Find your way with WiFi
By Simon Spagnoletti 
posted Jun 30th 2004 5:55AM
posted Jun 30th 2004 5:55AM
Next time you're in a city or mall and your GPS craps out on you,
WiFi may spring to the rescue. A new bit of software called Place Lab uses triangulation (the same method used to track
cellphone location) of signal strength from the three nearest hotspots (and a map of 26,000 base stations) to determine
location. It's inventors at Intel's labs have so far only managed to get an accuracy of 20-30 meters but are eventually
trying to equal GPS. It all goes according to plan this could mature into a viable alternative/complement to GPS.
There's no extra equipment to buy and the software is free. Since we're pushing for ubiquitous WiFi coverage anyway it
pays to wring as many uses out of it as possible.
The technology to do this has existed for quite some time. About a year ago, a friend and I canvased the island of Manhattan with a GPS mapping out hotspots, and sure enough we were able to make a reverse lookup directory based on MAC addresses. Caveat: when an access point moves, your 'map datum' changes. Hence, this technology will never even come close to paralleling GPS. GPS, in fact, is already a watered-down technology. The US Government restricts consumers from using the full power that the GPS offers because they fear that if the GPS units are too accurate, they could be used in home-brewed guided missiles or other nasty devices. In any event, this isn't news. http://www.INeedAttention.com staff did it first.
This is a very big topic for research atm. USCD have had ActiveCampus running for a while now (http://activecamous.ucsd.edu). I created an indoor/in office system as part of my undergraduate degree (http://emhain.wit.ie/~p02ac03/cpinfo.html). MS Research created a system called RADAR (http://research.microsoft.com/~padmanab/papers/infocom2000.pdf).
Could lead to some really amazing location based games, have a look at Pirates! (http://play.tii.se/projects/pirates/pirates.html)
:-)
With Metricom's Ricochet network there were similar applications years ago. Made even easier by the fact that a central system operator deployed all nodes and knew their exact location quite precisely. Glad to see it getting there with WiFi, but now with actual GPS chips getting quite cheap it seems that vice versa might be more useful... use your known location to tell you how many feet to move in what direction to get online.
We've been working on a Wi-Fi positioning system too. (http://www.herecast.com/)... the aim of this one is to make it easy for developers to create location-aware services. (As far as I'm aware, RADAR by Microsoft was actually the first.)
The signal strength can be a reasonable indicator of distance from an access point. It can also be a rough indicator of direction if you have a map physical area of coverage. The more access points in the vicinity, the higher the positional resolution. Of course, it gets better if you know what WiFi hardware the client is using! Using a WAP and a bridge, I've been very accurate in locating a mobile card in a 50m WAP radius. I just need simple (I can imagine) software to log, map and visualize locations.
I think GPS is stil better