If your cell phone is turned on, the phone company knows where you are. This fact is why your GPS doesn’t take 5 minutes to show your location every time you turn on your phone. The OS gets the cell towers to identify where you are and combines that with GPS to get a quicker lock and more accurate location.
The most secure Android OS cannot turn that off. If you transmit or receive data to a cell phone network, your location is known.
EDIT: Sorry, I am idiot. What I described IS triangulation.
Reeeeeee! Phones. Are. Not. Triangulated.
Most cell towers use phased antenna array, so they know relative direction all the time. And distance can be estimated from latency and signal strength.
Two cell towers allow to get precise location from angles. Angles are derived from phase differences on elements of array and can’t be manipulated like latency or signal strength.
What do you think the cell towers are triangulating and forming angles with? The person’s phone is the third point in the triangle. You only need two other points to triangulate something’s position.
I checked it. Damn. You are right. Point with unknown coordinates counts. Now I have to edit my comment and answer other subcomments of people I confused.
No that’s not very accurate. Cell phone tower triangulation only gives a rough approximation of location, and GPS is definitely able to be disabled by the software. I know a bit about these things as someone who has compiled their own android ROM from open source. I’ve been working on this stuff for more than a decade now.
Regardless of all of the above, anyone can turn off their cell phone or choose to not carry it to eliminate the ability for that cell phone to provide location data on them. This alone negates all the stupid “gotcha” comments about trying to preserve one’s privacy while owning a smartphone. So we are back to my first comment on this topic, with the point of STOP IT.
Cell phone tower triangulation only gives a rough approximation of location
That’s why I said they send that to allow the phone’s GPS to get a lock quicker and more accurate. All cell phone towers have GPS. Agps means the tower sends its GPS constellation to the phone so it doesn’t take 5 minutes to lock.
The GPS thing is different. The phone downloads the satellite positions from the net instead of having to receive the same data, very slowly, from the satellites themselves.
No, that’s not quite how GPS works. The satelites are constantly sending a signal, the GPS receiver is trying to pick up at least two satelites, and it computes your location off of the phase shift and whatnot of those constantly-broadcasting signals.
No, more is preferred, but the way the signals are designed, some positioning slowly works with only two satellites.
s/signals/receivers
I guess receivers that also measure angle to satelites do have 4 constants with only 2 satellites to get 4d solution(or rather 2 solutions, one of which is in future, while other is in the past, not sure which one is correct). Or maybe try to do some wierd math shit with Doppler shift. I was talking about original(cheap and easy) way receivers were solving coords with 4 latencies.
If we are really pushing the limits here, then receiver that knows it doesn’t move relative to Earth can get coords from one satelites, but this is just speculation. And it may require atomic clock.
Remember when GPS was slow and always a few meters off? Part of that was they were bad at or could not acquire more than two signals.
This doesn’t sound like reason for it. Slow start? Receiver first needs to receive ephemerides and almanac to be able to solve position. Quoting wikipedia article on A-GPS:
Every GPS device requires orbital data about the satellites to calculate its position. The data rate of the satellite signal is only 50 bit/s, so downloading orbital information like ephemerides and the almanac directly from satellites typically takes a long time,
Almanac can be stored on device for a long time to be used later in next start. It’s called warm start. Ephemerides don’t last as long. Start when they aren’t stale called hot start.
An ephemeris is valid for only four hours, while an almanac is valid–with little dilution of precision–for up to two weeks.
So bright minds thought “what if almanac and ephemeris” will be downloaded from the internet? And this is how A-GPS was born.
Now about precision. Few meters is normal precision for normal GPS. Getting better precision requires very scary math hiding behind Differential GPS and additional correctional data. Not that normal GPS doesn’t have scary math.
Lastly, about two satelites: old phones had one antenna per band(and usually only one band), so they did require at least 4 satelites.
Yes, but the receiver need the position of the satellites to compute its own position. That data is transferred very slowly, so if you can download it through the internet, then you only need the identifiers of the satellites to immediately compute.
I did not misspeak. I linked to a-gps which explains how the system works.
You do not need to transmit or receive cell data to receive a GPS signal. If you use GPS isolated, your location isn’t leaked.
But that’s irrelevant because if you use cellular data, the cell tower knows approximately where you are.
I have been using GPS since before cell phones had data. My boss back in 1994 brought in the man who wrote the accuracy encryption part of gps (that has since been turned off) to give a talk on the encryption that used to be in GPS to myself and my coworker just for the fun of it because they were old friends.
If your cell phone is turned on, the phone company knows where you are. This fact is why your GPS doesn’t take 5 minutes to show your location every time you turn on your phone. The OS gets the cell towers to identify where you are and combines that with GPS to get a quicker lock and more accurate location.
The most secure Android OS cannot turn that off. If you transmit or receive data to a cell phone network, your location is known.
Sure, there’s no way around that, even dumb phones are triangulated by default and that data is sold.
But doing just that is better than being triangulated AND leaking your GPS data to every Tom Dick and Harry that asks your phone.
EDIT: Sorry, I am idiot. What I described IS triangulation.
Reeeeeee! Phones. Are. Not. Triangulated.Most cell towers use phased antenna array, so they know relative direction all the time. And distance can be estimated from latency and signal strength.
