[Talk-GB] Conflicting tagging of london undergoundstations

Nick Folwell nick.folwell2 at btinternet.com
Fri Sep 21 08:27:01 BST 2007

I don't think you need a default layer value - layer should just be used
when lines (or other elements) cross, to show which is above and which

It's only the relative values that count, and you might need one line to
pass over one feature at one point, and under it at another. (I can't think
of an example now, but I'm sure there are some...)

Nick Folwell
nick.folwell at btinternet.com

-----Original Message-----
From: talk-gb-bounces at openstreetmap.org
[mailto:talk-gb-bounces at openstreetmap.org] On Behalf Of Mark Williams
Sent: 21 September 2007 08:17
To: talk-gb at openstreetmap.org
Subject: [Talk-GB] [Fwd: Re: Conflicting tagging of london

-------- Original Message --------
Subject: 	Re: [Talk-GB] Conflicting tagging of london undergound
Date: 	Fri, 21 Sep 2007 08:13:30 +0100
From: 	Mark Williams <mark.666 at blueyonder.co.uk>
To: 	Robert (Jamie) Munro <rjmunro at arjam.net>
<223020e60709190740k740fe615oc559f8e458ab6cb1 at mail.gmail.com> 
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<46F1A08A.9060402 at arjam.net> <fcsfbn$jms$1 at sea.gmane.org> 
<68e55ace0709200100lcee4bb6t5a917412ac93d614 at mail.gmail.com> 
<yekfy19g3v4.fsf at dellow.uk.cyberscience.com> 
<fcuagp$p86$1 at sea.gmane.org> 
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<fcucl3$1c0$1 at sea.gmane.org> <46F2D24B.2070501 at arjam.net>

Robert (Jamie) Munro wrote:
> Hash: SHA1
> Alex Mauer wrote:
>> I'm assuming that the vast majority of railway=subway in the world is
>> below ground,
> You're assuming wrong. Only 45% of the London Underground is actually
> tunnels. The other 55% is above ground. I expect other cities are similar.
>> and therefore that requiring an additional tunnel=yes tag
>> on 90% or more of the subway ways, is not as good as treating the
>> below-ground portions as a lower layer (whether it's -1 or -2 or -10000
>> is beside the point)
> It might be better to abolish rail=subway and just use rail=metro. It's
> then obvious that you only put tunnel=yes when it is in a tunnel.
> Robert (Jamie) Munro
For what it's worth, London underground is of course on many layers - to 
some extent, each line wants a different layer tag as they cross at 
varying depths.
OTOH I'm not sure how relevant it is, as the layer tag is largely for 
rendering & how important is it to render the levels right on a map?
I personally would want it right, because it's there.

Both tunnel & layer have their place, I would agree with the idea of the 
default for rail=subway/metro being tunnel=yes, even for London at 45% 
correct! I think I'd default layer as -3 though as not much goes under 
the Tube, but covered rivers go above it & I bet they're all -1 at least.


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