Acoustic/seismic vehicle locator
George W. Brooks, Gwynn M. Reel, N. Huffnagle, Martin Marietta · The Journal of the Acoustical Society of America · 1977
We are investigating an automatic range measuring/target classification method based on the relative velocity differences of airborne acoustic and seismic waves. The technique appears to be a promising way to measure target range to an accuracy commensurate with present target interdiction techniques. In brief, assumptions on the relative velocities and their variances appear to be sound: errors of ±20% do not materially degrade interdiction probabilities. C. F. Richter and others have determined that the relation between the three seismic waves (Prompt-P, Shear-S, and Rayleigh-R) is virtually invariant for many media. One of the methods being investigated takes advantage of this invariance to measure range. A closed-loop system using a 512-element CCD serial analog delay as one element of a seismic/acoustic correlator shows promise as a viable method. Replacing the seismic/acoustic inputs by the P and R waves (polarized at right angles to each other and having wide velocity dispersion), this correlator would work as a single medium range system. Coupling this target range-measuring method with a Martin Marietta-developed target classification technique that also provides range measurement using Doppler and the amplitude increase function on the narrow-band spectra of predetermined targets, target interdiction by this multipath method leads to a system that is very immune to countermeasures and natural events.