Originally Posted by
Hoopdriver
Yes, some phones have GPS receivers that can improve accuracy (some better than others). But even if they had no GPS chip, all phones use triangulation of signals between several nearby towers for location. You are pretty much never on a just a single tower (which as you said, would not be not that accurate), but when there are many towers in your area your location can be determined within an accuracy of 150-200 feet. Turning off permission for your apps to use your location does not mean that your location isn't known to the system.
Triangulation from cell towers is not nearly as accurate as triangulation from GPS
The effectiveness can vary WILDLY depending on the number of towers connected to. The big different is that GPS works by having all the satellites broadcasting the EXACT time. The GPS software in your phone measures the difference in the time that 3 or more sats are broadcasting, due to the difference in time is takes the radio signal to reach your from 3 different places in orbit. (You are 200 miles form 1 sat and it takes x time to reach you. But you are 205 miles from another sat so it takes x+ 0.00002688 sec. The software measures that 0.00002688 sec time difference from two synchronized clocks and figures out the only place that you can be where you'd have that exact time differential from those 2 sats. With 2 sats you could be in 2 places with that differential. With 3 says and calculating the difference between 3 pairs of sats you can only be in 1 place)
The extra fun part is that the GPS satellites are so far from the EArth that they are SLIGHTLY less affected by the Earth's gravity. Since they are further from the mass of the Earth than your phone is, time passes slower on the GPS sats than it does on Earth. Not VERY slower...but JUST enough that the GPS satellites have to be programmed to run their clocks just a little bit faster on Earth so that in space further from the mass of the Earth they are running at the right speed relative to your phone which is closer to a the mass of the Earth that causes time to move quicker. (This is Time Dilation and is part of Relativity. It has nothing to do with how accurate cell towers are. I just think it's cool.)
Cell towers aren't sending a hyper accurate time index to measure against to they can't be used to triangulate your position with much accuracy. You don't really triangulate using cell towers. What you can do is figure out where you'd have to be to get a signal from 3 different towers, and terrain / buildings can impact that.
At best in an urban environment it's accurate to a mile or so. Our in the country it's accurate to within 20-30 miles of the single tower you might be on.