Scan geometries for three dimensional synthetic aperture sonar tomography

Synthetic aperture sonar (SAS) exploits vehicle motion and coherent multi-ping signal integration to enhance image resolution. SAS is typically used to generate high-resolution 2D sonar imagery; however the generation of high-resolution, voxel-based 3D images of targets has also been demonstrated by synthesizing multi-dimensional apertures from scans conducted at diverse grazing-angles. In the latter case, the geometry of the multi-dimensional synthetic aperture can have significant ramifications for all stages of the beamforming process, ranging from navigation refinement and beamformer design to very practical experimental issues, such as the time necessary to scan a target. In this paper, the effects that different multi-dimensional scans have on three-dimensional SAS are considered. Results of field tests for different scan geometries are shown and interpreted in light of their various benefits and detriments.