Here, it seems the complete resort is mapped as this MP. Wouldn’t it be better to tag it landuse=winter_sport?
I’ve seen these odd rendering in Norway for years, so maybe it’s mapped according to the local community standard. In that case tell me and I can do something about it at opensnowmap ! On the contrary, if it is just a blind import, maybe it’s better to fix it.
These reason is simply that nobody has taken the time yet to split the polygons into the separate piste areas with piste:difficulty tagging. In many places the piste lines are also missing. Hopefully, somebody will eventually take an interest in mapping downhill pistes in Norway.
I do not think they look odd on the map. They clearly show the downhill area, just without difficulty given. Keeping them is a good start for further detailing at a later time. It corresponds to nordic pistes where grooming was not known at the time of the initial mapping.
By the way, do you need area=yes mapped for closed ways and multipolygons for your rendering to work, or is that not needed?
Quite the opposite. The polygons correctly represent the downhill area and I have found them very useful. Also when mapping manually, piste:difficulty is seldom assigned to areas here.
