The HORIZON program calculates the radio line-of-sight distances and elevation angles 360 degrees around a transmitter or receiver site using the digitized data from the terrain/topographic data base file. This file is useful in determining the minimum elevation angles for an antenna and in calculating the coordination contours of earth stations in shared bands. Since HORIZON uses the terrain/topographic data base, it will suffer from the deficiencies of that file, namely, data elements spaced every 30 seconds, no vegetation information, and no man-made obstacle data. Two plots are generated by this system. The first displays the radio horizon angle vs. azimuth angle and the second displays the radio horizon distance vs. azimuth. A file can be created with the x,y pairs from the two plots.