Alternative Map Projections for Air Traffic Control

Abstract

The stereographic projection is currently used for the representation of airborne targets on a situation display. A radar reports positions of targets within its range, in polar coordinates with respect to the radar site. In an area scanned by many radars, targets need to be represented in a single (stereographic) plane, and this is done via mathematical transformation from the local frame of reference to the common plane. The stereographic projection is conformal (that is, angle-preserving). Two additional conformal projections are considered by the authors for use in air traffic control, and it is demonstrated that (1) the mathematics needed to accomplish their transformation to the common plane is simpler than it is for the stereographic projection, and consequently the computation load is lighter (this may be critical during heavy traffic); (2) there is no loss in precision; and (3) in the case of Lambert conformal conical projection, there is the additional advantage of being able to use an ellipsoidal instead of a spherical earth.