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CHAPTER 5

SHORT RANGE AIDS TO NAVIGATION

DEFINING SHORT RANGE AIDS TO NAVIGATION

500. Terms And Definitions

The term “short range aids to navigation” encompasseslighted and unlighted beacons, ranges, leading lights,buoys, and their associated sound signals. Each short rangeaid to navigation, commonly referred to as a NAVAID, fitswithin a system designed to warn the mariner of dangersand direct him toward safe water. An aid’s function deter-mines its color, shape, light characteristic, and sound. Thischapter explains the U.S. Aids to Navigation System aswell as the international IALA Maritime Buoyage System.

The placement and maintenance of marine aids to nav-igation in U.S. waters is the responsibility of the UnitedStates Coast Guard. The Coast Guard maintains lighthous-

es, radiobeacons, racons, Loran C, sound signals, buand daybeacons on the navigable waters of the UnStates, its territories, and possessions. Additionally, Coast Guard exercises control over privately owned nagation aid systems.

A beacon is a stationary, visual navigation aid. Larglighthouses and small single-pile structures are both bcons. Lighted beacons are called lights; unlighted beaconsare daybeacons. All beacons exhibit a daymark of somesort. In the case of a lighthouse, the color and type of strture are the daymarks. On small structures, these daymaconsisting of colored geometric shapes called dayboards,often have lateral significance. Conversely, the markinon lighthouses and towers convey no lateral significance

FIXED LIGHTS

501. Major And Minor Lights

Lights vary from tall, high intensity coastal lights tobattery-powered lanterns on single wooden piles. Immov-able, highly visible, and accurately charted, fixed lightsprovide navigators with an excellent source for bearings.The structures are often distinctively colored to aid in iden-tification. See Figure 501a.

A major light is a high-intensity light exhibited froma fixed structure or a marine site. Major lights include pri-mary seacoast lights and secondary lights. Primaryseacoast lights are those major lights established for mak-ing landfall from sea and coastwise passages from headlandto headland. Secondary lights are those major lights estab-lished at harbor entrances and other locations where highintensity and reliability are required.

A minor light usually displays a light of low to mod-erate intensity. Minor lights are established in harbors,along channels, rivers, and in isolated locations. They usu-ally have numbering, coloring, and light and soundcharacteristics that are part of the lateral system of buoyage.

Lighthouses are placed where they will be of most use:on prominent headlands, at harbor and port entrances, onisolated dangers, or at other points where mariners can bestuse them to fix their position. The lighthouse’s principalpurpose is to support a light at a considerable height abovethe water, thereby increasing its geographic range. Supportequipment is often housed near the tower.

With few exceptions, all major lights are operated atomatically. There are also many automatic lights smaller structures maintained by the Coast Guard or otattendants. Unmanned major lights may have emergegenerators and automatic monitoring equipment to increthe light’s reliability.

Light structures’ appearances vary. Lights in low-lyinareas usually are supported by tall towers; conversely, listructures on high cliffs may be relatively short. Howevits support tower is constructed, almost all lights are simlarly generated, focused, colored, and characterized.

Some major lights use modern rotating or flashinlights, but many older lights use Fresnel lenses. These lens-es consist of intricately patterned pieces of glass in a hebrass framework. Modern Fresnel-type lenses are cast fhigh-grade plastic; they are much smaller and lighter ththeir glass counterparts.

A buoyant beacon provides nearly the positional accuracy of a light in a place where a buoy would normally used. See Figure 501b. The buoyant beacon consists heavy sinker to which a pipe structure is tightly moored.buoyancy chamber near the surface supports the pipe. light, radar reflector, and other devices are located atoppipe above the surface of the water. The pipe with its buancy chamber tends to remain upright even in sevweather and heavy currents, providing a smaller watch cle than a buoy. The buoyant beacon is most useful alnarrow ship channels in relatively sheltered water.

63

64 SHORT RANGE AIDS TO NAVIGATION

502. Range Lights

Range lights are light pairs that indicate a specific lineof position when they are in line. The higher rear light isplaced behind the front light. When the mariner sees thelights vertically in line, he is on the range line. If the frontlight appears left of the rear light, the observer is to the rightof the rangeline; if the front appears to the right of the rear,the observer is left of the rangeline. Range lights are some-times equipped with high intensity lights for daylight use.These are effective for long channels in hazy conditionswhen dayboards might not be seen. The range light struc-tures are usually also equipped with dayboards for ordinarydaytime use. Some smaller ranges, primarily in the Intrac-oastal Waterway and other inland waters, have just thedayboards with no lights. See Figure 502.

To enhance the visibility of range lights, the CoastGuard has developed 15-foot long lighted tubes called lightpipes. They are mounted vertically, and the mariner seesthem as vertical bars of light distinct from background

lighting. Installation of light pipes is proceeding on severalrange markers throughout the country. The Coast Guard isalso experimenting with long range sodium lights for areasrequiring visibility greater than the light pipes can provide.

The output from a low pressure sodium light is almostentirely at one wavelength. This allows the use of an inex-pensive band-pass filter to make the light visible even duringthe daytime. This arrangement eliminates the need for highintensity lights with their large power requirements.

Range lights are usually white, red, or green. They displayvarious characteristics differentiating them from surroundinglights.

A directional light is a single light that projects a high in-tensity, special characteristic beam in a given direction. It isused in cases where a two-light range may not be practicable.A directional sector light is a directional light that emits twoor more colored beams. The beams have a precisely orientedboundary between them. A normal application of a sector lightwould show three colored sections: red, white, and green. The white sector would indicate that the vessel is on the

Figure 501a. Typical offshore light station.

Figure 501b. Typical design for a buoyant beacon.

SHORT RANGE AIDS TO NAVIGATION 65

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channel centerline; the green sector would indicate that thevessel is off the channel centerline in the direction of deepwater; and the red sector would indicate that the vessel isoff the centerline in the direction of shoal water.

503. Aeronautical Lights

Aeronautical lights may be the first lights observed atnight when approaching the coast. Those situated near thecoast and visible from sea are listed in the List of Lights.These lights are not listed in the Coast Guard Light List.They usually flash alternating white and green.

Aeronautical lights are sequenced geographically inthe List of Lights along with marine navigation lights. How-ever, since they are not maintained for marine navigation,they are subject to changes of which maritime authoritiesmay not be informed. These changes will be published inNotice to Airmen but perhaps not in Notice To Mariners.

504. Bridge Lights

Red, green, and white lights mark bridges across naviga-ble waters of the United States. Red lights mark piers and otherparts of the bridge. Red lights are also used on drawbridges toshow when they are in the closed position. Green lights markopen drawbridges and mark the centerline of navigable chan-nels through fixed bridges. The position will vary according tothe type of structure. Navigational lights on bridges in the U.S.are prescribed by Coast Guard regulations.

