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Your Cell Phone Is Tracking You
PollGuy writes "I had never heard until this article in the New York Times (sacrifice of first born required) about services that let regular people track the locations of other regular people via their cell phones. Nor this: 'A federal mandate that wireless carriers be able to locate callers who dial 911 automatically by late 2005 means that millions of phones already keep track of their owners' whereabouts.'"
turn your cell phone off when you dont want to be tracked!
Its possible to track the location of people who have landlines too. It's called a phone book.
Just bought a phone for my wife tonight and I was interested to see that it has GPS included. Interesting privacy and safety issue.
Suddenly I wish I hadn't sold my old Nokia phones on eBay recently. They might have been worth much more in the next couple years when all phones come with GPS-tracking included. Of course, it wouldn't make much of a difference if providers require the feature in the future.
'A federal mandate that wireless carriers be able to locate callers who dial 911 automatically by late 2005 means that millions of phones already keep track of their owners' whereabouts.'
Seems unnecessary... Wouldn't it be possible to just have the cell phone programmed to export the necessary coord data when someone hits 911?
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Bleah! Heh heh heh... BLEAH BLEAH!!! Ha ha ha ha...
this service isnt really new, i bought my phone about a year ago (samsung a500, sprintpcs) and it had this feature. I disabled it, but i think that only turns off the ability for joe schmoe to track me, not the gov't.
....
i personally see a good use for this (911) and dont see the big deal since you could just not carry your cell with you for that ultra-top-secret-underground tinfoil hat clan meeting.
i am more worried about things you cannot opt out of, like face scanning in public places. or non-approval required phone taps etc
"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe." --Albert Einstein
On the few phones I've seen with this feature, they have a menu to enable it all the time, or to only have it on for 911 calls.
I think it's pretty easy for the phone to tell if you're dialing 911 or not, so when you turn it off, it probably means it's off.
Need a Catering Connection
they have been able to do this for a long time by triangulating on your location from 3 or more different cells. Every criminal knows not to leave their cell phone on exactly for this reason.
Investing forum
You're right, I wouldn't steal a car. But if it were possible, I sure as hell would download one!
We're about to hit comment #7777777 (seven sevens). That's got to be lucky!
Lost? Hiding? Your Cellphone Is Keeping Tabs
On the train returning to Armonk, N.Y., from a recent shopping trip in Manhattan with her friends, Britney Lutz, 15, had the odd sensation that her father was watching her.....
You've always been able to locate the position of a cell phone as it's making a call via triangulation with 2 towers. This is nothing new.
Phase II requires more precise location information be provided to the PSAP. Phase II requires the wireless service provider to provide the call back telephone number of the 9-1-1 caller, cell tower location, cell sector (antenna orientation) information, plus longitude and latitude (X, Y) information. Phase II E9-1-1 services exist today in a handful of locations, by a few wireless service providers, but these numbers will grow.
My phone has it. I can turn it off or on within the phone software. It's a sprint PCS phone, made by Samsung. I don't know what good it is, unless maybe I die in the middle of the woods, which of course, would mean I'd be out of cell phone range anyway, but whatever. Is there a website somewhere where I can type in my number and pull up my cell phone on a little map? If so, I have only this to say:
Here's to sweethearts and wives, may they never meet.
because I have been enjoined by this Holy Office to abandon the false opinion which maintains that the Sun is the centre
Spouses should not have the ability to spy on one another either.
Can now. It's called a private detective.
Without guidelines, tracking very well might become widespread because it is forced down the throats of people who get their cell phones through their companies, schools, or otherwise don't pay their own bill.
He who pays the piper calls the tune.
When they came for the communists, I said "He's next door. Take him away. Goddam commies."
Jerold Surdahl, 40, an administrator in a building management office in Centerville, Ohio, said he started using the uLocate service to communicate with colleagues. Now, he is intrigued by the possibility of stashing a location-tracking phone in the trunk of his wife's car.
