Human Systems Integration Division @ NASA Ames

Visual display systems such as the out-the-window or head-down displays of a simulator present a visual scene that is sampled in both the spatial domain (by the display resolution) and the time domain (by the display refresh rate). For a given human visual temporal sensitivity, spatial-frequency content of the scene, and speed of the image motion, spatiotemporal aliasing can occur when the image is sampled at a rate that is too low. The effects of spatio-temporal aliasing on visual perception are understood to some extend. However, not much is known about the effects on pilot performance in active control tasks. This paper presents the results of an experiment to determine the effects of spatio-temporal aliasing on pilot performance and control behavior in a target-tracking task. To induce different levels of spatio-temporal aliasing, the refresh rate of the experimental display was varied among five different levels. The results indicate that pilots adopt a different control strategy when the display refresh rate is increased from 60 to 120 Hz. The visual gain and neuromuscular frequency of the identified pilot model increase, while the visual time delay decreases. This change in control strategy allows for a higher tracking performance at higher display refresh rates as indicated by a decrease in root mean square of the error signal and an increase in crossover frequency.