Seafloor Characterisation Using Underwater Acoustic Devices

The problem of seafloor characterisation is important in the context of management as well as investigation and protection of the marine environment. In the first part of the paper, a review of underwater acoustic technology and methodology used in seafloor characterisation is presented. It consists of the techniques based on the use of singlebeam echosounders and seismic sources, along with those developed for the use of sidescan and multibeam sonar systems. In the second part, the review is followed by a description of the combined approach to seafloor characterisation developed by the authors. It is based on extraction of three types of information from multibeam sonar recordings, namely: 1) the sonar image of seabed surface, 2) the point cloud describing seabed surface shape, 3) the set of echo envelopes corresponding to particular sonar beams. Then the seafloor classification is performed using the set of parameters (descriptors) which are calculated on the basis of 3 types of sonar data mentioned above. The proposed approach has been tested using field sonar data recordings in the water region of the Southern Baltic Sea. In this region, four sites differing by seabed type were investigated.