mikh43 at googlemail.com
Tue Dec 15 11:45:12 GMT 2009
Fair points ... If it really doesn't matter to routers and other mappers and
doesn't interfere with anything else then I am happy to accept that there is
no fully logical solution and that it shouldn't matter to me either!
> -----Original Message-----
> From: Steve Bennett [mailto:stevagewp at gmail.com]
> Sent: 15 December 2009 11:18
> To: Mike Harris
> Cc: openstreetmap
> Subject: Re: [OSM-talk] Ditches
> On Tue, Dec 15, 2009 at 8:07 PM, Mike Harris
> <mikh43 at googlemail.com> wrote:
> >> 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
> > ditch runs downstream into a "level=0" stream / river -
> without a waterfall?
> Asbolutely nothing. You're waaaay overthinking this, both of you.
> Layers are just a hack to make stuff render. It's not like
> "bicycle=no" or something where we're making some statement
> of fact about the real world. Layers are *not* a statement of
> fact. Layer=3 does not, in the absolute, mean anything
> different from Layer=2.
> >> 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?
> You're trying to apply some sort of intuition or logic to this. Don't.
> It's not some logic puzzle where the layers all have to mean
> something. I've worked in areas where someone, for some
> reason, has tagged all the bike paths in a park as layer=1.
> It didn't matter. I eventually deleted the layer tags because
> they interfered with my own tagging scheme, but it was
> nothing more than personal preference.
> >> 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.
> I doublechecked the wiki, looks like "barrier=ditch, waterway=drain"
> might be the right way to go. Belt and braces, you know.
> > Also agree that the bridge, rather than the ditch, should carry the
> > layer tag (see my comment above).
> It. Really. Doesn't. Matter. :)
> Say you have a stream at layer=3, and somewhere else it
> crosses a big complicated bridge which for some reason
> someone has tagged layer=-2.
> You know what you do? You don't panic. You break the stream,
> you set the new part as layer=-3, and you carry on.
> >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)?
> I am curious to know if any routers look at layers when you
> have something like a big routable area (eg,
> highway=pedestrian) with barriers within it, though.
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