Growing emphasis on simulation of low altitude and air-to-air tactical scenarios has greatly increased the requirement for simulator visual systems capable of providing the pilot high-fidelity out-of-the-cockpit cues. Evaluation of visual system performance through simulator flying studies has been the primary measure of system quality. However, such studies can be costly and time consuming, and often they provide equivocal results. The present study investigated the use of psychophysical measurement methodology to provide a quick, low-cost evaluation of the altitude cues provided by five visual system displays.

Thirty Air Force pilots made estimates of the altitude above ground level (AGL) shown in slides of visual system displays varying in object density and object detail. Slides showed a 90° field-of-view scene taken in the F-16 cockpit of the Advanced Simulator for Pilot Training. Eight altitudes (range 50-400 ft AGL) were presented for each visual scene condition. A random sequence of 40 slides (8 altitudes X 5 scenes) was presented three times. Power functions relating perceived to actual altitude were determined. Reliable differences were found between the displays which accorded well with differences found in a simulator flying study using the same display environments. Results are discussed in terms of display features and the measurement methodology.