Multibeam sonar bottom detection using multiple subarrays

Two new bottom detection methods for multibeam bathymetric sonars are presented. Both of the methods are based on the early separate aperture method which combines amplitude and phase in the bottom detection. As a generalization of the separate aperture method, multiple subarrays are used to estimate the direction of arrival of the bottom echoes of oblique incident angles. An image transform is used to compute the bottom depth from the phase information. The methods were evaluated using Simrad EM3000 sonar data recorded from shallow water. The results show that both methods improve the bottom detection performance for oblique beams. The multiple subarray method is particularly useful for shallow water applications