building:part=column ‒ The tag building:part=* is only to be used on closed ways (areas). Use man_made=column instead.
This was discussed in the “OSMWorld Discord” server but I would like to discuss it also here with a broader audience. In my opinion this is wrong.
man_made=column should be used for important, distinguishable and historic columns, while building:part=column should be allowed for the 3D mapping of buildings.
Also building:part=column (as every building:part=* value, even building:part=no, but this is another story…) is already supported by 3d renderers, while man_made=column is not.
I agree that there are significant columns (freestanding, typically) often errected as memorials or similar, that should be distinguishable from columns and pillars in buildings.
building:part apparently has different uses? It is used by the 3d community to model building volumes, and is also used to distinguish conceptual building parts (still volumes, but structured conceptually and not merely on the requirement of drawing a volume, i.e. it has typically a name or a type), and for individual structural components like walls or columns?
I think that’s exactly what man_made=column tries to do. The historic, or “important” ones whould be tagged with historic=column or by adding historic=yes to the man_made=column. It’s still unclear to me, why the decision was made to allow man_made=column to be used instead of a building:part, because the latter is explicitly not to be rendered by 2D-renderers. Are we now getting 30 columns or so on non-3D-maps, because someone mapped every single column of arcades ?
I don’t see the point of replacing building:part=column nodes (which are not rendered) with man_made=column (which are not rendered). Wouldn’t be easier to push 3d renderers to make an exception in the 3d tagging schema to exclude columns from the “no-nodes” policy? (also, we are allowed to map entire buildings as nodes but not columns…?)
I agree that redirecting the whole page is confusing, since it seems that the tag hasn’t to be used at all, not just for nodes. Btw we have 3508 building:part=column, of which only 67 are nodes.
From my perspective as someone active in 3D mapping and rendering, I currently consider building:part=column polygons established mapping.
The redirect does indeed make it look as if this is not the case, so thanks for spotting that. At the same time, I also believe it’s a bad idea to create wiki pages for every possible building:part value because it would be impossible for anyone but the most active wiki users to keep track of changes on that many pages. Therefore, my preferred solution would be to either change the redirect’s target to point to Key:building:part, or to delete it.
That would indeed be a reason to give it a separate wiki page. But current usage establishes it firmly as a polygon tag, there are barely any uses on nodes. Building part nodes would be a new idea rather than documenting existing practice. (And my intuition is to be wary of carving out such an exception.)
Sorry, so what is the right way to create columns for buildings like this one:Imapa ? I thought that building:part key is used for all building parts needed for 3d rendering but this page . Key:building:part - OpenStreetMap Wiki redirects to building:part page with no information about columns.