"I'm not expecting or hoping or wanting to find something, but I would just like to explore the possibilities," Mr. Surdahl said. "I'd tell her about it later."
Umm.. can you say BUSTED? Having your name and your intentions printed in the NYT pretty much ensures your secret is out.
BTW, whats with all these controlling people? Relationships are about trust. If you can't trust someone to tell you where they were, then something more serious is wrong.
-molo
Using your sig line to advertise for friends is lame.
For the curious, it's all described on the uLocate FAQ.
Only works with Nextel now and free until the end of the year.
Another reason to hate Nextel for me. After having a boss that gave us all Nextels and having managers that would use the Instant-On feature to speak to us night and day (10:26pm Manager: "Hello, Hello, are you there?? The mail server seems to be a little slow, are you there?"), I will never consider Nextel again. I'm scarred for life!!
I'd be sure to remove the battery if a I didn't want to be tracked. I wouldn't trust the on/off switch for one second. Personally, if I was going to a tin-foil hat clan meeting, I would leave the phone at home. I'd be paranoid that even with the battery removed, there might still be some tracking mechanism. I think that the recent story about the FBI being ordered by a court not to use a certain method of monitoring computers in cars because they interfered with the use of the machines by the users just goes to show how the FBI has an attitude that it is their absolute right to snoop on anything and everything and use anything possible for surveilance.
/me dons tin-foil hat.
Wh47 d1d j00 541, 31337 15n't t3h r0xor5 ne m0r3???
Here in Holland the police was able to find a woman who was kidnapped because of triangulation. Her phone company could give them the whole route the kidnapper took her to her hiding place. IAANAMCS (also not a mobile comms specialist) but IIRC a GSM phone chooses the strongest station from three stations that are close by, so the position of the phone can in principle be determined fairly accurately.
-- Cheers!
I work (outsourced) for a major telecom manufacturer that's been mentioned two times before in these responses. A majority of our phones as well as our competitions' have the ability to track a user. It's not GPS, it's triangulation. a spot between any three available towers can be pinpointed to within thiry feet. Works out great for e911 services, in the areas that can access them (most major metropolitan areas). Also, these services cannot be turned off. The location-based services can be interrupted on a limited basis so that advertisements and offers (coming soon through your telecom companies) will not reach your phone, but e911 will always have access. Interesting to think that the avarge user is starting to get access to these services, however. (Don't know if I want all my friends and relatives to be able to plot out a map of my whereabouts.) ...just food for thought....
We have been able to do this in Norway for a couple of years now, and everyone could track each other, if they are on the persons white-list. (That is, you could say who you would like to be tracked by)
I am a Sheriff's dispatcher to a County of 1.5million people.
Cell phone tracking is currently available, and will always be available even without GPS. As you travel your cell phone communicates to various cell phone towers along the path.
Cell phone companies will provide Public Safety agencies with "tower" information and subscriber information for emergency situations. With the tower information, it will provide about a one mile radius to search if needed.
GPS ability is available to some beta site dispatch centers. Cell phone/GPS information is provided when 911 is dialed. Landline 911 will provide location, phone number(s) and subscriber information. Very important info for responding agencies.
GPS ability is very important to Public Safety agencies. I lost count of the number of times "we" were unable to find a cell phone caller. 911 cell phone callers often have a dificult time giving their location, especially in unfamilar areas. I've taken calls where the caller is in a trapped in a ditch or injured in the middle of nowhere. I have also taken calls where a victim or injured person has called and for one reason or another is unable to give the location. Dead battery, poor reception site, lost consciousness etc.
Put yourself or a loved one in that scenerio and think about it. You have to think of the worst case scenerio, it happens daily.
I leave my GPS data on all the time, never knowing when I myself will be involved in an emergency.
I have nothing to hide, and couldn't care less if anybody new where I was located. With hundreds of cell phones being used in any one region, the thought of somebody caring about your location is quite unrealistic.
