Performance of a buried object scanning sonar against targets buried in sand at the SAX‐04 (Sediment Acoustics Experiment 2004) site

The performance of synthetic aperture processing for imaging buried targets in the band of 3 to 20 kHz is quantified by measuring the SNR of 3‐D acoustic images of targets buried in sand at the SAX‐04 site. A buried object scanning sonar consisting of an omnidirectional projector and a 40‐channel hydrophone line array is towed within 10 m of the seabed at various horizontal offsets to buried targets to measure the SNR of target echoes as a function of grazing angle. Detections of the targets occurring at grazing angles smaller than the critical angle suggest that buried targets can be detected using the evanescent boundary wave thereby improving the range of the sonar for detecting shallow‐buried targets. Acoustic images of buried targets also show that backscattering from sand ripples, sediment variability, and sediment layer interfaces limit the performance of the sonar for detecting and imaging buried objects.