave correction values, and AB-44-1Miscellaneous operations in field survey

1-19 AB-4tables forMonthly Activities ReportAB-3transmitters of1-19, 5-1, 5-3Monthly progress sketch

1-19 medium-range position-fixingMonthly Ship Accomplishment Report1-19 AC-1 AC-15systemsMonthly Survey Status Report5-22 Omega long-range navigationMonument as a landmark

AB-1Motorola Mini-Ranger III short-range systemAD-4—AD-7 AB-1position-fixing system cesium beam frequency

AB-1(see also Position-fixing systems) charts to be used with4-9Mud and sand in bottom slopes determining systematic bias of AB-37-5Mylar smooth sheets, pencils used on AB-1equipment for

AB-1integration of components ofN AB-3lane counters values

AB-1operation of5-13, 5-23Names, geographicAB-1AL-2 range-range operation of theNansen bottlesAB-1AL-3 skywaves corrections, anddescription ofAB-1AL-3 stations formessengers, and

AL-4 AB-1tables forreversing thermometers, and4-75 AA- 1spacing of NOAA ship Davidson4-74water sampling, for NOAA ship Fairweather 1-2, AA-1AL-3winch used, and the Nomenclature

Nansen cast data in velocity 5-18, 5-21regarding landmarks4-77correction procedures 4-65-4-67standard, in echo sounding

4-29, 4-107National Bureau of Standards "North American Datum of 1927"' 6-12, 6-13National Geodetic Survey 3-1, 3-4 3-13"Notes to the Hydrographer"

data to be submitted to 3-7, 3-8 Nouns for bottom characteristics, symbols for B-63-2disks 4-4Numbering of control stations

3-7—3-8third-order control data submission toNumbering of projects 2-1—2-5

National Horizontal Control Network 3-2, 3-4Numbering of survey positions 1-12

National Ocean Survey 1-3, 1-5, 1-13, 1-14, 1-15,1-17, 1-18, 1-20, 2-1, 2-2, 2-6, 2-9, 3-1, 3-5, 3-8,

3-12, 3-14, 3-15, 4-1, 4-2, 4-7, 4-9, 4-18, 4-26,4-38, 4-41, 4-46, 4-57, 4-62, 4-66, 4-67, 4-70,

0

Objects4-74, 4-105, 5-1, 5-4, 5-15, 5-21, 5-23, 5-24, natural and cultural, as

7-3, AB-4, AH-1, AK-I 3-10—3-11hydrographic signals1-19nautical charting program of

verification of survey control 3-2AK-8State Map for Control Leveling 4-65Observed depths, term defined4-68Tide Tables of Obstructions

1-5Nautical chart construction 1-11finding ofNautical Chart Symbols and Abbreviations 4-46 7-9submerged, on the smooth sheetNavigable Area Surveys 1-5, 2-1, 4-1, 4-91, 4-92 Ocean Survey SheetsNavigation series numbers and limits 4-105, 4-107

aids to 4-105track line surveys plotted on(see Aids to navigation) Ocean surveys and the Continental Shelf 1-6

dangers to Oceanographic and limnologicdeterminations, velocity(see Dangers to navigation)

1-18 4-74---4-79navigational ranges of sound, and the

I-11

HYDROGRAPHIC MANUAL

3-12Oceanographic determinations Photogrammetry, aerial4-79 Photo-identification ofcombined with direct comparisons

AL-2—AL-10 3-14Oceanographic equipment aerotriangulation control5-252-6Oceanographic instructions Photographs and special reports1-19''Oceanographic Log Sheet-M, Photographs report3-13Bottom Sediment Data'' 4-44 Photography, infrared

Oceanographic stations Photo-hydro stations 3-82-2shown on Project Instructions charts location by radial intersection 3-9

4-6, AL-1, AL-2 location by transferOdessey protractors 3-91-104-10—4-11Offshore surveys, line spacing in positions

B-2 2-9Piers and docks, showing on sheetsOil or gas well, symbol forOmega long-range navigation system

