How Does the GPS System Work?

A carefully designed network of satellites at 20,200 kilometers altitude work together to find your position on earth so that you can navigate. Now a new and even more precise system is ready.

The idea of satellite positioning was born during the space race in the 1950s when it was discovered that it was possible to calculate where satellites were positioned using the Doppler effect by measuring the frequency of their radio signals. The United States tested satellite navigation as early as the 1960s, but it was the first radio navigation system to operate worldwide using transmitters on the ground. There were several different networks of radio lighthouses, such as Decca, Omega, and Loran, but several systems have been shut down over the past ten years and the systems that remain have few users.

The first GPS satellite was launched in 1978. Initially, the Navstar GPS (Navigation Satellite Timing And Ranging Global Positioning System, as the system is actually called,) was an entirely military project. A notable accident in 1983, when Soviet aircraft shot down a Boeing 747 from South Korea with more than 250 people on board changed it. The passenger plane had navigated incorrectly and to avoid similar tragedies in the future, Ronald Reagan promised that even civilian users would have access to GPS. More than ten years and several satellite launches later, GPS was in sharp operation.

The core of the Global Positioning System, the GPS system, is 31 navigation satellites, orbiting 19300 kilometers above the earth.

Each satellite has both a radio transmitter and an extremely precise atomic clock, which indicates the time with an accuracy of three billion parts of a second. The orbits of the satellites are planned so that there are at least four pieces above the horizon at all times, no matter where on earth you are.

Each navigation satellite constantly tells you what number it has, where it is, and exactly when it sent its message.

It does this with the help of radio signals, and it is these signals that a GPS receiver captures.

A GPS receiver is a device that guides, and there are a variety of variants depending on whether you plan to use your GSP in the car, on the boat, in the motor home, on the motorcycle, or similar. However, the very first thing that many people think of when mentioning GPS is the models used in regular passenger cars.

The GPS receiver takes advantage of satellites to find out exactly where in the world you are, and through its built-in maps, it can then provide one with instructions and directions so that you find the desired destination.

Developed for military use

The GPS receiver also contains a very accurate clock and can, therefore, calculate how far the signals from the satellites have traveled.

When the GPS receiver receives information from several satellites, a computer in the GPS receiver can compare the information and, using a mathematical model, determine the exact position, which is then dotted on a map.

The accuracy is generally 20-75 meters, but with various technical measures, it can be improved, so that the uncertainty drops to only a few centimeters. Furthermore, this technology is improved constantly.

Precision is necessary, among other things, when an area is to be mapped.

The GPS system is American and was originally developed for military use, but for many years it has been freely available.

A European and even more precise system called Galileo is scheduled to be ready by 2020.

The very core of the GPS receiver calculates the position – to get more information, smart software is needed. In order for GPS companies to concentrate on making better and more sensitive receivers and navigator developers like Garmin and Wayfinder adhere to interfaces and features, the different parts need to be able to communicate with each other.

It is a text-based protocol where the GPS receiver sends out position, speed, signal quality, and other values on a serial port or over a Bluetooth connection.

Many today use the GPS app on their mobile devices, such as Google Maps or Apple Maps to navigate. It works fine for many, but a dedicated GPS really has its benefits. GPS apps on mobile phones usually use a lot of mobile data, which is expensive – especially abroad. If you download the maps, it takes up a lot of space on your mobile, and it uses a lot of power which results in the mobile being dead when you need it for other things. In addition, you always run the risk of being called or receiving an SMS that interrupts navigation when you are in a complicated roundabout.

The position is determined by several satellites

As a result of the position of the orbits, a GPS receiver always has contact with four satellites.

Each satellite transmits a signal specific to that particular satellite and tells you how far away the receiver is.

Thus, the individual satellite cannot determine the exact position of the receiver – it can, however, four satellites.

1. Satellite A tells that the receiver is at a distance of 21000 kilometers from the satellite. The recipient can thus be anywhere on the surface of the globe.

2. Satellite B shows that the receiver is 22000 kilometers from it. This means that the receiver must necessarily be somewhere on the circle that occurs where the two spheres intersect.

3. Satellite C reveals that the receiver is 20000 kilometers from it. This means that the receiver must be in one of the two points where the three globules intersect.

Which of the two points the receiver is in is revealed by the fourth and last satellite.

The satellites are located in six orbits around the earth

GPS receiver without mobile

If you own a mobile, you may have noticed that there are some applications that act as a GPS while driving. However, these cannot be compared to actual GPS receivers as there are a number of disadvantages to the mobile versions.
First of all, the screen is usually quite small, which makes it complicated to keep track of the route – not to mention the fact that you do not have a holder for the mobile phone in the same way as a GPS. The mobile phone can always slide off or turn upside down, which becomes a big problem when you have to focus on the road.

Further disadvantages of mobile are all features not related to GPS. Maybe you suddenly get a notification, a call, a new text message or the program shuts down unexpectedly. This can take focus away from the road and create problems that you naturally want to avoid. With a modern GPS receiver, you avoid these annoying elements and will instead get a reliable device with current maps.

Various GPS receivers

When it’s time to buy a GPS receiver, you will quickly notice how there are not just a few variants to choose from. GPS receivers come in many different models with their own looks, features, and accessories. For example, how big the screen is on one’s GPS can make a big difference when a larger screen provides one with a simpler overview of one’s upcoming route.

There are also several different decisions that you have to make when choosing your GPS, such as how the narrator’s voice should sound, how the interface should look, how large the screen should be, how many maps to include, what accessories to come with your GPS and much more to it. With several different GPS receivers in several different price ranges, you can always find someone that fits you perfectly.


We monitors and writes about new technologies in areas such as technology, innovation, digitization, space, Earth, IT and AI.

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