John Oliver spent a few minutes yesterday highlighting some profoundly serious flaws in the 911 system, which you can see below. By far the most shocking to many people is the fact that if you call from a cell phone, 911 may not be able to find your location. Yet if you boot up, say, Facebook, it can tell you what building you’re in. So why can a site that lets millions read coleslaw reviews easily find you, but paramedics can’t?
An Accurate Illusion
The big misconception here is that Facebook and your other apps have access to technology that 911 operators don’t. In fact, the reverse is true: Facebook has access to technology originally developed for 911. Any app that can track your location is, in reality, pulling off a sort of magic trick, hiding the exact processes it uses to figure out where you are to seem more accurate than it really is.
Apps generally have access to GPS data on your phone; in fact, Facebook has attempted to activate that GPS without asking first in the past, but even that isn’t as accurate as you might think. The Global Positioning System is an amazing feat of engineering, but it’s also a satellite network with all the attendant weaknesses. If you’re in an urban area, or the GPS “constellation” has shifted position, it can take several minutes for a dedicated GPS device to lock onto a satellite and start giving you location data.
So your smartphone uses assisted GPS, or A-GPS. Basically, it gets a rough fix on where you are, and uses other data, such as triangulating data from cell-phone towers and other check-ins in the area or iOS’ secretly collected tracking data, to offer a guess. It helps that humans are more predictable than we like to think. If you go to the same bar every Friday, your phone will quickly twig to that, especially if you tag a post on an app or a photo you take with the GPS coordinates.