Originally Posted by
dekindy
...only uses the sensor if the GPS signal is lost. That is they way that the Garmin works. ....
Incorrect. Garmin uses primarily the wheel sensor. You can set the diameter or let it auto calibrate it. If it loses the sensor, it starts using GPS for distance and speed. GPS position is noisy over short distances and clips corners if you ride a tortuous path. That's why they have the wheel sensor.