Effects of environmental uncertainty on source range estimates from horizontal multipath

A method has been developed to estimate source range in continental shelf environments that exhibit three-dimensional propagation effects [M. S. Ballard, J. Acoust. Soc. Am., 134, EL340-EL343, 2013]. The technique exploits measurements recorded on a horizontal line array of a direct path arrival, which results from sound propagating across the shelf to the receiver array, and a refracted path arrival, which results from sound propagating obliquely upslope and refracting back downslope to the receiver array. A hybrid modeling approach using vertical modes and horizontal rays provides the ranging estimate. According to this approach, rays are traced in the horizontal plane with refraction determined by the modal phase speed. Invoking reciprocity, the rays originate from the center of the array and have launch angles equal to the estimated bearing angles of the direct and refracted paths. The location of the source in the horizontal plane is estimated from the point where the rays intersect. In this talk, the effects of unknown environmental parameters, including the sediment properties and the water-column sound-speed profile, on the source range estimate are discussed. Error resulting from uncertainty in the measured bathymetry and location of the receiver array will also be addressed. [Work supported by ONR]