Infrequently-used bridges may be unlighted. In foreignwaters, the type and method of lighting may be different fromthose normally found in the United States. Drawbridges whichmust be opened to allow passage operate upon sound and lightsignals given by the vessel and acknowledged by the bridge.These required signals are detailed in the Code of Federal Reg-

ulations and the applicable Coast Pilot. Certain bridges mayalso be equipped with sound signals and radar reflectors.

505. Shore Lights

Shore lights usually have a shore-based power supply.Lights on pilings, such as those found in the Intracoastal Wa-terway, are battery powered. Solar panels may be installed toenhance the light’s power supply. The lights consist of a powsource, a flasher to determine the characteristic, a lamp cher to replace burned-out lamps, and a focusing lens.

Various types of rotating lights are in use. They do nhave flashers but remain continuously lit while a lens or flector rotates around the horizon.

The whole light system is carefully engineered to prvide the maximum amount of light to the mariner for thleast power use. Specially designed filaments and spegrades of materials are used in the light to withstand harsh marine environment.

The flasher electronically determines the characteritic by selectively interrupting the light’s power supplaccording to the chosen cycle.

The lamp changer consists of several sockets arrangearound a central hub. When the circuit is broken byburned-out filament, a new lamp is rotated into positioAlmost all lights have daylight switches which turn thlight off at sunrise and on at dusk.

The lens for small lights may be one of several typeThe common ones in use are omni-directional lenses155mm, 250mm, and 300mm. In addition, lights using pabolic mirrors or focused-beam lenses are used in leadlights and ranges. The lamp filaments must be carefualigned with the plane of the lens or mirror to provide thmaximum output of light. The lens’ size is chosen accordito the type of platform, power source, and lamp characte

Figure 502. Range lights.


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tics. Additionally, environmental characteristics of thelocation are considered. Various types of light-condensingpanels, reflex reflectors, or colored sector panels may be in-

stalled inside the lens to provide the proper characteristic.A special heavy 200mm lantern is used in locations

where ice and breaking water are a hazard.

LIGHT CHARACTERISTICS

506. Characteristics

A light has distinctive characteristics which distin-guish it from other lights or convey specific information. Alight may show a distinctive sequence of light and dark in-tervals. Additionally, a light may display a distinctive coloror color sequence. In the Light Lists, the dark intervals arereferred to as eclipses. An occulting light is a light totallyeclipsed at regular intervals, the duration of light always be-ing greater than the duration of darkness. A flashing lightis a light which flashes at regular intervals, the duration oflight always being less than the duration of darkness. Anisophase light flashes at regular intervals, the duration oflight being equal to the duration of darkness.

Light phase characteristics (Figure 506a and Figure506b) are the distinctive sequences of light and dark inter-vals or sequences in the variations of the luminous intensityof a light. The light phase characteristics of lights whichchange color do not differ from those of lights which do notchange color. A light showing different colors alternately isdescribed as an alternating light. The alternating character-istic may be used with other light phase characteristics.

Light-sensitive switches extinguish most lighted navi-gation aids during daylight hours. However, owing to thevarious sensitivity of the light switches, all lights do notcome on or go off at the same time. Mariners should ac-count for this when identifying aids to navigation duringtwilight periods when some lighted aids are on while othersare not.

507. Light Sectors

Sectors of colored glass or plastic are sometimesplaced in the lanterns of certain lights to indicate dangerouswaters. Lights so equipped show different colors when ob-served from different bearings. A sector changes the colorof a light, but not its characteristic, when viewed from cer-tain directions. For example, a four second flashing whitelight having a red sector will appear as a four second flash-ing red light when viewed from within the red sector.

Sectors may be only a few degrees in width or extendin a wide arc from deep water toward shore. Bearings refer-ring to sectors are expressed in degrees true as observedfrom a vessel.

In most cases, areas covered by red sectors should beavoided. The nature of the danger can be determined fromthe chart. In some cases a narrow sector may mark the bestwater across a shoal, or a turning point in a channel.

Sectors generated by shadow-casting filters do nothave precise boundaries as directional sector lights do.

Therefore, the transition from one color to another is notabrupt. The colors change through an arc of uncertainty of2° or greater, depending on the optical design of the light.Therefore determining bearings by observing the colorchange is less accurate than obtaining a bearing with an az-imuth circle.

508. Factors Affecting Range And Characteristics

The condition of the atmosphere has a considerable effectupon a light’s range. Sometimes lights are obscured by haze, dust, smoke, or precipitation. On the other hand, reftion may cause a light to be seen farther than under ordincircumstances. A light of low intensity will be easily obscureby unfavorable conditions of the atmosphere. For this reasthe intensity of a light should always be considered when loing for it in thick weather. Haze and distance may reduce apparent duration of a light’s flash. In some conditions of atmosphere, white lights may have a reddish hue. In cweather green lights may have a more whitish hue.

Lights placed at great elevations are more frequenobscured by clouds, mist, and fog than those near sea leIn regions where ice conditions prevail, an unattendlight’s lantern panes may become covered with ice or snThis may reduce the light’s luminous range and changelight’s observed color.

The distance from a light cannot be estimated by its ap-parent brightness. There are too many factors which change the perceived intensity. Also, a powerful, distalight may sometimes be confused with a smaller, closer owith similar characteristics. Every light sighted should bcarefully evaluated to determine if it is the one expected

The presence of bright shore lights may make it difcult to distinguish navigational lights from backgrounlighting. Lights may also be obscured by various shore structions, natural and man-made. The Coast Gurequests mariners to report these cases to the nearest CGuard station.

A light’s loom is seen through haze or the reflectiofrom low-lying clouds when the light is beyond its geographic range. Only the most powerful lights can genera loom. The loom may sometimes be sufficiently definedobtain a bearing. If not, an accurate bearing on a light yond geographic range may sometimes be obtainedascending to a higher level where the light can be seen,noting a star directly over the light. The bearing of the scan then be obtained from the navigating bridge and bearing to the light plotted indirectly.

At short distances, some of the brighter flashing lighmay show a faint continuous light, or faint flashes, betwe


Figure 506a. Light phase characteristics. = = = = = = THIS FIGURE HAS TO BE REPAIRED!! = = = = = =


Figure 506b. Light phase characteristics.


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regular flashes. This is due to reflections of a rotating lenson panes of glass in the lighthouse.

If a light is not sighted within a reasonable time afterprediction, a dangerous situation may exist. Conversely, thelight may simply be obscured or extinguished. The ship’sposition should immediately be fixed by other means to de-termine any possibility of danger.

