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Re: FreightCorp Radios




David Proctor wrote in message <01bd1bfb$c74e9880$0a4a23cb@locxvcym>...
>
>

>There is a system currenlt in use in civil aviation called DGPS -
>Differential GPS - this could easily be utilised by the railways if
>accuracy was required, and provides an accurate position to within a few
>metres.
>
>The system utilises a ground station that knows its exact position - it
>then gets the GPS signal, and compares the position given by the GPS with
>the position that it is actually located at. It then works out the current
>error in the GPS system, and braodcasts it to all aircraft in the area. The
>GPS equipment on the aircraft then factor in this known arror to come up
>with an accurate position.
>
>Because of this, the US Defence Department is reportedly softening its
>stance on the application of the more accurate military band GPS in the
>civilian sector.
>
DGPS is used for other things than civil aviation. For example, there is a
system used at some seaports where it is used to accurately determine the
position of high spots on the harbour floor. This information can then be
supplied to a dredge which can dig much more accurately.

The main disadvantage for surface applications is that it requires
communication with land based transmitters. In a small harbour this is not a
problem but for a railway which is strung out over 1000s of km this might be
expensive.


Barry Campbell