Field studies were conducted in 2005 in Yuma, Arizona at the Yuma Proving Grounds (YPG) to document seismic signatures of walking humans. Walker-generated vertical ground vibrations were recorded using standard omnidirectional 4.5 Hz peak-resonance geophones. Walker position and speed were measured using portable GPS equipment.Collected seismic data were processed and hypothetical sensor performance predictions were made using an algorithm developed for the detection and classification of a walking intruder. Sample results for the Yuma study are presented in the form of sensor detection/classification vs. range plots, and color-coded animations of seismic sensor alarm annunciations during walking intruder tests. A perimeter intrusion scenario for a Forward Operating Base is defined that involves a walker approaching a sensor picket-line along a path exactly halfway between two adjacent sensors. This is considered a conservative representation of the perimeter intrusion problem. Summary plots derived from a binomial probability based analysis define intruder detection probabilities for different sensor spacings. For a 215 lb intruder walking in the Yuma test environment, a 90% probability of at least two walker-classified sensor detections is achieved at a sensor spacing of 140 m.Preliminary investigations show the intruder classification component of the discussed detection/classification algorithm to perform well at rejecting signals associated with a nearby idling vehicle and normal background noise.
A curved-grid velocity-stress formulation for viscoelastic wave modeling is used with an arbitrary number of relaxation mechanisms to model a desired [Formula: see text]-behavior. These equations are discretized by high-order staggered finite differences (FDs) in the interior of the medium, and we gradually reduce the FD order to two at the stress-free surface, where we implement our boundary conditions for an arbitrary topographic surface. A moving source is simulated along the surface of a relatively general and locally steep surface topography and, for comparison, along a plane surface. The topography consists of a significant hill surrounded by a valley. Similar two-layered geologic models are used with both topographic surfaces, with the upper layer being a lossy sedimentary layer having a relatively strong contrast with the lower, higher-velocity half-space. Local topographic highs create varying amplitude amplifications at different times during motion of the source. A pronounced wavefield accumulation is evident at the topographic highs in all components. This is very different from the even pattern produced by the same source along the same path for the plane topographic surface, even in the presence of the strong material discontinuity between the two geologic layers. The effect is, however, similar to real records for nonmoving sources of long duration; over time, the direction of incidence becomes less significant, and amplitude amplification occurs in all directions for waves trapped in a topographic high. These spatial focusing effects should be taken into account in inversion for vehicle tracking to avoid target mislocation and/or misidentification.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.