[Tagging] Tag highway that goes through/under a building

Randy rwtnospam-newsgp at yahoo.com
Mon Dec 28 18:12:10 GMT 2009


John Smith wrote:

>2009/12/28 Roy Wallace 
><waldo000000 at gmail.com>:
>>Is it? Can you explain why? Conceptually, all you need is layer=* and
>>the ability to detect the overlap of the building=yes area and the
>>highway=* way. But I guess you're saying this is hard to encode with
>>"render rules"?
>
>This may need to be fixed on osm2pgsql to handle this situation and
>add either tunnel or covered tags to the way so they render properly
>without adding redundent information.
>
>My take on the covered tag was for ways that are covered by a roof,
>but not a building, so tagging a way under a building shouldn't be
>needed as you said.

The problems I ran into, which caused me to propose "covered" were 
situations where a highway and a pedestrian way go through (or cut under 
but don't fully penetrate) a building at ground level, and the entrance to 
the building, which is under the covered part, is also at ground level. 
Question: Using the wiki definition of layering (Yes, I know, ignore the 
wiki), which of these: building, pedestrian way and/or highway, do you tag 
as being at a different layer than the other and still "map reality"? My 
answer was to propose "covered" which allows all of the entities to be 
mapped at the same layer.

As far as rendering is concerned, neither layering nor covered is properly 
rendered at this time on any of the renders that I'm aware of.

Depending on which entity is mapped last, rendering can be quite easy or 
very difficult. If the way is rendered last, which appears to be the 
current situation, then with the covered tag being on the way, it can be 
rendered in a different style without analyzing all of the overlapping 
entities and their areas. Layering,on the other hand, may require analysis 
of a relation implied by layering but possibly not overtly declared as a 
relation.

So, there are two options, layering and covered, to deal with the road 
going through a building. There are those who prefer each of these two 
options. And, I think there are situations where each one might be best. 
(Layering, for example, would probably be better where a road descends to 
a parking garage under a building.) And, personally, I don't see a problem 
with using both at the same time, if it clarifies the situation on the 
ground.

I don't want to kick the discussion off again, the issues have already 
been addressed in this talk group and in the discussion section of the 
covered proposal, I just wanted to provide some background. As always, do 
it your way, whichever one that is.
-- 
Randy





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