The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR), is an intermediate circular orbit (ICO) satellite navigation system used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit.
The first of 24 satellites that form the current GPS constellation (Block II) was placed into orbit on February 14, 1989. The 50th GPS satellite since the beginning in 1978 was launched March 21, 2004 aboard a Delta II rocket
The initial concept of GPS began to take form soon after the launch of Sputnik in 1957. ".... Some scientists and engineers realized that radio transmissions from a satellite in a well-defined orbit could indicate the position of a receiver on the ground" This knowledge resulted in the U.S. Navy's development and use of the "transit" system in the 1960's. This system, however, proved to be cumbersome to use and limited in terms of positioning accuracy.
Starting in the mid-1970s the U.S. Department of Defense (DOD) began the construction of today's GPS and has funded, operated, and maintained control of the system it developed. Eventually $12 billion dollars would take GPS from concept to completion. Full Operational Capacity (FOC) of GPS was reached on July 17, 1995 (U.S.C.G., 1996, www). At one point GPS was renamed NAVSTAR. This name, however, seems to be regularly ignored by system users and others. Although the primary use of GPS was thought to be for classified military operations, provisions were made for civilian use of the system. Nation