It is not going to affect, during the epidemic, in order to lock the close contact with the crowd, an application called big data itinerary card into people's lives. Some people doubt the authenticity of the data of this software, if we turn off our cell phone and take out the card, the telecommunication company can still find out your whereabouts track? In fact, it is possible. How does the application know our location information The software, Big Data Trip Card, was launched to meet the needs of people during the epidemic to check where they have been, and it has played an irreplaceable role in the investigation of close contact cases and other aspects of the disease, effectively curbing the further spread of the virus. Many cell phone applications can actually be networked even when the phone is turned off, which means that turning off the phone is just an action to trick yourself; as long as the phone is still in your possession, location information will be carefully recorded. The same goes for unplugging the card; as long as the phone is still in use, it will find the nearest nearby base station on its own and try to access it. In this case, the phone's identifier is recorded by the device in question and a trace is left behind.