Those who say it's a software problem do not know what they are talking about.
If you reset your settings, reinstall your phone and your apps and it still does not work then it is a hardware problem.
I and many others have fixed our malfunctionning GPS by replacing the antennas following this guide.
The reason why you think you get GPS when in fact you are not is that your location in the apps is not only given by GPS satellites but also from cell phone towers triangulation and home wifi routers you pass by.
Once you get away from cell phone reception and connected homes your location is gone because you never had a GPS connection to start with. Download the GPS Diagnostic app, it will show you wether you are connected to the satellites or not.
Even if we all think that the iOS upgrade broke our GPS you can check my previous post that shows that this "my gps broke since ios9/10/11 upgrade" has been going on for ages. I believe that the upgrade process put some strain on an already failing hardware and that's why we believe that it's a software problem and hope for a magical update that will never come.
Apple is just never going to tell you that their hardware fails, it would ruin the magic... If the replacement parts are sold on Amazon with 4,5 stars reviews it's because it solves a real problem.
The problem is that these parts don't seem to exist for models newer than the 6. It's not difficult to infer why.
All the best.
[Link edited by Host as following the procedures at the site may lead to damage to the user’s device]