Why does the speed display on Road Angel Mobile differ slightly to the speedometer in my vehicle?
At a constant speed, Road Angel Mobile gives a more accurate speedometer reading than that of the car. This is because the speedometer readout is governed by the rolling circumference of the tyre in contact with the road surface. Different tyre pressures, sizes and tread wear can all make a difference to the speedometer reading. For this reason every manufacturer has to calibrate the speedometer to ensure that at no point can the vehicle be traveling faster than is indicated. Road Angel Mobile speed lags because the Bluetooth GPS receiver only transmits the GPS location information once a second. As a result there will always be a delay under acceleration and deceleration.