(see Navigation systems)7-9Piles on the smooth sheet

Pilots' notes 4-21-10, 1-11, 4-40, AF-5Pipe drags4-46Ooze, definition of

4-10 Pipe, symbol for B-3Open coasts, line spacing along2-102-10 Plan of operationOperations planning

Plane table2-10Operations plans subject to changeDescriptive Reports 3-93-12Orthophoto mosaics

3-0,3-15use of4-44Overlapping survey areas, discrepancies in4-4Plane table control stationsOverlaps

Plane table methods and the7-20extensive, and the smooth sheet3-15Descriptive Report

1-11, 4-8junctions, soundings in, andPlanimetric detail in

7-1Overlays to smooth sheets1-16—1-19hydrographic surveys

3-12Planimetry, interior, in shoreline surveysP 2-1Planning, hydrographic survey

Platforms, symbols for B-3Pacific Ocean, thePlessey Environmental Systems Model 9090,

an expendable salinity, temperaturedepth units for 1-15

1-15hydrographic reference datum forAL-8and depth measurement system

Parallel straight sounding linesPlotters and the smooth sheet 7-5

4-11advantages ofPlotting

4-11disadvantages of 4-3automaticParallels 1-9—1-10control in hydrographic surveying

4-4adjacent 4-45errors listed4-85Peaks and deeps, time tolerances for scaling 7-2hand4-46Pelagic sediment 7-1smooth sheet

4-345-1Periodic reports required, list of sounding line4-24Phase comparison systems Polaris observations 3-3, 3-44-27 4-31buoy use in azimuth by

AF-34-29 Pole, soundingsignal must be uninterrupted in4-52 Polyconic projectionPhase corrections and frequency checks

7-5smooth sheets, used forPhase errors in graphic depth1-14 use of 1-6recording equipment

3-9Polyester drafting film for plane table surveysPhotobathymetric compilations,Position fixes4-8junctional soundings from

1-12additional, occurrences requiring3-13Photobathymetry1-4in hydrographic surveying3-13advantages of

4-14on sounding lines7-13smooth sheet, and thespacing in hydrographic surveying 1-46-9—6-10verification of

Position-fixing systemsPhotogrammetric

AC-2accuracy of3-13bathymetry ARGO System

control stations 1-7,44 AC-11principles of operationinstructions 1-7, 2-2 AC-12description of equipment

6-10locations of shoreline, verification of AC-13characteristics of3-8—3-9methods of locating control stations AC- 1circular pattern generation, and1-19,5-4 AC- 1precompilation field report Decca Hi-Fix and Sea Fix systems

3-13—3-15support data in shoreline surveys Del Norte Trisponder short-rangeposition-fixing systemPhotogrammetrists, experienced,

3-15 AD-1in shoreline survey basic unit

I-12

INDEX

AD-2 AC-5radiated power ofcharacteristics ofAC-5AD-3 range ofdata recording for

AD-3 AC-4range-range mode advantages ofdistance measurements, note onAC-5AD-2electronic drift, and readout resolution of

AD-1 AC-6shielding methods necessary withequipmentAD-4 AC-7error, update, for shore station checkout proceduresAD-3 AC-6fail-safe operation of slave or relay stations ofAD-2 AC-5system components offeatures ofAD-1 AC-4system manuals forfrequencies ofAD-2 AC-5wave transmission ofHYDROPLOT controller, and theAD-2 AC- 1Sea-Fix positioning systeminstallation ofAD-1 characteristics of AC-4microwave frequency energy of

AC-3AD-2 mode of operation ofmode of operation ofAD-1 AC-3operating range ofoperation of

AC-3AD-4 pattern transmission frequency ofposition-error possibility, andAD-1 AC-3round trip time of signal of power supply forAD-3 AC-3radiated power ofsignal overlap and interference prevented inAD-1 AC-3readout accuracy ofsignal time ofAD-1 AC-3stations of. receiver speed ofAD-2 AC-1time-sharing option of shipboard installation ofAD-3 AC-3Hi-Fix and Sca-Fix chains transmission, type of

