Best AnswerTo add to what the others have said, there is also an icon on screen when the GPS is active so it should be pretty clear in use that's it's off at all times except when certain exercise modes are active.
Mike | London, UK
Blaze, Surge, Charge 2, Charge, Flex 2 - iPad Air 2, Nokia Lumia 925 (Deceased), iPhone 6
Take a look at the Fitbit help site for further assistance and information.
Best Answer