[Tilesathome] rendering order of buildings

[Martin Koppenhoefer]

2009/2/15 David Lynch <djlynch at gmail.com>:
> On Sun, Feb 15, 2009 at 10:23, Martin Koppenhoefer
> <dieterdreist at gmail.com> wrote:
>> 2009/2/15 Knut Arne Bjørndal <bob+osm at cakebox.net>:
>>>
>>>
>>> I also seem to recall that if I drew the buildings above the road core
>>> roads could easily get swallowed completely in some cases, which is a
>>> bad idea.
>>>
>>
>> of course the road would get swallowed when the buildings are mapped
>> on them, but this is bad mapping, and not bad rendering.
>
> Is accurately mapping a building that was built above or below a road
> "bad mapping?"

well, it depends how it is tagged. "Accurately mapping" implies
clearly that the mapping is correct, but I wonder whether different
people have different ideas about what is considered correct.
- For a building above a road I would tag the road tunnel (less
correct but better rendering result) or the building bridge (more
correct but rendering worse).
- For a building below the road we are AFAIK still missing tags and
rendering rules, but I'm also interested in mapping them. The generic
layer=-1 for the building should at least solve the situation a little
bit regarding the rendering. This is not the most usual occurence of
neighbouring buildings and streets though, so I wouldn't consider it
the standard case for determining the best default rendering order.

> Or accurately mapping the pedestrian streets in
> Edinburgh, Scotland (and some other old European cities, I assume)
> that are only just wide enough for two broad-shouldered adults to
> pass?

well those for example I would not consider pedestrian but footway
(and bicycle=yes if applies), but anyway they would display better in
mapnik-rendering-order (the one I'm suggesting for t at h as well) than
in current t at h.

> It sounds like you're implying that anywhere that the rendering
> of a building happens to cover the rendering of a road is the mapper's
> fault, when there are plenty of places that pure geographic accuracy
> would result in an unusable map.

No, I don't even consider covering of a street by a building a
problem. Mapnik proves that it is better, just check various places in
densely mapped areas. Find solutions (proposals above) to get usable
maps AND geographic accuracy together. Btw.: we are not drawing maps
but feeding a geodatabase.

Martin