AC-2Hi-Fix positioning system slave and master stations inAC-3 AC-2accuracy of, claimed stations used inAC-4 1-12,4-32characteristics of Position frequencyAC-3 1-12mode of operation of Position numberingAC-3 4-32Position numbers, assigning ofoperating range ofAC-3pattern transmission frequency of 6-3Position overlay, verification of data and theAC-3 Positional data in recordspower supply for 4-55AC-3 1-7—1-8Positioning control, hydrographicreadout accuracy ofAC- 1hyperbolic pattern generation, and Positioning, electronic control systems 4-18—4-30AC-2increased accuracy requirement, and 4-14—4 18Positioning, visualAC-4 three-point sextant fixlane count in 4-14AC-1lattice patterns of Positioning lattices, electronic, on smooth sheets 7-6AC-3locking signals used in Positioning systems and requirements 4-14—4-31

Motorola MRS III system Positioning systems, electronic,AD-5 4-55characteristics of and data recording

Positioning systems, hyperbolicAD-4coding system of 4-20—4-23description of operating characteristics of Positioning vessel, theodoliteAD-6

intersection method forAD-4equipment of 1-8,4-47—4-18AD-4pulse radar system, a Precompilation field reports 5-4AD-6 4-68radiation patterns of Predictions, tidalAD-4 Preliminary sounding overlayrange of 6-7AD-5transponders for Presurvey Review 2-6—2-7,4-7AC-1operating principle of approval of 2-6AC-2range-range mode, and the examination of entries in 4-56AC-4Raydist DR-S system 1-4Primary shore stations in hydrographic surveying

all-weather system, an AC-4 Prior records furnished as presurvey data 2-6AC-6 4-7antenna coupler for Prior survey data transfer to field sheetAC-6 4-1—4-2antenna height, and Prior survey information in field surveyAC-6batteries use, and Priorities for hydrographic survey 2-1, 2-10AC-5 7-19characteristics of Private markers shown on smooth sheetAC-7checkout procedures 4-57Processing/Statistics block in survey records

high frequency band operation of AC-4 Progress Sketchcontents ofHYDROPLOT system integrated with AC-4 5-1

AC-7mobile station checkout procedures current measurement methods on 5-2AC-5mode of operation of 5-1registry numbers, andAC-4NAVIGATOR, and the scales to be shown on 5-1AC-5operating frequencies of sheet limits to be shown on 5-1

operating principle of AC-4 survey details to be shown on 5-1AC-5positional accuracy of 5-2symbols to be used onAC-5 2-1—2-6,2-10power supply for Project Instructions

I-13

HYDROGRAPHIC MANUAL

amendments to column entries in 4-542-2charts furnished with compass type used to be noted in2-2 4-55

4-55draft copies of course changes in2-2Project preparation 2-6—2-7 data identification in 4-57

4-56Projection intersection, plotted, day's work statistics indeletion of nonessentialand control station plotting 4-6

4-57Projection line intervals for various sheet scales 4-3 information from certain blocks4-48,4-57Pronounced topographic features, depth records

4-544-13sounding lines alongside deviations from standard value inAL-1Protractors digital depth readings in 4-62AL-1 distances, estimated, in 4-56OdesseyAL-1plastic three-arm 4-48electronic control information, and

4-56used in manual plotting equipment operation to be noted in4-66-4Pseudofixes, verification and feature investigations to be noted in 4-56

4-95Public relations-user evaluation 4-47field records, essentialGreenwich Mean Time used in 4-54Pulse radar position-fixing system AD-4

1-19inspection ofJulian dates in 4-48Qlane gains and losses in 4-62

6-14Quality control procedures 4-56latitudes and longitudes inQuestionable features and

4-48legibility requirements in1-17alongshore detail verification

4-47manually recorded data4-56notations on passing features inR4-48page headings in

Radar position-fixing system AD-4 4-55positional data in4-55—4-56remarks column in theRadar reflectors as an aid in finding buoys 4-28

5-22 4-56rock heights to be noted inRadar tower as a landmark4-48rubber stamps inRadial intersection location4-47of photo-hydro stations sheet registry number, and the3-8

Radiating sounding lines shipment of4-13 8-14-56shoal examinations inRadio in theodolite intersection

