Estimates of Source Range Using Horizontal Multi-path in Continental Shelf Environments

date September 5, 2014
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Friday, September 5, 2014 4:00 p.m. ETC 4.150

Dr. Megan S. Ballard
Applied Research Laboratories
The University of Texas at Austin
www.arlut.utexas.edu

A method has been developed to estimate source range in continental shelf environments that exhibit three-dimensional propagation effects. 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. To obtain an estimate of source range, the principle of reciprocity is used such that the rays originate from the center of the array with 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 technique is applied to data recorded on a horizontal line array located about 12 km east of the southern coast of Florida. The effects of unknown environmental parameters, including the sediment properties and the water-column sound-speed profile, on the source range estimate are quantified. Error resulting from uncertainty in the measured bathymetry and location of the receiver array will also be addressed.