Navigation Through Fog: A Mathematical Analysis of Folded Path Propagation

Report No. ARL-TR-2648
Authors: David H. Tofsted
Date/Pages: September 2002; 59 pages
Abstract: Wendall Watkins of the U.S. Army Research Laboratory has a currently pending patent, which provides a technique for solving the problem of navigation through fog. This technique entails the use of laser illumination of retroreflective targets on airfield runways, stereo detection of the return signal, and deblurring processing of the received imagery. The current analysis attempts a mathematical analysis of this same problem. Here, the propagation equations necessary to model the propagation of a Gaussian beamwave through a forward scattering fog aerosol are developed. Interaction of the propagated wave with a retroreflective material is postulated, and the returned reflected energy is evaluated. Also, backscattered diffuse energy is analyzed. Through this analysis, it should be possible to predict the angular structure of energy returning from a retroreflector embedded within the fog field. It should also be possible to predict the level of diffuse radiation which must be dealt with in order to discriminate between the directly reflected radiation and the diffusely scattered radiation, both in the forward and backward hemispheres.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2002