There are three sculptures within biking distance that are actually composed of separate sculptures, but named and presented collectively. What was the correct way to tag these, I wondered? Sculptures are pretty straightforward to map but these didn’t seem to directly map to the concepts of points, ways, or areas.

Photo by Phil Roeder (CC BY 2.0)

The first time I ran across this was with this piece at the Des Moines Art Center. As the name implies, it’s actually three parts that are not physically connected in any way. At the time I had only a vague notion of what a relation was in OSM. It didn’t make intuitive sense to tag each piece with the same data, duplicating information. So I just dropped a point on the center piece of the artwork and moved on.

Just north of that installation is an even better example – “Standing Stones” comprises six separate enormous blocks of granite distributed all across the front lawn of the museum. Again I wasn’t sure what made the most sense, so I tagged one of them and called it good.

By the third time I found a multi-piece sculpture, I realized I needed to figure out a better way to handle mapping. I had gained a little more confidence in OSM concepts and had switched to using JOSM for serious editing, and realized that a relation would probably make sense here. Unfortunately, the wiki makes no concrete recommendations on using relations with artwork.

A little bit of searching did reveal a mailing list post that implied I was on the right track:

2014-04-02 16:56 GMT+02:00 Andy Mabbett

There is also the case of sets; for example, four carvings which form a single artwork, but which are mapped as separate entities.

2014-04-02 21:34:39 UTC Janko Mihelić

You could put the four carvings into a relation, and put the wikidata tag there (along with the name=* and tourism=artwork).

I took that as validation that I wasn’t totally off-base, and set off to make it work. The first thing I found was that relations need to be given a type. What kind of type makes sense for a group of sculptures? The only one that didn’t seem obviously wrong was “site”, so I went with that.

After making the update, I realized I should have checked to see what everyone else has been doing. Taginfo verified that yes, people have been using relations with artwork. And the handy link over to overpass turbo revealed an example (relatively) close in Chicago.

The Chicago result was actually very similar to what I had wanted to do – group more than one sculpture together. I was gratified to see the relation type was the same as what I had settled on. In this instance, each node in the relation was also tagged with tourism=artwork and artwork_type=sculpture. This made more sense to me than leaving them bare, so I added the tags to my relation members as well.

Most of the other examples of relations used for artwork were multipolygons rather than groups of distinct pieces. But there were a couple other instances of site relations of artwork, so I felt justified in the mapping scheme I arrived at.

Now I need to back and update the first two scuptures to use the better solution. I do wish there was a more appropriate relation type than “site”, but I suppose it will do.