Broadband matched-field tracking with horizontal line arrays in shallow water

The use of three-dimensional matched-field processing to obtain time-dependent range, depth, and bearing estimates with a horizontal line array (HLA) can be computationally restrictive. The problem becomes much more tractable, however, when beam forming is first used to obtain bearing estimates versus time, which are then used to obtain range-depth ambiguity surfaces versus time. For the case of a moving source, matched-field tracking (MFT) compensates for source motion by integrating matched-field correlations over candidate source tracks through the bearing-range-depth space. The true track is determined by the highest integrated correlation, which also results in a gain in detectibility for the true source track. The effectiveness of this approach for the tracking of broadband sources in shallow water is studied via the analysis of HLA data collected during the Shallow Water Evaluation Cell Experiment 1996 (SWellEX-96), which occurred in 200 m water, 6 km southwest of San Diego. Broadband signals in this experiment included a narrowband comb and the broadband signature emanating from the source-tow ship. The MFT methoc can be used as a stand-alone tracker or as a tool to obtain initial track estimates for the initialization of a more efficient conventional tracker. [Work supported by ONR 321US.]