Ok.
Triangulation attempts to give a general area you were in by measuring the signal strength between your phone and the three nearest cell towers you pinged in your area to come to an approximate location. The problem with triangulation, as I said, is that it's only effective in areas with a higher density of towers. There's also another issue I didn't mention: Each tower for a given provider can handle a finite number of cellular devices. It's possible that the tower nearest to you could be busy, causing you to hit a tower farther away, throwing off triangulation by miles.
The only way to get fairly accurate with your location is via GPS, and on older phones it can be switched off with some degree of confidence that it can't be turned on by remote via instructions received from the base station to the baseband processor in every smartphone (most older 1xRTT and GPRS phones... basically everything pre-true 3G).