Shallow water multibeam sonar performance, results from a modern hydrographic survey system

SAIC conducted hydrographic surveys in April through September, 1995, in support of the first multibeam and side-scan work done under contract for the National Oceanic and Atmospheric Administration's (NOAA) Nautical Charting Branch Office of Coast Survey. These surveys were run using SAIC's Integrated Hydrographic Survey System (IHSS) in conjunction with a Reson SeaBat multibeam sonar and a Klein side-scan sonar. The surveys were done in Long Island Sound and Martha's Vineyard in water depths of 5.5 to 60 m. Contract requirements include proof of 100 per cent multibeam coverage and 200 per cent side-scan coverage; data meeting International Hydrographic Organization (IHO) standards (1/spl times/IHO) to a swath width of 45/spl deg/ and twice MO standard (2/spl times/IHO) at greater usable widths; no across-track multibeam footprints of greater than 3 m; no multibeam gaps of greater than 3 m/spl times/3 m; and the ability to detect contacts of 1m/sup 3/ in water depths less than 20 m, 2 m on each side in 20-30 m depths, and those with heights of 1% of water depth in greater than 30 m of water. This paper discusses selection, configuration, and calibration of the multibeam sonar, related sensors, and the IHSS in order to meet the exacting MO and NOAA standards. In order to use a multibeam sonar for modern hydrographic surveys, a number of issues (including multibeam accuracy, coverage, application of correctors, data volume and throughput, and contact identification) must be addressed. The real-time and processing tools, which are incorporated into SAIC's IHSS to tailor the system for hydrographic use, and the preliminary results of the first survey are described.