Wi-Fi signals permeate our cities. A newly revised tool, now available for Mac OS X, lets Web sites determine your location from those ubiquitous Wi-Fi networks found around your computer. A free package called Loki - the Norse god of mischief and a play on the word "loci" - asks your permission before revealing your location to Web sites that can use that location for various actions, such as identifying your position on a map. But how does Loki determine your location? Through a lot of brute force up front and elegance thereafter.
Skyhook Wireless, the firm behind Loki, started a few years ago with the mission of providing a location service with a high degree of precision by identifying the latitude and longitude of typically static Wi-Fi networks in homes and businesses. The company has dozens of trucks collecting data in major cities across the United States, Canada, and Australia, covering 70 percent of the population of those three countries so far, and a few cities in Asia and Europe. Wi-Fi gateways seldom move after networks are turned on, although gateways burn out or are replaced, and new ones installed all the time. But that's all a slight degree of motion compared to an ocean of stability.
Each truck is equipped with a Wi-Fi radio hooked up to a high-gain antenna, a GPS receiver, and a computer. As the trucks drive predetermined routes through a city, they collect snapshots of the Wi-Fi signals and map them to the current GPS coordinates. All that information is then combined into a massive database.
When Loki is installed on your computer and you're connected to a Wi-Fi network with an Internet connection, the software asks the operating system for the current network names and signal strengths. Loki passes that information to Skyhook's servers, which engage in quick mathematical magic and come up with a rough idea of where you are. In my testing in Seattle, even with just one or two distant Wi-Fi networks visible, the software was as accurate as a GPS, placing me within 30 feet, sometimes less. Loki also sends information back to Skyhook, allowing them to supplement their GPS/Wi-Fi scanning with user scans that can be incorporated as additional data points.
One of Loki's limitations is that the software can only produce a useful result if you are, in fact, connected via one of those Wi-Fi networks to the Internet: it sends a Wi-Fi snapshot of your vicinity, and Skyhook sends back the coordinates (if available). With more devices appearing that include both cell data modems and Wi-Fi - such as the iPhone, some other smartphones, and dozens of fresh cell/Wi-Fi voice handsets - Skyhook's software could take a Wi-Fi snapshot even without your device being connected to a Wi-Fi network, and then send that snapshot to their servers through the cell data connection. (Steve Jobs said last week that the iPhone would ultimately be opened to "secure" applications from third parties, and Loki would be an obvious one.)
Skyhook originally intended to make their location-mapping results available as a service to firms that would want to incorporate it into products; they've had a little success on that front. They recently released a plug-in for AOL that would allow instant-messaging buddies to see each other's locations, with permission controls.
Instead they decided to popularize their technology by releasing their first Loki product a year ago: a free toolbar for Windows XP. That toolbar allowed you to pre-fill location information into mapping sites, photographic sites that support geotagging (adding coordinates to the metadata of a photo), and store locators for companies like Starbucks or Office Depot.
Skyhook has partnered with the dominant GPS chip maker, SiRF, so an equipment maker like TomTom or Garmin could enhance GPS reception with Wi-Fi positioning. GPS signals tend to be hard to receive in urban canyons, where a fix on the three satellites necessary to get good data can be difficult to achieve, and that's exactly where Wi-Fi is most abundant. As GPS chip prices fall and more gadgets feature Wi-Fi as a connectivity tool, you could see a camera that automatically tags photos with the best coordinates it can calculate and then uploads those photos when it can reach a Wi-Fi hotspot.
While the Windows XP version 2.0 of Loki updates both the toolbar and adds this lower layer, the Mac release includes just the programmer support. A Windows Mobile release is a freestanding application. Skyhook told me that a Mac toolbar will follow shortly, as well as an update for Windows Vista. For now, the Loki finder works only in Firefox 2 or later for Mac, or Internet Explorer 5 through 6 or Firefox 1.5 or later for Windows XP.