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Possible Duplicate:
How does google My Location work?
How does precise GeoLocation in HTML5 work?

I fired up Google Maps in Chrome on my Mac Book Pro running Windows 7. To my astonishment, when I right clicked on an intersection and selected Directions To Here, it filled in My Location automatically in the A field. And it was ridiculously accurate too.

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Typically, I wouldn't be surprised - I've heard that there are databases of WiFi SSIDs out there. However, I just moved yesterday and plugged in my router this morning (12 hours ago). As far as I know Mac Book Pro does not contain a GPS. It is unlikely that a Google truck drove by my house in the last 12 hours and its data made it into the Google Maps database that quickly.

So, how did Google Maps determine my location?

P.S. I tried the same thing in IE and Google Maps said that it could not find the exact location, but could use the rough location. Which was also really close to my location (but across the street).

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marked as duplicate by Sathya Apr 23 '12 at 6:20

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Interesting info here too:… – Mike B Apr 23 '12 at 6:22
up vote 2 down vote accepted

According to a Google blog post, "My Location" is determined via the geolocation feature in your web browser. The features uses an algorithm based off of the logical location specified by your IP address. The technical inner workings of the geolocation service in your web browser are unbeknownst to me. tl;dr: Trade secrets

The "Types" section on the Wikipedia page for 'geolocation' explains possible technical means for deriving your physical location from signaling data.

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