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Matched-field tracking (MFT) algorithms have been successfully applied to both simulated and measured data to determine the most likely positions of a sound source that is localized ambiguously by a matched-field processing (MFP) system. They have been used to track sources moving linearly or on a circular path at constant speed and heading. The input to the trackers is a set of ambiguity surfaces, contiguous in time, generated by MFP. These algorithms assume that the track start and end times are known a priori; this restriction is removed in the piecewise MFT algorithm (PTA). The PTA was applied to narrow-band measured data collected during the PACIFIC SHELF 93 trial to successfully identify the significant source track segments 相似文献
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Dosso S.E. Yeremy M.L. Ozard J.M. Chapman N.R. 《Oceanic Engineering, IEEE Journal of》1993,18(3):232-239
A method for estimating properties of the ocean bottom such as bathymetry and geoacoustic parameters such as sound speed, density and attenuation, using matched-field inversion is considered. The inversion can be formulated as an optimization problem by assuming a discrete model of unknown parameters and a bounded search space for each parameter. The optimization then involves finding the set of parameter values which minimizes the mismatch between the measured acoustic field and modeled replica fields. Since the number of possible models can be extremely large, the method of simulated annealing, which provides an efficient optimization that avoids becoming trapped in suboptimal solutions, has been used. The matching fields are computed using a normal mode model. In inversions for range-dependent parameters, the adiabatic approximation is employed. This allows mode values to be precomputed for a grid of parameter values and stored in look-up tables for fast reference, which greatly improves computational efficiency. Synthetic inversion examples are presented for realistic range-independent and range-dependent environments 相似文献
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Filling of McNaughton Lake, with a capacity at full load of25 · 109m3 and maximum depth 191 m, was initiated on March 29, 1973. An earthquake swarm of 747 events (ML > 0) with largest eventML = 4.7 occurred within 17 km of the reservoir just prior to loading. Subsequent to this, three swarms of 194, 292 and 22 events with maximumML = 4.1 occurred in the same region; however, no earthquakes have occurred between the reservoir and the swarm area. The level of regional seismic activity is similar to that observed prior to loading. The distribution of this activity, excluding swarm events, exhibits a spatial pattern similar to that recorded earlier by regional seismic stations, except that several events appear to be associated with the fault underlying the Rocky Mountain Trench in which the lake is formed. During a loading-unloading cycle in which the maximum water depth varied from 98 m to 171 m to 131 m, the change ofvp was less than 2%. This indicates that no significant change in dilatancy or degree of water saturation occurred in the upper crustal layer during this cycle. 相似文献
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Ozard J.M. Wilmut M.J. Berryman D.G. Zakarauskas P. 《Oceanic Engineering, IEEE Journal of》1993,18(3):265-270
Selection of replica fields that are most like the data, i.e., the nearest neighbors (NNs) to the data, offers a way of reducing the computational search space in matched-field processing, thereby making larger physical search spaces or a larger number of frequencies practical. To enable selection of NNs a vector basis for the search space is required. The authors use the large eigenvectors of the covariance matrix for uncorrelated sources spread over the search region. This is not only a suitable vector basis of the search space, but also results in a dimensional reduction from the full set of eigenvectors, with a further computational saving. The replica vectors for the search region are partitioned by finding their projection on this vector basis. One can then select for matching only those replicas with similar squared projections on the vector basis. This selection process carries a modest cost in computing overhead, provided that the code, the partitioning, and the replica selection parameters are optimized. The detection performance and false alarm probability for the Bartlett beamformer, with and without selection of the replicas, were estimated from simulations of noisy data received on a vertical line array at practical time-bandwidth products. An order of magnitude speedup was obtained 相似文献
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Ozard J.M. Yeremy M.L. Chapman N.R. Wilmut M.J. 《Oceanic Engineering, IEEE Journal of》1996,21(4):377-383
This paper describes matched-field processing (MFP) of data collected in shallow water off the western coast of Vancouver Island in the Northeast Pacific Ocean. The data were collected from a vertical line array (VLA) as part of the PACIFIC SHELF trial carried out on the continental shelf and slope during September 1993, sensors in the 16-element VLA were evenly spaced at depths between 90 and 315 m, while the sound source was towed along radial paths or arcs. In this paper, we present results of the analysis of data from a continuous wave (CW) source which was towed downslope at a depth of 30 m in water from 150 to 375 m deep, in order to model the range-dependence of the acoustic propagation efficiently, the replica fields were calculated using the adiabatic normal mode approximation. This approximation was considered appropriate for the bottom slopes of the environment. Using sparse bathymetric data, a water sound speed profile and estimates of bottom properties, MFP correlations on individual ambiguity surfaces were found to be greater than 0.9 for the strongest signals. On account of environmental mismatch, the source position could not be determined unambiguously from most of the ambiguity surfaces even at high signal-to-noise ratios. Nevertheless, when an efficient linear tracker was applied to the ambiguity surfaces to find tracks, the source track was recovered at both low and high signal-to-noise ratios, this tracker performs the analysis at a constant depth and reports the track with the highest estimated track signal-to-noise ratio 相似文献
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