The apparent characteristic of a complex light maychange with the distance of the observer. For example, alight with a characteristic of fixed white and alternatingflashing white and red may initially show as a simple flash-ing white light. As the vessel draws nearer, the red flashwill become visible and the characteristic will apparently bealternating flashing white and red. Later, the fainter fixedwhite light will be seen between the flashes and the truecharacteristic of the light finally recognized as fixed white,

alternating flashing white and red (F W Al W R). This is bcause for a given candlepower, white is the most visicolor, green less so, and red least of the three. This fact accounts for the different ranges given in the Light Lists some multi-color sector lights. The same lamp has differranges according to the color imparted by the sector gla

A light may be extinguished due to weather, batteryfailure, vandalism, or other causes. In the case of unatteed lights, this condition might not be immediatelcorrected. The mariner should report this condition to tnearest Coast Guard station. During periods of armed cflict, certain lights may be deliberately extinguishewithout notice.

Offshore light stations should always be left well othe course whenever searoom permits.

BUOYS

509. Definitions And Types

Buoys are floating aids to navigation. They mark chan-nels, indicate shoals and obstructions, and warn the marinerof dangers. Buoys are used where fixed aids would be un-economical or impractical due to the depth of water. Bytheir color, shape, topmark, number, and light characteris-tics, buoys indicate to the mariner how to avoid hazards andstay in safe water. The federal buoyage system in the U.S.is maintained by the Coast Guard.

There are many different sizes and types of buoys de-signed to meet a wide range of environmental conditionsand user requirements. The size of a buoy is determined pri-marily by its location. In general, the smallest buoy whichwill stand up to local weather and current conditions ischosen.

There are five types of buoys maintained by the CoastGuard. They are:

1. Lateral marks.2. Isolated danger marks.3. Safe water marks.4. Special marks.5. Information/regulatory marks.

These conform in general to the specifications of theInternational Association of Lighthouse Authorities(IALA) buoyage system.

A lighted buoy is a floating hull with a tower on whicha light is mounted. Batteries for the light are in watertightpockets in the buoy hull or in watertight boxes mounted onthe buoy hull. To keep the buoy in an upright position, acounterweight is attached to the hull below the water sur-face. A radar reflector is built into the buoy tower.

The largest of the typical U.S. Coast Guard buoys canbe moored in up to 190 feet of water, limited by the weightof chain the hull can support. The focal plane of the light is

15 to 20 feet high. The designed nominal visual range is miles, and the radar range 4 miles. Actual conditions wcause these range figures to vary considerably.

The smallest buoys are designed for protected waSome are made of plastic and weigh only 40 pounds. Scially designed buoys are used for fast current, ice, aother environmental conditions.

A variety of special purpose buoys are owned by othgovernmental organizations. Examples of these organtions include the Panama Canal Commission, the Lawrence Seaway Development Corporation, NOAA, athe Department of Defense. These buoys are usually ngational marks or data collection buoys with traditionround, boat-shaped, or discus-shaped hulls.

A special class of buoy, the Ocean Data Acquisition

Figure 509. Buoy showing counterweight.


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System (ODAS) buoy, is moored or floats free in offshorewaters. Positions are promulgated through radio warnings.These buoys are generally not large enough to cause dam-age in a collision, but should be given a wide berthregardless, as any loss would almost certainly result in theinterruption of valuable scientific experiments. They aregenerally bright orange or yellow in color, with verticalstripes on moored buoys and horizontal bands on free-float-ing ones, and have a strobe light for night visibility.

Even in clear weather, the danger of collision with abuoy exists. If struck head-on, a large buoy can inflict se-vere damage to a large ship; it can sink a smaller one.Reduced visibility or heavy background lighting can con-tribute to the problem. The Coast Guard sometimesreceives reports of buoys missing from station that were ac-tually run down and sunk. Tugboats and towboats towing orpushing barges are particularly dangerous to buoys becauseof poor over-the-bow visibility when pushing or yawingduring towing. The professional mariner must report anycollision with a buoy to the nearest Coast Guard unit. Fail-ure to do so may cause the next vessel to miss the channelor hit the obstruction marked by the buoy; it can also leadto fines and legal liability.

Routine on-station buoy maintenance consists of in-specting the mooring, cleaning the hull and superstructure,replacing the batteries, flasher, and lamps, checking wiringand venting systems, and verifying the buoy’s exact posi-tion. Every few years, each buoy is replaced by a similar aidand returned to a Coast Guard maintenance facility forcomplete refurbishment.

The placement of a buoy depends on its purpose and itsposition on the chart. Most buoys are placed on charted posi-tion as accurately as conditions allow. However, if a buoy’spurpose is to mark a shoal and the shoal is found to be in a dif-ferent position than the chart shows, the buoy will be placed toproperly mark the shoal, and not on its charted position.

510. Lights On Buoys

Buoy light systems consist of a battery pack, a flasherwhich determines the characteristic, a lamp changer whichautomatically replaces burned-out bulbs, a lens to focus thelight, and a housing which supports the lens and protectsthe electrical equipment.

The batteries consist of 12-volt lead/acid type batter-ies electrically connected to provide sufficient power to runthe proper flash characteristic and lamp size. These batterypacks are contained in pockets in the buoy hull, accessiblethrough water-tight bolted hatches or externally mountedboxes. Careful calculations based on light characteristicsdetermine how much battery power to install.

The flasher determines the characteristic of the lamp.It is installed in the housing supporting the lens.

The lamp changer consists of several sockets arrangedaround a central hub. A new lamp rotates into position if theactive one burns out.

Under normal conditions, the lenses used on buoys are155mm in diameter at the base. 200 mm lenses are uwhere breaking waves or swells call for the larger leThey are colored according to the charted characteristicthe buoy. As in shore lights, the lamp must be carefully cused so that the filament is directly in line with the focplane of the lens. This ensures that the majority of the liproduced is focused in a 360° horizontal fan beam A buoylight has a relatively narrow vertical profile. Because tbuoy rocks in the sea, the focal plane may only be visifor fractions of a second at great ranges. A realistic ranfor sighting buoy lights is 4-6 miles in good visibility.

511. Sound Signals On Buoys

Lighted sound buoys have the same general configution as lighted buoys but are equipped with either a bgong, whistle, or horn. Bells and gongs are sounded by tap-pers hanging from the tower that swing as the buoys rolthe sea. Bell buoys produce only one tone; gong buoys pduce several tones. The tone-producing device is mounbetween the legs of the pillar or tower.

Whistle buoys make a loud moaning sound causedthe rising and falling motions of the buoy in the sea. sound buoy equipped with an electronic horn will producea pure tone at regular intervals regardless of the sea sUnlighted sound buoys have the same general appearas lighted buoys, but their underwater shape is designemake them lively in all sea states.

