The history of this is interesting. Development of the $10 billion GPS satellite navigation system was begun in the 1970s by the US Department of Defense, which continues to manage the system, to provide continuous, worldwide positioning and navigation data to US military forces around the globe. However, GPS has an even broader civilian, commercial application. To meet these needs, GPS offers two levels of service: one for civilian access and the second encrypted for exclusive military use. The GPS signals are available to an unlimited number of users simultaneously, and there is no charge for using the GPS Satellites.