Why is the actual driving distance longer than the navigation?

[Aragorn]

Car navigation uses GPS satellites to measure the speed and distance of the vehicle during travel, while the speedometer uses a wheel tester to measure the vehicle's speed. The two methods of speed measurement are different. Relevant explanations are as follows: 1. Speed accuracy: Although GPS is affected by the environmental signals at the time, causing the displayed speed to be unstable, the resulting error is relatively small, usually around 2-3 mph, making the speed display relatively accurate. 2. Warning function: Because the car's built-in speedometer is designed with normal safety considerations in mind, the speedometer's display is adjusted to be slightly higher than the actual speed, with an error of about 3-5 mph. The instrument shows a faster speed than the actual one to remind the driver not to exceed the speed limit, thus better avoiding speeding at critical points.