What Is Global Positioning System And It Is A Satellite Navigation System?

GPS (Global Positioning System) is a "constellation" of 31 widely spaced satellites that orbit the earth and allow people with terrestrial receivers to pinpoint their geographic location. Location accuracy is 100 to 10 meters for most devices and less than one meter with special military-approved equipment. GPS devices are widely used in science and have become so inexpensive that almost anyone can own a GPS receiver. GPS is owned and operated by the US Department of Defense, but is available worldwide.

How does GPS work?

• 21 GPS satellites and three spare satellites orbit 10,600 miles above the earth. The satellites are spaced so that there are four satellites above the horizon from any point on earth.
• Each satellite contains a computer, an atomic clock and a radio. With an understanding of its orbit and the clock, it constantly broadcasts its changing position and time. (Once a day, each satellite checks its time direction and position with a ground station and makes minor corrections.)
• On the ground, each GPS receiver contains a computer which "triangulates" its position by receiving bearings from three satellites. The result is a geographic position (longitude and latitude) for most receivers within 100 meters.
• If the receiver is also equipped with a display screen and a map, the position can also be displayed. If a fourth satellite can be received, the receiver/computer can determine the altitude and geographical position.
• If you are moving, your receiver can also calculate your speed and direction of travel, and give you estimated arrival times at specific destinations.

GPS is used in science to provide data never before available in the amount and precision that GPS makes possible. Scientists use GPS to measure the movement of Arctic ice caps, the tectonics of Earth's plates and volcanic activity.

Mobile GPS technology has enabled today's smartphones to provide end users with a convenient and highly efficient means of receiving navigation instructions through a Global Positioning System process called "trilateration". A phone's built-in GPS receiver also communicates with a series of satellites that provide navigational directions for those traveling by car or on foot. The most technologically advanced phones can identify individual streets and points of interest on maps and offer annotated tracking capability.