Global Positioning System (Gps)

Global Positioning System (GPS) is a space-based radio navigation system that provides accurate, velocity, and time, 24 hours a day, three-dimensional position, everywhere in the world, and in all weather conditions. Because the user does not communicate to the satellite, GPS serves an infinite number of users.

A GPS SATELITE

GPS satellites carry atomic clocks that measure time to a high degree of accuracy. The time information is placed in the codes broadcast by the satellite so that a receiver can continuously determine the time the signal was broadcast. The signal contains data that a receiver uses to compute the locations of the satellites and to make other adjustments needed for accurate positioning. The receiver uses the time difference between the time of signal reception and the broadcast time to compute the range to the satellite. The receiver must account for propagation delays caused by the ionosphere and the troposphere. With three ranges to three satellites and knowing the location of the satellite when the signal was sent, the receiver can compute its three-dimensional position.

24 GPS satellites orbit the earth

Applications include hand-held telematics, fleet tracking and vehicle management systems - wireless communication devices designed for automobiles providing drivers with personalized information, messaging, entertainment and location-specific travel and security services. GPS technology is used in a wide range of applications, including maritime, environmental, navigational, tracking and monitoring.

The Ionosphere

Ionosphere is the term given to a level or levels of ionized air in the atmosphere stretching from almost 50 to 500 kilometers above the earth. At these altitudes, having about the density of the gas in a vacuum tube, the air is extremely