The whole basis of the GPS cell phone data is in the interest of public safety. To assist you when you need it most.
I'd be more afraid of criminals my personal data for identity theft.
Each credit card/atm/club card transaction is telling somebody where you are and what you are purchasing. Nobody seems to be bothered with that.
I don't have an account, not because i'm a coward. I just have the desire to post here often. I'm also paranoid that somebody is going to steal my personal information.
-Ant-
Of course this technology has legitimate uses. If you'd bothered to read the article, you would have noticed that the privacy advocates were not objecting to the technology itself, but to the absence of control over who gets access to the data.
I haven't really been up to date on the latest cell tech, but maybe a few of you who are can address what I'm wondering about -
The signal from the GPS satellites is pretty weak...How does the cell phone reliably get its coordinates? Most of the handheld GPS units I have used will lose GPS lock if you have it in the car, in buildings or even under trees because of the line-of-sight obstruction. If you require E911 service, the chances are pretty good you will be in a location that doesn't get very hot GPS reception. Is there some kind of secondary location service?
Antennas must be tuned for optimum reception of a signal, which means that in a GPS enabled cell phone there is probably two antennas - one for GPS and one for cell service. Can anyone confirm that theory? It could theoretically use the same antenna for both GPS and cell service, but either way if you wanted to disable it you could cut the trace that carries the signal to the GPS controller.
But if you do this, how legal would that be?
-R
Good thing I have AT&T! I get so little coverage I bet they have no idea where I'm at.
To everyone who is freaking out that this will be a new way to for The Man (or government, employer, spouse, whatever) to track your every movement, I have a radical new idea:
Don't carry the cell phone
This may never have occurred to you, but if you are doing something or going somewhere and do not want to be tracked, you actually have the option of not carrying the cell phone with you. Now I know what you are thinking, but yes, your pants will stay up without the cell phone holster connected to your belt. Try it in the safety of your own home if you do not believe me. And legend has it our ancestors traveled across the country side without cell phones back in the olden days.
Or for a less radical option, just turn it off. If you still do not believe it is really off and could still be tracking you, take the battery out.
Finkployd
What if you're that person that everyone talks about when you're not around? I've found out because people tell me about these conversations.
What if you're that hot girl that everyone wants to meet, and you despise all those creepy geeks? All of a sudden you keep bumping into the same stalkers, at every club you go to, at every store you visit. Everytime you step out of the house?
Cool, so don't carry your cell-phone with you. Great solution, now that they've eliminated most public pay-phones. You too can live in a communications-free world. Hello? It's like stepping back in time a 100 years. It's particularly disabling when your car breaks down, and nobody will stop to help you - and there's no phone around to call for help. It's a problem when people *expect* to be able to reach you at anytime - you become a social pariah.
Time for a new solution. We just need to out-innovate these stupid restrictions.
-- Ender, Duke_of_URL
For privacy freaks this is old, old news. It is also one of things that give us freaks bad dreams and sleepless nights. The 911 justification has all the ear-marks of that tried-and-true privacy buster maxim - "If it will save the life of just one child, it will all be worth it!"
BUT, after cogitating on it for a few years now, I think that the decision to go with GPS has a lot of benefits for us freaks (and the criminals out there too). Since the trend is towards embedded GPS in cell phones, it is likely that all the typical anti-privacy black hats will build their uber-spying systems on the back of assuming the GPS data is valid. It does not have to be.
In fact, I envision a GPS "relocator" device becoming somewhat popular in the same stores that sell mini-spy cams, electronic bugs and electronic bug detectors. Just attach your relocator to your phone and it will overpower the signals from the GPS birds with its own false signals and convince the phone that it is really somewhere else. Similarly, I would expect to see software only hacks to future phones to do the same thing. As long as the dark powers that be are too lazy to cross reference the phone's own reported GPS location with the actual cell towers in use (and you know that such laziness *will* prevail it is government agencies we are talking about) then those people who want to appear as if they are somewhere else can do so easily. Thus invalidating much of the benefits (beyond the stupid 911 misdirection) to Big Brother and helping to maintain the privacy of the common man (and all those criminals the Feds thought they were going to be able to use this scheme against).
