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How mobile GPS works and ways to view connected satellites

The mobile phone became a smartphone after it not only served to call and send SMS, but also to do a thousand and one added things. One of them seemed almost magic, but it has ended up becoming something so everyday that we don't even pay attention to it. Why, Do you know how your mobile's GPS works?

Is open Google Maps, Waze, Pokémon GO… and in seconds we are located on the map precisely and with the option to follow our steps. This technological miracle is the most common, but to achieve it not only need sensors in the mobile, but also an extensive global satellite network. Let's see how it works.

What is GPS and how does it work?

All your GPS information: satellites to which it is connected, coverage ...

GPS satellite Block IIR. GPS.gov image

GPS is a multi-satellite positioning system which uses receivers placed on the phone to capture the emissions of specific satellites that orbit the Earth. Although we call this system «GPS» in a generic way today, our smartphone connects to different satellite networks, not just GPS itself (Global Positioning System).

Developed by the US military for military use, GPS ended up being enabled for civilians to use. Of course, with much less precision: in general the minimum is in the 4-8 meters of margin (the armies and companies that need an exact positioning geolocate their objectives with millimeters of error).

Apart from GPS There are other positioning systems. Countries with great military tradition have developed their own system: GLONASS in Russia and Beiou in China (both open for civil use). In addition, Europe has its own positioning system that has not been released for too long: Galileo. These four are the ones that are usually equipped on smartphones: depending on the range of your mobile you will have more or less; always with the GPS as a system default positioning.

All your GPS information: satellites to which it is connected, coverage ...

GPS.gov image

We have already seen that the mobile has sensors that capture the signal emitted by satellites and that they orbit around the Earth. Now: how is it possible that our mobile know exactly where we are just by picking up the signal of devices that are at over 20,000 kilometers away? The key is in mathematics.

  • Since the satellite's orbit is to regulate the mobile, it knows exactly where each of these satellites is: its signal is identified with the satellite number and other data, such as its elevation and azimuth (the angle that the satellite signal creates with respect to the surface of the Earth).
  • The mobile GPS capture as many signals as possible to position itself reliably. In the process you will see that the precision is reduced in meters until it is stable around 4-16 meters.
  • The signal takes a while from leaving the satellite until it reaches the mobile receiver. Since the speed is constant (speed of light, more than 299,792 km / s) the mobile can calculate the precise distance to the satellite.
  • When the mobile has at least four satellites captured, it can already be positioned in the three dimensions of the map using trilateration: the mobile draws a circle around each satellite; and the point where all the circumferences intersect will be the precise location.

All your GPS information: satellites to which it is connected, coverage ...

How trilateration positioning is calculated: point B is the position. Wikipedia image

Now imagine that you don't just use satellites GPS (24), your mobile can connect to the system GLONASS (24 satellites), Galileo (30 satellites) and Beiou (35 satellites): the most modern mobiles already incorporate compatibility with these four systems (and with others, such as the Japanese QZSS). This achieves precise positioning in much less time since the mobile can detect a high number of signals using trilateration to mark the position on the map.