[OSM-talk] Proposed automated edit: remove railway=* or highway=* tag on relations tagged type=route

[Christian Quest]

2014/1/13 Guillaume Rischard <openstreetmap at stereo.lu>

> Hello,
>
> Several relations have both type=route and highway=* or railway=* tags; I
> would like to remove the highway or railway tags from the relations, and
> leave them on the members. The relation highway tags are redundant with the
> member ways, make no semantic sense, and can cause rendering issues:
>
>     - Redundancy: A route typically contains highways or railways that
> each have a highway=* or railway=* tag. Because the information is already
> included in the members of the relation, it is redundant to tag the
> relation with that tag as well — you're tagging in two places when you only
> need one.
>
>     - Semantic meaning: These relations are not highways or railways, they
> are a *group* of them that make up a route. The tag belongs on the members,
> not on the relation. It causes semantic problems when the value of the tag
> differs on the relation and on the member: is the street a motorway like
> the relation's highway tag says, or residential like the way's tag says?
>
>
tags on relations can be seen as default values for the relation members,
so in such a case, the default tag is replaced by the member one.
I'm not saying it's right to do it that way, just a way to deal with data
in such cases.



>     - Rendering: if both a way and its relation are tagged as highway=* or
> railway=*, the line will get drawn twice on the map — once for the way, and
> once on top of that for the line formed by all the ways in the relation.
> While this is invisible in most cases, it will cause unexpected results if
> the tags disagree, e.g. a trunk that's part of a highway=motorway relation,
> or a railway tunnel that's part of a railway=rail relation.
>


This can also be managed at rendering level in several ways:
- do not render route=* (that's the option I choose)
- render route=* first in case there is one (may not render right in your
motorway/residential example, but fine with the railway tunnel)


I think it's better to deal with such cases at data consumption level as
the case may show up again and again in the future.

If this kind of tagging is indeed considered wrong, no problem to fix the
data with a mechanical edit but we should at least agree on what's
right/wrong first.


-- 
Christian Quest - OpenStreetMap France
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