Hey, just because you wear a tinfoil hat doesn't mean you can't see the brighter side.
When information is power, privacy is freedom.
The point is, they could. If they don't have the tools to do so, then they definately can't. This gives the government a easy tool to track people, especially as cell phone use becomes more and more widespread (as if it isn't already.)
While someone may not be sitting there tracking every movement, it would be feasible to assume that all your data gets dumped into a database for later use. We already store incoming and outgoing calls, why not locations?
Let's say a robbery took place at a store. You were on the other side of the building and didn't see it. However, the resolution of the GPS wasn't good enough to pinpoint which side of the building you were on, only that you were in proximity. The police come knocking on your door, and now your a suspect.
I go to public parks often to sit and read. I have no kids. I don't want some stupid computer program to assume I have no reason to be there, flagging me as a pedophile because I happen to read on kids playgrounds.
Umm, what fantasy world are you living in?
They've used OnStar to eavesdrop on people. The only reason that go shut down is because the person couldn't use OnStar to call for help - which will be solvable by the cops by promising to forward any such requests immediately to the OnStar system.
In '93 they were wiretapping all public phones in 'bad' areas in my town. I don't think they even bothered to get a warrant, which is why it made the papers.
Feds have *never* turned down an application for a warrant to themselves in Patriot related matters - which is not solely related to 'terrorist' activity - even when terrorist activity was rather loosely defined. They're now using it for domestic crimes.
The federal DB of records on every citizen is moving forward, all boat registration, car registration, credit records, etc.
Yeah: "Trust us, we're from the Gubbmint", sure, sure - as long as high standards are used, it shouldn't be a problem. As long as people follow the law, you should have no hackers attacking your computer systems, no viruses will be written, and all code won't cause catastrophic failure on your machines, or data corruption.
Must be nice to live in fantasy land.
-- Ender, Duke_of_URL
When you call 911 on a cell phone, chances are good that a) you will be in a poorly-defined location (ie, "I'm underneath the tire of a car!"), and b) you will need a speedy response. Why must you be forced to describe your location well enough for police to find you, instead of simply lettimg them track your phone and show up to where you called?
Calling 911 implies it's an emergency, you need the police NOW.
I'm sorry, but an important part of growing up is getting at least a taste of true freedom and yes, sometimes the risk that it entails. . When I was a teenager I probably did a few things my parents wouldn't have approved of, and I that was an important part of my experience.
I can't imagine imposing this on my own teenager, except (1) when he actively wants it, if say he goes into a strange part of town, or (2) as punishment if he gets into trouble - part of the punishment might be that he would be monitored for the next two months or whatever. If he wants to be monitored all the time,
I do feel kinda bad for these 16-year-old kids getting tracked by their parents. I mean, it's one thing for adults living in a democracy to have debates about privacy & technology, etc.-- that's all good-- but these kids don't have any say in the matter... which is too bad, because there are some legitimate arguments on their side.
As an adult, if someone were tracking me at least I would have some legal recourse. But what do you do when its your parents? Sue them? I guess that's been tried before too...
Time to make a mini hat for my cell phone..
(if I had one -- a phone that is)
--
"I'm not bright. Big words confuse me. But Wanda loves me and that should be enough for you." - Cosmo
So we can get evil spying technology but we still don't get GPS capability with our new cell phones. Fucking wonderful.
So I just got a new treo 600 and like all new cell phones it has e911. This means it has a GPS reciever and all that shit in it, however, like most new cell phones it lacks the code or chip to do the GPS processing. If you can now get commercial spying services why the hell can't they enable a GPS service without an expansion card.
