[OSM-talk] Key:layer update

Matthijs Melissen info at matthijsmelissen.nl
Sun Mar 9 22:26:59 UTC 2014


On 9 March 2014 10:30, Richard Z. <ricoz.osm at gmail.com> wrote:
> for some time now I have been working on the wiki page to state the rules
> as clearly as possible.. hope that most of the improvements are fairly
> uncontroversial.

Thank you for doing this, it's very useful to have this properly
documented. I have been working on layering in the main CartoCSS
stylesheet, and found that at the moment, indeed not all aspects of
the layering model are defined precise enough.

A question: a single road can contain sections on multiple layers, so
there will be a point where the sections that are on different layers
meet. At that point, there might even be a side street. However, no
vertical ordering should be assumed at such a point. It is written
that "The vertical ordering established by the layer values is valid
exactly only in the point where the ways cross or objects overlap."
Perhaps 'crossing' should be interpreted here as crossing without
node, but that causes problems with bridge/waterway.

In other words, I am wondering for each of the following situations if
the roads should be interpreted as meeting on the same or different
levels:
- A node where two waterways on layer 1 and two roads on layer 2 meet;
- A node where two roads on layer 1 and two roads on layer 2 meet;
- A node where two roads on layer 1 and one road on layer 2 meet;
- A node where one road on layer 1 and one road on layer 2 meet.

Perhaps some text that answers questions like this should be added to
the Wiki-page.

-- Matthijs



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