[Tagging] area=yes on polygones (was Block names)

Pieren pieren3 at gmail.com
Wed Apr 25 11:08:25 BST 2012

On Wed, Apr 25, 2012 at 11:05 AM, Komяpa <me at komzpa.net> wrote:

> OSM does not have "area" object,

not yet (maybe in API0.7)

> thus it needs something to mark
> object as polygon.

No. Most of the polygons do not require a tag "area" (amenity,
building, landuse, leisure, landuse).

> There are some tags that insist that a line/relation is filled inside.
> These are area=yes and type=multipolygon.

Sorry, I don't understand what you try to say here.
"type=multipolygon" is about relations or I miss something ?

> Sometimes context isn't clear. (Is a circular highway a
> roundabout or a filled square?..)

Agree. This case is why the tag area has been created.

> It is rather distinct that highway=*, railway=* are linear usually,

Hmm... "railway" yes, "platform" not sure. As many other features,
platform can be represented by a node, a line or a polygon. This just
depends on the contributor and his mapping level (and source accuracy
and/or motivation). Same issue with people symbolizing rivers with a
line and others with a polygon (and a centre line).

> We either need a complete machine-readable list of tags that are
> polygons or lines, or need to tag each object separately. For now I
> see just the second approach being used; telling that is't invalid
> without providing any reasonable fallback is a bad idea.
> Currently used list can be found at
> http://svn.openstreetmap.org/applications/utils/export/osm2pgsql/default.style

A closed loop tagged "highway" requires an additional information.
Until a new element type "polygon" is created in the futur, the
"area=yes" makes sens here. But a closed loop for "railway=platform"
does not require any thing more than the geometry (a closed way tagged
"railway=platform" is always a polygon. Are you asking contributors to
specially tag an object just to avoid some work in osm2pgsql (detect
if the way tagged "railway=platform" is closed or not) ?


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