Does anyone know if you have to have the GPS radio of the phone switched on for that to work? I keep my GPS and WIFI radios switched off for both privacy and to reduce the drain on the battery unless I specifically need it on when lost.

The OS overrides location service settings during emergency calls

> When using Emergency SOS to call emergency services, the call may include your location, regardless of whether you enable Location Services, to allow the dispatcher to assist you.

https://www.apple.com/legal/privacy/data/en/emergency-sos/

Android has a similar feature.

There is no legislation requiring this of device (or OS) vendors, but carriers are legally required to make location information available to emergency services, and I think are even prohibited from connecting phones that don’t make this possible. So market forces effectively ensure that all phones do this.

The exception is when the call is too short to get a lock for GPS and location can’t be determined. The phone will still transmit what it can (say, WiFi proximity derived location). Worse case is fall through to carrier triangulation.

There is no such thing as a GPS radio in a phone in the sense of something that broadcasts a signal. GPS signals are broadcast by satellites and any device on earth can choose to listen for the signal and triangulate their position by receiving the signal from multiple satellites. GPS doesn't send out any signal from your phone to work. In the same way that your eyeballs don't need to emit light for you to see (unless you're a superhero). Phones broadcast signal to connect to cell networks and wifi networks.

Now if you expect your phone to show your position on a map (using the GPS coordinates it calculated from the satellite signal) then it likely needs to retrieve map data from the internet (and in doing so it might be broadcasting over cell or wifi frequencies). But that's a different story.

Much confusion is caused by people saying "I tracked X with GPS" with the implication that GPS allows tracking of remote objects. It doesn't. It allows the remote object to know its own location. For that information to get to someone else (the spy in the chasing vehicle) the remote object needs to be broadcasting that location information through some other means (which has nothing to do with GPS).

Short answer: no.

The network knows the signal strength between you and the cell towers nearest you. You are usually within range of more than one cell tower. That can locate you fairly accurately. Network data like this is used to augment GPS which can have problems among tall buildings for example.

Probably not, the network towers are the ones being used to triangulate I think.

The cell towers know where your phone is whenever it has signal. It's not as accurate as modern GPS, but 5G especially can locate you to within about a hundred meter radius. Precision varies wildly depending on conditions, distance, etc.

GPS is entirely passive (it is receive only), so leaving it on is harmless for your privacy on Apple devices. For Android... well, if you have an Android phone, you're not a privacy-conscious consumer by definition, so just leave it on for the convenience of not having to turn it on and off manually all the time!

WiFi, again, is not that big a deal with Apple because they rotate your unique MAC address to preserve your privacy. Android is a mixed bag, depends on the model of phone you purchased.