[OSM-talk] Ditches

[Richard Mann]

Keepright fusses if highways with different layers meet at junctions
(because it messes up rendering if the highways are drawn differently). So
where you've got a bridge very close to a junction you have to put in a
short way for the bridge and a very short way linking the bridge to the
junction. Messy, and doesn't always solve the rendering problem, anyway.

Keepright doesn't fuss if waterways meet with different layers.

So the simplest is to consider highways to be layer=0 (and put that
explicitly on the bridge, cos some people take bridge=yes to imply layer=1),
and to make the waterway layer=-1.

Richard

On Tue, Dec 15, 2009 at 9:07 AM, Mike Harris <mikh43 at googlemail.com> wrote:

>
>
> Mike Harris
>
>
> > -----Original Message-----
> > From: Steve Bennett [mailto:stevagewp at gmail.com]
> > Sent: 15 December 2009 02:43
> > To: Anthony
> > Cc: openstreetmap
> > Subject: Re: [OSM-talk] Ditches
> >
> > On Tue, Dec 15, 2009 at 1:31 PM, Anthony <osm at inbox.org> wrote:
> > > In a park is a ditch.  There is a very small bridge going
> > over the ditch.
> > > I've tagged the ditch with barrier=ditch.  Should the ditch
> > be layer=-1?
> > > Even though the park is layer=0?
> >
> > Layers are only there to explain the relative heights of
> > things when they meet. No harm will result from marking the
> > ditch as layer -1.
>
> See my separate reply - I disagree - what happens when the "level=-1" ditch
> runs downstream into a "level=0" stream / river - without a waterfall?
>
> > Whether or not it needs to be a lower number than that of the
> > bridge is an unresolved question.
>
> I disagree - surely the bridge is above the water in the ditch and so - by
> your own defintion ('relative heights') it must have a higher level value?
>
> > > Should I use barrier=entrance on the node where the ways overlap,
> > > bridge=yes on the bridge (which means splitting the way for a very
> > > short bridge), both, something else?
> >
> > There shouldn't be a junction between the bridge and the
> > ditch, so no need to mark anything barrier=entrance. Just
> > mark the whole bridge bridge=yes.
>
> Agree - but the way has to be split for the bridge=yes section.
>
>
> > > http://wiki.openstreetmap.org/wiki/Image:IMG_6784.JPG
> > > http://wiki.openstreetmap.org/wiki/Image:IMG_6783.JPG
> >
> > The path:
> > highway=footway
> > (possibly bicycle=yes)
> >
> > It then meets a bridge:
> > highway=footway
> > bridge=yes
> > layer=1
> >
> > Then another path:
> > highway=footway
> >
> > Meanwhile, unconnected, but crossing the bridge:
> > waterway=drain
> >
> > Not sure I'd even mark it "barrier=ditch" after all that. I'd
> > also only specify a layer for the bridge, not the ditch/drain.
>
> Agree - enough to mark it as a stream or, if that is felt to be too 'big'
> then waterway=ditch.
>
> Also agree that the bridge, rather than the ditch, should carry the layer
> tag (see my comment above). Doesn't this rather imply that the ditch has
> the
> same layer value as the level=0 surroundings (as I suggest) rather than
> level=-1 (as per your 'no harm' suggestion) - and that the bridge has a
> layer value higher than 0, so presumably level=1 (as I suggest)?
>
> > Steve
> >
> >
> >
>
>
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