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Abstract
A 1:30,000 substratum map for an area off the north coast of Ireland is presented. The study area is bounded in the south by the Causeway coastline and in the north by the following coordinates: top left corner (6°43′36″W, 55°17′N) and top right corner (6°27′W, 55°17′N). This mapping has been made possible through the availability of full seafloor coverage multibeam swath bathymetry and backscatter data (both gridded to 1 m), together with ground-truthing data collected over the past 40 years. Bathymetry data were used to generate terrain indices such as slope, rugosity, aspect, fine- and broad-scale Benthic Position Index, whilst the backscatter data were interpreted visually, subjected to an unsupervised classification process using QTC Multiview, and combined with the bathymetry-derived parameters into a clustermap in ArcGIS. The resulting maps allowed us to divide the seabed into 10 distinct acoustic classes, which, linked to sediment samples, diver surveys, underwater video-tows and remotely operated vehicle surveys, were converted into a substratum map. This is the most accurate seafloor substratum map to date for the north coast of Ireland and could form the basis for more in-depth geological, biological and hydrodynamic studies of this highly dynamic coastline.
Software
Data gridding of the multibeam bathymetry was performed using IVS Fledermaus DMagic 7.0, while the backscatter data was mosaiced using IVS Fledermaus Geocoder 7.0. The automatic segmentation was carried out in QTC Multiview 4.0 and this unsupervised classification was interpolated in QTC Clams 4.0. All data were brought together in ESRI ArcGIS 9.2 for further analysis and final map creation.
