Bathymetry grids of Carnarvon Shelf

Brief description

Geoscience Australia carried out a marine survey on Carnarvon shelf (WA) in 2008 (SOL4769) to map seabed bathymetry and characterise benthic environments through colocated sampling of surface sediments and infauna, observation of benthic habitats using underwater towed video and stills photography, and measurement of ocean tides and wavegenerated currents. Data and samples were acquired using the Australian Institute of Marine Science (AIMS) Research Vessel Solander. Bathymetric mapping, sampling and video transects were completed in three survey areas that extended seaward from Ningaloo Reef to the shelf edge, including: Mandu Creek (80 sq km); Point Cloates (281 sq km), and; Gnaraloo (321 sq km). Additional bathymetric mapping (but no sampling or video) was completed between Mandu creek and Point Cloates, covering 277 sq km and north of Mandu Creek, covering 79 sq km. Two oceanographic moorings were deployed in the Point Cloates survey area. The survey also mapped and sampled an area to the northeast of the Muiron Islands covering 52 sq km. The dataset contains 6 bathymetry grids of the Carnarvon Shelf study area produced from the processed EM3002 bathymetry data using the CARIS HIPS and SIPS software. Please see the metadata for detailed information.

This dataset is not to be used for navigational purposes.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: Due to the exceptionally good quality data being acquired, post processing of the raw data was kept to a minimum. Swath data was processed through Caris HIPS/SIPS version 6.1. First a vessel configuration file was created that the coordinates of the motion sensor and DGPS antenna and patch test offsets were recorded. A new project was then created and the vessel configuration file was attached to the project file. The raw swath sonar data, in raw.all format, for each line was then imported into the project and the vessel information assigned to the data. The motion sensor, DGPS and heading data were then cleaned using a filter that averaged adjacent data to remove artifacts. Different 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. Then 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. The data was cleaned by applying several filters that removed any remaining spikes in the bathymetry data using user defined threshold values. A visual inspection of the data for each line was then undertaken 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 ArcINFO grid