Seriously though this is a somewhat worrying trend. Not so much because of the lose of privacy, although that isn't good but because of the *differential* loss in privacy. I think it was David Brin who commented that this was the real problem and while I don't know his reasons I agree with him. If corporate execs were as likely to have their minor transgressions traced as teenagers we would learn to forgive these transgression that have happened since the begining of time. As it is we will once again blame it on the moral failings of the youth.
Ironically it seems that it is our concern for privacy that will cause the problems. We will only let surveilance happen in certain specialized areas, those areas that "morally good upright" citizens won't be in. It will be okay to surveill only those people who regularly come within some many feet of a known drug hangout...but not a buisnessman who buys his coke from a friend at work.
If you liked this thought maybe you would find my blog nice too:
But privacy advocates say the lack of legal clarity about who can gain access to location information poses a serious risk.
Unfortunately technologies get deployed LONG before appropriate legislation get enacted. Governments are often like Dionsaurs living in the age of Mammals (ie they're just not built to react quickly to change).
"We are moving into a world where your location is going to be known at all times by some electronic device," said Larry Smarr, director of the California Institute for Telecommunications and Information Technology. "It's inevitable. So we should be talking about its consequences before it's too late."
Unfortunately, most people subscribe to the DKDC model of living. (Don't know, don't care) And it's often left to a vocal (and knowledgable) minority who end up being painted as "the lunatic fringe" by the mass media.
Advocates of location-aware technology insist that its safety benefits -- like locating a 911 caller or a stolen car -- outweigh the privacy issues.
The technology itself is not the issue (the technology is NEVER the issue), the issue is who has access and under what conditions. They're completely missing the point - why can we not have a situation where the privacy and the technology play together nicely in the sandpit?
Visit CryptoGnome in his home.
Anyways, back to the topic at hand. While the original "Find Friend" type services are generally harmless as long as the involved parties consent, and while similar use for real safety issues (i.e. firefighters on duty) is also generally harmless, further use of these services for other purposes than finding your mates in a discoteque queue or finding firefighters is obviously disturbing from a privacy standpoint.
It's unfortunate to see that these cellphones make parents think that they will make their kids tell the truth, etc. At the same time, it's unfortunate that the presumption of trust and goodwill is taken away from these children; children learn that they can't be trusted before they may or may not have done anything.
It's also unfortunate that parents are led to believe that if they think their kid is in danger, all they have to do is push a button and see where the kid is positioned and voila! Kid is found. It's not that simple. This quote was disturbing: Jason Pratt said there were advantages to being watched. He no longer has to call his mother to let her know where he is. Instead, she can press a "locate" button on her phone and see for herself. Not only do these devices break down communication between parents and children, communication which is necessary to provide good, trusting relationships, it gives a false sense of security. Jason could be mugged, his phone taken away from him. If he had told mommy where he was and where he was going, it would be easier to find Jason than chasing the cellphone which the mugger probably tossed into a trash bin some random location.
More than ever, technological devices are replacing good old fashioned parenting. OK, I don't have brats myself, but I used to be one. I was taught good common sense things like don't talk to strangers, call if we're going to be late home (and don't be afraid to call collect), stick to known streets and paths, be aware of your surroundings, etc. I never thought it was so diffucult to stick to. I did OK and so have a lot of other children from "my generation" (no, I'm not that old). Has society become so much worse today that kids have to be put under surveillance? Why don't good old fashioned rules work anymore?
If you have a kid that wanders away from "approved" areas or lies about which train she may have taken, then you have a problem that goes beyond what surveillance devices can solve. Somewhere, you f-ed up as a parent.
Another issue is the fantasy that these devices could be used to find kidnapped/missing kids. Problem #1 - most kidnappings are done by family members, not strangers. Technology may find the kid, but it doesn't resolve the real issue. Problem #2 - even if the kidnapping was at the hands of a stranger, the stranger (and even the family member) could throw away or destroy the GPS device.
Another thing is that children may be present in the "safety zone" or whatever you want to call it; parents check up on their kids and since they're in an area that is "OK" they let it be. Well, a kid may be in the "safety zone" but locked up in the pedophile neighbor's garage. So much good the cellphone has done!
