| Re: [railML3] Linear coordinates [message #1428 is a reply to message #1426] |
Tue, 11 October 2016 10:38   |
Dirk Bräuer
Messages: 311
Registered: August 2008
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Senior Member |
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Dear Martin,
the difference between theoretical and "practical" (historically
developed) mileage / kilometrage of a line is well-known also in other
countries and is, on my experience, typical for railways in general.
We've already had this distinction in railML 1.x and 2.x and therefore,
it will of course be available and necessary in 3.x.
So far, the theoretical mileage / kilometrage was named "relative
mileage" (relative = strongly distances to a origin; the origin can be
virtual and outside the line, the relative mileage needs not to be shown
anywhere in reality) and "absolute mileage" (historically developed,
shown in reality at mileposts and stations, not always strong
distances). Sometimes only one mileage / kilometrage is used containing
"fault locations", whereas a "fault location" can be either an
increasing or decreasing jump.
Anyway, there will be a common solution in railML 3.x and I hope
Christian will soon tell us how...
With best regards,
Dirk Bräuer
iRFP Dresden.
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Am 07.10.2016 um 18:29 schrieb Martin Karlsson:
> I understand that the main intention of the linear
> coordinate concept is to model kilometer positions, as
> traditionally used in railways. This is also how the example
> file uses it - the example layout runs from 0 to 5 km on a
> line, and this is modeled by lineCoordinates relating to
> positioning system lps_01.
>
> The problem is that a single attribute, "measure", is used
> to catch the kilometer value. In my opinion, this will not
> always work.
>
> When a track is rebuilt, the length of a signposted
> kilometer may deviate from its original 1000 meters. If the
> track is straightened, the length will be shorter - that can
> be handled by putting two coordinates in the same place,
> creating a "jump" in the counting. But if a curve radius is
> increased, the track will be longer, hence the kilometer
> will be longer than 1000 m. How do you handle the case where
> you have passed the 22 km sign by 1003 meters, but not yet
> reached the 23 km sign?
>
> In Sweden, this is solved by not using km with decimals, but
> km plus m. So a valid position can be e.g. 22+1003.4. This
> needs two numbers to be properly represented.
>
> Martin Karlsson
> -------------------------
> Bombardier Transportation
> Rail Control Solutions
> EAPD/ECC
> S-405 02 Göteborg, Swede
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