GSM Digital TrakNet with GPS Tracking Cellular and Internet Access (Pooled Messages)
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GPS Satellites circle the Earth twice a day in a very precise orbit and transmit signal information to Earth. GPS receivers take this information and use triangulation to to calculate the user's exact location. The GPS receiver compares the time the signal was sent to the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with the distance measurements of a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map. The GPS Receiver must be locked onto the signal of at least three satellites to calculate a 2D position (Longitude and Latitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (Longitude, Latitude and Altitude) Once the User's position has been determined, the GPS unit can calculate other information such as speed, bearing, track, trip distance, etc.