GPS not working on iPhone 6s
I bought a used iPhone 6s recently, and it has been working fine until now.
With WiFi off, the phone only has a rough idea of where I am, showing +/- several hundred meters. For comparison, that's my entire housing estate. With WiFi on, the phone knows what street I'm in. However, previously the phone could pinpoint my location accurately. Taking it out Geocaching today, it was clear that the issue wasn't due to houses or trees. Without WiFi and a weak 4G signal, the phone was completely lost - unlike before.
Would this be fixed by replacing the GPS antenna, or is the GPS chip dead?