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Warren Fox

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.

Department Affiliation



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

Energy consumption model for a broadband shallow-water acoustic communications network

Rouseff, D., and W.L.J. Fox, "Energy consumption model for a broadband shallow-water acoustic communications network," IEEE J. Ocean. Eng., 33, 335-340, 2008.

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29 Aug 2008

A multistatic active sonar system with several widely distributed sensors must share information between the sensors. If acoustic communication is the means used to share information, it can consume a significant fraction of the system's total energy budget. In this communication, an energy consumption model is developed for a shallow-water acoustic communications network. The model includes the environmental factors like the sound-speed profile in the water column and the composition of the seabed. The model uses the waveguide invariant concept to incorporate efficiently the broadband nature of the communications signals. Numerical results demonstrate how relaying messages between intermediate sensors can save substantial energy compared to direct communications. The calculations also show that energy consumption can vary by more than an order of magnitude depending on the seabed composition.

Underwater acoustic communications performance modeling in support of ad hoc network design

Fox, W.L.J., P. Arabshahi, S. Roy, and N. Parrish, "Underwater acoustic communications performance modeling in support of ad hoc network design," Oceans 2007, 29 September - 4 October, Vancouver, BC, 1-5 (IEEE: Piscataway, NJ, 2007).

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29 Oct 2007

This paper discusses a methodology for predicting underwater acoustic communications performance using high fidelity acoustic time series simulation and acoustic modem processing emulation. Multiple source/receiver combinations can be simultaneously simulated, so that aspects of a complete underwater network can be studied. Here, the fundamental modeling and emulation capability will be described, with examples of the propagation modeling, time series simulation, and modem processing over multiple realizations of example communications channels. The results show the dependence of source and receiver location in the water column with respect to the sound speed profile on communications performance. The utility of such simulations for ad hoc network design in the presence of moving communications nodes will be discussed.

A Screening Application for Image Data Collected by an Acoustic Lens Sonar

Hsieh, J.B., J.I. Olsonbaker, and W.L.J. Fox, "A Screening Application for Image Data Collected by an Acoustic Lens Sonar," APL-UW TR 0502, November 2005

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30 Nov 2005

High-resolution, forward-looking sonar systems are critical tools on autonomous underwater vehicle (AUV) platforms where they are used to detect, classify, and localize objects. Data collected by these sensors can be processed automatically and used for navigation (object avoidance) or detailed object examination and discrimination tasks. Once an object is detected, size and shape parameters can be estimated based on the acoustic shadow cast behind the object when ensonified by such sensors. This report discusses the development of adaptive algorithms for highlight localization and shadow segmentation from 1.8-MHz data collected by an acoustic lens imaging sonar — DIDSON (Dual-frequency IDentification SONar). The sonar was mounted in a forward-looking configuration on a REMUS AUV. Algorithms screen large data sets for interesting frames; they demonstrate considerable effectiveness for target detection when the target images are central to the data frame and where there is little platform motion.

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