Uncertainty in fish location using a split beam sonar

Abstract

The enumeration of fish is of critical importance to the management of both commercial and sport fisheries in Alaska and worldwide. Current methods for riverine fish enumeration are inaccurate and unreliable. Improved fish counting accuracy in Alaskan rivers by acoustic methods is required. A split beam sonar system in the presence of noise is modeled. The sonar system including the received sonar pulse, receiver system, transducer beam pattern, propagation losses, and noise are modeled. An analysis of the effects of noise, pulse duration and sampling frequency on the uncertainty in fish location is presented. Signal to noise ratios less than 5 dB can cause significant errors in the calculation of received signal phase. A stationary fish with a signal to noise ratio of 15 dB has approximately plus-minus 0.001 degrees of uncertainty in the angles of arrival. Reducing the SNR to 3 dB the uncertainty increases to plus-minus 3.6 degrees in the angles of arrival.