From: SCN User <bf578@scn.org>
Date: Sat, 14 Sep 1996 04:44:12 +0800
Subject: position of cellular phones
Message-ID: <Chameleon.960913085243.bf578@drink.aa.net>
MIME-Version: 1.0
Content-Type: text/plain


-->After seeing the messages about Federal Express doing something similar,
-->I thought this would be of interest:

Date: Mon, 09 Sep 96 17:41:31 GMT
From: campbellp@logica.com (Peter Campbell Smith)
Subject: Re: Locating the position of cellular phones (Stover, RISKS-18.41)

There is an interesting article in Traffic Technology International, 
Aug/Sept 96 issue about a system called CAPITAL that uses cellular phone 
calls as a probe to monitor road traffic around Washington DC.  It describes 
an experiment which has been running for two years and which has 
demonstrated that this is an extremely cost-effective alternative to 
conventional means of traffic monitoring.

The system is independent of the cellular phone system per se, but has 
antennae on the cellular phone masts which listen to the cellular 
frequencies. Every time a call is initiated, CAPITAL locates the caller by a 
combination of directional multi-element antennae and time-of-arrival 
analysis between different masts.  The geographical accuracy is reported to 
be to about 115m, and subsequent tracking allows the speed of the vehicle to 
be established within 30 to 50sec to an accuracy of 5mi/h.

At any time only less than 5% of vehicles are making calls, but this is a 
sufficient sample for analysing the traffic speed (though not presumably the 
traffic density).  Moreover, when the traffic slows down even more people 
make calls, so there is a better density of data from the areas most 
interesting to those monitoring traffic flows.

It is claimed that the boxes ignore the voice content of the call and that 
the data they deliver has randomly assigned identifiers for each call, so 
that nothing leaves the system which would allow calls to be associated with 
specific phones.

-->Until the government thinks it needs the info!



Peter Campbell Smith, Logica, London, UK  campbellp@logica.com