Long range active synthetic aperture sonar results

Chang, Enson; Marx, D.; Nelson, Matthew A.; Gillespie, WJ; Putney, A.; Warman, L. Kieffer; Chatham, Ralph E.; Barrett, B.N.

doi:10.1109/oceans.2000.881226

Cited by 9 publications

(7 citation statements)

References 4 publications

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“…Also, it is possible to apply the arrival time methodology to pressure estimates obtained directly from time-lapse seismic data Lumley 1999, Landro 2001), by-passing the estimation of deformation entirely. In addition, developments such as side-scan-sonar interferometry (Chang et al 2000) and acoustic positioning (Spiess et al 1998), may provide useful data. An extension of this work would allow for permeability changes to accompany deformation.…”

Section: Discussionmentioning

confidence: 99%

Estimating permeability from quasi-static deformation: Temporal variations and arrival-time inversion

2008

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Transient pressure variations within a reservoir can be treated as a propagating front and analyzed using an asymptotic formulation. From this perspective one can define a pressure 'arrival time' and formulate solutions along trajectories, in the manner of ray theory. We combine this methodology and a technique for mapping overburden deformation into reservoir volume change as a means to estimate reservoir flow properties, such as permeability. Given the entire 'travel time' or phase field, obtained from the deformation data, we can construct the trajectories directly, there-by linearizing the inverse problem. A numerical study indicates that, using this approach, we can infer large-scale variations in flow properties. In an application to Interferometric Synthetic Aperture (InSAR) observations associated with a CO 2 injection at the Krechba field, Algeria, we image pressure propagation to the northwest. An inversion for flow properties indicates a linear trend of high permeability.

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Section: Discussionmentioning

confidence: 99%

Estimating permeability from quasi-static deformation: Temporal variations and arrival-time inversion

2008

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“…In the past, SAS has been used in shallow and some very shallow water and Dynamics Technology, Inc. (DTI) processed data from eleven such systems [1] [2][3] [4]. The surf zone does not posses such a pedigree.…”

Section: Introductionmentioning

confidence: 99%

“…Since other works cover SAS processing in greater detail [1] [2][3] [4], this work will only touch upon the processing for completeness. The processing consists of three basic steps.…”

Section: Introductionmentioning

confidence: 99%

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Bottom crawling synthetic aperture sonar for very shallow water mine countermeasures

Putney

Savidge²,

Chang³

et al.

MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295)

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Synthetic aperture sonar (SAS) is a promising technology for rapidly detecting and classifying underwater mines. Previous SAS systems have been mounted on swimming vehicles that typically undergo smoothly varying motion. E D 0 Electro-Ceramics built a SAS for us and Foster-Miller, Inc. mounted it on one of their underwater crawling vehicles. This SAS-Crawler operates at 160 kHz, has a theoretical resolution of 2.54 cm (1 in) in range and 1.27 cm (0.5 in) in cross-range (azimuth) out to 50 m, and is intended to operate in the very shallow water and surf zones.The motion of a bottom crawling SAS is expected to be jerky as it follows the rough terrain. This presents new problems in motion estimation and correction. Furthermore, the acoustic environment, e.g., coherence properties, of the very shallow water and surf zones is less stable than the deeper waters. The slow speed of the vehicle in conjunction with a relatively high ping rate, however, yields many overlapping, or redundant, phase centers, which should help us overcome the motion estimation and coherence problems.

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“…A single exception is a subkilohertz data set collected in the Mediterranean for non-SAS applications [2]. We analyzed this data and demonstrated focusing of an oil platform at 26 km range to virtually theoretical resolution.…”

Section: Introductionmentioning

confidence: 99%

Coherence of pulsed signal and implications to synthetic aperture sonar processing

Chang

Tinkle²

MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295)

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Recent synthetic aperture sonar (SAS) processing of low-frequency active acoustic data suggests that coherent integration apertures on the order of several thousand wavelengths can be achieved by using data-driven adaptive compensation techniques. This paper uses a normal mode based simulation to explore the interplay between adaptive compensation and medium coherence in SAS processing. Our analysis concentrates on signal fluctuations induced by background internal waves in a shallow-water region of the Mediterranean. The results indicate that commonly used adaptive compensation techniques can overcome the internalwave-induced image smearing in azimuth. The range of internal wave spectral level tested is typical of shallow water areas.

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Long range active synthetic aperture sonar results

Cited by 9 publications

References 4 publications

Estimating permeability from quasi-static deformation: Temporal variations and arrival-time inversion

Estimating permeability from quasi-static deformation: Temporal variations and arrival-time inversion

Bottom crawling synthetic aperture sonar for very shallow water mine countermeasures

Coherence of pulsed signal and implications to synthetic aperture sonar processing

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