Fake High Accuracy GPS Location
Faking your GPS location .. or Mock Locations.

Mock Locations can be enabled using the Development Options, this will acquire your location provided by triangulation of the connected cell towers and then apply an offset, I'm fairly sure. 

If you use Network Location, your device could be calculating your location extremely inaccurately, by simply not reading the correct signal strength from a specific tower, maybe your body is on one side of the device and disrupting the signal to the Ariel.  

Using High Accuracy GPS is not using the " internet " ( Network Signal Strength Calculations ) rather it's using calculations based on recognising visible satellites, then checking where on earth those satellites are visible from, it uses a separate internet connection to do these calculations, you'll see the network is active when your GPS Icon is flashing.