512. Buoy Moorings

Buoys require moorings to hold them in position. Typ-ically the mooring consists of chain and a large concrete

Figure 512. A sinker used to anchor a buoy.


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or cast iron sinker. See Figure 512. Because buoys are sub-jected to waves, wind, and tides, the moorings must bedeployed with chain lengths much greater than the waterdepth. The scope of chain will normally be about 3 timesthe water depth. The length of the mooring chain defines awatch circle within which the buoy can be expected toswing. It is for this reason that the charted buoy symbol hasa “position approximate” circle to indicate its charted posi-tion, whereas a light position is shown by a dot at the exactlocation. Actual watch circles do not necessarily coincidewith the “position approximate” circles which representthem.

Over several years, the chain gradually wears out andmust be replaced with new. The worn chain is often castinto the concrete of new sinkers.

513. Large Navigational Buoys

Large navigational buoys are moored in open waterat approaches to major seacoast ports. These 40-foot diam-eter buoys (Figure 513) show lights from heights of about

36 feet above the water. Emergency lights automaticaenergize if the main light is extinguished. These buoys malso have a radiobeacon and sound signals. Their condis monitored by radio from shore.

514. Wreck Buoys

A wreck buoy usually cannot be placed directly ovethe wreck it is intended to mark because the buoy tenmay not want to pass over a shallow wreck or risk foulithe buoy mooring. For this reason, a wreck buoy is usuaplaced as closely as possible on the seaward or channelside of a wreck. In some situations, two buoys may be uto mark the wreck, one lying off each end. The wreck mlie directly between them or inshore of a line between thedepending on the local situation. The Local Notice To Mar-iners should be consulted concerning details of thplacement of wreck buoys on individual wrecks. Oftenwill also give particulars of the wreck and what activitiemay be in progress to clear it.

Figure 513. Large navigational buoy.


The charted position of a wreck buoy will usually beoffset from the actual geographic position so that the wreckand buoy symbols do not coincide. Only on the largest scalechart will the actual and charted positions of both wreck andbuoy be the same. Where they might overlap, it is the wrecksymbol which occupies the exact charted position and thebuoy symbol which is offset.

Wreck buoys are required to be placed by the owner ofthe wreck, but they may be placed by the Coast Guard if theowner is unable to comply with this requirement. In gener-al, privately placed aids are not as reliable as Coast Guardaids.

Sunken wrecks are sometimes moved away from theirbuoys by storms, currents, freshets, or other causes. Just asshoals may shift away from the buoys placed to mark them,wrecks may shift away from wreck buoys.

515. Fallibility Of Buoys

Buoys cannot be relied on to maintain their charted po-sitions consistently. They are subject to a variety of hazardsincluding severe weather, collision, mooring casualties, andelectrical failure. Report any discrepancy noted in a buoy tothe U.S. Coast Guard.

The buoy symbol shown on charts indicates the ap-

proximate position of the sinker which secures the buoy tothe seabed. The approximate position is used because ofpractical limitations in placing and keeping buoys and theirsinkers in precise geographical locations. These limitationsinclude prevailing atmospheric and sea conditions, theslope and type of material making up the seabed, the scopeof the mooring chain, and the fact that the positions of thebuoys and the sinkers are not under continuous surveil-lance. The position of the buoy shifts around the area shownby the chart symbol due to the forces of wind and current.

A buoy may not be in its charted position because ofchanges in the feature it marks. For example, a buoy meantto mark a shoal whose boundaries are shifting might fre-quently be moved to mark the shoal accurately. A LocalNotice To Mariners will report the change, and a Notice ToMariners chart correction may also be written. In somesmall channels which change often, buoys are not chartedeven when considered permanent; local knowledge is ad-vised in such areas.

For these reasons, a mariner must not rely completelyupon the position or operation of buoys, but should navigateusing bearings of charted features, structures, and aids tonavigation on shore. Further, a vessel attempting to pass tooclose aboard a buoy risks a collision with the buoy or theobstruction it marks.

BUOYAGE SYSTEMS

516. Lateral And Cardinal Systems

There are two major types of buoyage systems: thelateral system and the cardinal system. The lateral sys-tem is best suited for well-defined channels. Thedescription of each buoy indicates the direction of dangerrelative to the course which is normally followed. In prin-ciple, the positions of marks in the lateral system aredetermined by the general direction taken by the marinerwhen approaching port from seaward. These positionsmay also be determined with reference to the main streamof flood current. The United States Aids to NavigationSystem is a lateral system.

The cardinal system is best suited for coasts with nu-merous isolated rocks, shoals, and islands, and for dangersin the open sea. The characteristic of each buoy indicatesthe approximate true bearing of the danger it marks. Thus,an eastern quadrant buoy marks a danger which lies to thewest of the buoy. The following pages diagram the cardinaland lateral buoyage systems as found outside the UnitedStates.

517. The IALA Maritime Buoyage System

Although most of the major maritime nations haveused either the lateral or the cardinal system for many years,details such as the buoy shapes and colors have varied fromcountry to country. With the increase in maritime com-

merce between countries, the need for a uniform system ofbuoyage became apparent.

In 1889, an International Marine Conference held inWashington, D.C., recommended that in the lateral system,starboard hand buoys be painted red and port hand buoysblack. Unfortunately, when lights for buoys were intro-duced some years later, some European countries placedred lights on the black port hand buoys to conform with thered lights marking the port side of harbor entrances, whilein North America red lights were placed on red starboardhand buoys. In 1936, a League of Nations subcommitteerecommended a coloring system opposite to the 1889proposal.

The International Association of Lighthouse Au-thorities (IALA) is a non-governmental organizationwhich consists of representatives of the worldwide commu-nity of aids to navigation services to promote informationexchange and recommend improvements based on newtechnologies. In 1980, with the assistance of IMO and theIHO, the lighthouse authorities from 50 countries and rep-resentatives of 9 international organizations concerned withaids to navigation met and adopted the IALA MaritimeBuoyage System. They established two regions, Region Aand Region B, for the entire world. Region A roughly cor-responds to the 1936 League of Nations system, and RegionB to the older 1889 system.

Lateral marks differ between Regions A and B. Lateralmarks in Region A use red and green colors by day and night


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to indicate port and starboard sides of channels, respectively.In Region B, these colors are reversed with red to starboardand green to port. In both systems, the conventional directionof buoyage is considered to be returning from sea, hence thephrase “red right returning” in IALA region B.

518. Types Of Marks

The IALA Maritime Buoyage System applies to allfixed and floating marks, other than lighthouses, sectorlights, leading lights and daymarks, lightships and largenavigational buoys, and indicates:

1. The side and center-lines of navigable channels.2. Natural dangers, wrecks, and other obstructions.3. Regulated navigation areas.4. Other important features.

