Today I Learned

I work in 911 dispatch, so I have some relevant knowledge here

Cell tower triangulation is our bread and butter for locating a cell phone. It also kind of sucks.

With triangulation we get a set of latitude/longitude coordinates, a "confidence factor" which is a radius in meters around that point that basically shows you the potential error, and a "confidence percentage" which is how confident the cell provider is in that information (it's 90% I've literally never seen it be any number other than 90%)

The confidence factor depends on a few different things- geography, how many cell towers the phone is able to connect to, if you're inside/outside, etc.

The policy where I work is if it's within 300 meters we can enter the call as normal and send cops, fire, EMS, or whoever out to look for the emergency if we get no other location info from the caller. More than 300m and it's usually getting bumped down to an information call, cops will still go to check it out but even 300m is a pretty big area to have them check and can include potentially hundreds of houses, apartments, businesses, etc.

Usually we can get that 300m accuracy, but not always by a longshot, I sometimes see them in the thousands of meters which is basically useless. It also takes about 20-30 seconds to refresh so it's not a live location, and if they're, for example, in a moving vehicle, they can be a pretty significant distance away in 30 seconds, let alone in the several minutes it takes responders to arrive.

And once we're off the call, we don't get any further location updates. If we want to ping the phone again, that involves calling the phone company and faxing them paperwork or something like that (it's handled by our supervisor so I'm not directly involved in that part of the process) I think it normally ends up taking like 10 or 20 minutes for us to get a ping that way, and then it's only 1 ping at a time and they're going to be spaced out about that far or further.

Handset gps based location is generally more accurate (although occasionally it does happen that it's less accurate than the triangulation) but we don't necessarily get it on every call, it's still kind of a hacked-together system at a lot of dispatch centers and it doesn't always integrate well with the other software. It does update much faster, and we usually continue to get updated locations from it for maybe a couple minutes after we hang up.

We don't really have any way that I'm aware of to request a gps based ping on a phone we're not on the line with.

I'm sure the feds have some back doors and extra tools at their disposal that we don't have at a county 911 center, I really can't speak to that. I doubt they're able to get a much more accurate triangulation ping than we are, that seems like a pretty hard limitation of the technology to me.