JUNGLE VISION VII: SEASONAL VARIATIONS IN PERSONNEL DETECTABILITY IN A SEMIDECIDUOUS TROPICAL FOREST
ARMY TROPIC TEST CENTER APO MIAMI 34004
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The U.S. Army Tropic Test Center conducted a study to determine the effects of the tropical wet and dry seasons on the horizontal detectability of human targets in a semideciduous forest. Testing was conducted on three jungle sites in the Canal Zone in July, 1966. Thirty infantry EM observed standing, motionless human targets appear randomly within a 180 degrees field of search at distances ranging from 30 to 115 ft. Target detections, detection cues, search times, and distance estimates were recorded. Results of the present study were compared to those of an earlier dry season study conducted on the same sites. Visibility was significantly lower during the wet season. Total target detections dropped by 44 during the period. Most of the change occurred on two of the three sites and was apparently caused by a single type of vine that loses its leaves during the dry season. Visibility gradients were of the same shape, though different levels, for both seasons. Illumination levels, search times, and distance estimates were significantly different from season to season. Visual cues contributing most to target detection were the symmetrical outlines of targets trunk and legs against jungle foliage. The lines and color of the OG-107 fatigue uniform also contributed, particularly at farther distances.
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