The telephone survey of epidemic situation and air defense shows that the whole province is filled with air.

It may be that the signal is offset, or at the junction of the two provinces.

When the mobile phone network establishes a connection with the base station, the information of the mobile phone card will be registered. Even if you didn't use a mobile phone at that time, as long as your mobile phone card is on the network and moved, it will switch with the neighboring base station, and the base station will collect the information of the mobile phone card every time. Every mobile base station has GPS information. Once the mobile phone card is connected to the corresponding base station, the background can use the location information of the base station to determine the location of the mobile phone card.