Global Positioning System

:GPS redirects here. For other uses of the acronym GPS, see GPS (disambiguation).

Applications

The primary military purposes are to allow improved command and control of forces through improved locational awareness, and to facilitate accurate targeting of smart bombs, cruise missiles, or other munitions. The satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System.

Related Topics:
Smart bomb - Cruise missile - United States Nuclear Detonation Detection System

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The system is used by countless civilians as well, who can use the GPS's Standard Positioning Service worldwide free of charge. Low cost GPS receivers (price $100 to $200) are widely available, often combined in a bundle with a PDA, car computer, or Vehicle tracking system. The system is used as a navigation aid in airplanes, ships and cars. The system can be used by computer controlled harvesters, mine trucks and other vehicles. Hand held devices are used by mountain climbers and hikers. Glider pilots use the logged signal to verify their arrival at turnpoints in competitions.

Related Topics:
GPS receiver - PDA - Car computer - Vehicle tracking system

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On May 1, 2000, US President Bill Clinton announced that "Selective Availability" would be turned off. However, for military purposes, "Selective Deniability" may still be used to, in effect, jam civilian GPS units in a war zone or global alert while still allowing military units to have full functionality. In reality, the shortage of military GPS units and the wide availability of civilian ones among personnel resulted in disabling the Selective Availability in the time of the Gulf War. However, European concern about the level of control over the GPS network and commercial issues has resulted in the planned GALILEO positioning system. Russia already operates an independent system called GLONASS (global navigation system), although with only twelve active satellites as of 2004, the system is of limited usefulness.

Related Topics:
May 1 - 2000 - US President Bill Clinton - Global alert - Gulf War - European - GALILEO positioning system - GLONASS - As of 2004

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Military (and selected civilian) users still enjoy some technical advantages which can give quicker satellite lock and increased accuracy. The increased accuracy comes mostly from being able to use both the L1 and L2 frequencies and thus better compensate for the varying signal delay in the ionosphere (see above). Commercial GPS receivers are also required to have limits on the velocities and altitudes at which they will report fix coordinates; this is to prevent them from being used to create improvised cruise or ballistic missiles.

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Many synchronization systems use GPS as a source of accurate time, hence one of the most common applications of this use is that of GPS as a reference clock for time code generators or NTP clocks. For instance, when deploying sensors (for seismology or other monitoring application), GPS may be used to provide each recording apparatus with some precise time source, so that the time of events may be recorded accurately.

Related Topics:
Synchronization - Time code - NTP - Sensor - Seismology

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