Look-ahead bottom profiling with a small acoustic aperture

This paper describes a small-aperture sonar and processing technique that provides vertical profile information with a single ping without the large arrays of acoustic elements required for beamforming. The small acoustic aperture makes the sonar suitable for small vehicles and towfish. The sonar uses angle of arrival estimates, derived from a small number of acoustic elements, for determining the lay of the land in front of the transducer. Unlike two-element interferometric sonars, this sonar´s performance does not suffer from the presence of multiple time-coincident targets because multiple angles can be estimated. Examples of lookahead profiles derived from simulated and experimental data are given for different target geometries and propagation conditions. The results are compared with those that would be obtained using two-element interferometry. Potential applications of the sonar and processing technique, and direction of future research are discussed