Edit: Was informed my GPS does not actually think I am far away, something else is causing that.
(See edit above) Ive heard it’s GPS, but my phone always thinks I am in a city hundreds of miles away for some reason so just wondering more specifically how that would work?
In: Technology
All cell providers include an approximate location with your 911 call. They can obtain this via GPS from your phone (newer technology) or based on the cell tower you are connected to (older technology). This allows them to route you to a local dispatcher.
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Initially, it’s based on whatever cell tower receives the call. From there, GPS location is typically shared, but can take sometimes as much as a minute to provide meaningful information.
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The cellular networks, as part of their core functionality, always know which cell towers your phone is connected to. They already need to know this in order to route incoming notifications to your phone – there’s way too many active phones in even a small town to attempt to send alerts for every phone in the town from every tower, much less bigger areas.
The 911 routing systems exclusively use this information to know which dispatch center to send you to, because that information is always known to the system before you even dial a number. This was set up long before GPS in phones was even a thing, and continues to work fine.
After a decent number of phone had GPS, an additional system was set up to support routing GPS information from phones that had it to dispatch centers that could process that information. When it all works properly, this gives them faster and more accurate information about your location than you could have given them verbally. If it doesn’t work right for any reason, you’re still talking to the local dispatch and they can get your real location verbally. And they have common sense, so can figure it out if your GPS erroneously things you’re at another location far away. This is still just an add-on though, and the call routing method is still cell network based on tower location.
Your cell phone can only reach your nearest cell tower. 911 always connects you to the nearest emergency services from your cell tower.
Once you establish the call, they can also get your location via GPS, but that’s not what they get first. It’s your tower for the approximate location and then your GPS to pinpoint you.
FYI it has happened to me on an old phone with the same issue (it thought I was far away) where I’ve had to call 911 and it called the city far away, so maybe look into fixing that
A 911 call, placed in a particular area, will be answered by the P-PSAP (Primary-Public Service Answering Point) for that area.
That service will quickly determine which service(s) (Police, Fire, Ambulance) you are requesting and then forward you to the appropriate dispatch center (Also called Secondary PSAPs). Often, P-PSAP services are provided by local PD, so in that case they will simply keep you on the phone to gather more information.
If you are calling from one area, for someone who needs help in another area, the P-PSAP will simply transfer you to the distant area’s S-PSAP.
When you dial 911 your call data includes location and phone number information (ANI/ALI – Automatic Number Identifier and Automatic Location Identifier).
If you have made that call from a landline, the data will reflect the calling number and the location to which the phone bill is sent (which is not necessarily the location at which the phone itself is located).
If you have called from a cell phone, the data will provide (assuming the area where you live has invested in the technology) a GPS location for the phone from which the call was made. This location is very accurate.
Without the GPS tech. it is still possible to get a general idea of the location of a cell phone. The tower that is closest to the calling phone is available, which assists but is far from precise. In cases where we need to narrow that down, we can triangulate the phone’s location using the 3 closest towers to provide a more accurate location. This location can still be less than fully accurate.
All of that said, the simplest answer to your question is that we ask the caller where they are and forward the call to the agency responsible for responding in that area.
On top of what was said about cell towers, in many areas (particular large metropolitan counties) there is a primary PSAP (public service answering point) who will take all cellphone calls that come from a tower in that region. This will be the 911 operator that you talk to first. That operator will then ask you your location and use that information with mapping software to route your call to the radio dispatch for the correct jurisdiction.
If you cannot tell the operator where you are or do not know, the operator then can use location information from your cell provider to determine where you are and send it to the correct radio dispatch. There are many ways to determine this location information including your phone GPS and cell tower triangulation
The scope of the exact methods are probably beyond an ELI5 but there’s some good info on wikipedia at [https://en.wikipedia.org/wiki/Enhanced_911#Wireless_location](https://en.wikipedia.org/wiki/Enhanced_911#Wireless_location)
Generally speaking, when you call 911, you are connected to the PSAP located to the cell tower that your phone is connected to.
Are you on the border of two different counties, cities, states, etc.? And do you have WiFi calling enabled, and if so, have you updated your E911 address with your telco?
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