Accurate geolocation using IP address

Accurate geolocation using IP address: "To use the method you first need some servers that you know the location of. Wang used Google Map servers. Next a rough fix of the location of the target machine is performed in the usual way i.e by measuring packet transit time from a number of 'ping servers' spread out at known locations. You can determine where the target is located using triangulation from the transit time of the packets from each of the 'ping servers'. This gives a location fix that is generally accurate to around 200km. The clever part of the algorithm is that with this rough fix you can determine which of the known machines are  close to the target machine. You can then use a trace route to compare the routers that the known machines have in common with the target machine. Then, using transit times, the distance from a known server can be refined."