Many trainers have been reporting a small loophole that allows you to be at a specific location without actually being there. Before you think GPS spoofing, this loophole does not require any sort of hack or GPS tool to do.
This loophole has to do with your phone being able to switch your built in GPS settings which is completely fine. It’s a bug on Niantic’s part and nothing hacky or illegal.
Isantum from Reddit explains how he turns off his mobile data and changes his GPS to device only in order to be at a location he was prior in the day. This technique can be used to be at a gym you were at earlier in the day, but you don’t actually have to be there:
So, I’ll try to keep it quick and short.
A = Home aka place of residence
B = Gym 900m away
C = 2 Pokestops 300m away
I leave A at 6PM, play for about 3-4 hours and when my battery is down to 10%, I turn off mobile data and put my phone into flight mode, usually when I am at points B or C
Once I get back to A, and my GPS is on high accuracy, I stay at point A. If I turn the GPS to Device Only, I am at points B or C, depending on where I switched off mobile data. This can be done just about anywhere and the game registers it as an accurate location.
I’m not sure if this is due to my carrier, but I can see a lot of people taking advantage of this to be near gyms or pokestops in game while they are at home.
This technique has worked for many people and has not worked for others. The bottom line is that Niantic has some fixing to do with their GPS settings. Let us know if this worked for you in the comments below.