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Warren Fox

Acting Deputy Executive Director / EIS Department Head / Senior Principal Research Scientist





Research Interests

Autonomous Systems, Statistical Signal and Image Processing, Underwater Acoustics, Sonar


Dr. Fox manages projects and performs research in the areas of autonomous maritime systems; statistical signal, image, and information processing; underwater acoustic theory and applications; and optimal utilization of sonar systems. He has worked in the application areas of mine countermeasures (MCM), anti-submarine warfare (ASW), torpedo defense, and underwater acoustic communications. His experience includes planning and execution of major experimental sea trials, and project/program management for large interdisciplinary research teams. He is a Senior Member of the IEEE.


B.S. Electrical Engineering, University of Washington - Seattle, 1988

M.S. Electrical Engineering, University of Washington - Seattle, 1990

Ph.D. Electrical Engineering, University of Washington - Seattle, 1994


2000-present and while at APL-UW

Synthetic aperture sonar array gain measured at sea

Groen, J., M. Couillard, and W.L.J. Fox, "Synthetic aperture sonar array gain measured at sea," Proceedings, EUSAR: 9th European Conference on Synthetic Aperture Radar, 23-26 April Nuremberg, Germany, 74-77 (VDE, 2012).

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23 Apr 2012

A synthetic aperture sonar (SAS) typically consists of a directional transmitter and two vertically displaced receiving arrays, placed in a rigid frame. Many receivers permit an adequate area coverage rate and partly solve motion estimation issues. SAS motion estimation is crucial for image quality and is partly accomplished by using the ping-to-ping correlation obtained from overlapping elements. SAS gain depends on this ping-to-ping correlation. In this paper, theoretical impact of motion estimation accuracy and geometry on the SAS gain are formulated. Also, array gain is investigated using real data collected at sea with NURC's SAS.

In situ AUV survey adaptation using through-the-sensor sonar data

Williams, D.P., A. Vermeij, F. Baralli, J. Groen, and W.L.J. Fox, "In situ AUV survey adaptation using through-the-sensor sonar data," Proceedings, ICASSP: IEEE International Conference on Acoustics, Speech and Signal Processing, 25-30 March, Kyoto, doi:10.1109/ICASSP.2012.6288430 (IEEE, 2012).

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25 Mar 2012

An algorithm for the in situ adaptation of the survey route of an autonomous underwater vehicle (AUV) equipped with side-looking sonars is proposed. The algorithm immediately exploits the through-the-sensor data that is collected during the mission in order to ensure that quality data is collected everywhere in the area of interest. By introducing flexibility into the survey of the AUV, various limitations of pre-planned surveys are overcome. Experimental results demonstrate the benefit of the proposed approach in terms of higher area coverage in shorter mission times. The signal processing required by the algorithm is fast and computationally efficient such that real-time implementation is feasible. As proof, the proposed adaptive survey approach was implemented on an AUV and executed during a recent live scientific experiment at sea using real, in situ measured data. Results from this experiment are also shown.

Probability of target presence for multistatic sonar ping sequencing

Krout, D.W., W.L.J. Fox, and M.A. El-Sharkawi, "Probability of target presence for multistatic sonar ping sequencing," IEEE J. Ocean. Eng., 34, 603-609, doi:10.1109/JOE.2009.2025155, 2009.

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28 Jul 2009

In this communication, the problem of determining effective pinging strategies in multistatic sonar systems with multiple transmitters is addressed. New algorithms are presented to determine effective pinging strategies for generalized search scenarios. An important part of this work is the development of metrics to be used in the optimization procedures. For maintaining search coverage, a ldquoprobability of target presencerdquo metric formulation is used. This formulation utilizes sonar performance prediction and a Bayesian update to incorporate negative information (i.e., searching an area but finding no targets) into the optimization procedure. The possibility of targets moving into previously searched areas is accounted for by using a Fokker-Planck (FP) drift/diffusion formulation. Monte Carlo simulations are used to show the accuracy and efficiency of this formulation. This formulation is shown to be computationally efficient compared to Monte Carlo simulations. It is also demonstrated that by choosing the ping sequence intelligently, the field performance can be improved compared to random or sequential ping sequencing.

More Publications

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