On Fri, 11 Apr 2008 22:36:08 +0100, Paul Corfield
wrote this gibberish:

On Fri, 11 Apr 2008 13:54:58 -0700 (PDT), Mr Thant
wrote:

On 11 Apr, 19:04, Tom Anderson wrote:
Provided that the bus can get good GPS and GPRS signals. GPS is
notoriously inaccurate in built-up areas, as buildings block lines of
sight to the satellites, and introduce reflections which confuse the
receiver (like ghosting on the telly). I wonder what they're doing to deal
with this?

I've read a TfL paper that I can't find right now that found it to be
surprisingly accurate, something like dead on 98% of the time.
Presumably to do with being aerial mounting a large antenna on the bus
roof where it has a good view of the sky, rather than the tiny
internal one in consumer gear that gets blocked by the car roof.

My general experience of I-Bus has been good even though my route runs
out of the first garage equipped with it so we've had all the bugs and
changes to contend with. There is still the odd bus with non functioning
displays or visual but no audible (or vice versa) announcements. Only
twice has something really silly happened - the first was leaving Wood
Green and I-Bus believing we were still heading there. Even when we
passed ourselves going the other way (IYSWIM) the system did not correct
itself. The other was the system seeming to be completely dead and then
suddenly springing into life after leaving a stop. I have no idea how
GPS works but if it uses any form of cellular pattern to locate a
vehicle I did wonder if we had crossed from one cell to another in the
second example.

I was on a 38 the other day that gave it's location correctly at the
stops but always announced that it was going the other way!
messing with the tourists again :-D
--
Mark.
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