Mapping by Computer Graphics
Satellite Antenna Coverage
Description of computer preparation of maps and overlays, especially for satellite antenna coverage. The examples were produced with an IBM 360/65 and S-C 4060 graphical plotter, using a data tape of 10,500 geographic points stored as 374 strings of alternate latitude and longitude values. This is adequate for maps of scale 1:40,000,000 (at which a world map is 40 in. wide). Rectilinear maps, azimuthal maps, and polar perspective maps (which show the earth as seen from a particular satellite position) are explained, with coordinate transformation equations for each. The most efficient coordinates for rectilinear maps are latitude and longitude; for azimuthal maps, direction cosines. With satellite rays nearly tangent to the earth, using geocentric coordinates and a spherical earth model, coordinates can cause errors of hundreds of miles. Latitude and longitude corrections for the geosynchronous distance of 6.166 earth radii are provided.