Global Positioning System (GPS) technology originated within the U.S. Department of Defense in the 1970s as a way to assist military personnel in accurately determining their locations throughout the world. Today its role has expanded to provide navigational assistance to the general public. Built-in GPS units assist drivers, pilots and boaters while hand-held units are used in recreational activities like hiking and geo-caching. Scientists also utilize the technology to forecast weather, study ecological concerns and measure seismic changes during earthquakes. GPS technology relies upon satellites, receivers and a data center to function effectively. The system is comprised of 24 satellites that orbit the earth in six distinct orbital planes. Each satellite transmits information to Earth that is received by the GPS unit. Based upon the triangulation of the radio signals received, the latitude, longitude and height at the receiver can be determined.

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