Jungle Vision VIII. Visual Detection of Moving Targets in a Semievergreen Tropic Forest

The purpose of the study was to determine typical detection distances of moving targets in the tropic forest. Among the major factors considered were effects of season and type of target dress upon detection distances. A total of 120 enlisted men from TOE units in the Canal Zone were used as observers 60 during the wet season and 60 during the dry season. The observers did not use visual performance aids. Targets were viewed as they appeared randomly, one at a time, moving along one of 10 separate radii laid out over a 180 degrees field of view. Each observer received 30 trials. Targets wore either OD fatigues or black pajama-type clothing common to Vietnam. Target detection distances did not differ significantly with either season or mode of dress. Mean target detection distances for the wet and dry season were 52.6 and 55.8 feet, respectively. A difference in detection distance of only 1.2 feet was obtained among targets wearing OD or black clothing. Obscuration by eye-level vegetation appears to be the major factor in limiting detection distances of moving targets in semievergreen tropic forests. Differences in vegetation density from wet to dry season did not have meaningful effects upon detection distances.