"Blunkett u-turn on data privacy plans"

[Brian Beesley]

On Saturday 01 March 2003 10:52, Roland Perry wrote:
>
> >I gather that GPS receivers are on the list of
> >"wanted" features. This would enable the phone to be located to a few cm.
>
> IMHO they are much over-sold for this kind of application, needing a
> clear view of lots of sky,

Or access to a few local repeaters - which should be easy enough to 
locate on mobile phone masts. The repeaters could easily operate on a 
sub-band of the mobile phone "carrier" signal; the phones would not actually 
need to receive actual GPS satellite signals.

> a long time to "lock on" when powered up (at
> the same place as powering off helps a lot), and a general accuracy of
> about 10m.

Using repeaters fixes the lock-on delay. General accuracy of 10m is fine for 
tracking movements of targetted individuals - but again use of repeaters 
allows this to be improved markedly. Don't forget specialised GPS receiving 
stations are used to track minute movements (down to the order of 100 
microns) in e.g. earthquake research.

> These reasons are not a problem when you are out sailing :-)

Or flying, or mountaineering (though persuading electronics to work in low 
ambient temperatures is not always easy).

The fact that _raw_ GPS positioning is already used in e.g. car sat-nav 
equipment suggests that tracking targets around a city is very much feasible, 
despite the constricted skyline and the presence of a great deal of other 
equipment causing interference.

It will be very interesting to see how badly affected these applications will 
be affected when the US "detunes" GPS for military reasons during the 
forthcoming attempt to singe Saddam's moustache.

Brian Beesley