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PERSONNEL TRACKING USING SEISMIC SENSORS Michael S. Richman * , Douglas S. Deadrick, Robert J. Nation, Scott L. Whitney BAE SYSTEMS – IEWS ABSTRACT A method for the detection and localization of personnel using seismic sensors is described. This particular application of seismic signal processing is different from typical applications involving earthquakes or sonic well-logging, and thus requires the development of new techniques. The proposed approach consists of a matched filter-based detection algorithm, time of arrival association of detected footsteps from different sensors, and localization using a hyperbolic location estimator. This method was tested using data collected in southern New Hampshire from four vertical-axis geophones. The speed of sound at the test site was estimated using an impulsive source. Footsteps were reliably detected at ranges up to 30m. Localization errors were found to vary linearly with range, with an average estimation error of 8.4m observed. With improvements in the sensitivity of the seismic sensors, this approach will yield reasonable position estimates of personnel for use in a tracking algorithm. Keywords: seismic signal processing, personnel detection, localization, tracking 1. INTRODUCTION This paper explores a problem in seismic signal processing that has not received much attention in the geophysics and signal processing literature. Given a deployment of sensors in a field, the problem is to track any personnel that enter the field. Of the various types of sensors that could be deployed, seismic sensors (i.e. geophones) yield signals that provide sufficient information to allow a solution to this problem. The study of seismic phenomena has a rich history involving a variety of tried-and-true techniques. However, the majority of seismic signal processing research concerns itself with either the study of earthquakes or well-logging. The methodologies used to study these topics are fundamentally different from those used to study the seismic phenomena resulting from a person’s footsteps. Specifically, personnel tracking requires a different type of sensor deployment, involves shorter ranges from source to sensor, and must account for different source waveform characteristics than those found in other seismic applications. At the same time, the inherent challenges relating to the propagation of seismic waves affect the study of personnel tracking just as they affect the study of earthquakes or well-logging. The speed of sound is quite variable as a wave propagates in the Earth. Site to site differences can be upwards of 1000 m/s, and noteworthy variations can be present between locations within meters of one another. Dispersion is also significant, as different frequencies propagate at different speeds in the ground. A single footstep may result in received waveforms that are not very correlated from sensor to sensor. There are few articles describing methods applicable to the tracking of personnel via seismic sensors.
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