Apart from the use of Tor to surf anonymously, what is the current accuracy for investigators to pinpoint a 3G USB-modem connected to a laptop in a populated area? The laptop has no GPS/Bluetooth/IR or other any other communication device. Some say it's possible to be pyshically pinpointed with an accuracy of 150 meters, some say 50 meters but what is the current accuracy? I know they pinpoint by calculating the distances between the modem and the celltowers, but is it possible for them to pinpoint you with an accuracy of 10 meters or less? I know that pinpointing a GPS device is with an accuracy of 1 meter, but how is that in the case of a laptop with a 3G USB-modem? I want to know this because I want to use an anonymous and prepaid 3G connection for using Tor and not want to be marked as a Tor-user. They are recording and registering everything these days so if they can pinpoint the location of a 3G-modem with an accuracy of 10 meter then they record the coordinates of my appartment and they know there lives a Tor-user. In that case I have to use 3G --> VPN --> Tor. But imagine that if the accuracy would be around 100 meters, in that case it's more difficult for them to locate he Tor-user exactly (in an area of 100 meters live around 300 people). Any knowledge/suggestions/brainstorms on this issue would be very appreciated.