The Use of Interferometric Sonars for Acoustic Seabed Classification

Abstract

Seafloor mapping is of great importance for the management of marine resources. The past decades have seen the fast development of acoustic seabed mapping techniques. Of particular importance is the mapping of seafloor type. It has applications in marine geology and biology, environmental sciences, coastal engineering and fisheries. Traditional techniques relied on grab samples or scuba diving, so they were done only on spot observation and extrapolating the findings to the surrounding area. The use of marine acoustics helps in picturing the extents of various areas dominated by a specific bottom type. The paper discusses the use of interferometric sonars for seabed classification and provides examples from the Romanian Black Sea coast, on a 42 hectares site offshore Mangalia. They are devices that acquire both bathymetry and side-scan imagery and combined they prove to be better that approaches based on only one of them. Interferometric sonars can be deployed as pole mounted devices or AUV mounted. We have been able to discern between several acoustic facieses and correlate them to substrate type by grab samples and ROV inspections. The hard bottoms, such as rocky substrate appears as areas of high rugosity and are usually stand out from the surrounding landscape. The muddy and sandy areas show gentle sloping and a general featureless aspect.