Explain why a GPS works even without Internet?

Principle of satellite positioning

The principle is based on a set of satellites orbiting the Earth that continuously send radio signals. These signals primarily carry two pieces of information: the precise moment at which they were emitted and the exact position of the satellite itself at that specific moment. Your GPS device on the ground receives these signals and calculates the distance separating it from each satellite by comparing the send time and the reception time of the messages. With several satellites received simultaneously (at least four ideally), the GPS determines its own position on the ground using a method called satellite triangulation. There's no need for the internet for this: it is solely based on the passive reception of these radio signals continuously emitted from space.

Operation of the autonomous GPS receiver

The standalone GPS receiver is a small, discreet device, but really smart. It receives radio signals sent by several satellites orbiting around the Earth. Once captured, these signals provide two important pieces of information: the position of the satellite emitting the signal and the exact time it sends it. By precisely comparing the emission time with the reception time, the receiver calculates the distance to each satellite. Why multiple satellites? Because it needs at least four measurements to accurately determine your exact position and calibrate its internal clocks. And it does all this by itself, without Wi-Fi or mobile network. Not bad, right?

Use of offline embedded maps

When your GPS works without the Internet, it means that the maps are stored directly on your device. Since they are already there, there's no need to download anything in real time. These embedded maps contain not only the roads but also essential information like addresses, points of interest, or one-way streets. As a result, even when cut off from the world, your device can calculate routes, pinpoint your location, and guide you smoothly. This avoids hassles in the countryside or in the mountains when your connection is down. Of course, to enjoy always up-to-date maps, you need to remember to sync them at home or as soon as you have a network connection.

Autonomous position calculation by triangulation

To determine your position on its own, your GPS device uses a technique called triangulation. Basically, it receives signals from at least four different GPS satellites, calculates the distance between you and each satellite by measuring the time it takes for the signals to reach it, and voilà: where these distances intersect is precisely where you are. Why at least four satellites? Because your receiver needs to resolve a small uncertainty related to the exact time, and this fourth satellite allows it to account for that detail. The result is a precise location calculated right on the spot, in your pocket or in your car, without asking anyone else or using the Internet.

GPS signal autonomy in the absence of the Internet.

GPS signals come directly from satellites orbiting the Earth. They are completely independent of phone antennas, Wi-Fi boxes, or any internet network. As long as your GPS receiver has an unobstructed view of the sky, it picks up these satellite signals on its own. No subscription is required and no data connection. Your phone or GPS device manages to interpret this information to calculate your position, even in the middle of a mountain or lost in the forest. No internet, no worries; the satellite does its job all by itself.