On the determination of depth from overlapping side‐scan sonar images

Abstract

A method for obtaining depth determinations from overlapping side‐scan sonar is presented. The technique is analogous to the photogrammetic method of deriving topographic measurements from aerial photographic stereo pairs. In the aerial case, image overlap is in the along‐track direction and topographic measurements are based on image parallaxsis. The overlap of the sonar images is in the across‐track sense, and the look directions of the two images are opposed. In terrains where slope is the controlling factor of image intensity, the opposite look directions may yield radically distinct images, thus invalidating traditional photogrammetric measurement techniques. We present a new approach based on matching image edge features rather than image intensities. The algorithm is tested on synthetic imagery generated from a bathymetric model and the results are excellent. Application to actual imagery yielded viable depth determinations consistent with trend and ancillary data.