Re: FreightCorp Radios

[mauried@commslab.gov.au (Maurie Daly)]

>The Orange GPS is good when it works , it just doesn't work all of the
>time. It also gives out the wrong position of the train, and has
>phantom trains on the screen. Apart from that safe as houses.
>Peter


GPS on its own is only partially the answer.
The accuracy of GPS without differential correction is about 100 metres.
Differential correction is not available Australia wide , so its not practical 
for trains or things that move around a lot.
100 metre accuracy is good enough to tell a controller that a particular train 
is in a particular single line section , but its not good enough to tell 
whether a train is sitting in a main line or in a loop or if the rear end of 
the train is exceeding the length of a loop.
Also in order for the system to work properly the GPS information has to be 
transmitted back via the Radio System to the Controller on a frequent basis.
Most of the current Train radio systems are dimensioned to allow intermittant 
usage, ie they presume that the trains only transmit info backwards 
infrequently.
To allow GPS updates from each train on a basis such that accurate locational 
information could be obtained would require that the train radios were 
transmitting very frequently which could exceed the Radio System capacity 
if it were not originally designed for this purpose.
The other issue of standardization also comes into play.
Do we need yet another State specific safeworking system that requires that 
all trains running thru it be specially modified to carry the requisite radios 
& GPS receivers.
The downside of the PTCs ASW system on private operators like NR & SCT cannot 
be underestimated given that of all NRs loco fleet ,only 20 of its NRs can 
actually lead in Victoria,and there are only a handful of other locos so 
equipped.
Traditionally the only limitations to operating trains in Australia were that 
the locos were of the correct loading guage and had the correct distances 
between the wheels.
The last thing that Australia needs is more limitations on where locos can run.

cheers
MD


Maurie Daly
Sen Tech Officer
DCA Comms Lab
Canberra
Australia
06 2791331 (W)
06 2544422 (H)
041 4339563 (M)