[colug-432] precision of fixed platform browser geolocation

[Richard Hornsby]

I was on my bank website at home on my Macbook, and asked it where the nearest ATM was.  Safari dutifully asked if I would like to allow the website, and Safari, to use my location.

Sure, why not.  I know that geolocation from IP has been around for a long time.  I know that my hostname contains the name of the city I'm in.

I was floored, however, by how precise an address it chose as my "approximate" location - to within 4 units (feet?) of my actual address.  i.e. if my house number is 10003 Main Street, it said that it was going to use 10007 Main Street as the address from which to begin the search.

This is not a device with a GPS chip (that I'm aware of), and there is no cell signal to use.  Yet, there is nothing approximate about what it chose.  There are no public wifi access points anywhere close (I live in a somewhat rural area, but in a neighborhood, definitely not urban) like a coffee shop or other establishment.

How is Safari (google maps?) getting the location that precisely?  Does google maps really have an internal map of private wifi access points and their locations?  Is this from the street view car that they "inadvertently" collected wireless data they sniffed?  Are they possibly sharing the access point information from their Google Fiber service to their maps/geolocation services and figuring it out that way?

This can't simply be a browser thing alone - it is an OS level setting whether I want to allow geolocation services  to be enabled or not.  Anyone have insight into how this works?  If it is an OS protected call, is the OS making the request to somewhere for my location on behalf of and giving that to the browser?  If so, where is the information coming from?