When using a mobile phone, the mobile phone card will have a signal, which will generate roaming records, and the operator will record and filter these data, so as to get the personal travel trajectory.

Electrical signals can be used to query the travel trajectory. You can enter electrical signals and verification codes in Alipay's travel card to query. 1. After entering the travel card in Alipay, click Query Now. 2. Enter the telecom number and verification code, and click Query. After the verification is successful, you can query the travel trajectory.