Shellharbour Tharawal marine survey - backscatter (NSWENV20171130/GA4878)

Brief description

This resource includes bathymetry data acquired during the Shellharbour Tharawal marine survey collected by the NSW government (Department of Planning and Environment – DPE) during the period 25 May – 30 November 2017 onboard the RV Bombora using DPE’s R2Sonic 2022 multibeam sonar. The Shellharbour bathymetry survey was led by Dr. Bradley Morris (DPE Coasts and Marine) as part of SeabedNSW program funded by NSW Coastal Reforms package. The purpose of the project was to 1) provide a baseline dataset and 2) map the spatial distribution of seabed types. The data will provide a better understanding of nearshore sediment distribution/transport mechanisms for improved assessment of threats/risks associated with erosion events (i.e. East Coast Lows) and changing sea levels. This dataset contains a 32-bit floating point geotiff file of backscatter (5m gridded) for the study area, derived from the processed R2Sonic 2022 multibeam data, using Hypack, R2Sonic GUI, POSView, POSPac, Qimera and FMGT software. A detailed report on the survey is provided in: i) AusSeabed Survey Report and ii) NSW DPE Scientific Rigor Statement NSWENV_20171130_Shellharbour_MB_ScientificRigour.pdf. This dataset is not to be used for navigational purposes. This dataset is published with the permission of the Senior Team Leader and the department’s Hydrosurveyor, Coasts and Marine Science, NSW Dept. Planning and Environment.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: While AusSeabed aims to publish data based on the requirements stated in the AusSeabed multibeam guidelines (version 1, https://australian-multibeam-guidelines.github.io), we will also publish interim products (version 0) that are currently available, but have not yet been standardised (version 1). Users should be aware that V1 products will always supersede V0 products. This dataset was produced using QPS Qimera and FMGT software and the AusSeabed-recommended processing methodology as follows. 1. R2Sonic ‘true-pix’ amplitude and ‘snippets’ time-series were treated separately. Truepix files were exported as GSF from Hypack using MBMAX and then imported into a new QPS FMGT project. R2Sonic ‘snippets’ (time-series) paired files were imported into a separate QPS FMGT project and processed using the ‘time-series’ functionality. 2. A cleaned bathymetry DEM was also imported into each of the FMGT projects. 3. For each QPS FMGT project processing options were adjusted within the Processing Parameters tab as follows: Transmit/receive, Power Gain Correction and Apply Beam Pattern Correction were selected and a 60⁰ beam angle cut-off applied. 4. For the Sonar Defaults tab, system options are set to automatic and R2Sonic 2022 sonar type selected. Surface Sound Speed is set to 1520 metres/second and Angle Varied Gain set to ‘Trend’ with a default window size of 300. All other parameters are left as default. 5. Mosaics are generated at 5m grid scale either as a single mosaic or as tiles, depending on file size with the cleaned bathy surface activated. 6. The backscatter adjustment function was used to adjust line brightness for individual transects to provide a more uniform mosaic. 7. Once completed mosaics were exported as geotiffs and XYA from each project in grid co-ordinates WGS84 56S. 8. The final processed grid was exported as a 32-bit floating point Geotiff at 5m resolution.

Notes

Purpose
marine survey