[Tilesathome] steam over landuse

[D Tucny]

2009/2/4 Knut Arne Bjørndal <bob+osm at cakebox.net <bob%2Bosm at cakebox.net>>

> On Wed, Feb 04, 2009 at 12:37:50PM +0100, Chris-Hein Lunkhusen wrote:
> > D Tucny schrieb:
> >
> > >  <http://www.informationfreeway.org/?lat=51.912&lon=7.737&zoom=16>
> >
> > > > But the stream is tagged as layer -1, so is underground as landuse
> > > > will assume 0 (but render behind other layer 0 objects).
> > >
> > >     Yes, streams are often tagged as -1 so that they are rendered
> > >     under streets. In Wiki there is also the recommendation to
> > >     tag waterways as -1.
> > >
> > >     So landuse should never cover other objects.
> > >     Landuse should be assumed as layer -100. ;-)
>
> Virtual landuse things like residential and industrial are done at -5
> (the lowest layer osmarender processes).
>
> The practice of always tagging waterways as -1 sound stupid to me, the
> layer tag is meant to describe where something is in relation to the
> normal earth surface, and I'd say most streams are _at_ that height,
> not (significantly) below it.
>
> > > I thought there was a discussion about this at some point in the past
> > > and that the outcome was that the feeling was that landuse should be
> > > drawn first, though allowing layers within the landuse 'layer' then
> > > other features drawn over whatever the outcome of the landuse layer
> > > was... which, would be effectively the same as making landuse
> > > effectively exist at -100 to -90...
> > > Can't remember the details, but will try and find the mails...
> >
> > It makes no sense that a "virtual" object like landuse
> > covers any "real" object like streams or whatever, no matter
> > what the layer is.
>
> As forests are physical objects they are drawn in the normal order.
>

While forests are physical objects, they are drawn to represent an area, an
area that could have objects running through it below the level of the
surrounding land, tunnels, being a good example, but, I'd argue that water
is lower too, unless you're at sea or are dealing with an aquaduct...

I don't believe a forest should render over the top of a tunnel, I don't
think it shouldn't obliterate any lower layer features, I believe it should
just be drawn as a background layer...

I have an example of a road tunnel running under a range of wooded hills,
along the hills are footpaths, the tunnel passes under the woods and
footpaths... The tunnel is tagged as tunnel=yes, layer=-1, the woods are
tagged as natural=wood, no layer, the footpath is tagged as highway=footway,
no layer... I don't think it would be the 'right thing' to tag the woods as
layer -2 in this case just to make it render 'right' in the osmarender
layer...

So, I'd support forests and woods and marshes/wetlands/whatever the current
accepted tag for them is that are also used to represent potentially large
areas to also follow the same 'draw first' rule that landuse areas use...

d
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