Comparative analysis of split beam data

Abstract

Split beam data can provide high quality, in situ, fish target strength estimates, however a careful calibration is required to realize this potential. In same cases a standard target has been used to make a large number of measurements that cover the entire beam area of interest, then a general three dimensional surface is locally fitted to provide an expression for the beam pattern and a target strength calibration for all points. We use a simpler method that takes advantage of the known beam shape and requires relatively few data points. We also describe a new approach that optimizes the backscattering cross section, rather than the beam pattern estimation process. Preliminary work indicates that the attainable accuracy is comparable to that obtained with more elaborate methods.