Two cell towers allow to get precise location from angles. Angles are derived from phase differences on elements of array and can’t be manipulated like latency or signal strength.
But using two cell towers and angles would literally be triangulation…
2=3?
What do you think the cell towers are triangulating and forming angles with? The person’s phone is the third point in the triangle. You only need two other points to triangulate something’s position.
I checked it. Damn. You are right. Point with unknown coordinates counts. Now I have to edit my comment and answer other subcomments of people I confused.
Interesting, I stand corrected. Thanks for informing me.
Sorry, I am idiot. What I described IS triangulation. Alternative with distances is trilateration.
No that’s not very accurate. Cell phone tower triangulation only gives a rough approximation of location, and GPS is definitely able to be disabled by the software. I know a bit about these things as someone who has compiled their own android ROM from open source. I’ve been working on this stuff for more than a decade now.
Regardless of all of the above, anyone can turn off their cell phone or choose to not carry it to eliminate the ability for that cell phone to provide location data on them. This alone negates all the stupid “gotcha” comments about trying to preserve one’s privacy while owning a smartphone. So we are back to my first comment on this topic, with the point of STOP IT.
That’s why I said they send that to allow the phone’s GPS to get a lock quicker and more accurate. All cell phone towers have GPS. Agps means the tower sends its GPS constellation to the phone so it doesn’t take 5 minutes to lock.
https://en.m.wikipedia.org/wiki/Assisted_GNSS
So yes, even with GPS disabled, the phone company has a rough idea where you are.
If you are in the city on high band 5g, that location is known within 15 to 600 meters.
https://nybsys.com/5g-bands/
Yes, Android (and iOS) can turn that off: torn off mobile network or don’t have a mobile phone provider (SIM).
“if you send or receive data”
You could use WiFi only
The GPS thing is different. The phone downloads the satellite positions from the net instead of having to receive the same data, very slowly, from the satellites themselves.
No, that’s not quite how GPS works. The satelites are constantly sending a signal, the GPS receiver is trying to pick up at least two satelites, and it computes your location off of the phase shift and whatnot of those constantly-broadcasting signals.
That’s why GPS still works in airplane mode.
Four. GPS solves position in 4-dimensional space.
3 satellites for 2 dimensional space, 4 satellites gives you height as well (3 dimensional).
your wristwatch gives you your fourth dimension ;-)
GPS satelites are just fancy atomic wirstwatches hanging on Earth orbit
heh, this is true, but don’t they still only give you a 3 dimensional location?
I’m trying to understand your question. They broadcast both their orbit parameters and their time.
No, more is preferred, but the way the signals are designed, some positioning slowly works with only two satellites.
Like old phones. Remember when GPS was slow and always a few meters off? Part of that was they were bad at or could not acquire more than two signals.
s/signals/receivers
I guess receivers that also measure angle to satelites do have 4 constants with only 2 satellites to get 4d solution(or rather 2 solutions, one of which is in future, while other is in the past, not sure which one is correct). Or maybe try to do some wierd math shit with Doppler shift. I was talking about original(cheap and easy) way receivers were solving coords with 4 latencies.
If we are really pushing the limits here, then receiver that knows it doesn’t move relative to Earth can get coords from one satelites, but this is just speculation. And it may require atomic clock.
This doesn’t sound like reason for it. Slow start? Receiver first needs to receive ephemerides and almanac to be able to solve position. Quoting wikipedia article on A-GPS:
Almanac can be stored on device for a long time to be used later in next start. It’s called warm start. Ephemerides don’t last as long. Start when they aren’t stale called hot start.
Now goes quote from another article
So bright minds thought “what if almanac and ephemeris” will be downloaded from the internet? And this is how A-GPS was born.
Now about precision. Few meters is normal precision for normal GPS. Getting better precision requires very scary math hiding behind Differential GPS and additional correctional data. Not that normal GPS doesn’t have scary math.
Lastly, about two satelites: old phones had one antenna per band(and usually only one band), so they did require at least 4 satelites.
Yes, but the receiver need the position of the satellites to compute its own position. That data is transferred very slowly, so if you can download it through the internet, then you only need the identifiers of the satellites to immediately compute.
As I said, cell towers send information so that GPS can work better. I didn’t say that GPS needs cell towers.
https://en.m.wikipedia.org/wiki/Assisted_GNSS
The tower has its own GPS antenna. The cell tower knows approximately where you are.
You’re still misspeaking and implying the data is necessary. It is not. At all. Period.
How do you think Garmins and the like work when they have NO external data connection? They don’t magically take way longer to position…
I did not misspeak. I linked to a-gps which explains how the system works.
You do not need to transmit or receive cell data to receive a GPS signal. If you use GPS isolated, your location isn’t leaked.
But that’s irrelevant because if you use cellular data, the cell tower knows approximately where you are.
I have been using GPS since before cell phones had data. My boss back in 1994 brought in the man who wrote the accuracy encryption part of gps (that has since been turned off) to give a talk on the encryption that used to be in GPS to myself and my coworker just for the fun of it because they were old friends.
Misspeaking is not the same as misunderstanding.
Does GPS need cell towers? Yes or no.
Because I explicitly said that GPS does not need cell towers and you claimed I misspoke.
GPS does NOT need them to be “faster” for what an end user expects.
“I didn’t say GPS needs cell towers”
How is that a misspeak?