4-25 shore station information to be noted in 4-56positioning method5-22Radio mast as a landmark 4-57simultaneous comparison in5-22Radome as a landmark 4-55simultaneous soundings, of

4-514-5 sounding equipment, andRange arcs on field sheets4-31Range-azimuth positioning system 4-54,4-57soundings

4-23—4-25,AC-2Range-range positioning systems 4-47NOAA form 77-444-24distance-measuring 4-56speed of vessel in

AB-3 4-55supplemental angles inLORAN C navigation system, and the4-62supplemented by analog records4-24phase comparison systems

4-23—4-24 4-57phase-matching systems survey information blocks in the4-20 4-57tape number entries inversus hyperbolic system, table

4-59Range-visual system terms used in4-314-55theodolite intersection data inRapids, symbol for B-3

AC-4 4-56tidal anomalies to be noted inRaydist DR-S positioning system(see also Position-fixing systems) time of occurrence in 4-48

AH-1 visual control and 4-48Raytheon analog and digital depth soundersAH-5 4-48watches on ship, andRaytheon DE-719 depth recorderAH-5 4-54weather conditions, andRaytheon portable echo sounder

(see also Equipment, sounding) 4-91Reduced soundings, conversion of1-14,4-90Reconnaissance surveys Reduction of soundings4-1,4-94

1-144-47 datums of reference inRecords, hydrographic4-674-47 Reductions, tide and water levelsabbreviations used in

4-86analog depth, interpreting Reference datums in hydrographic1-14, 1-15, AK-8surveys4-56analog depth recorder phase to be noted in

3-2Reference mark disks4-62analog position data2-9—2-10Registry numbers, instructions on4-47automated data recording and

4-55—4-56Remarks column in records of survey4-57—4-58automated survey records1-19bar check in 4-57 Reports5-244-47 Chart Inspectionchronological recording method for5-244-54, AL-10 Dangers to navigationclocks used in hydrography, and

I-14

INDEX

4-39,5-4—5-13 4-41soundings along wharves and docksDescriptive1-20 4-34asounding intervalevaluation by Marine Center

1-19,5-1—5-25 4-34, 4-34bsounding speedfieldverification of charted features 4-42—4-435-18landmarks, on

4-34vessel speed, factors influencing5-1periodic, list of4-545-25 weather conditionsspecial reports and photographs4-415-21 wrecks and obstructionstide and water level station, on

6-15verification reportsS6-1Responsibilities of verifier of survey data

Restricted areas1-10Safety of personnel and equipment4-10line spacing in

Salinity4-110, 4-111tag line surveys, and4-74—4-75checks ofReversing thermometers

(see Thermometers, reversing) determinations 2-61-14, AL-5measurement of2-6—2-7Review, Presurvey

4-70temperature observations and4-56examination of entries inAL-5Salinometers

RocksAL-8Samplers, bottomawash4-44Samples, bottom, storage of7-9smooth sheet, on the

1-18,4-47Sampling of bottom7-9symbol for4-9Sand and mud, bottom slopes inbare

4-46Sand, definition of7-8description of4-62Sawtooth record described7-8elevations of4-83Scale errors and stylus arm length7-8photogrammetric manuscripts, on

Scale selection in hydrographic surveying 1-5, 1-67-8smooth sheet, and the4-84—4-90Scanning analog depth recordscartographic codes and symbols

Schedules for hydrographic surveys 2-1illustrated B-8, B-9, B-10Sea conditions and running hydrography 4-547-9dangerous, elevations ofSea-Fix medium-range position-fixing system

4-39Descriptive Report requirements, and(see Position-fixing systems)4-39determination of heights of

Seamountelevations on the smooth sheet 7-9definition of 4-1074-56heights to be noted in records

4-107track line surveys, insubmerged, on the smooth sheet 7-91-19Season's Progress Report

B-2symbol for5-4control stations and the4-9Rocky bottoms, and, soundings

Season's progress sketch 1-19, 5-24-9Rocky coasts, and, soundingsSecond-order, Class II surveys,Root mean square error in uncertainty

requirements for 3-14-22exampleSecond-order directions and azimuths 3-3AH-3—AH-5Ross depth-sounding systemSecond-order traverse 3-2—3-3(see also Equipment, sounding)

directions in 3-34-66Rough seas and heave correctiondistances in 3-3Ruins, symbol for B-2, B-3