Yet another issue is that this teaches children to accept surveillance, whether willingly or unwillingly. To go even further, "good kids think that surveillance is good." "If you don't accept us watching over you, then you're a criminal with something to hide." Again, this takes away the presumption of innocence, and children learn that their parents don't trust them from day one. What kind of society becomes created when nobody trusts the other?
People say I'm crazy, I got diamonds on the soles of my shoes...
Several messages here have covered the topic of persons/authorities beeing able to spot your current location.
Actually, it goes much farther. I dont' know about other countries, but here in Denmark, your location can not only be found but is actually continuously logged by the phone companys "for accounting purposes".
I know at least two criminal trials were these logs have been used by the prosecutor to prove that the accused was at a given location several months or even a year earlier.
We should make cell phones really small.. kinda triangular shaped.. and pin them to our chest! We can have a speakerphone system and voice recognition, you can just tap it and speak!
And now people can go "Computer, locate Liutenant Worf."
Err.
Smoke me a kipper, I'll be back for breakfast.
It's true, Europe generally trails the US in all things stupid, but in one respect we're showing you how dangerous life can be:
http://www.mapamobile.com/
"mapAmobile is a service which can give you the peace of mind of knowing where your children, loved ones or colleagues are at any time, without intruding on their day to day activity. It uses the mobile phone network to locate a mobile phone anywhere in the UK. You can access this information from this website, via text message, via WAP or by making a simple phone call."
I work in the telecom industry. I have been doing so for quite som time. Back in 1999, we did system test on locating in GSM. At that time, locating was based on using several measurements:
+ signal strengths measured at two or more towers,
+ the so-called timing advance measurements,
+ measurements done over several frequencies (GSM uses frequency hopping).
Usually, in urban areas, we'd get the location within 10 meters. In rural areas, it was more like 100 meter. It was a bit of a hassle to order the system to start the tracking, and there was no nice user interface for the resulting trace data. We made a few hacks to make our lives easier. Some of those hacks still lives... Today, the radio base stations comes with the option of a built-in GPS. That makes the position of the base statio very well known (that was a problem back in 1999). You can still use the measurement reports from the cell-phone to get the current location (cell-phones have to make measurement reports, or they won't work in the system). You don't need to have GPS capability in the cell-phone. But if you do, and it reports coordinates that doesn't agree with known data frpm the base stations, the cell-phones data will be ignored, and real measurements will be used. The user interfaces of today are mcu better. Using the IMSI (International Mobile Subscriber Identity) or even the equipment identity number, you can order the system to log all movements of the cell-phone. The only way to avoid this, is to keep the battery out of the cell-phone, and only put it in when you need the service.
If you have secrets, ANY secrets, especially BUSINESS secrets, under NO circumstances mention anything over the telephone!
1 0. html
http://www.pbs.org/cringely/pulpit/pulpit200307
"The typical CALEA installation on a Siemens ESWD or a Lucent 5E or a Nortel DMS 500 runs on a Sun workstation sitting in the machine room down at the phone company. The workstation is password protected, but it typically doesn't run Secure Solaris. It often does not lie behind a firewall. Heck, it usually doesn't even lie behind a door. It has a direct connection to the Internet because, believe it or not, that is how the wiretap data is collected and transmitted. And by just about any measure, that workstation doesn't meet federal standards for evidence integrity.
And it can be hacked.
And it has been.
Israeli companies, spies, and gangsters have hacked CALEA for fun and profit, as have the Russians and probably others, too. They have used our own system of electronic wiretaps to wiretap US, because you see that's the problem: CALEA works for anyone who knows how to run it."
...here's another dirty little secret of the wireless industry: many phones have the ability to enable the microphone without the owner of the phone even knowing it. I only recently heard about this, and I can't vouch for how valid it is (I don't have much intimate knowledge about how cell handsets work), but even if it isn't true today, it's interesting to consider the possibility that cell phone users are carrying 'bugs' around with them 24/7...
