5 ms·

Pretty cool. I wonder how often the wifi database needs to be refreshed? How often do the wifi points change, go offline. I assume that database also uses some

Pretty cool. I wonder how often the wifi database needs to be refreshed? How often do the wifi points change, go offline. I assume that database also uses some info from the IP address as well.

scraplab 12y ago
It uses Apple's CoreLocation framework. The data was, I believe, initially bought from Skyhook, and then augmented by iOS devices reporting SSIDs from a known GPS fix. It's abstracted away behind the API, but I think the framework uses trilateration of SSIDs with signal strength. The fix is often very precise - even shifting slightly between the front and back of my house. It doesn't use any IP geolocation - it's just not precise enough. http://www.skyhookwireless.com http://www.skyhookwireless.com Disclaimer: I wrote the app! Nice to see it here.
- spott 12y ago
  You sure it doesn't use IP geolocation to narrow down the SSIDs it should search for? I'm thinking of an R-Tree like structure based on IP to get your search for SSID coordinates most of the way there. On the other hand, maybe simple database searches for SSIDs are fast enough?
  - dsl 12y ago
    It is a common misconception that the SSID is used in these types of databases. What it is actually looking for is the MAC address of the wireless access point.
    - scraplab 12y ago
      You're right - I mean BSSID, which is the same as the MAC address.
sneak 12y ago
The databases are online, run by Apple and Google for their respective platforms. They are constantly being refreshed by devices with GPS lock and wifi reception, such as the installed base of handsets/tablets, as well as street view cars.