Under the older/earlier technology you could be triangulated fairly accurately if there were multiple towers within reach. With the new enhanced 911 this gets even more accurate. The newest technology includes a GPS receiver in the phone itself that can report your exact location within a few yards. You currently cannot turn it off without turning off the phone and have no control over when or to whom it is reporting your position.
The bottom line is that if don't want to be tracked everywhere you go then turn off your cell phone.
Federal officials are routinely asking courts to order cellphone companies to furnish real-time tracking data so they can pinpoint the whereabouts of drug traffickers, fugitives and other criminal suspects, according to judges and industry lawyers.
In some cases, judges have granted the requests without requiring the government to demonstrate that there is probable cause to believe that a crime is taking place or that the inquiry will yield evidence of a crime. Privacy advocates fear such a practice may expose average Americans to a new level of government scrutiny of their daily lives.
Such requests run counter to the Justice Department's internal recommendation that federal prosecutors seek warrants based on probable cause to obtain precise location data in private areas. The requests and orders are sealed at the government's request, so it is difficult to know how often the orders are issued or denied.
The issue is taking on greater relevance as wireless carriers are racing to offer sleek services that allow cellphone users to know with the touch of a button where their friends or families are. The companies are hoping to recoup investments they have made to meet a federal mandate to provide enhanced 911 (E911) location tracking. Sprint Nextel, for instance, boasts that its "loopt" service even sends an alert when a friend is near, "putting an end to missed connections in the mall, at the movies or around town."
With Verizon's Chaperone service, parents can set up a "geofence" around, say, a few city blocks and receive an automatic text message if their child, holding the cellphone, travels outside that area.
"Most people don't realize it, but they're carrying a tracking device in their pocket," said Kevin Bankston of the privacy advocacy group Electronic Frontier Foundation. "Cellphones can reveal very precise information about your location, and yet legal protections are very much up in the air."