From: "Leon Heller"
Subject: Re: Can anyone explain the design of tracking systems?
Date: Thu, 19 Dec 2002 18:22:02 -0000
NNTP-Posting-Date: 19 Dec 2002 18:45:31 GMT
X-Newsreader: Microsoft Outlook Express 5.50.4920.2300
"Frithiof Andreas Jensen" wrote
in message news:email@example.com...
> 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)
> so that the optimal "base" site can be chosen. Not triangulation, but
> damn close.
> > It's not very precise, either. Cells are fairly large, so simply
> > 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
> 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.
Someone has just been convicted of killing his niece, in the UK. He claimed
he was in a DIY outlet at the time she went missing, but the police found
that he was in fact somewhere else, from the mobile phone records. This was
an important piece of evidence, as the body has not been found.
Leon Heller, G1HSM