Shallow water High Resolution Bathymetric Side Scan Sonar

Abstract

With about 2 years' work, the Instituted of Acoustic, Chinese Academy of Sciences (IACAS) and the Teledyne RD Technology (Shanghai) Inc. (RDT) have developed the Shallow water High Resolution Bathymetric Side Scan Sonar (SBSSS). It is mainly composed of sonar deck control unit, sonar housing (include electronic unit and watertight pod) and two sonar arrays. The SBSSS can obtain the incidence angle of the backscatter from the water bottom on sonar array, directly. Using this system, the grazing angle, distance and signal intensity (acoustic intensity) of the target on the water bottom or in the water can be measured. Working with motion sensor, CTD sensor and GPS (or RTK) system, the SBSSS can get the high resolution terrain and geomorphy of the water bottom, synchronously. After post-processing, the contour map and side scanning map, which is better than the normal side scanning map, can be obtained. The SBSSS also can be used to detect the target on the water bottom or in the water. The technique of sea bottom automatic detect and estimation direction of arrival (DOA) based on multi-subarray subspace fitting (SBAD-EDMSF) is researched and progressed. It can improve the accuracy of depth measurement. Some other theory about the SBSSS, such as estimation technique about the number of signal sources, signal copy technique, attitude correct technique, real time signal processing technique and etc., is studied. Using these methods, the sonar can get better result in the complex acoustic field in the shallow water. So the theory info about the SBSSS is found. It is used to design the sonar and processing the sonar data. The good results are obtained. The maximum working depth of this system is 300 meters. The maximum working range for the depth is 12 times water depth, and for the side scan is 400 meters per side. The cross track resolution is 5 cm, and the minimum detect height is 10 cm. The lake test at Qiandao Lake, P. R. China and the ultra shallow water sea test (5 to 10 meters) in Qingdao, P. R. China are implemented. A water area of 2000 m x 800 m is surveyed. The contour map and the side scan map are obtained. Using the SBSSS, a 30 cm diameter buoyant plastic sphere is detected. After the post processing for the survey data, the measurement accuracy of depth is basically corresponded with the special order standard of IHO. The SBSSS also can be mounted on the automatic underwater vehicle (AUV), remote operated vehicle (ROV), towed body and other underwater vehicles. It can be used to measure the small target, the terrain and the geomorphy of the sea bottom. This paper makes a brief introduce of the system structure, the theory info, the lake test results and the sea test results of the SBSSS.