06/15/2017 - 4:00pm
8820 Shellback Way La Jolla, CA 92037, US Room 330
Please join us for the following AOS Seminar Thursday, June 15 at 4:00pm in Spiess Hall 330:
Speaker: Chomgun Cho, Scripps Institution of Oceanography
Title: The array-invariant based source range estimation using a vertical array in underwaterAbstract: The array invariant approach using a vertical array for passive localization utilizes multiple arrivals separated in beam angle and travel time via conventional plane-wave beamforming in shallow-water. This approach is essentially equivalent to the waveguide invariant β based on the dispersion between the group and phase speeds when β = 1, which is the generic value for many shallow water environments. Therefore, the array invariant can be applied to many shallow-water environments without knowing the value of the waveguide invariant. In range-dependent shallow-water environment, the array invariant theory needs to be generalized by incorporating the waveguide invariant that is not close to 1 (e.g., a sloping bottom). In a sloping-bottom shallow-water waveguide, the generalized array invariant approach can be implemented by iteratively estimating the source range β until the estimated range is converged. This iterative approach demonstrates the mean relative range error of 18% using a vertical array (2.8-m), where a high-frequency source (2–3.5 kHz) was towed between 0.5 and 5 km in range with the water depth varying from 80 to 50 m. However, in the presence of array tilt, the beam angle estimates are shifted by the array tilt, which potentially affects the range estimation based on the array invariant. Even a small tilt angle (e.g., < 2 deg) of a 1.2-m long vertical array can cause a relative range error of 20% or more, for a high-frequency source (7–19 kHz) at 3-km range in ∼100-m deep water. Thus, this approach needs to be compensated for the array tilt to correctly estimate a source range.
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