Instead of paying for LoJack for my new car, I'll just sign up for the family plan and leave a cheap Nokia in the trunk.
You'd have to be liable for the charges if you abused the system, and the "button" would really have to be something like a pull-out slip so i would be both permanent and hard to set off by accident, but imagine what a help it would be.
This is in daily use at 911 centrals, at least here in Scandinavia. Whenever someone calls 911 (or our local version of it) a trace is automatically performed and the operator can see the approximate position of the caller on the map. This actually works with information from just one base station. The directional antennas will know the sector of the caller and the signal strength is used to calculate the approximate distance. The area in which the caller is positioned is highlighted on the map. No GPS, no triangulation, just one single base station. And no, the police does not have access to the same information, at least not here in Norway. Maintaining this application is part of my current assignment so I do have some first hand experience... -Allan
Whats a good material to block cellular/gps signals? I think that making cellphone holders that can block the signals would be a great product to sell....
For what it's worth, many years ago when I crossed paths with some cell-phone product design types, there was a hybrid product concieved, originally to improve service and battery life -- a pager/cell phone. (We're not talking SMS here, but plain old POCSAG paging.)
Anyway, with this approach you could work if you wished to retain positional anonymity -- have a conventional pager (which is just a reciever) notify you of calls, then choose to power up the cell or not.
As practically every other post has pointed out, positioning by radio has no requirement of GPS being present. Any transmitter can be position located. Amateur radio opertators actually have contests to do this -- foxhunts -- and the equipment to do position finding of non-spread-spectrum tranmitters is pretty trivial to make or buy.
If you want your whereabouts to remain unknown, don't transmit. Simple as that.
Phone companies should just make it optional to use 911 with tracking or no 911 at all, they can market it as the 'Do or Die' service.
"Not knowing when the dawn will come, I open every door." - Emily Dickinson
The description above is OK as far as it goes. But radiolocation by cellphone is MUCH more accurate than that, because it uses an extra piece of information.
In addition to signal strength (which varies not just with distance but with transmission path artifacts, like trees and moisture), digital cellphone base stations keep track of out-and-back signal turnaround time - to an extremely fine granularity. They do this to assign timeslots for the phone-to-tower signals, to make maximum use of the channel.
Assuming the strongest path is the line-of-sight path (rather than, say, a bounce off a building), this gives them the distance to the phone, within a few feet. (This assumption is usually true.)
The geometry is the same. But with the distance information added, each tower can put the phone on a sphere of a particular radius around the tower. Assuming the phone is on or near roughly flat ground (not in an aircraft or climing a steep mountain - also usually true), that becomes a circle where it intersects the ground, with an uncertainty stripe width of a few feet.
Add a second tower and you get two intersecting circles - and two lozenge-shaped patches where they intersect. A third cell tower can tell you whitch patch (and shrink it further by cutting off the long ends).
The advantage of adding a GPS to the phone is that you only need a SINGLE cell tower to interrogate the GPS in order to locate the user to GPS acuracy. This is handy for trouble calls where only one or two cells can reach the phone, so you don't have to dispatch two ambulances (for two cells) or a search plane (for one).
The distance information is available any time the phone is on. When it's switched on, switched off, and about every five minutes in between, it checkes in with the cell system. (Get one of those "cell-phone jewels", a blinky antenna, or a battery pack with a blinks-when-transmitting gadget to see when. Or just lay the antenna on a cheap transistor radio tuned to a quiet spot and listen to the pops and buzzes.) This is to update the system's database so it knows where to send incoming calls. But it also updates the distance information necessary to locate the phone within a few feet.