Most lighted and unlighted beacons other than leadingmarks are included in the system. In general, beacon top-marks will have the same shape and colors as those used onbuoys. The system provides five types of marks which maybe used in any combination:

1. Lateral marks indicate port and starboard sides ofchannels.

2. Cardinal marks, named according to the four pointsof the compass, indicate that the navigable waterlies to the named side of the mark.

3. Isolated danger marks erected on, or moored direct-ly on or over, dangers of limited extent.

4. Safe water marks, such as midchannel buoys.5. Special marks, the purpose of which is apparent from

reference to the chart or other nautical documents.

Characteristics Of Marks

The significance of a mark depends on one or morefeatures:

1. By day—color, shape, and topmark.2. By night—light color and phase characteristics.

Colors Of Marks

The colors red and green are reserved for lateral marks,and yellow for special marks. The other types of markshave black and yellow or black and red horizontal bands, orred and white vertical stripes.

Shapes Of Marks

There are five basic buoy shapes:

1. Can.2. Cone.

3. Sphere.4. Pillar.5. Spar.

In the case of can, conical, and spherical, the shahave lateral significance because the shape indicatescorrect side to pass. With pillar and spar buoys, the shhas no special significance.

The term “pillar” is used to describe any buoy which smaller than a “large navigation buoy (LNB)” and which ha tall, central structure on a broad base; it includes beabuoys, high focal plane buoys, and others (except spar buwhose body shape does not indicate the correct side to p

Topmarks

The IALA System makes use of can, conical, spheri-cal, and X-shaped topmarks only. Topmarks on pillar andspar buoys are particularly important and will be uswherever practicable, but ice or other severe conditiomay occasionally prevent their use.

Colors Of Lights

Where marks are lighted, red and green lights are served for lateral marks, and yellow for special marks. Tother types of marks have a white light, distinguished ofrom another by phase characteristic.

Phase Characteristics Of Lights

Red and green lights may have any phase charactetic, as the color alone is sufficient to show on which sithey should be passed. Special marks, when lighted, hayellow light with any phase characteristic not reserved white lights of the system. The other types of marks haclearly specified phase characteristics of white light: vaous quick-flashing phase characteristics for cardinal margroup flashing (2) for isolated danger marks, and relativelong periods of light for safe water marks.

Some shore lights specifically excluded from the IALSystem may coincidentally have characteristics correspoing to those approved for use with the new marks. Careneeded to ensure that such lights are not misinterpreted

519. IALA Lateral Marks

Lateral marks are generally used for well-definedchannels; they indicate the port and starboard hand sidethe route to be followed, and are used in conjunction witconventional direction of buoyage.

This direction is defined in one of two ways:

1. Local direction of buoyage is the direction takenby the mariner when approaching a harbor, river etuary, or other waterway from seaward.


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2. General direction of buoyage is determined bythe buoyage authorities, following a clockwise di-rection around continental land-masses, given insailing directions, and, if necessary, indicated oncharts by a large open arrow symbol.

In some places, particularly straits open at both ends,the local direction of buoyage may be overridden by thegeneral direction.

Along the coasts of the United States, the characteris-tics assume that proceeding “from seaward” constitutes aclockwise direction: a southerly direction along the Atlanticcoast, a westerly direction along the Gulf of Mexico coast,and a northerly direction along the Pacific coast. On theGreat Lakes, a westerly and northerly direction is taken asbeing “from seaward” (except on Lake Michigan, where asoutherly direction is used). On the Mississippi and OhioRivers and their tributaries, the characteristics of aids tonavigation are determined as proceeding from sea towardthe head of navigation. On the Intracoastal Waterway, pro-ceeding in a generally southerly direction along the Atlanticcoast, and in a generally westerly direction along the gulfcoast, is considered as proceeding “from seaward.”

520. IALA Cardinal Marks

A cardinal mark is used in conjunction with the com-pass to indicate where the mariner may find the bestnavigable water. It is placed in one of the four quadrants(north, east, south, and west), bounded by the true bearingsNW-NE, NE-SE, SE-SW, and SW-NW, taken from thepoint of interest. A cardinal mark takes its name from thequadrant in which it is placed.

The mariner is safe if he passes north of a north mark,east of an east mark, south of a south mark, and west of awest mark.

A cardinal mark may be used to:

1. Indicate that the deepest water in an area is on thenamed side of the mark.

2. Indicate the safe side on which to pass a danger.3. Emphasize a feature in a channel, such as a bend,

junction, bifurcation, or end of a shoal.

Topmarks

Black double-cone topmarks are the most importantfeature, by day, of cardinal marks. The cones are verticallyplaced, one over the other. The arrangement of the cones isvery logical: North is two cones with their points up (as in“north-up”). South is two cones, points down. East is twocones with bases together, and west is two cones withpoints together, which gives a wineglass shape. “West is aWineglass” is a memory aid.

Cardinal marks carry topmarks whenever practicable,with the cones as large as possible and clearly separated.

Colors

Black and yellow horizontal bands are used to colocardinal mark. The position of the black band, or bandsrelated to the points of the black topmarks.

Shape

The shape of a cardinal mark is not significant, bbuoys must be pillars or spars.

Lights

When lighted, a cardinal mark exhibits a white light; icharacteristics are based on a group of quick or very quflashes which distinguish it as a cardinal mark and indicits quadrant. The distinguishing quick or very quick flashare:

North—UninterruptedEast—three flashes in a groupSouth—six flashes in a group followed by a long flasWest—nine flashes in a group

As a memory aid, the number of flashes in each grocan be associated with a clock face as follows:

(3 o’clock—E, 6 o’clock—S, and 9 o’clock—W).

The long flash (of not less than 2 seconds duratioimmediately following the group of flashes of a south cadinal mark, is to ensure that its six flashes cannot mistaken for three or nine.

The periods of the east, south, and west lights are,spectively, 10, 15, and 15 seconds if quick flashing; and10, and 10 seconds if very quick flashing.

Quick flashing lights flash at a rate between 50 and flashes per minute, usually either 50 or 60. Very quiflashing lights flash at a rate between 80 and 159 flashesminute, usually either 100 or 120.

It is necessary to have a choice of quick flashing very quick flashing lights in order to avoid confusion if, foexample, two north buoys are placed near enough to eother for one to be mistaken for the other.

521. IALA Isolated Danger Marks

An isolated danger mark is erected on, or moored onor above, an isolated danger of limited extent which hnavigable water all around it. The extent of the surroundnavigable water is immaterial; such a mark can, for exaple, indicate either a shoal which is well offshore or an isseparated by a narrow channel from the coast.

