A new method for range and depth source localization in shallow water

Abstract

Range and depth source localization in shallow water amounts to the estimation of the normal mode structure of the acoustic field. As “seen” by a vertical array, and from a modeling point of view, the normal mode structure appears as a set of nonplane coherent waves closely spaced in angle. The technique presented in this paper uses the eigen decomposition of the data cross‐correlation matrix in order to resolve this set of nonplane waves and to estimate the subspace spanned by the normal modes that are significantly excited by the source(s): the mode subspace. The projection of the replica pressure vector onto the mode subspace for all possible range/depth source locations gives the final ambiguity surface. Results obtained on realistic environments show that its performance is always greater or equal to that of the generalized MLM processor [A. B. Baggeroer, W. A. Kuperman, and H. Schmidt, J. Acoust. Soc. Am. 83, 571–587 (1988)]. Good performance results have been obtained on short time records; this suggests the method may be applicable to localizing moving sources and/or sources emitting transient signals. Preliminary results obtained on real data will be discussed and compared with those obtained by the conventional and MLM processors.