Randall W. Smith
Jaime F. Nualart
David E. Grant
Appl. Res. Lab., Univ. of Texas at Austin, P.O. Box 8029, Austin, TX 78713-8029
The basic characteristics of multipath propagation from a shallow source to a bottomed receiver in shallow water are investigated, with an emphasis on application to the problem of source localization. For this fundamental study, the environment is assumed to be ideal (perfectly reflecting bottom and surface, range invariant depth, isovelocity). The delays between travel times along different propagation paths depend on the location (range, depth, and bearing) of the source relative to the receiver. Measurements of several such time delays can be used to determine the location of the source. It was found that the travel time difference between paths having differing numbers of traversals of the water column depends strongly on range but weakly on depth. In contrast, the travel time difference between paths having an equal number of traversals but which have different source angles (i.e., up or down) depends strongly on depth but weakly on range. As an example, these observations are applied to localize a towed sound source in a real environment. The example provides a background for an assessment of how accurately a real environment must be modeled in order to obtain reasonable results.