Low-Error Bearing Estimation in Shallow Water

The multipath effect due to sound propagation in shallow water causes bearing errors in horizontal line arrays for all angles different from broadside when conventional resolution methods like beamformer or maximum entropy method are used. Error-free bearing estimates can be achieved only by means of generalized power estimators which use a priori knowledge about the spatial channel statistics. This a priori knowledge is usually unknown. The method described makes use of a pilot source which transmits training signals in order to achieve an estimate for a suboptimum spatial signal covariance matrix which is used for field matching.