How does Google gather foot traffic data? I assume from cell phone location? Then I have more questions... That makes sense for the average unsuspecting Andr

How does Google gather foot traffic data? I assume from cell phone location? Then I have more questions... That makes sense for the average unsuspecting Android user who keeps location on all the time. "Proper" Android is more or less spyware from Google, so this is not surprising. But Pentagon people keep their work/personal Android location on all the time? Otherwise, for iPhones, can Google get real-time location data when someone is not actively using Google Maps?