does pokemon go absolutely require mobile data

I recently downloaded and installed pokemon go on my galaxy s3 which for some reason is not available on the app market for this device...

on installing it succeeded with no problems on an unrooted unmodded device and it opened and ran through the screens of setup and logged in to the created club account. but once that process completed I am now stuck at a blue screen with a pink banner up top saying it cannot find gps signal.I returned to the home screen and the location icon did say it was still trying to find my location but when I pulled up my google maps app it was able to pin point me just fine....but the locating message was still present....this device is not presently active with any carrier but I use it on wifi which I was still connected to at the time...

is the app required to be connected to an active mobile carrier network and gps to work or is this more likely to be one of the many things that was botched by the samsung corp by using custom instructions "for security purposes" like how many apps will not be allowed to access external storage because of the programming?

could there be some other step I could try to get the app to work....I have heard of people making the game work by rooting and installing cm recovery images but I really dont want to do this to my phone....