Can someone explain to me why my vehicle speed according to my speedometer and my speed according to my GPS/SatNav are out of sync by about 3 km/h? And which is more accurate? Thanks in advance.
In: Physics
It could be either one.
Speedometers work by counting tire rotations, which can be affected by wear, inflation and temperature. Also, some manufacturers adjust their speedometers to read high so you can’t blame them if you are caught speeding.
A typical GPS reads your position once per second, if you are on a curve, it can cut the corner and make it seem like you are going faster. But they also can be off by several meters, giving a zig-zag path when you are really going straight, and reading slower.
A well-calibrated speedometer will beat most GPSs, but a GPS will beat most speedometers.
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