The Global Positioning System (GPS) is comprises a group of 24 satellites that orbit Earth at 10, 907 nautical miles (20,200 km) above Earth. GPS satellites provide precise location information anywhere on Earth. Full accuracy only available to the military, which own and operate the satellites, but there are numerous commercial applications for GPS. By the 1990s, GPS receivers became small enough to be hand held, increasing public interest in the technology.

At a cost of $3 billion, GPS was developed by the United States military beginning in the 1970s, first in the Navy, and later by the Air Force. Their initial goal was to guide missiles and tanks. The Department of Defense launched the first GPS satellites in the 1980s, and all 24 were in orbit by 1996. GPS was first used by the military in the Persian Gulf war in 1991. Each GPS satellite has four atomic clocks, and continually...