"What second stage are you talking about?"

OK, it may not be formally called "second stage", but logically there must be a multi-step process here:

1) Acquire GPS location
2) Attempt to refine (1) with GPRS 'triangulation' algorithm
3) Send location to server to obtain textual geotag labels.

Why this can't be done with a WLAN connection is odd. OK, so you don't have the (2) GPRS-refined location, but you could still be in the right ballpark.