Slashdot Mirror
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.'"
Triangulation requires equipment located in several places and a certain amount of nontrivial effort.
GPS allows one person to instantly pinpoint you to within two meters. Information this easily obtained is potentially valuable to abusers.
While GPS certainly helps, it is by no means necessary in order to pinpoint the location of a mobile. As long as you are within coverage of at least three cells (less than that and you lose accuracy), it is perfectly possible to triangulate the position of the mobile terminal, regardless of what support there is or is not on the actual mobile itself.
I say this with some authority, as I used to be working one floor above the guys developing the MPS (Mobile Positioning System) solution. That was, ummm, about four or five years ago. So no, this is nothing new... these aren't the droids you're looking for; move along.
All cellular phones require base-stations to communicate with a telecommunications system. These base-stations are quite deliberately placed as to have contiguous coverage in a given region with a reasonable degree of overlap. The region in which a base-station can service a cellular phone is called a cell; hence the term cellular.
When a cellular phone is in coverage, which is to say when you can actually use your phone to call 911 in the first place, there are usually at least three base-stations which your cellular phone can contact (though it only uses the strongest signal for obvious reasons).
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.
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-
GPS doesn't even need to come in to play. An analog phone from 1985 can give out positioning information with a little help from the service provider through triangulation. Newer cell phones, yes, use GPS systems for easier coordinate sending for 911/411 type services, it's just a cleaner system than using cell phone towers and relying on the wireless phone service providers to take the time to bounce the signal off at least three towers, get a fix, and relay it to the other end of the phone call. But it's all through the same process...GPS uses at least 3 satellites to do the same thing.
My understanding at this point is digital phones are easier to track because they're always in communication with the towers, but older analog-only phones are only trackable when they're being used, because they can go passive. I may be mistaken on that.
I think you've missed the point. Your boss or parent or boyfriend (or stalker) doesn't have the ability to triangulate on you -- it's not an easy thing. If the police do it, there'll be records, and it probably falls under wiretapping statutes. The issue here is: There are no legal guidelines for the ubiquitous surveilliance mentioned in the article.
The Mongrel Dogs Who Teach
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
That's not completly true. Yes, you're right when using "normal" triangulation. :) (this goes for any kind of cell, but a micro-cell can cover very small areas (often even only buildings), making the pin-pointing accurate enough)
:)
With GSM base stations you also to consider the fact that a cell is divided into several sectors, which are nothing more than oriented antenas that face a certain direction. This means that in many cases you only need data from 2 base stations, because (as you mentioned) you get cross points for 2 circles, but you can discard one point as it doesn't lie in the sector my phone is in.
This also means that often records from a single base station are enough to prove me lying. If you take a micro-cell for example (having a range of up to a kilometer, I think), you can actually see whether I was north of the cell, like I'm claiming, or that I was in fact to the south, where a crime was commited...
Hope this makes any sense, I have to get some sleep...
.
/\ 2 \ The base station one knows that you /\XX/ \ / signal.
/. people didn't this in
A <== A cell phone base station.
________ ________
/ \/ \ Here you can see how this thing works.
/
/ / \ \ are within the range of the circle
/ . / \ . \ around it away from it. it knows it by
\ 1 A \____/_A_ / measuring the strength of your phone's
\
\ / \/ \ / The same way, base station 2 knows
\____/___/\_______\/ your distance from it, too and can draw
/ . \ a circle, as well. Now, with these two
\ A / base stations we know that the phone
\ / user is in one of the two intersections
\ 3 / of the circles around base stations one
\________/ and two.
Then there is the base station three. It
only needs to know that its signal is not strong enough to reach the
northern intersection of circles of base stations 1 and 2. That way we
know that the user must be in the southern one of the intersections of
circles drawn by base stations 1 and 2. Please note that in this drawing
base station 3's circle doesn't tell the distance from the phone user,
but the maximum possible range it can reach. (Because I didn't think
when I drew the pic.)
Even if the distance info isn't that accurate (meaning that you're using
an old crappy analog cell phone most of you americans use), we can still
plot your location quite exactly. If we just know that the phone is
within the maximum ranges of all three base stations pictured here, the
phone must be in the area I've marked with X letters. Often there are
even more than three base stations around you. That makes getting the
location info even more accurate. So, in a city you can be located with
an error marging of only few tens of meters. In suburbs the error
margin is at least here in Finland some 500m. (Actually less, but this
distance is used by the cell phone company to make sure the phone is
100% surely in the area shown.
Here it just became legal to see where your kids' phones are going if
you've signed a contract in advance. You go to internet and give your
username and password. Then the site will plot your kid's location on
a map.
I'm really surprised that this many of the
advance. Here in Europe right about everyone knows that. And has known
since something like 1995 or so. Tracking people by their cell phones
has been possible as long as there has been cell phones.
Guess your government and media hasn't for some "odd" reason wanted its
servants to know too much of what is possible.
I don't see what damn problem it is if you can be located if you're
dying in a pit. I remember seeing in the TV program 911 how one woman
almost died when she didn't know where she was while she called the 911
from a landlined phone. I didn't understand why they didn't just look
where she was calling from and send an ambulance there. It only takes
about 0,0000000(and so on)0001 seconds to find out that info, not a
minute like in the hollywood movies.
The info about who's calling can be asked from a telephone company. It
has to know it to be able to bill someone for calling.
Before you had to know where you are to get an ambulance. If you didn't
know, you died. Cute. Now you just need to call 911 or 112 depending on
what continent you're in and say "I'm dying. Get me to hospital." and
the ambulance will come.
Where have your banknotes been?!
I know pretty much all the newer SprintPCS phones have some tracking capability... they also have a "location on/off" option though, which can be used to disable the tracking on all but 911 calls.
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.
I'm curious where that information came from. For a typical 5ESS installation, in my experience the Solaris box connected to it is 1) behind the same locked door as the switch itself, and 2) not connected to the 'net. Maybe the CLEC that I work for is just more secure than other telecom companies.
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