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Robert[_3_] · March 19th 09, 04:40 PM posted to uk.railway,uk.transport.london

On 2009-03-19 06:38:09 +0000, (Neil
Williams) said:

On Wed, 18 Mar 2009 16:17:22 -0700 (PDT), wrote:

No, because the wheels are not a fixed diameter, but get gradually
smaller as they are turned on lathes to remove flats and
imperfections. A small difference in diameter will lead to a large
cummulative error, if no corrections are made. There are other systems
which measure distance travelled (for example radar), but I don't know
how they are affected by different track formations etc.

A more clever system could use the GPS data to derive how far the
train travels on one revolution on that day and use it later when the
GPS was not available.

OTOH, the Mk1 eyeball would also do the job, though I hear that there
was an incident of it failing to do so at Bletchley last week.
Fortunately, the Mk1 eyeball of the passengers prevailed, and (as one
would expect) nobody fell out.

Neil

AIUI some trains have been fitted with forward facing TV cameras as
well as the ones looking down the side of the train. If these were
coupled with some pattern recognition software and a set of images of
the stations served by the train then an electronic version of the Mk.
1 eyeball could be produced. It should be easy-peasy to work out if a
platform is beside the train or not. Not only that it could probably
work out which side of the train the platform is. If an infra-red
sensitive camera was used then it could also be used in fog and under
roofs in the dark.

If too much responsibility and action is removed from people operating
machinery or other things, then it can happen they are not as alert as
they could be when you really need it. If you see what I mean.
--
Robert