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The first type: base station positioning.

To make a call, our mobile phone must have a signal, that is, it must be connected to a nearby communication base station. An ordinary communication base station is an iron tower (left), but now many base stations in urban areas will pretend to be trees for beauty (right).

When our mobile phones are looking for signals, they usually look for the three base stations with the best signals nearby. In this way, after a simple triangulation operation between base stations, you can get a more accurate mobile phone location!

There is also a little joke about the location of base stations.

It is said that a young man struggled in Beijing for many years and finally bought a house in the suburbs. As a result, on the first day he moved in, a short message appeared on his mobile phone to remind him: Welcome to Hebei Mobile!

Many people have this experience. When you go to a distant place by car, when you pass a city, your mobile phone receives a short message from this city. In fact, the base station in this city receives your signal and knows that you are here!

The second type: GPS positioning.

Although base station positioning is fast and convenient, there are two problems:

First, the accuracy is not high; So, if you are in the suburbs of Beijing, you may be located in Hebei;

The second is that when the phone has no signal, it can't be located.

So there is a more accurate positioning method: GPS positioning.

GPS, the full name of Global Positioning System, mainly refers to the GPS in the United States and the Beidou navigation system in China. Satellite signals can be used for global real-time three-dimensional navigation, positioning and speed measurement. GPS positioning needs the support of mobile phone chip, and the positioning accuracy also depends on the chip.

Nowadays, general smartphones will have GPS chips, and many domestic mobile phones such as Huawei and ZTE will also support Beidou positioning. The positioning accuracy of high-precision chip satellite can reach centimeter level, and the positioning accuracy of mobile phone GPS can also reach 5- 10 meter.

Of course, there are also problems with GPS positioning. First, its positioning is slow: the GPS chip needs to receive the models of multiple satellites at the same time to accurately locate;

There is also the fact that GPS signals are easily blocked by ground obstacles (poor indoor positioning), which is also related to the weather. In addition, if the GPS positioning is turned on, the power consumption of the mobile phone will be very fast.

Xiaomi 8, released not long ago, adopts the design of dual-frequency GPS positioning, which not only improves the positioning accuracy, but also improves the positioning speed, and is also a practical innovation.

As can be seen from the above, GPS positioning does not need mobile phone communication signals, and it can be positioned even if the mobile phone is turned off (unless the battery is unplugged, the current all-in-one machine cannot unplug the battery).

Therefore, there are often plots of mobile phone tracking in movies and TV series. For example, in last year's TV series "in the name of people", the mobile phone of Ding, the vice mayor of the drama, was still tracked even if the Sim card was removed.

The third type: WiFi positioning.

The principle of WiFi location is similar to that of base station location. The WiFi connected to your mobile phone will eventually access the telecom network through the router, and the telecom naturally knows the approximate location of this router.

Because the coverage of WiFi is quite small, locating a router is equivalent to locating a mobile phone connected to this router.