A new invariant method for instantaneous source range estimation in an ocean waveguide from passive beam-time intensity data

Abstract

A new method is derived for instantaneous source range estimation in an ocean waveguide from passive beam-time intensity data received on a horizontal or vertical line array. While the method is as simple and robust as the ‘‘waveguide invariant’’ method described by Brekhovskikh and Lysonov (2003), it does differ significantly from the latter. Some advantages are that (1) it only requires source signal measurement at a single rather than many ranges so that range can be instantaneously estimated, and (2) it is invariant over all horizontally stratified ocean waveguides. The paramter β of the waveguide invariant method, on the other hand, varies significantly with vertical sound-speed structure. Since the invariant parameter of this new method varies only with the geometry of the array, the term ‘‘array invariant’’ method is here introduced. The method does not rely on near-field processing techniques but is also applicable at arbitrary far-field ranges. The method is applied to data from the Main Acoustic Clutter Experiment 2003 for source ranges between 2 to 10 km, where it is shown that simple, accurate, and efficient source range estimates can be made using this new method.