Optical variables and control strategy used in a visual hover task

Determinants of performance in a simulated hover task are examined. This task uses an extremely simplified vehicle model with only three degrees of freedom: longitudinal (fore/aft), lateral (left/right), and vertical (up/down). No rotational motions are simulated. Only one control manipulation is allowed, namely control of vertical craft velocity. The task uses a fixed base simulator with three adjacent windows each spanning a 40 degrees visual field. Subjects view computer-generated scenes of either (1) a randomly textured and colored background plane 2000 ft below; (2) a regularly patterned see-through grid plane 1000 ft below; or (3) both the grid and the ground. Results show that vertical optical motion is a primary source of information for altitude control even with a forward buffeting disturbance. This is confirmed by the fact that the addition of peripheral visual cues does not improve performance.<>