Shallow Water Survey with a Miniature Synthetic Aperture Sonar

Naval operations such as IPOE (Intelligence Preparation of Operational Environment) and explosive ordnance detection often requires high-resolution surveys in shallow water and surf zones. Surveying in such shallow water presents a variety of operational challenges. The two fundamental constraints to operating in shallow water are vehicle size and performance degradation related to environmental constraints. To effectively access shallow water, lightweight man-portable Autonomous Underwater Vehicles (AUVs) are often desired. The sonar system design and processing must also be equipped to handle the challenges of the very shallow water environment, which include sloping seabed surfaces, strong multi-path environments, and highly nonlinear vehicle motion, all of which can impair target detection and analysis. Synthetic Aperture Sonar (SAS) performance can be optimized using performance prediction models; however, currently available performance models do not sufficiently include the challenges of working in shallow water. In this paper we will develop a shallow water SAS performance model and validate the results of SAS performance from two different shallow water surveys conducted using Kraken's Miniature Synthetic Aperture Sonar (MINSAS). The results show that the MINSAS is particularly adept in shallow water conditions where its narrow vertical beamwidths and coherent integration help reject multipath and enhance target detection.