Occlusion and height estimation using the coherence of multi-static synthetic aperture sonar images.

Objects in synthetic aperture sonar imagery that lie proud above an interface will occlude a portion of the background behind it. This occlusion may appear as a shadow in the imagery whose dimensions can be used to infer the height of the object. Volume scattering from beneath the object, however, may prevent such shadows from being visible in imagery. Regions of occlusion can be detected using the coherence between two images collected from different horizontal baselines. Using controlled laboratory experimentation, this approach is shown to detect occluded regions for accurate estimation of the height of an object.