A vector-hydrophone~s minimal composition for finite estimation-variance in direction-finding near a rigid reflecting boundary

Vector-hydrophones have been recently introduced to address the underwater acoustic direction finding problem. A vector-hydrophone configuration consists of three spatially collocated but orthogonally oriented velocity-hydrophones and an optional pressure-hydrophone. In this paper, we assess the different combinations of the vector-hydrophone components to identify an efficient vector-hydrophone construction which still enables the directional of arrival estimation. The optimum vector-hydrophone structure is found by evaluating the necessary and sufficient vector-hydrophone composition non-singularity in the Fisher information matrix. Recommended for direction finding near a rigid reflecting boundary are a pressure hydrophone composed with a collocated pair of x-axis and y-axis velocity hydrophones