2 – 4 o c t o b r e 2 0 0 6 o h i machc seminar - acapulco hydrographic surveys « instrumentation...

O H I MACHC Seminar - Acapulco 2 – 4 O c t o b r e 2 0 0 6

Hydrographic surveys

« Instrumentation and methodology »

Serge Allain - SHOM

2 - 4 O c t o b er 2 0 0 6O H I MACHC Seminar – Acapulco

Strategy adopted for a survey depends on objective…

Several criteria :

- reconnaissance surveys

- systematic coastal surveys

- traffic lanes

- searches for wrecks

- type of survey: topography, landmarks, currents, bathymétry

What users?

What draughts?

Navigation threshold?

Ocean bottom changes?

Knowledge a priori?


An example : strategy for bathymetric surveys by SHOM hydrographic vessel (1100T)

140+ standardizing documents, guides, procedures, user manuals

for hydrographic surveys

S-44



The strategy adopted a survey depends on the means actually available…

Several criteria:

- platforms (launches, vessels)

- instruments, sensors (calibrated)

- logistics (vehicles, radiocom., maintenance),

- and… IHO trained, qualified, certified personnel!



The strategy adopted for a survey depends on the means actually available…

Objectives + Means + Duration + Hazards (weather, frequency of breakdowns of equipment, obstructions, etc.)

Optimization

Organization

Methods


The various phases

Preparatory Work

Execution

Monitor time actually spent onshore or at sea

Data processing ashore (UKHO)


Preparatory work (1/2)

Positioning

geodetic systems, search for geodetic points, GPS targets, radiopositioning, interference, masks, projections

Tide

measurements of water height, models available for reduction of soundings offshore, observatories

Sound velocity depending on the zone, the depth


Preparatory Work (2/2)

Exploitation of existing documents

charts, fair sheets, local guides, sailing directions, aerial photographs, satellite images

Preparation of plotting sheets

drawing of sounding lines, identification of narrow zones, coverage

Writing particular instructions

« how? » : sensor parameters, associated, measurements, spacing of sounding lines, adjustments, applicable references


Execution

Calibration,

Deployment of instruments (mooring, positioning beacons, tide gauges)

Monitoring of defined routes

Possible deployment of towed sensors

Navigational warnings

Measurements (bathymetry, oceanography, sedimentology…)

Inspection of landmarks, coast views, buoys

Topography, Toponymy

…


Instrument type (1/2)

Multibeam and vertical echosounders for bathymetry,Side scan sonar for detection of obstructions and wrecksMagnetometer for detection of metal objets Tide gauges and current metersGrabs for bottom samplingClassification system for the superficial layer of sea bottomSub-bottom profilerBroadcasting stations of GPS differential corrections (port and

offshore soundings)GPS receivers and other measuring instruments for geodetic

work (theodolite, level)


Instrument types (2/2)

Computer systemPC and UNIX stations set up in real-time networks (data collection) And offline (processing) linked to a server - A0 plotter, A4 printer

Data collection and processing softwareHYPACK for the preparation, collection and processing of single beam and sonar soundingsCARIS HIPS/SIPS for processing multi-beam soundings (shallows / VH)CIRCE for processing multi-beam soundings (medium depths / BH)CARAÏBES for the display of MBS data


Vertical echo sounder


Vertical echo sounder

z = 0.5 c dtCalibration at the helm

Geometry of the beam

e = 2z tg (/2)


Defects and corrections

heave

Lateral echo


Sound Velocity measurement

Sound Velocimeter


GPS

GPS

Differential GPS


Tides

Pressure tide gauge


Principle

h = (Pgauge - P atm) / Rho.g

Rho= voluminal mass of waterg= gravity acceleration

h

Instrument zero


Adjustment of tide gauge

h

Instrument datum

Chart datum

H


Current meters

Doppler effect Rotor


Detection of obstructions

Objective To detect obstructions between the regular sounding

lines

Means Side scan Sonar Magnetometer for detecting metal wrecks


Side scan sonar


11

1

D

D1.Hh


Sounding

Monitoring of sounding lines Evenly spaced out, corrected if uneven

Direction of sounding lines Perpendicular to isobaths

Cross lines of sounding Checking of consistency of measurements at

intersections

Interlines Increase the density of soundings by bringing lines

closer together if the sea bottom is very uneven


Verification at sea and on land

Follow-up the first results in practically real time (exploitability, obstructions, wrecks, shallows)… in order to react before leaving the zone!

