lidar b th t i slidar bathymetric survey in golfe du lion ... · lidar bathymetric survey in golfe...

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LiDAR B th t i SLiDAR Bathymetric Survey in Golfe du Lion, France

www.fugro.com

Hugh Parker

Fugro LADS Corporation Pty Ltd

Hydro 2010

Rostock, Germany, 2-5 November 2010

LiDAR Bathymetric Survey in Golfe du Lion, France

Introduction Survey Objectives Survey Requirements Project Teamj Survey Area LADS Mk II ALB System Survey Control (Datums) Data Collection Plan

– Reconnaissance– Tides– GPS

Data Processing

www.fugro.comHydro 2010, Rostock, Germany, 2-5 November 2010

Data Processing Quality Control Conclusion

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Survey Objectives

Survey was conducted for the Regional Directorate for Environment of Languedoc-Roussillon (DREAL), Littoral Zone Division to for Coastal Zone Management purposes

Objectives of the survey were:

– Map the sand reserves along the Languedoc-Roussillon coastline to assist decision making and strategy development by Local Government and coastal planners.

– use the data in the creation of a seamless regular digital altimetric model of the sea and on adjoining portion of land (as part of SHOM’s Litto 3d program

Data requirements


Data requirements

– coastal topographic elevation data

• Coverage required from the vegetation line (back of the beach)

– coastal bathymetric elevation data

• Coverage to 10m isobath

Hydro 2010, Rostock, Germany, 2-5 November 2010


Survey Requirements Airborne LiDAR Bathymetric Survey of

Languedoc-Roussillon Coastline– Vertical accuracy

IHO d 1b• IHO order 1b– Resolution

• 5m average ungridded point spacing– Sounding coverage

• Gap minimisation by managing turbidity

• A minimum coverage requirement of 85% in all required areas

– Survey of Bathymetric Control Areas


– Provide Aerial Imagery– Heights relative to the IGN69 Datum

Hydro 2010, Rostock, Germany, 2-5 November 2010

14 coastal areas awarded totalling ~313 sq.km

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Project Team Members

Fugro LADS Corporation

– Collect data using LADS Mk II Airborne LiDAR Bathymetry (ALB) system along entire Coastal region

– Install and recover all temporary tide gauges

– Process all LADS Data

Eurosense

Pro ided contract administration s pport


– Provided contract administration support

– Geodetic support

– Provision of additional French speaking pilot


Fugro LADS Mk II ALB System

Laser Airborne Depth Sounder (LADS)(LADS)

Hydrographic Survey / Coastal Mapping system mounted inside an aircraft

Pulses of laser light are used to measure the depth of water and height of features (ie rocks, islands, beach


gradients)

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LADS Mk II ALB Capabilities

1Khz System

Variable spot spacing: 2x2, 2.5x2.5, 3x3, 4x4,

5x5 or 6x6 metres5x5 or 6x6 metres

Swath width 50 - 300 metres

Variable altitude 1200 – 2200 feet

Tidal and / or Ellipsoidal datum

Maximum depth capability to 70m (subject to

suitable water clarity)

Topographic height range 0 to 50m


p g p g g

Aerial Photography (0.25m Resolution)

Relative Reflectance

IHO Order 1 position, depth accuracy and

target detection (subject to water clarity)

Hyperspectral scanner


Survey Control and Datums

Horizontal Control

– Real Time Horizontal control

GS O S G S• WGS 84, OmniStar Wide Area DGPS

– Post Processed Horizontal control

• ETRF89 Ellipsoid, Post Processed KGPS positions using Temporary GPS Base Stations at Montpellier and Port-la-Nouvelle.

Vertical Control

– IGN69 Vertical Datum, through tidal reduction using Permanent Gauges (via SHOM) at Port


using Permanent Gauges (via SHOM) at Port Vendres, Sete and Marseilles, and temporary gauges installed at Post-la-Nouvelle and Port Camargue

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Reconnaissance

Conducted over 1 week between 20 – 28 July 2009, and included:

– Kick off meetings with Customer and SHOMSHOM

– Meetings with airport authorities to discuss low level flying operations

– Locate suitable locations for GPS Base Station and Temporary tide gauges

– Conduct water clarity measurements to evaluate nature of water clarity in the area in different weather conditions

– Coastline study to understand nature of


coastline

– Liaise with locals regarding weather and nature of


Outcomes of Reconnaissance:

The water clarity in the survey area is highly dependant upon the weather conditions:

St th t i d t h d b ki– Strong south east winds generate heavy seas and breaking waves along the coastline stirring up the inshore water and degrading the water clarity.

– Strong north west winds push water from the adjacent coastal lakes into the sea; this also degrades the water clarity along the coastline, especially around the inlets/marinas.

Even after 48 hours of good weather, water with degraded clarity was still evident around marinas and inlets.


