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2015/07/01

Unstuck in Time and Space: An Investigation into Location over WiFi.

I track my location with Google and my phone, because I lack sufficient paranoia. To the right is my June 30.

I swear that I didn't leave the Greater Lafayette area. I certainly didn't teleport to the southern suburbs of Indianapolis.

This happens to me all the time, and it has bugged me a lot. But, normally I've just looked and griped, rather than trying to work it out.

Today, however, I'm watching a compiler or two, so I have some time I can use to work this out.

The protocol is KML, and this is what it looks like:

That isn't all day's results, merely the point in time I jumped 67 miles to the southeast. I was going to try to use a KML-specific Perl module, but found that the ones I could find were more about generating it than parsing it, and it's XML, so I figured what the heck.

I had previous code to work out the distance between two points, so it was an easy case of parsing to find the jump:

Breaking it down, at 2015-06-30T13:13:05.103-07:00 I go 67 miles to Greenwood, and at 2015-06-30T13:53:31.467-07:00 I pop back.

Let me bring up an other map.

 I didn't have any mapping software going, and I was using wifi, so this data is location via wifi not GPS. I know, though, that the group that runs my servers has a weekly "coffee break" on Tuesdays, that I met with my admin there, and I walked around toward his office before goign back to mine. His building is off S. Grant St., and I walked next to Hawkins Hall, in front of Pao Hall, near the Forestry Building and down to my office in Whistler.

So, question is, how does location over WiFi work? I recall hearing that routers and access points report location, but I'm not sure of the protocols involved. I can imagine two possible scenarios that cause this.

First is that one of Purdue's routers is misreporting location, either in Forestry or Pao. This is possible; I have another issue that I haven't worked through yet where I leap instantly to the EE building, and it seems that's entirely based on location within my building.

The second scenario, one I'm taking more and more seriously, is that there's a replicated MAC address or something between the apartments across from Pao Hall. I say "or something" because MAC addresses should be unique. The thing that makes me suspect this is that it points me to a residential neighborhood south of Indy, and I could see that mistake happening with two residential routers or two experimental electronics projects.

I'm curious about how to test this, because I do want to know it has something to do with Purdue's networking gear before I complain. I'm also curious about how these things actually work. I could very much see me walking around, looking at Google Maps and tripping over things, then trying to dump my ARP tables or something.