Sedimentology 4-454-32—4-43Running hydrographySensors4-41aids to navigation

precision of 4-754-57—4-58automated survey recordsAL-8salinity, temperature, and depth4-32beginning the surveyAL-8temperature, depth, and conductivity4-44—4-47bottom, characteristic of, and

Settlement and squat4-42bridges and cable crossingsbuoy used to measure 4-704-42cable crossings and bridgesinstruments for measuring 4-704-33course change limitations

1-14soundings, in4-39dangers and shoalstransducer displacements, and 4-694-35depth units

Sextant angle observations and4-43field sheet inspectionhybrid positioning systems 4-314-35field sheet soundings

Sextant angles to locate hydrographic4-42floating aids to navigationstations 3-94-33, 4-34following proposed sounding lines

Sextant control stations 4-44-35measuring depthsSextant-controlled hydrography 1-74-42nonfederal aids to navigation

4-41 changes of fix required in 4-11nonfloating aids and landmarksSextant-controlled launch hydrography4-34, 4-35 3-11plotting sounding line

4-54 Sextant cuts to locate hydrographic stationsrecords in 3-9

I-15

HYDROGRAPHIC MANUAL

Sextant fixes height values, note on 4-254-31position control, and information to be noted in records 4-56

special problems in 4-17 site selectionvessel position from 4-17 factors in 4-29

Sextant positions, erroneous, local topography and 4-304-14verification procedures and 6-5 used in vessel positioning

Sextant surveys and the numbering 4-107Shore ties in track line surveysof control stations 4-4 Shoreline

1-17Sextant three-point fix 1-7 actual and apparentSextants 7-6, 7-7delineation on smooth sheets

AE-1 detailadjustment ofAE-2 1-17star in, use of changes inAE-2angles to faint objects, and on field sheets 1-16, 1-17, 4-6AE-4electronic digital type features verification 6-10AE-5 1-10adjustment and calibration of manuscriptAE-4 1-17description of and approximate shoal and channel limitsAE-5 3-13direct readings from drum, and prints as support data

encoder scale of 7-7AE-4 not to be smoothed or generalizedAE-4error-free digitizing of 7-7revisedAE-4HYDROPLOT system, and the surveys ofAE-1index mirror of 3-13aerial photogrammetry inAE-5 3-12observer safety, and Atlantic Ocean, methods forAE-6 3-12operation of Caribbean Sea, methods for

sturdiness of AE-4 3-11—3-15Coastal mappingAE-5 3-13telescope attachment use, and compilation photography inAE-1horizon mirror of control identification 3-12—3-13AE-4 3-14—3-15inclined angles, and discrepancy examples inAE-1 3-14index error of discrepancy prints inAE-1 3-14micrometer drum sextants field edit of manuscripts inAE-1 3-12mirrors, position of Great Lakes, methods forAE-1 3-12Gulf of Mexico, methods fornavigating sextant, description ofAE-2 3-1—3-15horizontal control, andscaling angles from field sheets, andAE-1screw clamp type, use of hydrographer and field editor in,

3-144-111tag line survey, in coordination essential betweenAE-2three-point fixes using 3-11importance of topographic features inAE-2 3-14use of Marine Center Director's role in

2-7—2-9 3-11Sheet layout orthophoto mosaics in3-12Sheet limits on progress sketches photobathymetry in5-13-15plane table methodsSheet planning3-152-7—2-10hydrographic plane table surveys in

2-9 3-11subplans and insets planimetry, interior, and3-14Sheets, field relief displacement errors in

3-13—3-14(see Field sheets) support data, photogrammetric, inSheets, hydrographic 3-11topographic survey methods in

Side echoes(see Hydrographic sheets)Sheets, smooth (see Echoes, side)

Side Scan Sonar(see Smooth sheets)AI-14-40,4-56Shoal examination to be entered in records General principlesAI-1B-3 applicationsShoal, symbol for

