Which speed is more accurate, the speedometer or cell phone navigation?

Hello, dear car enthusiasts! Today I would like to talk to you about an interesting topic: when we drive, should we trust the speedometer on the car or the speed display on the cell phone navigation? This is not only a technical issue, but also an important topic related to our driving safety. After all, no one wants to get an unpleasant ticket because of a speed error, right?