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Joint CGS-AOML (Charting and Geodetic Service-Atlantic Oceanographic and Meteorological Laboratory) acoustical bottom echo-formation research, Part 2: Field experiment results and recommendations for echo-sounder design.
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1989
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[PDF-128.32 MB]
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Description:Field experiments were conducted to test and verify a mathematical model that has been developed to assess the effects of bottom roughness and material properties on bottom echo shape. The physical basis of the model is reviewed and model output is presented. The experiments were conducted in lower Chesapeake Bay and involved taking high resolution acoustic data at a number of frequencies and taking supporting sediment samples. A unique, high-resolution bottom profiler was used to measure bottom roughness profiles for input to the model. While model predictions were in general agreement with the data, fine structure was observed in the echoes that could not be explained by the existing model. An extension to the model has been developed that is able to account for this structure. The essential ingredient of this extension is to consider bottom surface scattering as arising from a number of statistically independent patches within the transducer beam. This revised model should lead to improved predictions of bottom echo waveforms for echo-sounder design. The algorithm developed for removing ship motion from the observations suggests a design for a new type of echo-sounder detector circuit based on an energy threshold. This circuit could be easily implemented with modern digital signal processing (DSP) circuits, and it might be suitable for retro-fitting to existing echo-sounders.
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Rights Information:CC0 Public Domain
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