Shallow Water Surveying Using Experimental Interferometric Synthetic Aperture Sonar

Abstract

A B S T R A C TThis paper describes an interferometric synthetic aperture sonar system based on an unmanned surface vehicle customized for shallow water environments. Synthetic aperture sonar enables imagery of high resolution that is independent of range by using the displacement of the sonar platform to create a large virtual array. If two geometrically displaced images are obtained, the construction of threedimensional topographic maps is possible through the use of interferometric techniques. The use of an unmanned surface vehicle presents several advantages that alleviate some problems related to the formation of synthetic aperture images, which are mainly related to the fact that a precise navigation system can be used for the boat control and sonar imagery motion compensation. Also, a small unmanned surface vehicle is advantageous in terms of cost of operation, maintenance and ease of deployment. Mapping of shallow water areas is an important task for many commercial and scientific applications like river navigability, infrastructure maintenance and natural resource monitoring. These tasks can be done efficiently with this system. Sample data obtained during test trials illustrate how synthetic aperture can be used to generate underwater imagery and bathymetric data. A B S T R A C TThis paper describes an interferometric synthetic aperture sonar system based on an unmanned surface vehicle customized for shallow water environments. Synthetic aperture sonar enables imagery of high resolution that is independent of range by using the displacement of the sonar platform to create a large virtual array. If two geometrically displaced images are obtained, the construction of threedimensional topographic maps is possible through the use of interferometric techniques. The use of an unmanned surface vehicle presents several advantages that alleviate some problems related to the formation of synthetic aperture images, which are mainly related to the fact that a precise navigation system can be used for the boat control and sonar imagery motion compensation. Also, a small unmanned surface vehicle is advantageous in terms of cost of operation, maintenance and ease of deployment. Mapping of shallow water areas is an important task for many commercial and scientific applications like river navigability, infrastructure maintenance and natural resource monitoring. These tasks can be done efficiently with this system. Sample data obtained during test trials illustrate how synthetic aperture can be used to generate underwater imagery and bathymetric data.

Precision, accuracy, and application of diver-towed underwater GPS receivers

“…They are not directly useful in underwater applications. Various methods such as acoustic tools like multibeam sonars, omnidirectional sonars, and interferometric synthetic aperture sonar have been developed during the last two decades to geo-reference underwater sites (Brehmer et al 2003;Silva et al 2009) and to facilitate the orientation of divers (Prichard and Guthrie 1996). Surface-based underwater video- Corresponding units are given in brackets graphy with submeter-accuracy differential GPS was used by Schultz (2008) and towed underwater video is a widely used method for bottom habitat mapping, producing narrow bands of video imagery that can be recorded together with GPS data for geo-referencing (Grizzle et al 2008).…”