You can turn off GPS when you are training indoors or to save battery life. When running or walking with GPS turned off, speed and distance are calculated using the accelerometer in the device. The accelerometer is self-calibrating. The accuracy of the speed and distance data improves after a few outdoor runs using GPS.

When cycling with GPS turned off, speed and distance data are not available unless you have an optional sensor that sends speed and distance data to the device, such as a speed or cadence sensor.