On 13/03/2019 13:59, David Marchal wrote:
I mapped a forest made of several pieces of woodland, some contiguous and some isolated, with differents leaf_types. I mapped this (https://www.openstreetmap.org/relation/9393253) with a landuse=forest multipolygon, with common tags such as name and operator on the relation, and with leaf_type tags on the outer members, as each has a different value. It seemed a good way to model the fact that these woodlands were considered part of the same forest but had differents leaf_types, but I am unsure now: the JOSM validator claims that contiguous outer members is an error, and openstreetmap.org renders a misplaced name and no leaf_type. Is it a modelling failure or a renderer and validator error? In the first case, how should I map this?

Using a multipolygon relation like this makes sense when the objects are exactly the same, but not when they aren't, so that probably explains the validator issue.


Name placement on multipolygons like this is actaully a renderer decision - some will use one name per group of trees, some one name placed somewhere near the biggest.


I'd probably map your trees as either:


1) natural=wood; name=whatever; operator=whatever; leaf_type=whatever on each group of trees.  This will result in duplicated names, but isn't that different to the way we split roads when other tags change.


or


2) natural=wood; leaf_type=whatever on each group of trees, and create a landuse=forest multipolygon relation with name=whatever; operator=whatever that includes each group of trees.


or


3) If the "managed forest area" by operator=whatever includes significant area of no trees currently, natural=wood; leaf_type=whatever on each group of trees, and create a landuse=forestry multipolygon relation with name=whatever; operator=whatever that includes each group of trees or no trees managed by the same organisation.


The whole landuse=forest/natural=wood thing is fairly contentious though, so please don't take the above as "what everyone does in OSM"; it's just how I'd map it.


Best Regards,


Andy


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