1. Multi-Sensor Hydrographic LiDAR Operations
Mark Sinclair – Tenix LADS
Dushan Arumugam – BLOM Aerofilms
(Carl-Johan Stigermark BLOM Aerofilms)
Sean Cullen – Geological Survey of Ireland
(Fergal McGrath – Marine Institute)

2. INtegrated Mapping FOr the sustainable development of Ireland’s MArine Resource (INFOMAR) Program
Successor to Continental Shelf Delineation project 1995 – 1996 and Irish National Seabed Survey (INSS) 1999 – 2005 which mapped all Irish designated waters > 200 m deep and collected bathymetric, magnetic, gravity and ancillary datasets to support a range of activities and research
INSS also included ground truthing to acquire seabed samples, video transects and photographic evidence
In 2002, INSS included an initial trial airborne laser survey in Clew Bay

3. INFOMAR Program INFOMAR program commenced in 2006
priority to inshore areas
Joint management by Irish Marine Institute and Geological Survey of Ireland (GSI)
Program to collect, integrate and supply data to support a number of value added products and projects, including nautical charting, habitat mapping, infrastructure support and research
20 year initiative, with first 10 years to map 26 priority bays and 3 offshore areas
In the initial 3 years a multi-platform mapping strategy has been adopted using vessels offshore and lidar in inshore areas and over the shoreline

4. INFOMAR 2008 LiDAR project
Areas surveyed included Donegal, N side Galway Bay, NW coast Aran Islands, Tralee Bay, Sligo Bays, Blacksod Bay and Lough Foyle
Nature of areas:
Donegal and Sligo bays, shallow and mostly intertidal
Galway bay, shallow sandy inter-tidal bay with moderate turbidity & west of Galway, steep-to rocky coastal area with kelp
Aran I and Blacksod Bay, sand and rock
Tralee Bay, sandy inter-tidal bay with extensive high ground close south
Lough Foyle, highly turbid bay on international border between Northern Ireland (UK) and Republic of Ireland

5. Strategy for LiDAR survey
Multi-sensor approach using 2 complementary LiDAR systems
In general, areas were allocated to each sensor as follows:
Hawk Eye 2 (BLOM Aerofilms) to survey shallow inter-tidal areas and small rocky bays
LADS Mk II (Tenix LADS) to survey larger coastal areas where the water was deeper and areas in vicinity of high ground. Shallow inter-tidal bays with turbidity were also surveyed.

6. General GSI Requirements
IHO order 1 position and depth accuracy
Depths to 20 meters (minimum of 10 meters)
5x5 meters laser spot spacing
Caris readable data
Data to Malin Head datum in ASCII format (CZM) and to LAT datum in CARIS readable format (navigation / charting)
Data to ellipsoidal datum for checking new separation models
Seabed reflectivity data for interpretation of bottom-type

7. Hawk Eye – survey areas Data capture in 3 areas
Donegal Bay
Sligo Bays
Greatmans & Cashla Bays (west of Galway)
Data captured from coastline down to the 10m contour

8. Hawk Eye – system description

9. Hawk Eye – calibrations
Factory Calibrations
Laser alignment
Pixel range calibration
Absolute range calibration
Hydro Laser Pixels
Topo Laser Pixels

10. Hawk Eye – calibrations
Field Calibrations
Pitch, Roll and Heading
Absolute range in water and on land
Terramatch
Identify Heading, Roll and Pitch misalignments
Apply corrections to point cloud

11. Hawk Eye – verification
Sea Control Areas (SCA)
2 SCAs at each area
Singlebeam echo-sounder survey
30mx30m area
Ground Control Areas (GCA)
2 GCAs at each area
PPK Survey
10mx10m area

12. Hawk Eye – data collection

13. Hawk Eye – data processing
Applanix POSPac
Process trajectories
AHAB Coastal Survey Studio (CSS)
Bottom detection algorithm processing
Export point clouds to TerraScan cleaning software run on Microstation
TerraSolid (extension for MicroStation)
Data cleaning and output CARIS
Orthophoto production
CARIS
Creation of final data products

14. Hawk Eye – datums
Data was initially processed on the ellipsoid and then transformed to Malin Head datum and LAT
Ellipsoid to orthometric height using OSGM02 geoid model
Orthometric height to Malin head using a static offset at each bay (0.13m – 0.17m)
Orthometric height to LAT using a static offset at each bay (2.09m – 2.68m)
The static offsets were determined for each bay using tidal benchmarks and tide gauge data

15. Hawk Eye – Donegal coverage

16. Hawk Eye – Sligo coverage

17. Hawk Eye – Greatmans coverage

18. LADS – survey areas Data capture in 3 areas:
Galway Bay (N side) including Aran Islands
Tralee Bay – operations near high ground
Blacksod Bay
Data was captured from coastline down to the m contour (depending on water clarity in respective areas)

