3D satellite mapping of Coral Sea reefs
James Cook University helps Australia’s government in applying Geoscience in their environmental challenges. Thanks to QPS' regional partner; Acoustic Imaging, they have been among professional Fledermaus users since 2005. Dr. Robin Beaman who is a marine geologist has been involved in many ocean mapping projects to unlock the secrets of Australia's underwater landscape. He has completed detailed 3D bathymetry maps of Australia’s Coral Sea reefs, shedding new light on the likely distribution of coral diversity and sea life in the area. Mapping the reefs and their underwater landscape had always been a challenge, because their remote locations and shallow nature made it difficult to use modern surveying techniques, such as vessel-mounted echo sounders. Dr. Beaman worked together with the German Earth observation company EOMAP (another Fledermaus client) and used satellite imagery to develop 3D bathymetry (or depth) data over a large group of Coral Sea reefs.
The project focussed on the reefs and atolls within those waters of the Coral Sea that fall within Australia’s Exclusive Economic Zone, also called the Coral Sea Marine Reserve. While many of the largest reefs had been progressively mapped by the Royal Australian Navy (Fledermaus client since 1995) using their LADS airborne LiDAR bathymetry system, there were still large areas of shallow reefs with no detailed depth data over them.
Dr. Beaman puts: “These reefs lie in clear, sunlit waters, so the Landsat8 images were able to provide high-resolution data to a depth of about 50 metres. By refining the satellite data and merging it with existing data, 3D depth maps for these reefs and atolls are produced. That gives us a much more detailed picture than was previously available.The Flinders Reefs, about 230km offshore from Townsville, were an ideal place to start, being close to the Australian mainland and lacking an accurate 3D map. These are atolls that grew upwards from tilted continental blocks created when Gondwana was breaking up. The 3D images we now have of North and South Flinders Reefs are really stunning, showing classic atoll shapes with a shallow coral rim around a deeper lagoon. With this new 3D information we can now better predict where coral diversity is located around the edge of these reefs, because we know where we’re likely to find the shallow and deeper coral communities. That information will help marine researchers to plan future scientific expeditions, and it will help managers of the various conservation zones determine what other marine life they can expect to find there.”
Dr. Beaman hopes the maps will be a valuable resource in the ongoing discussion as to what levels of protection should be given to different areas of the Coral Sea Marine Reserve. More broadly, oceanographers could use the 3D data to more accurately model how oceanic currents move over and past these reefs before reaching the Great Barrier Reef.
North-westerly view of the Coral Sea reefs towards Cairns. Depths are coloured red (shallow) to purple (deep), over a depth range of about 4000 metres. Exposed land is coloured grey. Includes material © (2015) EOMAP GmbH & Co.KG.
North-westerly view of the Flinders Reefs in the Coral Sea, about 230 km offshore from Townsville. Depths are coloured red (shallow) to purple (deep), over a depth range of about 50 metres. Bathymetry data © (2015) EOMAP Bathymetry