1-12 AI-3Shoal water digital echo sounders operations, considerations of1-12-1-13preference for Signals, hydrographic

(see Hydrographic signals)1-12, 4-52Shoal water echo sounders4-46Silt, definition of4-88Shoalest depths and side echoes

4-110, 4-1111-11Shoaling, investigation of Skiff, tag line survey, used inShoals Skywave correction values,

AB-44-39—4-41,4-92and dangers inaccuracies of predicted1-11,4-40 Skywave corrections and thedevelopment of

AB-14-39indications of Omega navigation system4-40—4-41record of examination of Slant distance to shoal and side echo 4-90

1-10Small-boat hydrographyShore stationSmithsonian Institution,4-21configurations, accuracy of

I-16

INDEX

4-45 8-2nautical chart and the, contemporarybottom sediment samples to7-11 numbersSmooth bottom soundings, plotting 2-9, 2-10

6-1—6-20 7-9Smooth plotting obstructions, submerged, shown on7-9obstructions, visible, shown onSmooth sheet

annotation of control stations on 7-2 7-3orientation of lettering onarrows used on 7-4 7-1overlays, material for

7-13, 7-14bottom configuration shown on 7-5pencils used on7-10 7-1permanent record of survey, is thebreakers shown on7-19buoy symbol on 7-13photobathymetry and the

7-4cartographic specifications and conventions 7-5 placement of lettering on7-5cartographic standards for polyconic projection used for7-1

7-19characters, standard, used on private markers shown on7-57-22 7-1chief of party to be named in protection o

composite, may be a registry numbers2-9 2-9, 2-107-3control stations beyond sheet limits, and retention in government archives7-2

control stations to be described on rocks shown on7-6, 7-20 7-8, 7-9scale ofdanger areas shown on 7-8 1-5, 7-1

7-14definition and purpose of 7-1 selection of depth contours, and7-13, 7-14 8-1depth curves and the shipment of

7-20 7-13depth curves in overlap areas shoaler soundings plotted on7-20descriptive notes on 7-6, 7-7shoreline details on

7-1Descriptive Report and 7-1 size and layout7-1dog ears and smooth position overlay, with2-10, 7-1

drafting aids for delineating depth sounding numerals on 7-3, 7-107-13 7-10, 7-11, 7-13curves on soundings, and the

7-1 7-13drafting film used for soundings overlap, and7-4drafting materials for soundings, selection of 7-11, 7-13

7-22drafting standards for special projects and7-3electronic position lattices, and 7-1specifications, general7-1, 7-6

7-10erasures on tide rips and eddies shown on7-57-20, 7-22extension of survey coverage on 7-2 title block on

7-6final approval of 8-1 topographic details on7-10fixative used on 7-5 wire-drag hangs, and7-14formula for determining area of coverage 2-9 zero-depth curve and the

7-19geographic names on 7-8zero soundings, and7-10grass shown on B-3Snag, symbol for7-10 4-109groundings and clearances, and Solar observations

AI-1-AI-3hand plotting of 7-2 Sonar, Side Scan1-13hydrographic features on 7-8 Sounder, echo, calibrations for

7-20identification block on 1-12, 1-13Sounders, types ofink for 7-4, 7-5 5-13Sounding correction abstract

1-10, 1-127-2insets and subplans Sounding line(s)4-146-20, 7-1inspection and approval of abnormal tides and

2-7instructions for layout of beach observation advantage, and the 4-13instruments, drafting, used on 7-5 beaches, and 4-8

7-20 4-7junctional notes lettering on bottom profile, and the7-20junctions and adjoining surveys and changes and turns in course, and 4-337-10kelp on the channels, in 4-13

labels for meridians on 7-6 control, visual, and 4-33labels for parallels on 7-6 4-33course change limitations, and

7-14, 7-19 crosslineslandmarks symbols on 4-13—4-14lattice labels on 7-6 4-39dangers and shoals, and

2-7—2-9 4-11layout deep ridges and valleys, inledges and reefs on 7-8 4-11,4-35depth curves, andlettering on 4-9Descriptive Reports, and7-3, 7-4limit lines and the 7-8 echo sounders, and 4-7, 4-52low water lines on 7-7 estuaries, system for 4-13margin areas, note on 7-2 following of proposed 4-32—4-33margins and extensions frequencies of positions along7-2 4-31

