Active Regulation of Speed During a Simulated Low-Altitude Flight Task

This study examined active regulation of speed during a low-altitude flight task as a function of global optical flow rate, speed, and the presence or absence of a concurrent altitude disturbance. The results showed that altitude clearly had an impact on speed control. Control of speed was much more difficult when altitude disturbances were present. Even in the no altitude disturbance conditions, performance tended to be best at lower altitudes. Consistent with previous research, the results suggest that speed and altitude changes have additive effects on speed judgments. This is inconsistent with the simple global optical flow rate hypothesis that had suggested multiplicative effects. However, it is consistent with the general notion that judgments of self motion are based on properties of optical flow fields (i.e. angles and angular rates) that depend on distance and motion relative to textured surfaces.