<div>AusSeabed follows the recommended processing methodology as prescribed by the AusSeabed Multibeam Guidelines ( https://australian-multibeam-guidelines.github.io/). Please note that certain products are subject to routine update (e.g. resolution, coverage, temporal variation, guidelines/best practice). The client is advised to refer to the latest version of all documents and products for the most up-to-date material. For eCat records the version is expressed in the record title whilst products incorporate date of production as per AusSeabed’s file naming convention.</div><div><br></div><div>The Shark Bay satellite-derived bathymetry was produced in 2021 at The University of Western Australia to support student research projects. The dataset was processed following the workflow of Lebrec et al. (2021) using 673 Sentinel 2 satellite images acquired between January 2017 and December 2020. The dataset includes a digital elevation model as well as an image count grid and a standard deviation grid with a spatial resolution of 10 m.</div><div>&nbsp;</div><div>Survey metadata:</div><div>The satellite-derived bathymetry (SDB) was acquired by the following survey:</div><div>·&nbsp;Dataset name: Shark Bay Satellite-derived bathymetry.</div><div>·&nbsp;Institution: The University of Western Australia.</div><div>·&nbsp;Country: Australia.</div><div>·&nbsp;Sensor: Sentinel-2</div><div>·&nbsp;Start date (Sentinel-2 satellite images): January 2017</div><div>·&nbsp;End date (Sentinel-2 satellite images): December 2020</div><div>·&nbsp;Year of production of the bathymetry: 2021.</div><div>·&nbsp;Depth range: +5 to -30 meters (Depth negative).</div><div>·&nbsp;Coverage: 14,450 km2 (calculated using UTM49 projection).</div><div>·&nbsp;Number of grids: 3 (DEM, Count and STD).</div><div>·&nbsp;Grids bin size: 10 x 10 metres. </div><div>·&nbsp;Vertical accuracy: see note below.</div><div>·&nbsp;Horizontal Datum: WGS84.</div><div>·&nbsp;Vertical Datum: EGM2008.</div><div>·&nbsp;Use Limitation: This dataset is not to be used for navigation.</div><div><br></div><div>Processing methodology:</div><div>The bathymetry data was processed following the workflow of Lebrec et al. (2021) [ https://doi.org/10.5194/essd-13-5191-2021]. The main processing steps to produce this dataset can be summarised as follow:</div><div>1. Data Selection<strong>:</strong> The bathymetry was created using 673 Sentinel 2 satellite images acquired between January 2017 and December 2020 with a grid resolution of 10 m. During this period, all images captured between August and January each year with less than 1% cloud cover were processed.</div><div>2. Preliminary processing<strong>:</strong> A bathymetry file was produced for each of the 673 satellite images using the equation from Stumpf (2002) and calibration points from the Australian Hydrographic Office.</div><div>3. Filtering<strong>:</strong> The resulting files were filtered and reviewed according to a coefficient of correlation calculated between AHO depth soundings and the image reflectance. A total of 505 images had a coefficient of correlation > 0.7 and were further reviewed manually to discard images containing significant artefacts. At the end of this step, 244 images were validated with an average coefficient of correlation of 0.85.</div><div>4.&nbsp;Correction<strong>: </strong>All remaining images were corrected for regional changes in image reflectivity using an error model based on the integration of the AHO calibration points.</div><div>5.&nbsp;Time stack<strong>: </strong>The final satellite-derived bathymetry data was calculated as the median value of all individual overlapping bathymetry files.</div><div>Notes about the accuracy of the data.</div><div>·&nbsp;The vertical accuracy of the Shark Bay satellite-derived bathymetry could not be precisely measured due to the lack of independent reference datasets. Instead, the mean standard deviation of the bathymetry (1.12 m) is used as an approximation of the vertical accuracy. </div><div>·&nbsp;The bathymetry and standard deviation grids are supported by an image count raster. The raster displays, for each pixel, the number of images that were included in the final statistical analysis. The reliability of the data is expected to increase with the number of images.</div><div>The data are locally heavily affected by seagrass meadows. In these areas, the morphology shown by the satellite-derived bathymetry may not represent the morphology of the seabed. These areas tend to have a granular pattern with intersecting channels appearing as relief rather than depressions. The workflow used here does not allow such artefacts to be filtered out.