How It Is Used

GPS was originally intended only for military use, but a civilian service was added. The civilian service was less pre­cise-in fact, errors were deliberately included to make it even less accurate so that enemy military forces could not make use of it. The civilian service offered what was called Selective

О GPS is used aboard military aircraft for pin­pointing targets to be destroyed. Soldiers in the field use handheld survival radios equipped with GPS for search and rescue missions.

О The GPS IIR satellites were designed to last longer and be more accurate than earlier GPS equipment. GPS technology is constantly improving.

Availability, a system that enabled receivers to calculate their position only to within about 300 feet (100 meters). In 2000, President Bill Clinton ordered the Selective Availability system to be turned off. The accuracy of the civilian GPS service was immediately improved.

Most receivers are now designed to provide extra features. If they are in a moving vehicle, such as an aircraft, they compare a series of positions and use them to calculate the vehicle’s speed and direction. If this information is com­bined with a digital map, GPS can be used for navigation. Professional map – makers and surveyors also use GPS to produce very accurate maps. Farmers even may use GPS to map their fields and calculate how much fertilizer or weed killer is needed in different places.