[Tagging] Road hierarchy

Paul Allen pla16021 at gmail.com
Sat Aug 10 17:34:11 UTC 2019


On Sat, 10 Aug 2019 at 17:27, Julien djakk <djakk.geographie at gmail.com>
wrote:

>
> The "old" highway tag can give default values to the 5 new tags, so it
> is not necessary to re-map everything :)
>

If it is a guaranteed 1:1 relationship then there is no point doing it.
Maybe if the
semantics became clearer (like migrating landuse=grass to landcover=grass)
but that doesn't appear to be the case.

But your scheme appears to offer much more details and more precision.  So
you might say that highway=primary automatically becomes a=x + b=y + c=z
but that implies that a highway=primary might actually be a=x + b=y + c=w.
So it is necessary to remap.everything in order to check whether the primary
highway has c=z or c=w.  It might not be urgent if there's no great
practical
difference between c=z and c=w, in which case there isn't much need for
the new scheme.

>
> Yes you are absolutely right : I need my own renderer to populate the
> new tags. I was thinking about putting anything (roads, summits,
> footways, towns, trees …) with importance = 1 to the lower zoom, etc.
> (Actually tag importance already exists, used for railways, has main
> values regional or national).
>

Then you not only need your own renderer, you need your own database.
Two of them, in fact.  One to hold a regularly-updated copy of the OSM
database and one holding your extra tags.  Because you'll probably
get a lot of opposition to the idea of you shoving your own tags into
the OSM database for no reason than that you like the idea even though
nobody else does.

People have managed to get their own tagging sub-schemes accepted: the
sea mark and historical objects tags come to mind.  A lot of their stuff
isn't
rendered by anything other than their own carto (some things are, but most
are not).  BUT those tags aren't applied to every object in the database.

Oh, and there's the problem that "importance" seems, at this stage, to be a
subjective value decided by you but applied to everything.  Even though for
many practical purposes renderers make their own decisions about what
to display at different zooms, you wish to impose your view on everything.

The more you try to justify this idea, the less feasible it seems.  The
first law
of holes comes to mind...

-- 
Paul
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