Matched-field source tracking by ambiguity surface averaging

The method of matched-field source tracking by ambiguity surface averaging is demonstrated using low-frequency shallow-water acoustic data recorded on a vertical array. In this method, source motion is taken into account by a veraging values from individual, short time-average matched-field ambiguity functions; each resulting average value corresponds to a trial source trac k. The result is a new ambiguity function which depends on six parameters: the three-dimensional coordinates of the initial and final source positions . A simplification to four parameters is made by assuming the source remain s at a constant depth. Only mild restrictions are made on trial tracks cons idered, and the resulting ambiguity surfaces can be plotted as a function o f final coordinates by holding the initial coordinates fixed at the optimal position. When applied to experimental data, the number of high sidelobes present in individual matched-field ambiguity surfaces is greatly reduced. Also, the technique appears robust to uncertainties in replica computation (due to various mismatch problems) and periods when the signal-to-noise rat io is low. (C) 2001 Acoustical Society of America.