Aliased seabed detection in fisheries acoustic data

Abstract

Aliased seabed echoes, also known as "false bottoms" or "shadow bottoms", are a form of echogram corruption caused by seabed reverberation from preceding pings coinciding with echoes from the current ping. These aliases are usually either avoided by adjusting the survey parameters, or identified and removed by hand - a subjective and laborious process. This paper describes a simple algorithm that uses volume backscatter and split-beam angle to detect and remove aliased seabed using single frequency, split-beam echo sounder data without the need for bathymetry.