</div><div><br></div><div>At Geoscience Australia, the received geotiff in MSL was shifted to EGM2008 using AusCoastVDT and CARIS HIPS and SIPS. The final processed grids were exported as a 32-bit floating point Geotiff at 10m resolution, referenced to EGM2008.</div><div><br></div><div>DATA QUALITY</div><div><br></div><div>This dataset has been subject to independent post-production validation and testing. Tests have been performed for data completeness, correct spatial representation, attribute accuracy, logical consistency, metadata completeness and correctness, and where appropriate for compliance with Geoscience Australia's data dictionaries.</div><div>Errors found in this dataset should be reported to:</div><div>Corporate Data Manager</div><div>Geoscience Australia</div><div>GPO Box 378</div><div>Canberra ACT 2601, Australia</div><div>Email: Sales@ga.gov.au</div><div>Reported Errors will be rectified in subsequent data releases, if any.</div><div><br></div> Sales@ga.gov The main processing steps to produce this dataset can be summarised as follow:</div><div>1. Data Selection<strong>:</strong> The bathymetry was created using 673 Sentinel 2 satellite images acquired between January 2017 and December 2020 with a grid resolution of 10 m. During this period, all images captured between August and January each year with less than 1% cloud cover were processed.</div><div>2. Preliminary processing<strong>:</strong> A bathymetry file was produced for each of the 673 satellite images using the equation from Stumpf (2002) and calibration points from the Australian Hydrographic Office.</div><div>3. Filtering<strong>:</strong> The resulting files were filtered and reviewed according to a coefficient of correlation calculated between AHO depth soundings and the image reflectance. A total of 505 images had a coefficient of correlation > 0.7 and were further reviewed manually to discard images containing significant artefacts. At the end of this step, 244 images were validated with an average coefficient of correlation of 0.85.</div><div>4.&nbsp;Correction<strong>: </strong>All remaining images were corrected for regional changes in image reflectivity using an error model based on the integration of the AHO calibration points.</div><div>5.&nbsp;Time stack<strong>: </strong>The final satellite-derived bathymetry data was calculated as the median value of all individual overlapping bathymetry files.</div><div>Notes about the accuracy of the data.</div><div>·&nbsp;The vertical accuracy of the Shark Bay satellite-derived bathymetry could not be precisely measured due to the lack of independent reference datasets. Instead, the mean standard deviation of the bathymetry (1.12 m) is used as an approximation of the vertical accuracy. </div><div>·&nbsp;The bathymetry and standard deviation grids are supported by an image count raster. The raster displays, for each pixel, the number of images that were included in the final statistical analysis. The reliability of the data is expected to increase with the number of images.</div><div>The data are locally heavily affected by seagrass meadows. In these areas, the morphology shown by the satellite-derived bathymetry may not represent the morphology of the seabed. These areas tend to have a granular pattern with intersecting channels appearing as relief rather than depressions. The workflow used here does not allow such artefacts to be filtered out.</div><div><br></div><div>At Geoscience Australia, the received geotiff in MSL was shifted to EGM2008 using AusCoastVDT and CARIS HIPS and SIPS. The final processed grids were exported as a 32-bit floating point Geotiff at 10m resolution, referenced to EGM2008.</div><div><br></div><div>DATA QUALITY</div><div><br></div><div>This dataset has been subject to independent post-production validation and testing. Tests have been performed for data completeness, correct spatial representation, attribute accuracy, logical consistency, metadata completeness and correctness, and where appropriate for compliance with Geoscience Australia's data dictionaries.</div><div>Errors found in this dataset should be reported to:</div><div>Corporate Data Manager</div><div>Geoscience Australia</div><div>GPO Box 378</div><div>Canberra ACT 2601, Australia</div><div>Email: Sales@ga.gov.au</div><div>Reported Errors will be rectified in subsequent data releases, if any.</div><div><br></div>