My guess is the geolocation service or app in the phone uses an Internet connection to send the location of the phone to the service provider.
Internet access can be by cellular or wifi connects. Well, if the Find
service is polling, that means the phone could move between the
intervals of when the location got reported. Geolocation is polled, not
a constant connection between phone and account providing the service.
I don't know the polling interval, but it's zero when you attempt to
find the device when the phone is using wifi.
https://support.google.com/android/answer/6160491?hl=en
"Some of these functionality uses Google Play services."
https://support.google.com/android/answer/3265955
The Find service is in the Android OS. On my old LG V20 Android 8.0.0
phone, enabling the Find feature is under Android settings -> General ->
Lock screen & security, and where the "Find My Device" option is listed
(can be turned On or Off). Google's Find My Device app is not needed.
It is when you use one phone to find/lock/erase another phone. I only
have 1 phone, so there's no point in installing the app on it. The app
is just a web-centric app (most are) that gives you the same features as logging into your Google account using a web browser at:
https://www.google.com/android/find/
When I [re]load that web page, my phone reacts by popping up a
notification saying:
Locating device
Find My Device is locating this device
and, when found, shows a new notification saying:
Device located
Find My Device located this device
When I did this test, my phone was connected via wifi to my cable modem,
so it has an always-on Internet connection. I'd have to test away from
home, and when /not/ on a wifi connection (i.e., only cellular
available, and a nearby tower that contracts with my cellular carrier)
to see if there was a lag in the test to see what might be the polling interval, or if the test doesn't complete until I connect to a tower
when making a cellular phone call.
The Find My Device service only finds the phones under the Google
account under which you login, not the phones assigned to other Google accounts. Log into the above web site to see where it says is her phone assuming she has the Find My Device option enabled in the Android OS on
her phone, and hopefully with high-accuracy location enabled which would
work best if she has recent A-GPS data and strong GPS signals (her phone
isn't in a basement or elsehwere the GPS signals would get blocked).
Use an app to see how far away is the cell tower to which she connects,
and what other towers are in the area (that contract with her same
cellular carrier).
GPS is not required to find the location of the phone. Under Android
settings for location, there can be multiple choices. Mine are:
- High accuracy (GPS and networks)
Use GPS, wi-fi, and mobile network to estimate location.
- Battery saving (Networks only)
Use wi-fi and mobile networks to estimate location.
- Device sensors only (GPS only)
Use GPS to pinpoint location.
If you pick the 2nd option, GPS is not used. When the phone connects to
a cell tower, the location of the cell tower is known (the tower reports
its location). The location of the tower is known, not your phone;
however, I suspect more than 1 tower, if reachable, is used to find the
phone, like using 3 towers to triangulate position. However, accuracy
depends on how many towers the phone can reach. With just 1 tower, the
only location that can be reported is the tower, not the phone. I don't
what the location function on the phone is going to do with just 2
towers.
https://www.safetrax.in/how-gps-cell-tower-and-wi-fi-triangulation-help-in-tracking-location
There are apps that will show your cell data, like to which tower you
are connected along with other towers within reach that also carry your
cell carrier since you cannot connect to different carriers, and towers
carry more than 1 carrier. Your phone connects to your subscribed
carrier on the towers that have that carrier. Very few towers are owned
by carriers. They rent service on a tower. I use (and paid $2.14 for
the Pro version) the Network Cell & Wifi Info app (there is a free Lite version) which shows my current cell tower connection, nearby towers (in layered view), and even my wifi connections. I also have the OpenSignal
app (free version w/ads), but haven't used it for a long time. That was
back when I wanted to leave it running to map coverage (signal strength)
when I was moving around, like when driving, since the carrier coverage
maps are highly inaccurate (my carrier's map shows I'm in a high/red
coverage, but that's not true and signal strength is poor since I'm in a
dip in the geography by a major river, and the towers are elevated above
me, and towers don't well transmit in a downward direction).
Even for GPS, 3 satellites are needed for location triangulation. Some
apps will show the satellites, and to which you are connected if the GPS
radio is enabled in your phone (e.g., GPS Status app). GPS also
incorporates helper data (A-GPS data) which can get old, and needs to be refreshed. GPS Status app will let you reload A-GPS data. I don't
remember seeing a phone including the option to do that.
https://www.diffen.com/difference/A-GPS_vs_GPS
Instead of hunting for satellites by searching for them, A-GPS tells the
phone were are the satellites to look there first. This article notes 3
GPS sats are needed for triangulation, and 4, or more, to also get the
phone's altitude.
Aside: Many, maybe most, cell phone users don't realize the magnometer
in their phones will get out of calibration. Occasionally you have to
rotate your phone in all 3 axes, like a 3d twisted figure eight, and
repeat 3 times (I do it 8 times). Else, you might use a compass app
that points in the wrong direction for north.
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