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×IHO) to a swath width of 45° and twice MO standard (2×IHO) at greater usable widths; no across-track multibeam footprints of greater than 3 m; no multibeam gaps of greater than 3 m×3 m; and the ability to detect contacts of 1m³ 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