Re: genapts not respecting taxiway order in apt.dat in overlaying?

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On Fri, 26 May 2006 11:23:54 -0500
Curtis L. Olson wrote:
>
> I believe the reason is that originally the taxiways were in no=20
> particular order and dropping them down in this order with the biggest=20
> on top looked better than any other random or non-random approach we=20
> thought of.  Are you saying that the taxiways are now intelligently=20
> ordered in the airport file?  Is this true of the entire file, or just=20
> true of taxidraw produced airports?

The tutorial on the TaxiDraw web page, at

http://taxidraw.sourceforge.net/taxidraw/tutorial.html

asserts two things that don't seem to be borne out by how genapts handles
the taxiway list:

1) that taxiways vs. aprons are differentiated by aspect ratio:

	"Currently there is no way to differentiate apron from
	taxiway, but FlightGear's scenery building tools (called
	TerraGear) try to differentiate the two based on aspect
	ratio and/or width. Taxiway's get a yellow line and tire
	marks down the middle, apron doesn't."

2) that their ordering in the list (and thus in the file) indicates
what overlaps what:

	"The screenshot below shows our layout with the apron moved
	up three spaces in the order. Note how it will now be rendered
	above the spur taxiway."


Unfortunately, looking at the about 20 airports I've done with TaxiDraw
recently, it looks like neither of these things are true.  "Taxiway vs.
apron" is determined entirely by whether the taxiway has blue outline
lighting -- blue outline lighting =3D taxiway, no lighting =3D apron (so if
you want an apron with blue outline lighting, you need to have two taxiways
sitting on top of each other, with the one without lighting slightly larger
so it'll be on top).  And as Ralf said, ordering is determined by size.

While the way that the taxiways are described as handled by TaxiDraw's
tutorial seems very sensible to me, in hindsight it's probably absurd
to imagine that the all the non-TaxiDraw-done airports (presumably
the majority in apt.dat) will obey this prescription.  So the way that
genapts does it is fine with me.  But then it's probably a good idea
to advertise this fact (so I'm cc'ing Dave to make sure he sees this).

-c


--=20
Chris Metzler			[email protected]
		(remove "snip-me." to email)

"As a child I understood how to give; I have forgotten this grace since I
have become civilized." - Chief Luther Standing Bear

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