High‐frequency current tomography in coastal regions

In deep-water tomography refracted ray paths can provide accurate account of travel time for the inverse problem. However, in shallow coastal regions, due to the geometry of the source-receiver as well as the waveguide dimensions, most acoustic energy is a multiple reflection from sea surface and sea bottom. This makes the forward problem which deals with resolving the multipath structure of the arriving signals difficult. In this paper, we discuss the limits of reciprocal acoustic transmission as a function of waveguide temporal and spatial parameters for the purpose of tomography application in coastal regions. Results from a high-frequency (0.5–24 kHz) quasi-reciprocal tomography experiment in a very shallow-water coastal region are presented. Using these data, the accuracy and limit of current tomography for variable sea states are examined for different center frequencies and bandwidths. [Work supported by ONR.]