Interferometric height estimation of the seafloor via synthetic aperture sonar in the presence of motion errors

An end-to-end simulated processing chain related to an existing synthetic aperture sonar (SAS) system is developed and described, including motion compensation, efficient image formation and autofocus procedures. The processing is extended to include interferometric height estimation capability. It is the goal of the paper to study the application of interferometry to SAS systems in the presence of motion errors. The system is analysed with respect to motion errors and the subsequent damaging effects to both imaging and height estimation. Results using both measured and simulated data are presented. The problem is addressed with respect to both one-pass and two-pass imaging geometries, and it is hypothesised that for slowly varying target height, one-pass SAS interferometry may be a more robust imaging tool than conventional SAS alone. The simulated results suggest that height information is recoverable even in some situations in which the conventional SAS reflectivity image is completely ruined by phase error induced blur. High-resolution SAS imaging coupled with interferometric height estimation for seafloor imaging has military applicability in mine detection or classification and in topographic mapping in preparation for an amphibious assault. Civilian uses would include surveying of objects such as oil pipelines and seabed mapping.