A dropline is a vertical line connecting an object within a 3-D display to an underlying horizontal surface and is meant to enhance information about the relative position of objects in the 3-D space. On a 3-D cockpit display of traffic information, many aircraft may be depicted, and it may be difficult to judge the relative positions of aircraft. However, droplines that connect aircraft to the ground surface with lines may help pilots resolve the height/distance ambiguity. This article reports the results of a study that investigated the effects of droplines on target acquisition performance on a 3-D perspective display. Participants were required to move a cursor into a target cube as quickly as possible. The goodness of fit of the data to a modified Fitts function varied widely among participants, and the presence of droplines did not have observable impacts on the goodness of fit. However, droplines did help participants navigate via straighter paths and particularly had benefits in range dimension acquisition.
Abstract