Exploitation of predicted tide for checking at crossing points of the lines of sounding

Positioning checks

Checking of archiving of data (AND back-ups)

Checking of calibration documents

Analysis of raw measurement data


Positioning

validation reprocessing

Positioning of soundings Link-up to antenna base Attitude corrections

Reduction of soundings Velocity immersion of the base tide

Processing


CompilingSheet papers

Track lines bathymetry Obstruction research

Files Wrecks Obstructions Tidal observations Current observations Surveys

Chart marked up

Technical Report


Conclusion

To ensure the quality of a survey it is necessary to:

Define what is required To adapt the methodology and means to the requirement

Assess what has been done Soundings Detection Measurements accuracy

O H I MACHC Seminar - Acapulco 2 – 4 O c t o b r e 2 0 0 6

Hydrographic Surveys

« New Developments »


Main methodology principles

Systems qualification

Mastering the configuration

Quality control

• Bathymetry at SHOM

• ISO 9001:2000 certification

• SMF system


ConclusionsAlgorithmeContexte Historique Tests

«BH1 l’Espérance »

1993 1999

«BH2 : Lapérouse, Borda, Laplace »

2000

«VH 90 »Simrad EM12D

Simrad EM1002S

AtlasFS20

«BHO Beautemps Beaupré »

Simrad EM1002S

EM120

2002 2005

6 Fassmer launches

Simrad EM3002

200m à 12000m

10m à 400m

0m à 100m

50m à 11000m

0m à 150m


ConclusionsAlgorithmContext Reviews Trials

Multibeam data capature

Multibeam data capature

Several measurements per cycle

Almost 100% coverage


Example : Europa – May 2003« Beautemps Beaupré »

Data collected in

ConclusionsAlgorithmContext Rewiews Trials

Data Volumes Data Volumes

EM120

1.6 M soundings

16 hours

Challenges

Advantage

Management, interaction, display, validation

Statistical Exploration of the sea bottom relief

10.1 M soundings

EM3000

4 hours

x25

EM 1002S 0.386 M soundings

2 hoursx2



1999 2000 2002 2005

Improvement of display tools



Types of errorsTypes of errors

Noise of the sounder

Systematic Errors

Occasional errors

Performance estimation of the sounder

xy

z

Pitching axis Heave axis

Heading

MBS

attitudeP

GPS

Relative Position of the various sensors

Time evolution of the orientation and of the position of the sensors


Quality control – system integrity

• Calibration and specific SHOM sea trials at the time of installation

• Trials on flat sea bottom to serve as a reference : verification of the calibration in roll,

calculation of the accuracy to 95% of the sounder, detection rates :


Quality control – system integrity

•Trials on uneven seabed – wreck identification

• Trials on detection capacity on submerged targets


Inclusion of an SMF system

Attitude control unit

Hull velocimeter

Sound velocimeter

GPS positioning

Synchronisation


Inclusion of an MBS system

MBS

EM 3000

POS/MV

GPS Receiver

AQUARIUS 5002

Hull velocymeter

Smart SV

Signaux GPS

MBS system

Actions inertielles

Sounded area

Environnement Réel

Computing system

LECTEUR DAT ?

Sound velocymeter

SV 5XX

GPS Antenna

Application VH Fassmer

Roll, Pitch, heading control + GPS


Thales Navigation Aquarius

Special Order Bathymetry (PS44)

Geodesy, Topography

WAAS/EGNOS, L1/L2, DGPS, LRK©, RTK

Quantity : 25

Cost : 30 k€

Return


Applanix POS/MV

Attitude and heading control unit

Corrects heave and roll for MBS

WAAS/EGNOS, L1/L2, DGPS, RTK

Quantity : 10

Cost : 80 k€

Return


Future developments linked to main development and integrated coastal zone management

Bathy-topography laserMBSPhotogrammetry, spatial imageryhydrodynamic digital models


Conclusion

La technologie au service de l’hydrographie…et des navigateurs

Maîtrise totale de la qualité car responsabilité de l’Etat est engagée

It is better not to know where you are and know that you don’t know, than to be convinced you know where you are when you are not

Cassini

2 – 4 o c t o b r e 2 0 0 6 o h i machc seminar - acapulco hydrographic surveys « instrumentation...

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