An exocentric SGS display format: design and evaluation

With a conventional 2-D plan view display, the resolution of the presented position data is independent from its location in display space, and is inversely proportional to the displayed range. As a result, the available preview will be severely limited when the range is based on providing sufficient position resolution for manual control and vice versa. With a perspective display, the resolution of the position data is a function of the distance along the line of sight. As a result, a perspective exocentric guidance display provides the possibility to combine a high position error resolution with a large visible range. To benefit from this possibility, the designer has to specify a viewpoint for the virtual camera, typically tethered to the vehicle under control. The parameters that determine range and resolution to a large extent are the length and elevation of the tether(lever) arm. In order to try to establish a useful range for the values of these parameters, this paper starts with a review of a number of exocentric displays. Following this, an approach is presented that aids in the selection of values for the parameters that determine the location and orientation of the viewpoint relative to the vehicle. Finally, the results from an evaluation in which pilots could manipulate the values of lever arm length and elevation are provided.