Understanding How GPS Works

Have you ever wondered how GPS works? The secret to understanding how GPS works lies in understanding how the numerous satellites orbiting the earth are able to communicate with each other and then communicate with the GPS device that is in your vehicle or in your hand.

How does a GPS work?

The Orbiting Satellites
Although you can’t see them, there are currently 27 satellite orbiting around the Earth. 24 of these satellites are operating at this very moment, with the other three satellites serving as backups in case one of the 24 in operation happens to fail. Each of these satellites, which weighs anywhere from 3,000 to 4,000 pounds, is powered by solar energy and makes two complete rotations around the earth every day.

GPS Interactive

These satellites were initially launched into orbit as part of a military initiative. With the help of these satellites, the military was able to develop a better navigation system. Over time, however, the technology became available to civilians and GPS devices have actually become quite commonplace.

Using the GPS Device to Communicate with Satellites
As the satellites orbit around the Earth, they are positioned in such a pattern that at least four of the satellites are “visible” in the sky. While they may not be visible to the naked eye, GPS units are able to access the satellites that are “visible” to them. So, how GPS works involves communicating with these four satellites and then calculating the distance between each. With this information, the GPS device is then able to determine where it is currently located. Although this may sound complicated, it is all a matter of completing a few mathematical calculations that the GPS device can complete within a fraction of a second through a process called trilateration.

How is that GPS working for you?

Understanding Trilateration
In order to better understand how GPS works, you have to gain a better understanding of the concept of trilateration. There are actually two different types of trilateration: 2-D trilateration and 3-D trilateration. Although GPS systems use 3-D trilateration, it is easier to understand how GPS works by first understanding 2-D trilateration.

With 2-D trilateration, you can determine where an object is located by intersecting three circles. For example, if someone were to tell you that you are 625 miles away from Boise, Idaho, you still cannot be sure where you are because you don’t know which way to go in order to reach Boise. If they were to then tell you that you are 690 miles away from Minneapolis, Minnesota, you would be able to narrow down your location to different points by drawing a circle around each location and noting where they intersect. If you were then told that you were 615 miles away from Tucson, Arizona, you could draw a third circle around Tucson and you will now know exactly where you are at based upon where the three circles intersect.

Enhanced Safety of Flight

When it comes to how GPS works, the same basic method is used. The only difference is that GPS systems use 3-D trilateration because the Earth is a sphere rather than a flat surface. This adds more equations to the calculations, but the basic idea remains much the same.

written by Darren