Re: "lost" trains

[Jackson Harding <jaxsonjo@camtech.net.au>]

Bill Bolton wrote:
> 
> Jackson Harding <jaxsonjo@camtech.net.au> wrote:
> 
> > Not so.
> 
> So.
> 
> > This gets accuracy down to 1m or less in most situations.
> 
> Well, it was trialled for train positioning purposes in Western NSW
> and wasn't accurate enough when there are multiple tracks.
> 
> Cheers,
> 
> Bill

I don't think there is DGPS coverage in Western NSW, it's limited to
coastal areas where it is used in busy port areas.  In that case you are
quite right, there would be insufficient accuracy in multiple tracks as
the accuracy of such systems is only within +/- 100m 95% of the time,
although in my own usage I've seldom seen it out by more than 20 m or
so.  CASA are considering putting DGPS coverage around all aerodromes
where there are regular flights to allow precision GPS approaches, as
opposed to the non precision approaches that are available for aircraft
now.  This would extend the coverage of DGPS considerably, however if
the railways wished to take advantage of the much improved accuracy of
differential systems over standard commercial off the shelf (COTS) GPS
systems then they would probably have to invest in the differential
ground stations themselves.

Cheers,
	Jackson
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