Source localization in a wedge shaped shallow sea

This paper looks into the problem of localization of an acoustic source in shallow sea with a sloping bottom as found in the continental shelf area. A vertical array of sensors, either floating or secured to the sea bottom, is used to receive the acoustic signals from the source including those travelling by different paths. First, a spectral matrix of the array signal is computed and it is then subjected to eigenvalue decomposition. The space spanned by the eigenvectors is partitioned into two subspaces, namely, a signal subspace spanned by the eigenvector corresponding to largest eigenvalues and a noise subspace spanned by the eigenvectors corresponding to repeated eigenvalues. The signal subspace is also spanned by a linear combination of direction vectors corresponding to all multipaths These two subspaces are orthogonal. We exploit this property of orthogonality in the estimation of range, bearing and depth of a source. Some of the significant findings are as follows:(1) Unlike in the flat bottom channel it is now possible to measure the bearing with respect to upslope or downslope direction.(2) The azimuth scan shows a sharp peak at the correct location for steep slope(>1/spl deg/) (3) A study of finite data effect has shown that the background generally remains unchanged as the number of snapshots increases. However, the signal peak amplitude increases roughly at the rate of 3dB per doubling of the number of snapshots.