Mapping the ocean floor in extreme resolution using interferometric synthetic aperture sonar

The synthetic aperture (SA) principle is based on coherent combination of multiple pulses in order to improve angular resolution. The SA principle is used in radar (SAR), seismic imaging, ultrasound (SAFT), and sonar (SAS). SAS has matured substantially the last two decades. Today, SAS represents the state-of-the-art in sonar imaging, being able to produce images and maps of the seabed in extreme resolution. The Norwegian Defence Research Establishment (FFI) collaborates with Kongsberg Maritime to develop the HISAS family of interferometric SAS systems for the HUGIN autonomous underwater vehicle (AUV) and other underwater platforms. In this work, we describe the SA principle, the link between the different SA imaging domains, and the particular limitations in SAS. We show example images from the HISAS system illustrating its capabilities and performance limitations.