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Point-source violations: split-beam tracking of fish at close range

  • James J. Dawson (a1), Daniel Wiggins (a1), Donald Degan (a2), Harold Geiger (a3), Deborah Hart (a3) and Barbara Adams (a4)...

Abstract

Split-beam positional estimates of fish detected in a river at close range often do not correspond to the actual position of the target. These inaccuracies create problems in determining whether a fish is moving upstream or downstream. We hypothesize that these positional estimates are degraded by two factors: size of target relative to beam diameter, and the complex scattering of the fish. These parameters create a near-field effect, within which the phase measurements of the returning echoes are corrupted. Examples of fish tracks from near and far range fish detected by a split-beam echo sounder are provided to illustrate these inaccuracies. Experimental data from tethered spheres and complex targets show increasing distortion with target complexity and proximity to the transducer.

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Point-source violations: split-beam tracking of fish at close range

  • James J. Dawson (a1), Daniel Wiggins (a1), Donald Degan (a2), Harold Geiger (a3), Deborah Hart (a3) and Barbara Adams (a4)...

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