From: "Frithiof Andreas Jensen"
Subject: Re: Can anyone explain the design of tracking systems?
Date: Mon, 16 Dec 2002 12:02:10 +0100
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"Mike Poulton" wrote in message
> On 12 Dec 2002, "Frithiof Andreas Jensen"
> > *Any* Cell-phone can, and is, continually tracked!
> > --- Otherwise, How would an incoming call be directed to your phone @
> > you
> > location?
> They know what cell you're in, but no more than that. Any more precise
> location requires triangulation of the signal,
In GSM at least, on entering a new cell and periodically after that, the
handset reports the signal strengt from the nearest (up to six) transmitters
so that the optimal "base" site can be chosen. Not triangulation, but pretty
> It's not very precise, either. Cells are fairly large, so simply knowing
> what cell someone's in is not very useful.
With GSM the accuracy in practice is in the order of 30 - 100 m; with
3G/UMTS the accuarcy is ten times better, 3 - 10 m, and there are API's to
*use* the location information for advertising etc. "localised information",
I think the name is.
> They don't keep records of
> movements between cells, either --
Oh Yes they *do* - for Billing Purposes. The Danish Telco's will keep
records for up to five years - and the Police have been supplied with the
tracking information on requet in several court cases now.
The Thorsen/Trads fraud case was one, high-profile, case - maybe even
reported abroad? The recent "honour killing" of a 13 year old daughter by
her own muslim family another.
The Telco's charge the police for *that* service too ;-)
> But like I said, all of
> this becomes impossible if you leave your phone off.
Yep - until you switch it on again.