MATCHED-FIELD SOURCE LOCALIZATION IN A RANGE-DEPENDENT ENVIRONMENT

In this paper source localization results obtained by matched-field (M F) processing of vertical line array (VLA) data from the PACIFIC ECHO III sea trial are presented. The experimental site was located in a re gion of significant bathymetric variation. An harmonic source was towe d on a series of arcs, providing data for a sequence of different rang es and azimuths. In spite of the significant bathymetric variation, go od MF localization results were obtained for a large fraction of the t rial time. In the first part of this analysis it is assumed that the a zimuth of the source is known. Substantial improvements in MF localiza tion were obtained by using an adiabatic normal mode model to calculat e replica acoustic fields for the range-dependent bathymetry. The impr ovement over the results obtained with flat-bottom waveguide replicas is demonstrated for data from the longer range arcs. In the second par t of the analysis, the concept of environmental signal processing, an enhancement to MF processing that is obtained by making use of the com plexity of the oceanic waveguide environment, is investigated. The azi muthal variation of bathymetry for the source tracks along the arcs wa s used to obtain estimates of the source bearing from the VLA data. In many instances, the bearing estimates were in reasonable agreement wi th the known source bearings.