19. LADS – additional survey area
INFOMAR also engaged other stakeholders for a potential survey of Lough Foyle.
GSI, Marine Institute, Loughs Agency, Port of Londonderry, Environment NI and AFBI (Department of Agriculture) are relevant agencies
Lough Foyle is an environmentally sensitive marine habitat in a cross border region
Survey was extended to include this area
Turbidity management in this area was crucial

20. LADS – data collection
Data collected relative to the instantaneous mean sea surface
Data reduced to LAT and Malin Head datums through tide models using observed tides
Variable height capability important in managing low cloud and high ground, particularly on the south side of Tralee Bay
Flexibility to move between areas significantly separated

21. LADS – calibrations
Static and dynamic position checks and checks over known features were conducted
Benchmarks used for depth checking – common SCAs used in areas where both systems operated
Cross line comparisons
Analysis of overlapping data in common survey areas

22. LADS – operations
Operations based primarily on managing water clarity in the most turbid areas
When conditions unsuitable, diverted to alternative areas
Management of water clarity significantly impacted by flood / ebb and spring / neap tides
Wind strength and direction also significantly impacted selection of survey area
Cloud height and the vicinity of high terrain also had to be considered

23. LADS – survey life cycle including data processing
Data processing during field operations to keep up to date
Pre-validation to progressively appraise quality of data collected and identify where additional data is needed
Detailed validation and checking in depot following field operations
Approval of data by IHO cat A surveyor following quality control

24. LADS – coverage
Galway Bay and N coast

25. LADS – coverage
Aran Islands – west of Galway Bay

26. LADS – coverage
Tralee Bay

27. LADS – coverage
Blacksod Bay

28. LADS – coverage
Lough Foyle

29. Integration - datums
Typically Malin Head datum is determined at tide gauge sites.
LAT values are defined by software PolPred for each survey area relative to Malin Head datum
An important challenge for this survey has been the integration of data from an both an ellipsoidal datum (ETRF89 / GRS80) and geoidal datums (Malin Head / LAT)
This has been complicated by weaknesses in geoid / ellipsoid separation models in the survey areas on the west coast of Ireland
New software provides a model for this (VORF), but it has not been extensively verified

30. Integration – datums / formats
Malin Head datum in ASCII format
LAT datum in Caris readable format
Ellipsoidal datum – customer requested fields for ETRF89 / GRS80 to be added to ASCII format records
Hawk Eye 2 ASCII Data Format
One file for each survey run
One record per sounding
Space separated fields for:
Latitude
Longitude
Depth
Easting
Northing

31. Integration - formats
LADS in CARIS Export Format (CAF), readable by CARIS and Fledermaus:
One ASCII file for each area containing:
Survey summary data
Area Bounds
Spheroid
UTM zone etc
For each sounding
Sounding ID (run, frame, scan, sounding numbers)
Latitude
Longitude
Depth
Easting
Northing
Possible contending depth and positions

32. Integration - formats
ASPRS (The American Society for Photogrammetry and Remote Sensing) LAS Version 1.1
One binary file for each line containing:
Public header block
System Information
Total number of records
Min / max values
Variable length records
Developer defined (Project Info etc)
Point data
XYZi
Return number
Number of returns
Scan information
Classification (e.g. Ground, Low / Medium / High Vegetation, Buildings, Water)

33. Integration - checks Comparisons between datasets
Datasets available for each area:
Seabed and Ground Control Areas (SCAs & GCAs)
Hawk Eye 2 Lidar data
LADS MKII Lidar data
A “mean” 1m grid was created for all datasets
Artefacts excluded (eg cars over GCA)
Compared using CARIS Base Editor – Surface Difference functionality

34. Example of Hawk Eye 2 data against SCAs and GCAs in Sligo Bay
Integration - datums
Integration is still in progress and results are preliminary only
Example of Hawk Eye 2 data against SCAs and GCAs in Sligo Bay

35. Integrating data and products
Preliminary results from Greatmans / Cashla between LADS and SCAs and Hawk Eye 2 data

36. Integrating data and productsQC
Area based reviews of each survey area conducted on ASCII data for both systems
Emphasis on:
Datums
Excessive noise spread due to artefacts e.g. turbidity
Data coverage
Anomalous soundings (large depth difference with respect to surroundings)
Primary tool used was QCTools (LADS proprietary software)

37. Integrating data and products
QC (Cont)
Key functions:
Depth difference grids
Profiles
Tinned 3-D images
Tinned contours
3-D Editor in Fledermaus and CARIS also used
Queries logged and forwarded to respective survey teams for comment / action

38. Integrating data and products
Combined image of vicinity of Greatmans / Cashla (Hawk Eye) and Galway / Aran Islands (LADS)

39. Comments on management of turbidity

40. Overall comments on multi-sensor approach