7-10marine growth on the harbors, spacing in 4-104-8—4-9material used for 7-1 inshore limits of surveys, and

I-17

HYDROGRAPHIC MANUAL

junctions and overlaps1-4intervals and spacing 4-8lead-line, note on4-11—4-13locus arcs 4-53, 4-55

marine vegetation, and 4-7 NOAA form 77-44 to be used to record 4-47,4-654-35measuring depths, and numerals on the smooth sheet 7-3

4-10—4-11offshore surveys, in plotted, uniformity of 4-35parallel straight preliminary, overlay4-11 6-7

1-12recording, between fixes4-10parallel system of4-34 1-14—1-15parallel to shoreline reduction of

4-33—4-34plotting of 4-9rocky bottoms, and1-15—1-164-32position identification, and rules for recording of7-11, 7-134-31 selection ofpositions along, factors influencing

pronounced topographic features, along 4-13 settlement and squat, and 4-69,4-704-13radiating 4-55simultaneous, by two instruments4-39rock heights, and small docks and piers, in,

4-9rocky coasts, and smooth sheet, and the 7-2recording of numbered 4-47Sounding Volumes

4-31—4-32positions along 4-52sources must be shown in recordsspacing of plotted4-10 7-11restricted areas, spacing in

shallow water, in 4-14 symbols, cartographic, tabulated B-4, B-54-10 4-32taken at highest speedside echoes' desirability, and4-34 transfer to field sheet 4-7sounding intervals, and4-32 7-11soundings taken at highest speed units and rounding

4-541-10, 4-9—4-10, 4-33spacing of units, changes to be noted in records4-70—4-804-32steering arcs, and velocity corrections, and

streams, and verification of 6-74-84-10—4-11systems of 4-39visible evidence of dangers during

4-8 Spacing of sounding lines 1-10, 4-9, 4-10tidal areas, in7-224-14vessel positioning, and Special projects and smooth sheets

4-13 1-19vessel steered along arc, from Special report (field report)4-1, 4-2, 4-105visual control 4-33 Special surveys

with S indicatorwind and current difficulties, and 4-13, 4-33 2-1—2-21-13, AF-3 Speed of sounding vesselSounding pole

4-33factors influencingSounding record, conversion of4-91reduced soundings on 4-11survey errors, causing

to be noted in records 4-56Sounding(s)5-22(see also Echo sounding(s); Sounding line(s)) Spire as a landmark

4-54 4-13accuracy and units used in Splits and sounding line spacing reduction4-8 1-11beaches, and Split lines, use of

1-12 B-3Spoil area, symbol forchange in vessel speed, and4-53 3-6comparison of equipment for Spur points, check on geomeric position of4-57completion of records of Squat and settlement, combined

4-69—4-704-74 effects ofcorrections, incremental, scaling of4-691-13, 1-14, 4-65—4-91 Squat, definition ofcorrections to5-224-41detached breakers, and Stack as a landmark

1-13digital B-2Stake, symbol forAK-74-65discrepancies dsovered in Standard tape gage

4-54 Standard conversion table C-1entry in recordsAF-1 Standardizations recorded in aequipment4-51records, entered in 4-53Sounding Volume1-13 1-3—1-4erroneous, reconciliation of Standards, general, hydrographic survey

5-22Standpipe as a landmark4-45errors, lists of4-35fathom as depth unit in Static draft

4-7 measurement of 4-69first operation, a4-1, 7-10 4-69variations inimportance of

Station control errors listed 4-45in hydrographic surveying, verticaldatum reference and 1-5 Stations

established by other organizations, use of4-40 3-2information sought from local persons5-134-34,4-85 list of, in Descriptive Reportintermediate

3-24-34, 4-34a, 4-34b marks and descriptionsinterval(s)4-34, 4-34a, 4-34b monumentedguidelines regarding 3-2

AC-2used in position-fixing systems4-34hydrographer responsible for determining

I-18