Synthetic aperture sonar interferometry for detailed seabed mapping: Performance considerations

Abstract

Synthetic Aperture Sonar (SAS) interferometry is a technique for detailed mapping of the seabed, with the potential of very high resolution and wide swaths simultaneously. There are several specific challenges to overcome for the technique to reach its full potential. These differ from other mapping sensor technologies, e.g., multibeam echosounders (MBES), and interferometric sidescan sonars (ISSS). In this talk, we describe the principle of SAS interferometry with emphasis on the estimation part, strongly inspired by the similar principle in synthetic aperture radar (SAR). We describe the limiting factors in using SAS interferometry for seabed depth estimation. These are related to the host platform, the measurement geometry, the sonar array design, and the signal processing. We construct an error budget where we categorize the different components that affect the overall performance. We also describe the choices and tradeoffs available in the signal processing for a given set of measurements. We show example images and depth estimates from the Kongsberg HISAS interferometric SAS collected by a HUGIN autonomous underwater vehicle.