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Dear Aunt TUAW: iPhone 3G and GPS

Dear Aunt TUAW,

I've been a faithful reader for awhile and purchased a 3G iPhone a couple weeks ago. Everything is great - except for one thing which is extremely unusual (genius words), I wanted to share with you guys. When I am in my home (and only when I am in my home) my phone believes I am in Springfield PA. I live in Minneapolis MN. It doesn't matter if I am on the 3G network or my personal WiFi network (I've isolated each), Google Maps always centers on Springfield PA. If I walk down my street, watching Google Maps- the phone re-orientates itself back to Minneapolis MN. The Genius tried to re-set the time-zone and a couple other things, but it didn't work.

Anyway, I've got a bunch of screen caps if you guys want to see them. I just can't figure out why BOTH 3G and WiFi would both point to the same (incorrect) uses cell towers and one uses IP addresses right? Anyway, I'm not necessarily looking for you guys to fix it or anything - just thought you might want to know. I Googled "iphone Springfield PA" or "google maps iphone Springfield PA" and several iterations, but it seems I am alone in my situation.



Read on for Auntie's reply.

Dear Jeff,

Clearly, someone's WiFi router has been on the move. Skyhook's WiFi location uses router MAC addresses to create correspondences between real world GPS locations and WiFi routers. When routers move, Skyhook data goes out of date.

The iPhone uses a fallback system for geolocation. So when it can't get a strong GPS signal, it moves back to WiFi location, and from there back to Cell Tower triangulation and from there possibly to IP location. GPS may fail when you're inside buildings or near lots of trees or tall people. (So keep away from basketball teams!)

The problem you're having is that WiFi location is working -- but it's working with a router that Skyhook thinks is in Pennsylvania. Not that there's anything wrong with Springfield, PA. (We hear the Simpsons like it there very much.) You might get better results by stepping outside, away from those ceilings. But the best way to test this theory is to TURN WIFI OFF. Go on. Disable it and try to locate yourself. Auntie TUAW guesses that you'll end up located a lot closer to Minneapolis than Pennsylvania.


Aunt "My other nephew is a PC" TUAW

Update: Being on a 3G/EDGE network does not automatically disable WiFi scanning for local MAC addresses. You must switch off WiFi. Also, reader Thomas suggests submitting your router's details to Skyhook directly, so they can figure out where you really are.

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