N Points up Black above yellow.S Points down Black below yellow.W Points together Black, yellow above and below.E Points apart Yellow, black above and below.


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Position

On a chart, the position of a danger is the center of thesymbol or sounding indicating that danger; an isolated dan-ger buoy may therefore be slightly displaced from itsgeographic position to avoid overprinting the two symbols.The smaller the scale, the greater this offset will be. At verylarge scales the symbol may be correctly charted.

Topmark

A black double-sphere topmark is, by day, the most im-portant feature of an isolated danger mark. Wheneverpracticable, this topmark will be carried with the spheres aslarge as possible, disposed vertically, and clearly separated.

Color

Black with one or more red horizontal bands are thecolors used for isolated danger marks.

Shape

The shape of an isolated danger mark is not significant,but a buoy will be a pillar or a spar.

Light

When lighted, a white flashing light showing a groupof two flashes is used to denote an isolated danger mark. Asa memory aid, associate two flashes with two balls in thetopmark.

522. IALA Safe Water Marks

A safe water mark is used to indicate that there is nav-igable water all around the mark. Such a mark may be usedas a center line, mid-channel, or landfall buoy.

Color

Red and white vertical stripes are used for safe watermarks, and distinguish them from the black-banded, dan-ger-marking marks.

Shape

Spherical, pillar, or spar buoys may be used as safe wa-ter marks.

Topmark

A single red spherical topmark will be carried, when-ever practicable, by a pillar or spar buoy used as a safewater mark.

Lights

When lighted, safe water marks exhibit a white light.This light can be occulting, isophase, a single long flash, orMorse “A.” If a long flash (i.e. a flash of not less than 2 seonds) is used, the period of the light will be 10 seconds.a memory aid, remember a single flash and a single sphtopmark.

523. IALA Special Marks

A special mark may be used to indicate a special aror feature which is apparent by referring to a chart, sailidirections, or notices to mariners. Uses include:

1. Ocean Data Acquisition System (ODAS) buoys.2. Traffic separation marks.3. Spoil ground marks.4. Military exercise zone marks.5. Cable or pipeline marks, including outfall pipes.6. Recreation zone marks.

Another function of a special mark is to define a chanel within a channel. For example, a channel for deep dvessels in a wide estuary, where the limits of the chanfor normal navigation are marked by red and green latebuoys, may have its boundaries or centerline markedyellow buoys of the appropriate lateral shapes.

Color

Yellow is the color used for special marks.

Shape

The shape of a special mark is optional, but must conflict with that used for a lateral or a safe water mark. Fexample, an outfall buoy on the port hand side of a chancould be can-shaped but not conical.

Topmark

When a topmark is carried it takes the form of a singyellow X.

Lights

When a light is exhibited it is yellow. It may show anphase characteristic except those used for the white lightcardinal, isolated danger, and safe water marks, In the cof ODAS buoys, the phase characteristic used is groflashing with a group of five flashes every 20 seconds.

524. IALA New Dangers

A newly discovered hazard to navigation not yet show


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on charts, included in sailing directions, or announced by aNotice To Mariners is termed a new danger. The term cov-ers naturally occurring and man-made obstructions.

Marking

A new danger is marked by one or more cardinal or lat-eral marks in accordance with the IALA system rules. If thedanger is especially grave, at least one of the marks will beduplicated as soon as practicable by an identical mark untilthe danger has been sufficiently identified.

Lights

If a lighted mark is used for a new danger, it must ex-hibit a quick flashing or very quick flashing light. If acardinal mark is used, it must exhibit a white light; if a lat-eral mark, a red or green light.

Racons

The duplicate mark may carry a Racon, Morse codedD, showing a signal length of 1 nautical mile on a radardisplay.

525. Chart Symbols And Abbreviations

Spar buoys and spindle buoys are represented by thesame symbol; it is slanted to distinguish them from up-right beacon symbols. The abbreviated description of thecolor of a buoy is given under the symbol. Where a buoyis colored in bands, the colors are indicated in sequencefrom the top. If the sequence of the bands is not known, orif the buoy is striped, the colors are indicated with thedarker color first.

Topmarks

Topmark symbols are solid black except when the top-mark is red.

Lights

The period of the light of a cardinal mark is determinedby its quadrant and its flash characteristic (either quick-flashing or a very quick-flashing). The light’s period is lessimportant than its phase characteristic. Where space oncharts is limited, the period may be omitted.

Light flares

Magenta light-flares are normally slanted and insertedwith their points adjacent to the position circles at the baseof the symbols so the flare symbols do not obscure the top-mark symbols.

Radar Reflectors

Radar reflectors are not affected by the IALA buoyarules. They are not charted for several reasons. It can besumed that most major buoys are fitted with radar reflectoris also necessary to reduce the size and complexity of bsymbols and associated legends. Finally, it is understood in the case of cardinal buoys, buoyage authorities site theflector so that it cannot be mistaken for a topmark. For threasons, radar reflectors are not charted under IALA rules

The symbols and abbreviations of the IALA MaritimBuoyage System may be found in U.S.. Chart No. 1, NautChart Symbols and Abbreviations, and in foreign equivalen

526. Description Of The U.S. Aids to Navigation System

In the United States, the U.S. Coast Guard has incorrated the major features of the IALA system with the existiinfrastructure of buoys and lights as explained below.

Colors

Under this system, green buoys mark a channel’s pside and obstructions which must be passed by keepingbuoy on the port hand. Red buoys mark a channel’s sboard side and obstructions which must be passedkeeping the buoy on the starboard hand.

Red and green horizontally banded preferred channelbuoys mark junctions or bifurcations in a channel or ostructions which may be passed on either side. If topmost band is green, the preferred channel will be flowed by keeping the buoy on the port hand. If the topmband is red, the preferred channel will be followed by keeing the buoy on the starboard hand.

Red and white vertically striped safe water buoys maa fairway or mid-channel.

Reflective material is placed on buoys to assist in thdetection at night with a searchlight. The color of the refletive material agrees with the buoy color. Red or grereflective material may be placed on preferred chan(junction) buoys; red if topmost band is red or green if ttopmost band is green. White reflective material is usedsafe water buoys. Special purpose buoys display yellowflective material. Warning or regulatory buoys displaorange reflective horizontal bands and a warning symbIntracoastal Waterway buoys display a yellow reflectivsquare, triangle, or horizontal strip along with the reflectimaterial coincident with the buoy’s function.

Shapes

Certain unlighted buoys are differentiated by shape. Rbuoys and red and green horizontally banded buoys withtopmost band red are cone-shaped buoys called nuns. Greenbuoys and green and red horizontally banded buoys withtopmost band green are cylinder-shaped buoys called cans.


