If you use a mobile phone to connect with the base station, then telecommunications, mobile and China Unicom must have location data. The "health code" is based on real data and can be generated by citizens or people who have returned to work through their own online declaration and background audit.
As an individual entering and leaving electronic certificate locally, the QR code can be declared once, which is universal in the whole city. The introduction of the health code aims to make the work of returning to work more accurate, scientific and orderly.