GPS or global positioning system, is a system created by the US Department of Defense to determine information such as exact location and speed. It is a system that utilizes a total of 27 satellites—24 of these satellites are currently being and the extra three are for backup in case one of the other working satellites fails. This system has been open fully operational since 1994 and is open for use by the public.
In order for a GPS receiver to determine the user’s location, it needs to get certain information from GPS satellites. A GPS receiver needs to calculate first the distance of the user from one satellite. The distance is calculated using the difference in the time that the satellite transmits the signal and the time the receiver receives that signal. Once that information has been calculated, the GPS receiver knows the actual distance from one satellite to the user. For instance, the distance that the receiver calculates is 676 miles. This information is still insufficient because the distance of 676 miles could be one of the many points of circle with a radius of 676 miles.
The receiver gets similar information from another satellite. If for example, the receiver’s calculated distance is 732 miles, the receiver now knows that the user’s location could possibly be one of two points where the circle of radius 732 miles and 676 miles intersect.
To pin point the exact location, the receiver needs to calculate the distance of the user with a third satellite. For example, if the calculated distance from the third satellite is 580 miles, the receiver can now triangulate the three distances, find the point where all three circles of radii 676 miles, 732 miles, and 580 miles meet. The point where all three distances meet is the location of the user.
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