World view from a satellite

A world map data base is processed by an APL program, called SATMAP, to represent the view of the earth seen from a satellite at any altitude, latitude, and longitude. The data base is processed by line segments characterized in terms of maximum and minimum latitudes and longitudes. This permits a more cost effective searching of the data base against a line-segment-visibility criterion than would be possible testing each point separately for visibility. The resultant view can then be presented on a suitable graphics and/or printer terminal such as a Tektronix 4015.