How Does GPS Work?
We’ve come a long way since Bugs Bunny missed his left turn at Albuquerque. Thanks to in-dash navigation systems, portable GPS units and even smartphones, driving to an unknown destination is easier than ever. I can’t remember the last time I fumbled with a map or stopped to ask for directions, but until recently, I didn’t really know how the technology behind GPS actually works.
When most people say “GPS”, they’re referring to an electronic device that will get them from point A to B. However, GPS actually stands for the Global Positioning System, which is a network of 27 satellites that constantly orbit the Earth. Three of the satellites are backups in case a satellite fails, but at any given time, 24 active satellites make up the Global Positioning System.
Thanks to in-dash navigation systems, portable GPS units and even smartphones, driving to an unknown destination is easier than ever.
About 12,000 miles above us, each satellite orbits Earth twice daily. Their paths are organized so that at any time, at any location on Earth, at least four satellites are visible to GPS-enabled devices.
A GPS receiver – such as your car’s navigation system or smartphone – locates the satellites and calculates your distance from each one. To hone in on your exact location, a GPS receiver needs to be able to locate at least three satellites in the sky and calculate your exact distance from each satellite.
The way the whole system works is fairly complex, but if you distill it down to the basics, your GPS receiver and the satellites both generate an identical random code at the exact same time. When the satellites’ code reaches your receiver, it will lag behind the receiver’s code because it had to travel from space. Your GPS receiver uses that delay to figure out how far away it is from the satellite.
While your navigation system can judge its distance from the satellites using radio waves, it still needs to know their exact location in the sky in order to effectively locate you and provide directions. Since each satellite orbits the Earth twice daily in a predetermined pattern, GPS receivers simply store an almanac that tells them where each satellite is positioned at any given time.
While gravitational pull from the sun and moon can vary the satellites’ orbits slightly, the Department of Defense tracks these changes and transmits any adjustments through the radio waves generated by the satellites. When the waves hit your GPS receiver, the data is updated to keep your location accurate.
Since each satellite orbits the Earth twice daily in a predetermined pattern, GPS receivers simply store an almanac that tells them where each satellite is positioned at any given time.
At this point, your GPS receiver knows your position on the globe, and displays it on maps that are stored in its memory. In addition to showing your location on a map, most GPS receivers can also provide additional information because they maintain communication with the satellites overhead. Typically, this can include the distance your vehicle has traveled, your current speed and your estimated time of arrival at the destination you’ve entered.
A tremendous amount of thought went into our Global Positioning System which helps countless motorists who are off to new, unknown destinations.