You can turn GPS off when you are training indoors or to save battery life.
Select
> Run Options > Use Indoors.
The device enters timer mode.
Select
Start to start the timer.
Go for a run.
When GPS is 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. The next time you turn on or unlock the device, it searches for satellite signals.