Working from Top to Bottom with the ME70 Multibeam Echosounder

Abstract

The recently developed Simrad ME70 fisheries multibeam echosounder has been designed primarily for investigations of marine organisms in the water column, with some stark differences between typical bottom mapping multibeam sonars (greatly increased dynamic range, much lower sidelobes, far fewer beams, and shorter aperture lengths). Ideally, the same multibeam sonar would be used simultaneously for both water column and seabed investigations, because both types of data have demonstrated value in defining Essential Fish Habitat. Our approach to using the ME70 for both water column and seabed investigations is to generate bathymetry and backscatter from standard water column modes. To achieve high resolution on the seabed despite the ME70's relatively low beam count (<45), we have developed a hybrid multibeam/phase-differencing approach that generates several soundings per beam (away from nadir), resulting in 100's of independent soundings per beam. Further, because this system can be fully calibrated using standard target spheres, we can generate angle-dependent bottom backscattering strength curves that are useful for classifying the substrate. This talk will be focused on the ability of the ME70 to perform seabed characterization work, including comparisons of the predicted and empirically derived sounding uncertainty, and examinations of angle-dependent backscattering strength in known sites. Field work on board the NOAA FRV “Oscar Dyson” conducted in both the Bering Sea and the Gulf of Alaska will be highlighted.

Department

Center for Coastal and Ocean Mapping

Publication Date

2010

Journal Title

ICES Working Group on Fisheries Acoustics, Science and Technology

Series

2010

Pages

4

Conference Date

Apr 26 - Apr 30

Publisher Place

San Diego, CA, USA

Publisher

International Council for the Exploration of the Sea (ICES)

Document Type

Conference Proceeding

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