On SAR we do not believe the GPS - we check the map too. GPS units have famously sent people on the same team in different directions, despite good satellite connection and confirmation that everyone put in the same coordinate and calibrated it before the mission started. Mileages are off a lot - yesterday I did the same hike as someone else who has the same model GPS, and apparently he did less hiking than I did despite being on the same trail.

I use them, but it doesn't mean I trust them completely.