Wireless LAN in London

This is a map I built up over a few runs. Each red triangle represents a Wireless LAN Access Point, sometimes multiple AP's appear as a single red triangle if they are very close to each other. Some of these AP's broadcast a few hundred metres but due to London being pretty built up, they are usually only good for around 50-75 meters with my omni-directional low gain antenna. You may notice from the map however that a few AP's go straight over the Thames with no problems at all. Clear line of sight and all that. 

I also noticed whilst hammering up the M3 motorway at a undisclosed location in Hampshire that you can clock wireless networks from a couple of hundred meters at speeds over 70 mph, which is nice. Additionally, placing the antenna outside of the vehicle by strapping it to the roofrack with a hair-band improved range and detection considerably.

This is the result of running a few roads and is likely to represent no more than 5% of the wireless networks in central London. Since most of the runs were on sunday afternoons I am assuming that these networks are permenant/semi-permenant as most of the businesses where these networks may reside would have been closed. 



click for a larger version (~100 kb)

WEP usage is currently around 35% (Jan 2002.) Since no attempt to associate with these networks was made I know not how many WEP enabled networks were using default keys but I suspect it's most of them.

Equipment used included : Netstumbler software, Thinkpad Laptop, Elsa (Lucent) AirLancer PCMCIA card, Elsa range extender antenna (~ 2.5 dBi gain), Garmin Etrex GPS and a Jeep Cherokee. The map was created by exporting Netstumbler data, fiddling with it in Excel as delimited text and then importing into Autoroute. The accuracy of this map has been degraded a smidge for consumption by the screaming masses because you just can't be trusted. 

I'd like to consider chartering a small hot air baloon or building a large kite as I think you may get better detection from travelling over the buildings rather than between them. I'll keep you posted on those developments.