Abstract
Experiments examined the accuracy of passive visual aimpoint perception during a simulated final approach for landing. Displays represented a range of glideslopes (1.5 –15 ) towards a ground plane consisting of either: (i) randomly positioned dots (with or without an explicit horizon at optical infinity); (ii) a runway outline; or (iii) a grid. In a two-alternative forced-choice task, participants judged whether their perceived aimpoint for each display was above/below a probe that appeared at a random vertical position following each display. We found that vertical aimpoint judgments were unacceptably imprecise and consistently biased upwards (towards the horizon) for all moving dot displays, even when they were supplemented with an explicit runway outline. While this bias could be removed by increasing the simulated distance and placing an explicit horizon line at optical infinity, the imprecision of vertical aimpoint judgements was not reduced. Accurate and unbiased aimpoint estimates were only found using grid displays — which provided explicit expansion and additional information about the inclination of the ground plane. While the optic flow information provided by random-dot and runway outline displays did not appear to be sufficient for a pilot to safely land an airplane, the systematic aimpoint errors found in these conditions could explain the common occurrence of short landings in so-called ‘black hole’ situations.