Cell phone GPS. Active when phone turned off?

As mentioned in this Wired article, most cell phones now can report your location via GPS.

Is your location transmitted even when the phone is turned off?


That article does not have anything to do with GPS in phones. The tracking has to do with tracking what cell sites your phone is in contact with. Which happens when the phone is on but not necessarily in a call.

Any cite for that?

That’s the answer I would expect, but you wonder how useful the tracking is if all you have to do is turn off your phone.

You are not going to get a cite for how all phones work. It is certainly possible to create phones that look like they are turned off but still talk to the cell towers. It would be difficult to have a large number of phones act like that and have it go unnoticed.

The tracking is extremely useful because people don’t turn off there phones often. Do you leave your phone off except when you want to make a call? Most people don’t. Most people leave the phone on all the time so that they can be called. A phone that is not on is pretty useless.

Many modern cell phones can’t be turned all the way off without physically removing the battery. Some phones can be remotely activated as microphones, apparantly even if the phone in question is turned off. Other phones such as the iPhone will download e-mail even when turned off. It seems to me that in both of those situations, the phone is communicating with local cell towers, so your location could be identified.

That iphone article is misleading the iphone was not off. It was on but the owner did not understand that it would try to download email without being specifically commanded to.

My Wife and I leave ours off unless we are out of town or have made other arrangements to have them on.

In any case, this was initiated so that the com center can try to locate you when you make a 911 call. If you call from a land line an address comes up. No such feature for a cell phone.

If you’re allowed to modify the phone’s software, you can make it do almost anything. That’s because the on/off switch is not connected to the power supply. Its state is polled by the microcontroller in the phone on a periodic basis. The microcontroller, under software control, manages the power in the phone. It’s like most modern television sets that can be turned on and off with a remote control. That said, when off, most of the circuits in the cell phone are powered down, including the RF circuits. The microcontroller is running in a low-power mode, doing the minimal housekeeping needed to allow the user to turn the phone on and do things like updating the internal clock. All of the high-power circuits are shut down to preserve battery life. Keeping the RF circuits on would drain the battery and raise significant safety issues. Users rely on the fact that turning off a cell phone means that it doesn’t pose a hazard in areas with explosives or RF sensitive equipment.