GPS - Global Positioning Systems

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GPS System
GPS System

A GPS navigation device receives Global Positioning System (GPS) signals, for the purpose of determining the device's current location on Earth. GPS devices provide latitude and longitude information, and some may also calculate altitude, although this is not considered sufficiently accurate or continuously available enough due to the possibility of signal blockage and other factors. GPS devices are used in military, aviation, marine and consumer product applications.

The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else. Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles per hour (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky. A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration.

GPS devices may also have additional capabilities such as: containing maps, which may be displayed in human readable format via text or in a graphical format, providing suggested directions to a human in charge of a vehicle or vessel via text or speech, providing directions directly to an autonomous vehicle such as a robotic probe, providing information on traffic conditions (either via historical or real time data) and suggesting alternative directions, providing information on nearby amenities such as restaurants, fueling stations, etc.

GPS devices use a process called Dead reckoning. Dead reckoning is the process of estimating present position by projecting course and speed from a known past position. It is also used to predict a future position by projecting course and speed from a known present position. The DR position is only an approximate position

GPS Tracking: A GPS tracking unit is a device that uses the Global Positioning System to determine the precise location of a vehicle, person, or other asset to which it is attached and to record the position of the asset at regular intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location data base, or internet-connected computer, using a cellular radio, or satellite modem embedded in the unit. This allows the asset's location to be displayed against a map backdrop either in real time or when analyzing the track later.

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