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Timothy Marston

Principal Engineer

Email

marston@apl.washington.edu

Phone

206-221-5267

Department Affiliation

Acoustics

Education

B.S. Electrical Engineering, Seattle Pacific University, 2004

M.S. Acoustics, Penn State, 2006

Ph.D. Acoustics, Penn State, 2009

Publications

2000-present and while at APL-UW

Multi-sensor towbody: Expandable platform detects, geolocated and classifies UXO

Williams, K., T. Marston, and T. McGinnis, "Multi-sensor towbody: Expandable platform detects, geolocated and classifies UXO," Sea Technol., 62, 8-11, 2021.

1 Sep 2021

Spatially variant autofocus for circular synthetic aperture sonar

Marston, T., and J. Kennedy, "Spatially variant autofocus for circular synthetic aperture sonar," J. Acoust. Soc. Am., 149, 4078-4093, doi:10.1121/10.0005198, 2021.

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1 Jun 2021

Circular synthetic aperture sonar (CSAS) is a method for improving the resolution and target detection capabilities of a synthetic aperture sonar system. CSAS data are difficult to focus because of their large aperture sizes and elevation sensitivity. This difficulty has sometimes been addressed by using transponders or distributing isotropic scatterers in the field of view of the system; however, this comes at the cost of reduced practicality. As an alternative, map-drift based multipoint autofocus ("multilateration") was proposed by Cantalloube and Nahum [IEEE Trans. Geosci. Remote Sens. 49, 3730-37 (2011)] for autofocusing analogous circular synthetic aperture radar data. Multilateration also solves the problem of aberration spatial variance by providing a three-dimensional navigation correction. In circular synthetic aperture focusing problems, though, correcting aberrations is a joint navigation and elevation estimation problem, and the present work extends the multilateration approach to simultaneously solve both a navigation solution and coordinate corrections for the multilateration control patches. Additionally, methods for addressing the stability and behavior of the inverse problem are addressed, and an adaptive weighting scheme for reducing the influence of outliers is presented. The field results demonstrate near optimal point-spread functions on distributions of natural isotropic scatterers and robustness in regions with bathymetric variability.

Utilization of aspect angle information in synthetic aperture images

Plotnick, D.S., and T.M. Martston, "Utilization of aspect angle information in synthetic aperture images," IEEE Trans. Geosci. Remote Sens., 56, 5424-5432, doi:10.1109/TGRS.2018.2816462, 2018.

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1 Sep 2018

Synthetic aperture sonar and synthetic aperture radar involve the creation of high-resolution images of a scene via scattered signals recorded at different locations. Each pixel of the reconstructed image includes information obtained from multiple aspects due to the changing position of the sources/receivers. In this paper, the aspect-dependent scattering at each pixel is exploited to provide additional information about the scene; this paper presents a framework for converting and utilizing multiaspect data, as well as several examples. For sonar data, as is presented here, the aspect dependence may be leveraged to separate objects of interest from the background, to understand the local bathymetry, or for visualizing acoustic shadowing in full circular synthetic aperture sonar images. Several examples of images of the seafloor containing objects of interest are presented for both circular and linear apertures. In addition, the aspect dependence of low-frequency elastic scattering from objects may be used to understand the underlying scattering physics, which is of potential use in fields such as target recognition and nondestructive testing; a laboratory example is presented.

More Publications

Inventions

Synthetic Aperture Processing for Down-Looking Sonar Systems

Record of Invention Number: 48984

Kevin Williams, Timothy Marston, Daniel Plotnick

Disclosure

5 Nov 2019

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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