Comparative study between acoustic signals and images for detecting seabed features

Abstract

This study aims to provide a recent seabed characteristic of ridges along the eastern coast of Alexandria on the Egyptian Mediterranean Sea. Side scan sonar was used for acoustic imaging and Quester Tangent Corporation (QTC) VIEW for acoustic signal survey. ROV was applied to detailed video survey and sediment sampling to provide ground truth data. The integration between acoustic signal classes and the acoustic images can divided the study area into three acoustic categories; 1) weak backscatter corresponds to very fine sand to silt sediments, 2) strong backscatter confined to coarse to medium sand, and 3) isolated reflections, which appear widespread along the whole study area and represent two discrete parallel discontinuous hard limestone ridges. These discrete parallel ridges are found to be trending parallel to the coastline. A seabed feature map for the study area is obtained from the integration of output results of side scan sonar backscatter analysis with the QTC acoustic classification and ground-truthing using ROV and grab sampler. The high resolution of acoustic image help to detect the variation of the wavelength and amplitude of sand ripples in the study area.