Shortly after the launch of 1. health code, under the guidance of China's Ministry of Industry and Information Technology, China ICT Institute, China Telecom, China Mobile and China Unicom jointly launched the itinerary inquiry service.

2. The purpose of run-length encoding is to grasp the user's travel trajectory more accurately, which can be used as an important evidence to judge whether the user has reached the middle and high risk area, and can prevent the occurrence of missing reports.

3. When the mobile phone turns on the wireless network, it will automatically search the surrounding wireless networks. Once the mobile phone is connected to the wireless network, Big Data will instantly collect information according to the unique MAC address of the wireless network router in the world. The train code from Zhenjiang to Baitu will be displayed.