A Shallow-Water Swath Bathymetry System

LONG-TERM GOAL. Our long-term goal is to understand the processes which create and modify the sea bed in the coastal zone and to understand how seabed morphology can be studied using high-resolution swath mapping techniques for bathymetry and backscatter. OBJECTIVES. Swath-mapping techniques have proven extremely valuable to the study of sea-floor morphology on continental shelves, slopes and margins, mid-ocean ridges and in the deep ocean, but systems designed for continental shelf and deeper-water environments are not optimized for the shallow-water of coastal settings. Swath-mapping systems optimum for shallow water have recently become available however, until our system became operational in late 1998 no shallow-water system existed in the U.S. academic community for use in research programs. Our objective is to fill this critical gap by obtaining, installing and using a research-grade shallow-water swath bathymetry system that can be moved between vessels as required. This kind of high-resolution morphological data will contribute to ONR programs in the coastal zone such as STRATAFORM and SAX99. APPROACH. We are building a shallow-water swath bathymetry system designed around a Kongsberg Simrad EM 3000 multibeam echosounder which can operate in water depths of 0.5 to over 100 m. Other major system components include a TSS POSMV navigation and attitude, Sun and SGI computers data processing and display, gyroscope heading, CTD sound velocity structure and tide gauge water level. The EM 3000 is a research-grade shallow-water multibeam echosounder that operates at 300 kHz and creates echosounding beams with nominal widths of 1.5 deg.