This information has been available to law enforcement for a while.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
It seems like it would be pretty easy to jam the GPS signal with a little gadget that sat right next to the phone. This only solves half the problem. You could still be tracked by the towers, but might sell well to the paranoid crowd. Open source hardware anyone? uPower 1575.42 transmitter
It is true that it takes non-trivial effort to implement triangulation based upon the signal strength of your cellular phone, but it also would take non-trivial effort to put a GPS solution onto a cellular phone. What is more important is which system is more precise, accurate, and reliable -- that would be GPS.
No, that would probably be the cell-based system.
It's not really "triangulation". Triangulation uses the observed DIRECTION of the signal, locating the transmitter on a (hopefully) narrow fan based at the reciever. Two receivers locate the transmitter where the "beams" intersect, and the "beams" plus the baseline between the receivers form a triangle.
This system uses the round-trip transit time, much like radar, to locate the transmitter on a circle around each "receiver" (actually an active transciever), putting the transmitter where the circles intersect. (You still get the triangle of the locations. But it's a different system than "triangulation".)
You can also locate the transmitter if all, or all-but-one, of the receivers is passive, but they can compare notes on signal arrival time.
If all are passive, two receivers locate the transmitter on a hyperbola, three narrow it to two intersecting hyperbolas, four pin it (or three if one or more can distinguish the two intersections by antenna sectoring).
If one "receiver" is active, it locates the transmitter on a circle, the second adds a hyperbola intersecting the circle at two points, the third (or sector antennas) adds another hyperbola that intersects differently with the circle to distinguish the points. (This is much like LORAN.)
The accuracy depends on the angles, the accuracy of the arrival-time measurements, and the accuracy of the knowlege of the locations of the base stations. Ground-based systems have an advantage in the angles (being roughly in a plain with the transmitter). They also have better knowlege of antenna location than orbiting satellites. Both have comparable time bases (based on atomic-clock-referenced Stratum-III clocks in the cell base stations and atomic clocks in the satellites). GPS was optimized for location tracking so it MAY measure the signal arrival time more accurately. But that's a "maybe", since the base stations need it accurate, too, and can throw more electronics at the problem than the portable GPS receiver. (Anybody have the real stats?)
Now that selective availability is turned off GPS MIGHT be as accurate as cell systems. But it's still fighting some handicaps, so I'd be surprised if it's better.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Okay, when I originally got my sprintpcs-capable phone, a Sanyo 4900, I read up on the location feature and it essentially told you that if you turned it off, the only ones who would have access to your location info would be the police. I didn't like the way it sounded, and between the bad ears and Big Brother, it went back to The Shack inside a day.
I later bought the same phone again and decided to use a headset for the hearing problem.
The real problem with the technology is not that the cops can track you. As far as I know, they have *always* had that ability: the machinery knows that the signal from your phone is strongest between n points on the network and if you make a call, your approximate location is knowable by the system in realtime.
Another problem, of course, are what they keep mentioning on 'Law and Order,' your LUDs or 'Local Usage Details.' It's a record of everyone you call and everyone who calls you.
Big hint, before calling anyone for a criminal transaction from your own cell phone, try on some bright-orange clothing and make sure you look good in it. It is one of the stupidest things you could possibly do--especially when you can buy anonymous, 'pay-as-you-go' cell phone service for minor amounts of money.
The real problem that the 'Law-and-Order' people, the ones who never met a form of privacy they didn't loath, is not that the cops can track you, illegally search you, or sweat a false confession out of you. All in all, American police can be great, but they can and have done all these things at one time or another.
The problem with technology is that the law is a game and it has to be a game for it to work. It would be bad for society if it were possible to automatically find someone guilty and technology is bringing us closer to the day when that will be possible in more and more areas.
From traffic-cams to face-recognition software, technologies are bringing us closer to a national security state where you don't do only good things because you want to, but because common sense tells you you should be scared shitless of doing anything else.
To mail me, remove the 'mailno' from my email addy.
"Yeah. It smells, too..."
Apparently, the teen(s) cited in the NYT article never thought to just turn the phone off or leave it at home when they didn't want their parents tracking them. They must subscribe to the Paris Hilton school of Personal Priorities.