An Information-Centered Analysis of the Tunnel-in-the-Sky Display, Part Two: Curved Tunnel Trajectories

A theoretical information-centered analysis that studies the effectiveness of the information presented by a tunnel-in-the-sky display in the aircraft guidance task of following curved trajectories is described. The analysis reveals important differences in the information as compared to the task of tracking straight trajectories investigated in a companion paper (Mulder, 2003). The optical gradients of perspective and compression that support pilot control behavior in straight tunnels are less useful in curved tunnels. First, curved trajectories yield no vanishing point or any other stationary optical invariant that can act as a reference for the change in the optical information. Second, only the optical gradients conveyed by the nearby elements of the tunnel provide valuable information about the aircraft locomotion. Third, due to the limitations of using a perspective display, the projection of a curved tunnel results in a biased pilot perception of the aircraft position and motion relative to the trajectory. The lower information-content of the display makes curved trajectories more difficult to follow than straight trajectories, deteriorating pilot path-following performance. A simulator experiment provides substantial evidence for these findings.