A very simple test. I look at the map location zoomed in on the map where the blue dot is. Then I physically go to that locaton and low and behold, it's a cell tower. Not only that, but the closer I get to the tower the smaller then "larger circle area" gets in tollerance. Granted that I've only done that with one tower, but each and every time I've had GMM up with a dot and I look in the direction of where the dot is on the map in relation to where I am, there's a cell tower. I don't think it's triangulating right now, from what I have observed throughout the day it's definatly a cell tower location with some kind of distance tollerance for the larger circle. The signal strength of your radio's db readout could certainly be used to get "an idea" of how far you are from the tower you're currently echoing from.