Lord Howe Bathymetry (GA-2461 only)

Brief description

This dataset contains the processed bathymetric dataset from the Lord Howe and Lord How Island survey area held by Geoscience Australia. This dataset includes multibeam echosounder data and was gridded at 50m resolution of the Lord Howe survey area and a 10m resolution of Lord Howe Island, based on the optimal resolution for the depth range encountered. The objective of the survey on the Lord Howe Island shelf (NSW) in 2008 (SS062008) was to map seabed bathymetry and characterise benthic environments through co-located sampling of surface sediments and infauna, rock coring, observation of benthic habitats using underwater towed video, and measurement of ocean tides and wavegenerated currents. Subbottom profile data was also collected to map sediment thickness and shelf stratigraphy. Data and samples were acquired using the National Facility Research Vessel Southern Surveyor. This dataset is published with the permission of the CEO, Geoscience Australia. Not to be used for navigational purposes.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: The vertical datum is MSL, while the horizontal datum is WGS84. This dataset was produced using CARIS HIPS/SIPS version 7.2 For additional metadata questions, please download the Metadata.txt file located with the dataset. Processing methodology: Following the CARIS HIPS/SIPS workflow, 1. A vessel configuration file was created that the coordinates of the motion sensor, DGPS antenna and patch test offsets were recorded. 2. A new project was created and the vessel configuration file was attached to the project file. 3. The raw swath sonar data files, in raw.all format, for each line was then imported into the project and the vessel information assigned to the data. 4. The motion sensor, DGPS and heading data were then cleaned using a filter that averaged adjacent data to remove artifacts. 5. Sound velocity profiles data for each block were attached to the corresponding raw swath sonar data files to correct the depths for changes in the speed of sound through the water column. 6. A new blank field area was defined that specified the geographic area of study and the coordinate system used. The coordinates for all the study areas were WGS84. 7. The data was cleaned by applying several filters that removed any remaining spikes in the bathymetry data using user defined threshold values. 8. Data were inspected visually for each line where artefacts and noisy data not removed by the filtering process were removed manually using Swath and subset editors modules of the Caris HIPS/SIPS software. In addition, WXTide32 software (http://www.wxtide32.com) with reference to the mean sea level and UTC time was used to obtain tidal information, which in turn was used to correct for the tidal variations in the processing. All the data for each bathymetric, motion sensor, DGPS, heading, tide and sound velocity profile data were merged to produce the final processed data file. A weighted grid of the processed data was then created for each Block. The processed data was finally exported as XYZ grid soundings and converted into 32-bit geotiff grid. The grid was then checked using ArcMap for accuracy