Side scan sonar target detection in the presence of bottom backscatter

Abstract

The effect of bottom backscatter on target detection ranges for 100-kHz Klein and EG&G side scan sonars was investigated. Glass spheres of 16-cm diameter with measured target strengths of -24 dB were deployed in 30-m water depth, 0.7 m above sand and shale bottoms. Controlled test runs past a linear target configuration were performed. For a sand bottom, the Klein system yielded target detections at a maximum range of 150 m with 100% success. The EG&G system yielded 100% detection out to 152-m range, with detection 46% of the time at 259 m and 865% at 228 m. A shale bottom masked all target returns negating detection. Detection thresholds were estimated by comparing field results to theoretical ranges calculated from the sonar equation using applicable backscatter coefficients. The results show that is possible to determine the geophysical and side scan system inputs sufficiently well to allow determination of the efficient spacing of survey lines in shallow water hydrographic applications of side scan sonar.