Early morning flights are advised for the following reasons:

– Calmer sea conditions

– Less boat activity on the water

– Beaches are less populated

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Tidal Reduction

Temporary tide gauges installed at Port-la-Nouvelle and Port Camargue were

Sete (SHOM)

Port Camargue (FLC)

and Port Camargue were connected to datum (IGN69) via levelling from local IGN benchmarks at each area

Pole/Gauge comparisons were conduced at each location to ensure gauges were calibrated and operating correctly.

Port-la-Nouvelle (FLC)

( )

Marseille (SHOM)


Port Vendres (SHOM)


Horizontal Positioning

2 Temporary base stations established at Port-la-Nouvelle and at Montpellier on the roof topand at Montpellier on the roof top of prominent buildings (i.e. hotel rooftop)

Ensured maximum baseline lengths <55 kms for the entire survey area

positioned via network solution using surrounding stations from the National IGN CORS network

<55 kms

Montpellier


the National IGN CORS network

<55 kms

Port-la-Nouvelle

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Fugro LADS Line Planning

Line planning prepared that divided the area up as to survey the areas as

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efficiently as possible



Bathymetric Control Areas

SHOM determined location of Three Bathymetric Control Areas

Saintes Maries de la MerAreas– Canet-Plage– Cap d’Agde– Saintes Maries de la Mer

Located in depths of water between 2-6m of water

Cap d’Agde


Fugro LADS flew over one of these control areas at the beginning and end of each sortie to confirm system accuracy.

Canet-Plage

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Bathymetric Control Areas


Canet-Plage


Fugro LADS LiDAR Data Collection

Aircraft arrived in Montpellier on Friday 21 August 2009

Data collection commenced 24 AugustData collection commenced 24 August

9 flights flown of which all were fully effective

Average 4:49 on task (collecting data) per flight

Average 1:00 transit/Benchmarks per flight

Total 43:23 hours of on task time achieved

Over 280 lines flown, over 470 sq.km of data collected

Aircraft departed Montpellier 09 September 2009


p p p

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Data Processing

Automated Initial Processing and depth selection

I iti l Fi ld Ch k C d t d (i Initial Field Check Conducted (in Adelaide for this project)

Field cleaned pre-validated data set produced with 24 hours of last flight

Comprehensive validation and checking process conducted in Adelaide office

Data quality checked on completion of


process

Data then approved for use in products by Senior IHO Cat A Surveyor


Field Processed Data

Automatic data processing and initial Pre-Validation was conducted in the field directly after each flight to confirm system performance after each sortie

High quality “Pre-Validated” interim LADS data available on completion of data collection

Coverage plots generated and refly lines identified where


needed

Data then released for detailed and comprehensive validation and review in accordance with Fugro LADS quality processes

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Control by SHOM:• Coverage• Density• Data check by a SHOM’s operator:

all the data are checked (720 cases of control)• Crosscheck for crossline and line by line• Comparison with SHOM’s database• In Situ control• Comparison with SHOM’s control areas (3 areas)• Comparison with non SHOM surveys• Conform for the 46 requirements (technical specifications from SHOM)

For QC Fugro LADS Provided to SHOM:


For QC, Fugro LADS Provided to SHOM:• Approved data in LADS proprietary CAF format which included the raw

laser waveforms• This format is compatible with both CARIS and Fledermaus

software. SHOM used both packages during the QC process• Individual digital images from the Downward looking camera in the

LADS Mk II ALB system.


Case of control example by SHOM’s operator

Same Feature


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Comparison with SHOM’s control areas (3 areas)


Cap d’AgdeOne of the 3 Shom’s control area

Mean Depth Difference 5 cm

Standard Deviation 9 cm (95%)


Coverage Achieved

Results were achieved with depths down to the required 10 m obtained and in most areas depths beyond 20 metres were achieved

Coverage of >95% achieved in all areas

IHO order 1 accuracy achieved

Mean Depth Difference between the cross lines and

1 Persistent turbidity around Cap l'Espiguette. Operations within these areas were attempted throughout the survey, however conditions in

2 A small gap exists at the mouth of the Petit Rhone River in the eastern extent of the area deeper than 7-8 metres


main lines was 0.01 ±0.08 metres (1)

Some localized gaps in the coverage occurred as indicated

survey, however conditions in these areas remained marginal and depths to only 6-7 metres were achevied in this area.

area deeper than 7-8 metres where persistent turbidity was evident.

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Conclusions A successful LiDAR Bathymetry survey was of >310 sq.kms was conducted in

9 flights over

Data quality exceeded customer expectations in terms of coverage and i lvertical accuracy agreement

A seamless topographic / bathymetric data set has been produced


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Acknowledgements

Additional Author’s

– Mr Mark Sinclair, Managing Director, Fugro LADS Corporation Pty Ltd

– Mr Yves Pastol, Hydrographic Surveyor, Service Hydrographique et Oceanographique de la Marine (SHOM)

Mr C ril Vanro e Unit Manager Sedimentar


– Mr Cyril Vanroye, Unit Manager Sedimentary Dynamics and Coastal Hazards, Regional Directorate for Environment of Languedoc-Roussillon (DREAL)


Thank You


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