Bathymetric Capabilities of the HISAS Interferometric Synthetic Aperture Sonar

Multibeam echo-sounders have until now been the leading technology in seabed mapping, but typically have resolutions of around half a metre. Recently, synthetic aperture sonar (SAS) technology has matured to a commercial level, delivering sidelooking imagery with a resolution of a few centimetres to a range of several hundred metres. High resolution sidelooking imagery makes interferometry an extremely interesting technique for bathymetric processing. In this paper we discuss the theoretical accuracy in relative height mapping of the new HISAS interferometric SAS and compare the results with processing of simulated data. We also demonstrate SAS interferometry on real data collected with a prototype SAS mounted on a HUGIN AUV. Different filtering techniques are applied to the data, illustrating the trade-off between resolution, robustness and smoothness.