GPS - Global Positioning System

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What is GPS? The Global Positioning System (GPS) was developed by the Department of Defense and consists of a group of 24 satellites which are monitored by five ground stations. It essentially allows you to pinpoint your location anywhere on the surface of the Earth, even in cloudy weather, with the use of a GPS receiver. The GPS receiver is a navigational device that uses these satellites as reference points to calculate your position on the ground. It does this by triangulating your position between at least 3 satellites. The GPS receiver uses the time it takes the coded radio signal to get from the satellite to the receiver to calculate the distance it is from that satellite. So, by accurately measuring the distance from the ground to these satellites, it can triangulate your position. GPS consists of 3 basic parts: 1. Control The control part is the central part of GPS. This is where the satellites are monitored and adjustments (atmospheric corrections, timing corrections, etc.) are made. There are 5 stations located worldide and each satellite passes over a monitoring station twice a day. 2. Space The space part is the NAVigation Satellite Timing And Ranging (NAVSTAR) group of satellites that bradcast the GPS signals. There are 24 satellites orbiting at about 20,200km above the Earth. They each make one revolution approximately every 12 hours. 3. User Consists of a user and a GPS receiver. The possible applications of GPS are limitless. Satellite Ranging GPS is based on satellite ranging. This technique of measurement is based on timing how long it takes a radio signal to travel from the satellite to the GPS receiver a... ... middle of paper ... ...or short, consists of both satellites and ground based stations that supply correction information for your GPS receiver. This correction information can provide an improvement in positional accuracy of up to five times greater. It corrects for GPS signal errors caused by atmospheric disturbances, timing, and other errors. WAAS was developed by the FAA in order to help increase the accuracy of precision flight approaches. The corrected information is broadcast through two geostationary satellites that are located at a fixed location over the equator. Works Cited Trimble: http://www.trimble.com/gps/ The Aerospace Corporation: http://www.aero.org/publications/GPSPRIMER/index.html CMT: http://www.cmtinc.com/gpsbook/index.htm Garmin: http://www.garmin.com/aboutGPS/ GPS Mapping for GIS., 2001, Trimble Navigation Limited.
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