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Unlighted red and white vertically striped buoys may bepillar shaped or spherical. Lighted buoys, sound buoys, and sparbuoys are not differentiated by shape to indicate the side onwhich they should be passed. Their purpose is indicated not byshape but by the color, number, or light characteristics.

Numbers

All solid colored buoys are numbered, red buoys bear-ing even numbers and green buoys bearing odd numbers.(Note that this same rule applies in IALA System A also.)The numbers increase from seaward upstream or towardland. No other colored buoys are numbered; however, anybuoy may have a letter for identification.

Light colors

Red lights are used only on red buoys or red and greenhorizontally banded buoys with the topmost band red. Greenlights are used only on the green buoys or green and red hor-izontally banded buoys with the topmost band green. Whitelights are used on both “safe water” aids showing a Morse Acharacteristic and on Information and Regulatory aids.

Light Characteristics

Lights on red buoys or green buoys, if not occulting orisophase, will generally be regularly flashing (Fl). For ordi-nary purposes, the frequency of flashes will be not morethan 50 flashes per minute. Lights with a distinct cautionarysignificance, such as at sharp turns or marking dangerous

obstructions, will flash not less than 50 flashes but not mthan 80 flashes per minute (quick flashing, Q). Lights preferred channel buoys will show a series of groupflashes with successive groups in a period having differnumber of flashes—composite group flashing (or a quilight in which the sequence of flashes is interrupted by reularly repeated eclipses of constant and long duratioLights on safe water buoys will always show a white MorCode “A” (Short-Long) flash recurring at the rate of approximately eight times per minute.

Daylight Controls

Lighted buoys have a special device to energize light when darkness falls and to de-energize the light whday breaks. These devices are not of equal sensitivtherefore all lights do not come on or go off at the samtime. Mariners should ensure correct identification of aiduring twilight periods when some light aids to navigatioare on while others are not.

Special Purpose Buoys

Buoys for special purposes are colored yellow. Whbuoys with orange bands are for information or regulatopurposes. The shape of special purpose buoys has no siicance. They are not numbered, but they may be letterelighted, special purpose buoys display a yellow light usuly with fixed or slow flash characteristics. Information anregulatory buoys, if lighted, display white lights.

BEACONS

527. Definition And Description

Beacons are fixed aids to navigation placed on shore oron pilings in relatively shallow water. If unlighted, the bea-con is referred to as a daybeacon. A daybeacon is identifiedby its color and the color, shape, and number of its day-board. The simplest form of daybeacon consists of a singlepile with a dayboard affixed at or near its top. See Figure527. Daybeacons may be used to form an unlighted range.

Dayboards identify aids to navigation against daylightbackgrounds. The size of the dayboard required to make theaid conspicuous depends upon the aid’s intended range.

Most dayboards also display numbers or letters foridentification. The numbers, letters, and borders of mostdayboards have reflective tape to make them visible atnight.

The detection, recognition, and identification distancesvary widely for any particular dayboard. They depend uponthe luminance of the dayboard, the sun’s position, and thelocal visibility conditions. Figure 527. Daybeacon.


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SOUND SIGNALS

528. Types Of Sound Signals

Most lighthouses and offshore light platforms, as wellas some minor light structures and buoys, are equipped withsound-producing devices to help the mariner in periods oflow visibility. Charts and Light Lists contain the informa-tion required for positive identification. Buoys fitted withbells, gongs, or whistles actuated by wave motion may pro-duce no sound when the sea is calm. Sound signals are notdesigned to identify the buoy or beacon for navigation pur-poses. Rather, they allow the mariner to pass clear of thebuoy or beacon during low visibility.

Sound signals vary. The navigator must use theLight List to determine the exact length of each blast andsilent interval. The various types of sound signals alsodiffer in tone, facilitating recognition of the respectivestations.

Diaphones produce sound with a slotted piston movedback and forth by compressed air. Blasts may consist of ahigh and low tone. These alternate-pitch signals are called“two-tone.” Diaphones are not used by the Coast Guard, butthe mariner may find them on some private navigation aids.

Horns produce sound by means of a disc diaphragmoperated pneumatically or electrically. Duplex or triplexhorn units of differing pitch produce a chime signal.

Sirens produce sound with either a disc or a cup-shaped rotor actuated electrically or pneumatically. Sirensare not used on U.S. navigation aids.

Whistles use compressed air emitted through a circum-ferential slot into a cylindrical bell chamber.

Bells and gongs are sounded with a mechanically oper-ated hammer.

529. Limitations Of Sound Signals

As aids to navigation, sound signals have serious limi-tations because sound travels through the air in anunpredictable manner.

It has been clearly established that:

1. Sound signals are heard at greatly varying distancesand that the distance at which a sound signal can beheard may vary with the bearing and timing of thesignal.

2. Under certain atmospheric conditions, when sound signal has a combination high and low tonit is not unusual for one of the tones to be inaudibIn the case of sirens, which produce a varying tonportions of the signal may not be heard.

3. When the sound is screened by an obstructithere are areas where it is inaudible.

4. Operators may not activate a remotely controllsound aid for a condition unobserved from the cotrolling station.

5. Some sound signals cannot be immediately start6. The status of the vessel’s engines and the loca

of the observer both affect the effective range of taid.

These considerations justify the utmost caution whnavigating near land in a fog. A navigator can never reon sound signals alone; he should continuously man bthe radar and fathometer. He should place lookouts in sitions where the noises in the ship are least likelyinterfere with hearing a sound signal. The aid upon wha sound signal rests is usually a good radar target, but lision with the aid or the danger it marks is alwayspossibility.

Emergency signals are sounded at some of the light fog signal stations when the main and stand-by sound nals are inoperative. Some of these emergency sosignals are of a different type and characteristic than main sound signal. The characteristics of the emergesound signals are listed in the Light List.

The mariner should never assume:

1. That he is out of ordinary hearing distance becausefails to hear the sound signal.

2. That because he hears a sound signal faintly, he isfrom it.

3. That because he hears it clearly, he is near it.4. That the distance from and the intensity of a sound

any one occasion is a guide for any future occasion.5. That the sound signal is not sounding because he d

not hear it, even when in close proximity.6. That the sound signal is in the direction the sound

pears to come from.

MISCELLANEOUS U.S. SYSTEMS

530. Intracoastal Waterway Aids To Navigation

The Intracoastal Waterway (ICW) runs parallel to theAtlantic and Gulf of Mexico coasts from Manasquan Inlet onthe New Jersey shore to the Texas/Mexican border. It follows

rivers, sloughs, estuaries, tidal channels, and other natwaterways, connected with dredged channels where nesary. Some of the aids marking these waters are marked yellow; otherwise, the marking of buoys and beacons follothe same system as that in other U.S. waterways.


