Comment by PeterisP

Using your phone's GPS requires cooperation from your phone, however, triangulation by timing is not only possible, but even required by the GSM standard, the signal continuously measures and encodes your "latency" to the tower needed so that you'll start transmitting your block slightly earlier if you're farther away so as not to overlap with the time slot possibly allocated for some other device.

It's not as accurate as GPS, but it gives a solid estimate of your location that neither you nor your phone can prevent unless you totally disconnect.