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Your Guide To Types of GPS Units
How GPS Tracking Works
In order to provide accurate, real-time location information, your GPS unit relies on a network of about 30 satellites that are constantly orbiting the Earth. Hovering more than 12,000 miles above the Earth, these satellites were first installed by the U.S. government for military applications. Today, anyone can make use of this satellite network in order to figure out where they are.
Wherever you stand on the planet, your GPS can pick up a radio signal from at least four different satellites, each transmitting a different set of information about its position and the current times. Your GPS unit receives this information and determines how far away a satellite is based on how long it took to get that information. Once it receives info from three satellites, the GPS can present you with an accurate location thanks to trilateration.
The concept of trilateration might seem complicated at first, but it’s surprisingly straightforward. Think about it this way. When you’re standing on a given point in your city, your GPS is in communication with three or more satellites. Your GPS can determine how far away you are from one satellite, and determine that you might be within a given range around the satellite, not unlike a circle. The GPS repeats this process for the other two satellites, ultimately finding the point where the three circles intersect, providing you with your location information.
But what allows our GPS units to know where the satellites are? It’s all thanks to a series of ground stations here on Earth. These ground stations use radar to pinpoint where in the sky the satellites are.