How Do GPS Systems Work?

A Global Positioning System or GPS is a technological innovation that uses a number of satellites in the earth’s orbit, to transmit signals back to earth enabling GPS receivers to calculate and identify the exact location, time information and speed to the user. The GPS receivers can be able to pinpoint the person’s location at anytime using signals from either three or more satellites. Originally, the GPS was created by the US Department of Defense to be used for military purposes. Though the system started being used in the 1980’s it became available to public use in the 1990’s. The main advantage of the GPS is that it can be able to function even in all weather condition any time, day or night. 

The working of the GPS is very simple. The Global Positioning System is made up of 27satellites that are orbiting the Earth. Out of the 27 satellites, only 24 are in use while the rest are used in case any satellite malfunctions. All the satellites are able to circles the earth at speeds of 12,000 miles and make two complete rotations daily. The satellites have been arranged in such a way to enable at least four satellites to be visible in any location on the planet. The receiver’s task is to locate any four or more of the satellites, calculate the distance to each satellite and then use the information acquired to calculate its own location. The GPS receiver uses a mathematical principle referred to as trilateration to be able to pinpoint the exact location of the object. 

A simple explanation of how the GPS is able to effectively locate the position of a person is as follows. Assume that the exact positions of the satellites to the earth can be computed accurately, and that the GPS receiver is able to calculate the distance, between at least three satellites simultaneously and the receiver. By making use of the longitude, latitude and height to define the location of the receiver, one can come up with and solve three equations relating to the known coordinates of the three satellites and that of the receiver. The distance between the receiver and the satellites is calculated by time signals that are transmitted by the three satellites. Since the signal normally travels at the speed of light, the time the signal from the satellites reaches the GPS receiver is accurately registered to be able to calculate the distance as well as the accurate position of the receiver. 

GPS receivers operate using clocks that are less accurate while the satellites use accurate atomic clocks. Because of this, there is a timing error when the GPS receiver gets the satellite signals. Since the signals arriving to the receiver from the three satellites are measured simultaneously, the distance measurements are falsified by the receiver’s clock error. Therefore, to accurately measure the position of the receiver, four unknowns are required namely; the three satellite coordinates and the receivers clock error. To solve the four unknowns at least four satellites are required. The use of four satellites allows the GPS to determine the location with a pinpoint accuracy. With the four satellites, the receiver can now be able to calculate accurate estimates of the receiver’s clock and its location. The functioning of the Global Positioning System may sound quite complicated but it is simple if followed keenly.