ANALYTIC VISUAL SEARCH CALCULATIONS

An attempt was made to demonstrate the utility of analytic approximations in visual search analyses. This has been accomplished by choosing a simple example in which apparent contrast did not change with observer altitude and vertical downward line of sight was assumed. The use of analytic approximations are in no way restricted to these simple cases. With analytic expressions for visual thresholds, equations can be derived which describe area search rates for any combination of altitude, optical aid magnification, target area, and apparent target contrast. Equations can also be derived which describe the optimum optical aid magnification for a given altitude, target area, and apparent contrast. The analytic determination of optimum magnification makes it possible to define maximum area search rate attainable for a specified target area and apparent contrast. (Author)