How Does the GPS Work?
Alright, are you ready for some fun physics? Here goes!
The GPS network has roughly 30 satellites in orbit at all times, at an altitude of 20,000 kilometers. Because there are so many satellites, and they’re at such a height, anywhere you go on Earth (with very rare exceptions, which we’ll get to…) you should have at least four GPS satellites visible. That doesn’t necessarily mean you’ll be able to see the satellite, of course, but that if you could see that far, you would.
And the fact that you’re always in range of four GPS tracking satellites means that those satellites can send information to your GPS device—whether a car GPS tracker or handheld GPS tracking device—about how far away they are. More precisely, each satellite sends information about its position at regular intervals. Your device intercepts those information packets and calculates the time it took to receive that information, which travels at the speed of light. The GPS receiver in your device then can calculate how far away each satellite is based on the time it took for the message to travel from the satellite. And as long as your device gets that information from at least three of the four satellites, it can pinpoint your location using a process called trilateration.
So what’s trilateration? Think of a Venn diagram with three circles. Your device, which knows the distance to each satellite, can create a circle to represent the area that is that distance from satellite A. It can likewise create circles that represent the areas of the right distance from satellite B and satellite C, respectively. The point where all three of those circles intersect? That point is your location.
That’s an oversimplification in some senses—after all, the surface of the earth isn’t a flat plane, so instead of circles for each satellite, your GPS receiver maps spheres—but that’s the general idea of how your GPS tracking device works to determine your location.
As you can imagine, the more satellites there are above your location, the more accurate your car GPS tracker or other devices can determine your location. Similarly, if you are in the mountains or thick woods, the sphere for each satellite may be less accurate, making your location tracking less accurate.
Further complicating things, there are three different ways that GPS devices can track location: Data loggers, data pushers, and data pullers.
Let’s look a little more closely at each type.
Types of GPS Trackers
- GPS Data loggers work by logging the position of the device regularly in their internal memory, whether a memory card, USB port, or internal flash memory card. That memory can sometimes be downloaded to a computer later, allowing for analysis of the track log data. Digital cameras or simple phone apps are both common examples of data loggers.
- Live GPS trackers or data pushers work by pushing (or sending) their location at regular intervals. They may also send related data, like the speed or altitude at which the device is moving, to a separate server. If you have a car GPS tracker, for instance, it likely utilizes a data pushing system. Many personal GPS tracking devices are also data pushers, including ankle bracelets used for individuals on house arrest, tracking devices used in races, live GPS vehicle trackers, devices for elder care, trackers for adventure sports and other sorts of remote adventures, or even collars used for animal tracking.
- Data pullers, which are sometimes also known as GPS transponders, are similar to data pushers, but instead of sending their position at regular intervals, they send their position only when queried or pulled. That can happen as often as needed, of course, and is most often used for items where the location only needs to be known occasionally. Many anti-theft devices, for instance, utilize data pulling, as they can be located when needed, but otherwise, don’t need to drain the battery or other power sources.
While most GPS tracking devices utilize data pushing, there are also instances in which devices can switch between types. For instance, many cars utilize data pushing for real time GPS trackers, but also may have anti-theft transponders that utilize data pulling. Many phones, for instance, can toggle between types of GPS to track location depending on service or user preference.