As 'missingm' noted, GPS determines your position via satellites, so no cell coverage is needed. However, in order to tell *others* where you are, you need coverage. The location services, like 'findmyiphone,' need cell coverage to work. She had it turned off anyway, though. I have no doubt a cell phone would have been immensely valuable in this situation. But I want to hear just how she went from going for a 3-mile jog to becoming hopelessly lost or stuck. Does she like to jog off-trail through dense forest? This makes no sense.