Motion Estimation for Synthetic Aperture Sonar using Redundant Phase Center Interferograms

Synthetic Aperture Sonar (SAS) systems provide high-resolution sonar data at lower frequencies compared with real aperture sonars. This high-resolution data is achieved by producing long synthetic apertures, which in turn require precise motion compensation to ensure that the array remains coherent. Precise motion estimation is often determined using redundant phase center (RPC) motion estimation techniques that use cross correlation results to determine the delay between the overlapping phase centers across consecutive sonar transmissions. However, an interferogram of the overlapping phase centers can also providean estimate of this delay. We describe a method here to use the interferogram of the overlapping phase centers to estimate the vertical and range-axis displacements for consecutive transmissions of a SAS system. This technique is tested against simulated data to verify accuracy and then against field-collected data to verify in situ performance. Results and potential improvements are discussed.