The general GPS feature on iOS can be found under apple Settings, Privacy and Security, and Location Services. Toggle on “Location Services” for GPS.
Here are the steps I used to get my GPS tracking to work with my Inspire 3. This tracker uses the phone for GPS as it does not exist on my tracker. When I use this capability, I do my walk with the device on my wrist and the phone with me.
1. Open the Fitbit app, go to today tab, go to Activity section, click on “Exercise Days,” “Add exercise,” and click “Start Tracking.” You should see a map display.
2. Swipe up to leave the Fitbit app and go to apple settings, go to apps, then locate and click on Fitbit app.
3. You should see a location selector. Pick either “Always” or “While Using the App.”
4. Leave apple settings and go back to the Fitbit app.
5. Now you should be able to track your walk using “start tracking” as indicated under step 1 or by auto-tracking your walk.
6. After completing the walk, sync your device with the Fitbit app. To see time, distance, and mapped route, go under Activity section, click on the walk you logged, and view/look at the details of that walk.
Hope this helps.
