The equivalent beam angle and its effective value when applying an integrator threshold

Abstract

In a noise-limited echo integration system, a threshold is applied in order to avoid the contribution from noise. As the signal-to-noise ratio decreases with range, the effective observation volume for small targets is reduced. Direct estimates of the effective value of the equivalent beam angle have been made by combining data from echo integration, trace-counting, and in situ target strength measurements. Large deviations from the nominal value of the equivalent beam angle were found using this method on resolved registrations of cod and haddock.