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Yellow symbols indicate that an aid marks the Intrac-oastal Waterway. Yellow triangles indicate starboard handaids, and yellow squares indicate port hand aids when fol-lowing the ICW’s conventional direction of buoyage. Non-lateral aids such as safe water, isolated danger, and frontrange boards are marked with a horizontal yellow band.Rear range boards do not display the yellow band. At ajunction with a federally-maintained waterway, the pre-ferred channel mark will display a yellow triangle or squareas appropriate. Junctions between the ICW and privatelymaintained waterways are not marked with preferred chan-nel buoys.

531. Western Rivers System

Aids to navigation on the Mississippi River and its trib-utaries above Baton Rouge generally conform to the lateralsystem of buoyage in use in the rest of the U.S. The follow-ing differences are significant:

1. Buoys are not numbered.2. The numbers on lights and daybeacons do not have

lateral significance; they indicate the mileage froma designated point, normally the river mouth.

3. Flashing lights on the left side proceeding upstreamshow single green or white flashes while those onthe right side show group flashing red or whiteflashes.

4. Diamond shaped crossing daymarks are used to in-dicate where the channel crosses from one side ofthe river to the other.

532. The Uniform State Waterway Marking System (USWMS)

This system was developed jointly by the U.S. CoastGuard and state boating administrators to assist the smallcraft operator in those state waters marked by participatingstates. The USWMS consists of two categories of aids tonavigation. The first is a system of aids to navigation, gen-erally compatible with the Federal lateral system ofbuoyage, supplementing the federal system in state waters.The other is a system of regulatory markers to warn smallcraft operator of dangers or to provide general information.

On a well-defined channel, red and black buoys are estab-lished in pairs called gates; the channel lies between the buoys.The buoy which marks the left side of the channel viewedlooking upstream or toward the head of navigation is black; thebuoy which marks the right side of the channel is red.

In an irregularly-defined channel, buoys may be stag-gered on alternate sides of the channel, but they are spacedat sufficiently close intervals to mark clearly the channel ly-ing between them.

When there is no well-defined channel or when a bodyof water is obstructed by objects whose nature or location issuch that the obstruction can be approached by a vessel

from more than one direction, aids to navigation having cdinal significance may be used. The aids conforming to cardinal system consist of three distinctly colored buoys

1. A white buoy with a red top must be passed to tsouth or west of the buoy.

2. A white buoy with a black top must be passed to tnorth or east of the buoy.

3. A buoy showing alternate vertical red and whistripes indicates that an obstruction to navigatiextends from the nearest shore to the buoy and he must not pass between the buoy and the neashore.

The shape of buoys has no significance under USWMS.

Regulatory buoys are colored white with orange hoizontal bands completely around them. One band is attop of the buoy and a second band just above the waline of the buoy so that both orange bands are cleavisible.

Geometric shapes colored orange are placed on white portion of the buoy body. The authorized geometshapes and meanings associated with them are as follo

1. A vertical open faced diamond shape meadanger.

2. A vertical open faced diamond shape with a crocentered in the diamond means that vessels arecluded from the marked area.

3. A circular shape means that vessels in the markarea are subject to certain operating restrictions.

4. A square or rectangular shape indicates that dirtions or information is written inside the shape.

Regulatory markers consist of square and rectangushaped signs displayed from fixed structures. Each sigwhite with an orange border. Geometric shapes with same meanings as those displayed on buoys are centerethe sign boards. The geometric shape displayed on a relatory marker tells the mariner if he should stay well cleof the marker or if he may approach the marker in orderread directions.

533. Private Aids To Navigation

A private navigation aid is any aid established andmaintained by entities other than the Coast Guard.

The Coast Guard must approve the placement of pvate navigation aids. In addition, the District Engineer, U.Army Corps of Engineers, must approve the placementany structure, including aids to navigation, in the navigabwaters of the U.S.

Private aids to navigation are similar to the aids estalished and maintained by the U.S. Coast Guard; they specially designated on the chart and in the Light List.


some cases, particularly on large commercial structures, theaids are the same type of equipment used by the CoastGuard. Although the Coast Guard periodically inspectssome private navigation aids, the mariner should exercisespecial caution when using them.

In addition to private aids to navigation, numeroustypes of construction and anchor buoys are used in variousoil drilling operations and marine construction. Thesebuoys are not charted, as they are temporary, and may notbe lighted well or at all. Mariners should give a wide berthto drilling and construction sites to avoid the possibility offouling moorings. This is a particular danger in offshore oil

fields, where large anchors are often used to stabilize thepositions of drill rigs in deep water. Up to eight anchorsmay be placed at various positions as much as a mile fromthe drill ship. These may or may not be marked by buoys.

534. Protection By Law

It is unlawful to impair the usefulness of any naviga-tion aid established and maintained by the United States. Ifany vessel collides with an navigation aid, it is the legalduty of the person in charge of the vessel to report the acci-dent to the nearest U.S. Coast Guard station.

Chapter 5Short Range Aids to NavigationDefining Short Range Aids to Navigation500 . Terms And Definitions

Fixed Lights501 . Major And Minor LightsFigure 501a . Typical offshore light station.Figure 501b . Typical design for a buoyant beacon.

502 . Range Lights503 . Aeronautical Lights504 . Bridge Lights505 . Shore Lights

Light Characteristics506 . Characteristics507 . Light Sectors508 . Factors Affecting Range And Characteristics

Buoys509 . Definitions And Types510 . Lights On Buoys511 . Sound Signals On Buoys512 . Buoy Moorings513 . Large Navigational Buoys514 . Wreck Buoys515 . Fallibility Of Buoys

Buoyage Systems516 . Lateral And Cardinal Systems517 . The IALA Maritime Buoyage System518 . Types Of Marks519 . IALA Lateral Marks520 . IALA Cardinal MarksTopmarksColorsLights

521 . IALA Isolated Danger MarksPositionTopmarkColorShapeLight

522 . IALA Safe Water MarksColorShapeTopmarkLights

523 . IALA Special MarksColorShapeTopmarkLights

524 . IALA New DangersMarkingLightsRacons

525 . Chart Symbols And AbbreviationsTopmarksLightsLight flaresRadar Reflectors

526 . Description Of The U.S. Aids to Navigation S...ShapesNumbersLight colorsLight CharacteristicsDaylight ControlsSpecial Purpose Buoys

Beacons527 . Definition And Description

Sound Signals528 . Types Of Sound Signals529 . Limitations Of Sound Signals

Miscellaneous U.S. Systems530 . Intracoastal Waterway Aids To Navigation531 . Western Rivers System532 . The Uniform State Waterway Marking System (U...533 . Private Aids To Navigation534 . Protection By Law

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