Global Positioning Systems Demystified - How Do They Work?
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How Do They Work?
"It's all fine and dandy but how do they work?" In this chapter we will discuss in a nutshell their operation method. Utterly simplified, the process is the following: the GPS receiver measures the distance between itself and three or more GPS satellites.
Those 30 satellites are on a very specific orbit and they circle around the Earth twice per day. All of them emit radio information signals (which carry data about the source satellite) to our planet. Ultimately the receiver uses trilateration (think of it as triangulation) to calculate its exact location with the data that was "picked up."
Moreover, the distance between the receiver unit and satellite(s) can be calculated because the signal travels at a specified speed. This is possible because the sent radio-wave data contains the precise time when that "packet" was sent by the satellite. Therefore, the receiver compares that time with current
time and finds out the correct location.
This aforementioned process happens with multiple satellites to maintain enhanced precision. After the location is determined, the receiver unit can display the results on an electronic display screen by drawing maps, reporting coordinates, etc.
It is important to realize that it takes a minimum of three satellites for the receiver to calculate the longitude and latitude. With the help of one more, the altitude can be computed, too. After the location has been determined the rest of the additional satellites are used to report useful information to the user: sunrise and sunset time, trip distance from location A to B, speed and so forth.
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