GPS Gone Wild

Does anyone have a theory for why some the photos I posted yesterday from Golden Gate Park have EXIF data that says they were taken in Toronto or Brooklyn?

% exiftool photo-848.jpg
...
GPS Altitude: 82.3 m Above Sea Level
GPS Latitude: 43 deg 37' 46.20" N
GPS Longitude: 79 deg 24' 40.20" W
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22 Responses:

  1. Sam says:

    No theory, but you aren't the only one. Family was asking what we were doing in Toronto on their "Find my Friends".

  2. phuzz says:

    Huh, the only time I clicked on the location tag on one of your photos and it lies to me. I was thinking to myself that New York was a bit of a hike from SF. What was the gig/festival you were at?

    • phuzz says:

      Just had a thought, both the other locations look like likely venues for other festivals. Perhaps either a mobile cell tower or a wifi point was brought in to cope with demand, but whatever location service you were using had previously located that tower when it was used somewhere else?

      • dolface says:

        FWIW I can confirm that they bring in a mobile cell tower; it's usually parked on Overlook Drive or the trail that connects Marx Meadow with the NW end of the Polo Fields.

  3. rwatkins says:

    Conflicting data from Skyhook perhaps? Likely GPS being slow to respond, so getting location of the MAC address any wifi in the area. Possibly wifi equipment that moves with the tour, or just people that have traveled, and have an access point turned on.

    I run into this all the time at airports, where it puts me in a different airport. I assume its the gogo-inflight access points getting associated with one location and then are wrong when the plane flies off to another airport.

  4. I'd bet on someone's mobile hotspot widget which previously got geocoded elsewhere.

  5. Sam Nordemann says:

    iPhone uses wi-fi access points location data over gps if wi-fi is turned on, regardless of if you are connected to the access point.

    Have to turn off wi-fi completely for it to default to gps recording only in urban environments.

    The downside to turning off the wi-fi, it seems as if you don't let the camera app stay open and give it time to narrow your location, it will tag with a seemingly random location within the circle defining it's margin of error at the time you take the picture.

    I have some pictures I took in that are close to a mile off from actual location.

  6. Symptom of a larger conspiracy?

  7. Rosy Rouge says:

    Just admit you are omnipresent.

  8. Jay Sittler says:

    For once the comments on your blog are correct and logical. GPS data is taken as a secondary to WiFi data, and the MAC addresses were probably previously recorded as being in Brooklyn or Toronto. Could have been someone's mobile hotspot, cell phone hotspot, laptop, or even someone's EyeFi...

  9. Jim says:

    Not directly related however Google maps on my Android phone initializes the location with "nearby" WiFi while it acquires the satellites.

  10. James says:

    GPS dithering is still a thing, but they don't turn it on unless you're around military establishments. Maybe since we are on Terror Alert Nemo, they are also turning it on around crowds? The Nike Missile base on Angel Island still has it because that's where they first tested local dither. Do a search on photos from Angel Island and look at their EXIF.

    • Dusk says:

      GPS SA is no longer used, and only induced an error of ~100 m even when it was.

      • James says:

        I'm not talking about selective availability. I'm talking about dithering by jamming overlay signals in a small locale.

  11. jal says:

    No good theory, but I've seen it, too. A lot of the time (as in, when I remember) I run a tracker when I'm out walking somewhere. The most impressive incident was a GPX track showing me teleporting from around Market and 4th to somewhere near Detroit and then back to around Market and 3rd.

  12. nfoonf says:

    Heya!
    we had the same phenomenon last year at 30C3 Con in Germany. We lended WLAN-APs from a donor in .uk which also gives them to other cons. the first day or so, geolocation on most devices went berzerk, as it pinned down your location using AP Signals.

    So my guess: wireless access points used on other venues.

  13. Nick Lamb says:

    The wireless AP answers are by far the most likely cause, and a firm reminder that the location data on phones is mostly dubious database look-ups and not necessarily "GPS".

    Still, the error in GPS locations is statistical, the DOP numbers (sometimes displayed as a circle with the implication that you're "somewhere in this shaded area") are more like 95% confidence intervals, and in principle you might be hundreds of kilometres away from the indicated position, with a very unlikely and thus rare error.

    Early GPS-enabled satellite beacons did a single divination, but the standard was updated to permit the beacon to send a new location each time it transmits (about once per minute), because life rafts drift and survivors might have to leave their crash site. Data structure size limits in the radio comms mean that the high precision is lost anyway.

  14. 205guy says:

    Man, all those explanations sound plausible, but I was hoping someone was spoofing the GPS signals.