> the cops say “we pinged your phone”. What that entails exactly I have no clue.
The cell phone infrastructure knows where your phone is. It has to in order for it to operate. The police routinely ask cell phone companies for locations of cell phones. Many (most?) not only won't require a warrant, but provide an official portal the police can use to conduct their queries without having to get a phone company employee to do it.
Note that it is not just police. The core of GPS network, SS7 system, is more than 50 years old in this point. It is often exploited by authoritarian states, sometimes to the end to get human right activists and journalists murdered.
> Note that it is not just police. The core of GPS network, SS7 system, is more than 50 years old in this point. It is often exploited by authoritarian states, sometimes to the end to get human right activists and journalists murdered.
You must mean the phone network, because GPS doesn't run on SS7.
Correct me if I'm wrong, but cell phone companies only know which tower you are currently connected to. So it's pretty inaccurate. The only thing that is "house accurate" is the GPS on your phone. That means they need access to your phone to get that info.
Remark that GPS doesn't need to be turned on. Google mapped all Wifi's and so can locate you without GPS.
You are wrong, although I don’t know the exact mechanism. I once witnessed first-hand a somewhat shady situation where a private investigator was trying to find someone’s whereabouts for the purpose of serving them for a lawsuit. As a last ditch effort, they reached out to a somewhat shady contact who was known to have some kind of internal access to the phone system and gave them the target’s phone number and sent $200 with Paypal. 10 minutes later we get an email back with a specific address and as it turns out that address was the target’s lawyer’s office. One of the process servers goes over there and catches the target on his way out.
I was a bit shaken. I believed what you believe before then too.
No it doesn't. Beam steering is adaptive and will work with signals getting reflected, for example. It's just noting where the return signal from the phone comes on 8 antennas and then narrowing the signal to the phone while increasing bandwidth. It does not use location (because it uses wave interference the "location" these beams is an interference pattern, not a position in cm)
Phone triangulation works by getting signal strength on 3 or more towers, and getting location from that. That's how it works on WiFi as well. Access points see the clients, and each other, and if you have enough data points, you don't even have to configure the locations of the access points. Of course, the location you get back is relative to the access points and the distance between them, so systems provide a quick way to convert to distances based on one or two measurements.
So please don't think 3G is going to protect you from triangulation. It isn't. Now they're decommissioned but even hospital pagers can be triangulated (some of them aren't even 1G, though anything remotely recent is just a cell phone in disguise)
Because of the "emergency services" mandate from governments it works without the sim being registered. Phones MUST be able to immediately call emergency services so sim or no sim, they are registered on the cell phone network using the number of the cellular modem hardware in the phone, the IMEI number. Phones without a SIM or eSIM can be triangulated. Phones that have never had a sim can be triangulated. Phones that had a sim, but now don't (you keep your phone on but have taken the sim out), can be triangulated based on the phone number of the sim (by looking up the IMEI that last used that SIM, then triangulating the IMEI). These systems can track mobile phones as they move, even in places where the signal is so weak phone service doesn't work (though of course, this doesn't exactly help with accuracy)
Of course whether all this works depends on the competence of the large telcos and the police in a specific country. What I said above is what's possible, not what is actually done. What another poster said is true: telcos have internet portals, accessible to the police (and ...) where you enter some information and get location back. This is generally demanded by governments, as the telco is not allowed to know WHO gets tracked by the police in most countries. Yes, in the US telcos are allowed to know, and they can even legally refuse to track someone, but in most of the EU this is not true.
Whether airplane mode prevents your location from being monitored depends on the phone.
iirc, Your phone sends signal to all nearby towers and then pick the closest one to connect with, which means the signal towers can also triangulate your location based from your distance to the nearby towers
> Correct me if I'm wrong, but cell phone companies only know which tower you are currently connected to. So it's pretty inaccurate. The only thing that is "house accurate" is the GPS on your phone.
That was the case before 5G. They'd only have your location to within a mile or so. 5G gives them your location to within feet. It's because they need to so many more towers.
It depends on the area. In very dense areas, it can be more accurate than you expect. It's also possible that they triggered a GPS response that told them rather precisely where the phone is.
A few years ago, when I was studying, my friend and I did a project on that in Xamarin. It took us two evenings, and the accuracy was 300 meters at worst, and 30 meters at best. It's worth noting that this was in a larger city.
So, if two students can achieve even 30 meters accuracy in two days, big telecom corporations will certainly do better in a few decades.
EDIT: By the way, it wasn't only triangulation but also signal strength change analysis. It wasn't as serious as it sounds, there are formulas already made for calculating that.
In the past, ~1 mile. One of the complaints people had about 5G was that it could make it much more accurate. Accurate enough to find a house or someone's location with it. It works because 5G needs towers all over the place to function.
Did the friend park the car out the front of his house, with a license plate that would have been shared by the sister? In the suburbs you don’t need to be overly precise, do a drive by and stop at the house with the car?
I think the question was "how did the phone company know the location", and GPS may be part of the answer.
In the US, E911 requires all phones to be able to report their physical location. Phone companies may use this ability to respond to police location requests. I don't know one way or another, but it seems likely.
Even if they don’t, they can use trilateration/triangulation (for which I assume they always have the necessary information: signal strength and approximate distance) to pinpoint the exact location.
They won't use that if the GPS / "Location" service is turned off. But the cell network still knows where you are anyway, within ten meters or better. The FCC asks for z-axis accuracy within 3 meters; good enough to determine what floor of a building you're on (for E911 purposes.) 5G Rel 17 can supposedly locate people within a meter.
The cell phone infrastructure knows where your phone is. It has to in order for it to operate. The police routinely ask cell phone companies for locations of cell phones. Many (most?) not only won't require a warrant, but provide an official portal the police can use to conduct their queries without having to get a phone company employee to do it.