GPS ( GLOBAL POSITIONING SYSTEM )

                                  GPS (GLOBAL POSITIONING SYSTEM)

GPS is a satellite base navigation system made up of a network of 24 satellite  placed into orbit by the US Department of Defense. GPS was originally intended for military applications. In the 1980's , the government made the system available for citizen use . GPS works in any weather conditions, anywhere in this world ,24 hours aday.

          There are no subscription fees or setup charges to use GPS.

HOW GPS WORKS :

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 trilateration to calculate the user's exact location.
Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far way the satellite is . Now ,with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.

A GPS receiver must be locked on to the signal of at least 3 satellites to calculate a 2-D position (latitude and longitude) and track movement. With four or more satellites in view ,the receiver can determine the user's 3-D position (latitude,longitude and altitude). Once the user's position has been determined ,the GPS unit can calculate other information , such as speed, bearing, track,trip distance,distance to destination ,sunrise and sunset time and more .