Use and installation problems with the smartphone
Read here what you can do if the app cannot be installed on your smartphone.
How do I turn on the GPS (location determination)?
By default, the app asks if the GPS is on. This is necessary to determine your location in relation to the spearhead. The GPS also helps you with the route to the spearhead.
Activate GPS with Android device
Go to Settings, location. Set this to "on"
Activate GPS with I-phone
Go to settings, Privacy, Location services. Set it to "on".