2. Travel tracking of health codes pays more attention to the reliability and stability of data. In addition, for the sake of data integrity, the data source of health code comes from our mobile phones to a great extent.
3. When we use the mobile phone, the mobile phone will constantly send out radio signals to be captured by the operator's base station and Internet companies, and operators and Internet companies will track our journey by filtering these signals.
Under normal circumstances, the mobile phone will communicate with the nearest base station once every few seconds, and the operator will know the location after communication. Naturally, I know which cities I went to.
5. The health code of WeChat is mainly to judge whether there is a cross-city. WeChat sends the user number to the operator, and the operator tells the WeChat user whether he has left the current city, thus completing the whole judgment process.