Matched-field source localization in a range-dependent environment

Abstract

In this paper source localization results obtained by matched-field ͑MF͒ processing of vertical line array ͑VLA͒ data from the PACIFIC ECHO III sea trial are presented. The experimental site was located in a region of significant bathymetric variation. An harmonic source was towed on a series of arcs, providing data for a sequence of different ranges and azimuths. In spite of the significant bathymetric variation, good MF localization results were obtained for a large fraction of the trial time. In the first part of this analysis it is assumed that the azimuth of the source is known. Substantial improvements in MF localization were obtained by using an adiabatic normal mode model to calculate replica acoustic fields for the range-dependent bathymetry. The improvement over the results obtained with flat-bottom waveguide replicas is demonstrated for data from the longer range arcs. In the second part of the analysis, the concept of environmental signal processing, an enhancement to MF processing that is obtained by making use of the complexity of the oceanic waveguide environment, is investigated. The azimuthal variation of bathymetry for the source tracks along the arcs was used to obtain estimates of the source bearing from the VLA data. In many instances, the bearing estimates were in reasonable agreement with the known source bearings.

Clutter depth discrimination using the wavenumber spectrum

“…Some of these methods include matched field processing which attempts to maximize an objective function which correlates the modeled and measured acoustic fields (Bucker, 1976;Baggeroer et al, 1988;Fawcett et al, 1996); modal decomposition methods which seek to match the modeled and measured modal amplitudes as a function of depth (Shang, 1985;Yang, 1987;Glattetre et al, 1989); matched mode methods which endeavor to match modeled and observed mode amplitudes as measured on a horizontal line array by use of the frequency-wavenumber (f-k) transform (Nicolas et al, 2006); and waveguide invariant approaches which are based on Chuprov's (1982) parameterization relating range and frequency to the slope of the striations in acoustic pressure in a frequency-range plot (Brekhovskikh and Lysanov, 1991;D'Spain and Kuperman, 1999). The waveguide invariant is commonly interpreted in terms of constructive and destructive interference of propagating normal modes (Turgut and Orr, 2010), but it has also been described in terms of ray theory (Gerstoft et al, 2001) and variations in eigenray arrival times (Harrison, 2011), and related to the wavenumber integration technique (Cockrell and Schmidt, 2010).…”

Error Bounds in Matched-Field Inversion for Geoacoustic Properties

“…The VLA consisted of 16 hydrophones spaced 40 m apart, with the topmost element at a depth of 200 m. The array was located at a range of 2 km from a 10-Hz source at a depth of 46 m. This geometry simulated the experimental arrangement in one of the PACIFIC ECHO sea trials that was carried out near the Juan de Fuca ridge in the North Pacific. 10 For these conditions, there were 14 modes. The KRAKENC 12 solutions were benchmarked against SAFARI 15 calculations to confirm that the code was indeed satisfactory for this environment.…”

“…The environment and experimental geometry were chosen to simulate the conditions at the site of one of the PACIFIC ECHO experiments in the Northeast Pacific. 10 Inversions were carried out using replica fields that were calculated for known amounts of error in the geometrical parameters. Both the MF correlation (i.e.…”

Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

“…ULF band is very attractive for detection, localization, and geoacoustical parameter estimation purposes, because propagating acoustic waves are almost not affected by absorption and thus can propagate at very long ranges. In this context, mainly two approaches are used: Matched-Field Processing (denoted MFP) [2,3] and Matched-Mode Processing (denoted MMP) [4][5][6]. The com-parative study of both approaches is given in [7].…”