It is my understanding that smart phones will ping cell towers even if tracking, etc., is turned off no matter what. This includes when the phone is off or powered down - as long as it has battery power it will ping and can be tracked.
“smart phones”
Any cellphone
” is turned off no matter what.”
Source?
Your phone occasionally pings looking for nearby cell towers. It will usually pick the one that it gets the strongest signal from and associate with that tower. The tower in return sends that info back to the phone company. That way, if someone calls you, the phone company routes the call to that tower and then to your phone. Incoming calls go to one tower, not all of them. That would quickly overload the towers if they didn't have some sense of who was where. Obviously if you call someone on Verizon it is not going out over every Verizon tower. Instead the call goes to Verizon, it says "Oh, phone # xyz? That's currently associated with tower PDQ..." and routes the call there. That information alone is enough to locate you within a reasonably short distance from the tower. Typically within several miles.
As I understand it, the phone company can poll towers and "dump logs" or some such - see which phones are not only currently connected to each tower, but also which phones have recently pinged it then said "thanks but no thanks, I'm getting a better signal from this other tower." With that additional information about what towers your phone "sees" but decided not to connect to, they can triangulate your position down even tighter. Depending on the number and location of towers in the area they can probably get your phone's location down to within a couple dozen yards - without GPS, without asking your phone anything, without you even knowing. Just by having your phone on.
There are some people who claim even if your phone is off it can be remotely turned on. I'm not sure I believe that, or at least that it works the way you might think. Off is off, no CPU, no RF links, etc. However... If your phone is accessed and compromised it *may* be possible to install code into it that takes over. Then if/when you turn it off it only gives the appearance of being off. It may still be on, just running in a very low power mode and only doing what the attacker wants it to do - recording locations or audio or video, maybe communicating that out. But from all outward appearances it is off. If you cannot remove the battery from your phone and you're not sure off is really off... There are things like RF shielding bags and such that block the phone's ability to get GPS information or send out any information. You'd still have to keep it where it could not see or hear you. Or just leave it behind...