risu wrote:
The closest they can track your phone is to the last cell tower it connected to... which means your phone could be anywhere within a 3 - 5 mile radius of the tower.
The billing system only tracks the cell site, true. However, if you make friends at the store or "know" people, a network technician can pinpoint calls down to a sector of a cell site AND the distance from the site. A sector, depending on the site, is either a 1/3 or 1/6th pie shaped area propagating from the site. Some sites only have one sector. Next, they can then calculate the distance from the site. You see, the network knows the distance the phone is from the site based on something called "round trip delay" and can calculate how long it takes a radio signal to get from the site to the phone and back, this is on the order of microseconds. With both pieces of information, the location can be narrowed down to an arc around a portion of the cell site. Triangulating is also possible. The network knows where the phone is because it allocates resources to the phone. In some cases, the network coordinates up to three cell sites to transmit a phone call to phone phone (not a very good use of resources, but if it improves voice quality it does work). So the network knows, for instance, three sites and the round trip delay to the phone from each site. Triangulation "can" work with two sites, but you'd have to calculate the intersection of two arcs and the phone can be in one or the other arc. Wow... my brain hurts. The phones that have the Chaperone feature use GPS to locate the phone, then send the location data to a server. That's easy so long as GPS signals make it to the phone. Google also has some app that can do this, I haven't seen it in action though.
