"Dan Holdsworth" wrote in message
...
On Tue, 18 Nov 2003 19:46:09 -0000, Oliver Keating
was popularly supposed to have said:
[...]
The problem is that fuel duty is an incredibly crude lever, because the
"true cost" of your journey depends strongly on time of day and location,
only a satellite based congestion charging system could account for this.
Actually, a satelite-based system is one of the poorer options for this
sort of pricing. GPS satelites are USA-controlled systems. If, as has
happened in the past, the US military decide that their enemies are using
it, the US government has the option to degrade the signals.
So, if you use satelites, you're beholden to a foreign power which
although
it is our friend at the moment, may not be so in future. This is not a
sensible course of action.
The question of over-reliance on GPS systems (in general) is quite an
interesting one. However, in my opinion we will become more reliant on GPS
as time goes on, rather than less, especially with people like Air traffic
control talking about moving to a GPS based system rather than ground based
radar systems for aircraft. If this happens it would have such far-reaching
implications if the USA did turn off the signals that I doubt they would do
it.
However, even if they did, I don't see why Europe couldn't set up its own
system. You need a minimum of 4 satellites with atomic clocks on board
(although typically 7 is better for improved accuracy). I reckon these could
be launched into orbit for around ~£1billion - not a huge cost spread over
all of Europe.
The other problem is that the signal from the satelites is pretty weak,
and
thus susceptible to jamming from the ground. Whilst jamming detectors
could
be built in, this would not stop people deploying jammers near motorways
to
deliberately trigger such sensors. That sort of shenanigans would annoy an
awful lot of people, and lead to the system getting a reputation for being
crap.
But satellite-based navigation systems rely on other information too, like
current road speed and compass heading, and along with knowing what the road
map looks like, it can make a good estimate of where you are even if it
looses the signal for some time.
Mind you, that'd happen anyway. This government seems to automatically
out-
source big IT projects to the likes of Crapita and Electronic Disaster
Systems,
neither of whom have what you'd call an impressive track record.
Now, if you went with a system that used mobile phone cells as a means of
tracking vehicles [1] you might well be onto a winner. Mobile phone units
have a much, much stronger signal than do GPS satelites, they're much more
robust, and the tracking technology already exists. This sort of thing
could
also be used to spot and fine speeding motorists, rendering obsolete all
Gatso, Truvelo and other speed cameras at a stroke; think of the savings!
There is one key problem here, and it is to do with privacy.
The thing is, a GPS system works one way only, despite what people think it
cannot be used to track you. A sat nav congestion system would rely on the
system itself working out the charges, and information on where you have
travelled never needs to be sent to a central authority, therefore ruling
out any misuse of that data, not to mention the various privacy issues that
could make such a scheme unpopular.
With a mobile phone system, the authority knows *exactly* where you have
been, at what time etc. etc. That has to be a disadvantage, not just the
risk of misuse, but simply because a lot of the public may simply find that
unnacceptable.
[1] Doing it this way, you could also look for mobile phones that appear
to
be in use and moving along a motorway, and flag these locations up to the
local police, for much improved enforcement of anti-mobile laws.
Although of course, with hands-free kits being legal, and legitamate use by
passengers, I think the police would ignore it.
--
Dan Holdsworth PhD
By caffeine alone I set my mind in motion, By the beans of Java
do thoughts acquire speed, hands acquire shaking, the shaking
becomes a warning, By caffeine alone do I set my mind in motion