Environmental and system effects on source localization in shallow water by the matched-field processing of a vertical array

This paper presents simulated and experimental results on source localization in shallow water by the matched-field processing of a vertical array. Range-depth ambiguity surfaces are obtained by the spatial correlation of the incident field (modeled or real) with a modeled replica of that field. All modeled fields are generated by the Centre’s normal-mode program. The simulated results indicate that a high-quality ambiguity surface can be obtained provided that the incident field is formed by a significant number of contributing modes, and that the array spans a large fraction of the water column. Changes in the acoustic environment that reduce the effective number of modes result in a degraded surface. The effect of mismatches between the ‘‘true’’ environmental parameters and those used to compute the replica field is also investigated. Errors in the bottom parameters do not severely effect the results, but small mismatches in sound-speed profile or water depth can degrade the result significantly. Examples of localizations obtained with real data from a Mediterranean site are presented, for source ranges up to 19 km from a vertical array that spanned half the water depth. Successful localizations were obtainable, though high sidelobes were also present.