The Geostar satellite navigation system is designed to provide a number of user services through inexpensive terminals (transceivers). The services include precise positioning, location radio (the reporting of position back to a fleet headquarters), digital message transmission both send and receive, and connection to non-Geostar digital communications systems through a single node point. A number of additional user services (terrain and shoreline avoidance, warnings of hazards to navigation, ship or aircraft collision avoidance, emergency location and rescue communications, etc.) are provided relatively inexpensively because all messages and positionings in Geostar flow through a single location where powerful computers are available.