SATELLITE ELEVATION USED FOR SELECTABLY PROVIDING SERVICE TO A USER

摘要

The angle of elevation X to a satellite (10) allowed for communications to proceed is limited in sympathy with local terrain or sea conditions by means of a terrain map which keeps track of the minimum elevation X for a particular user terminal (14) by foreknowledge of the terrain or sea conditions in the area occupied by the user terminal (14), or by gathered statistics based on success in audibility, or both.