[Tagging] objects mixing linear and area (for ex fence and landuse)

[Minh Nguyen]

Vào lúc 23:00 2020-12-30, Eugene Alvin Villar đã viết:
> 
>     For cases where the whole perimeter is fenced (or walled), I prefer
>     avoiding overlapping ways on the same shape. So I would create a way
>     and tag it as barrier=fence/wall and then create a type=multipolygon
>     relation having the first way as an outer member and tag the
>     relation as landuse=*.
> 
>     If there is a gate that is large enough to be mapped as a linear
>     way, then we can have two ways, one for the fence/wall and the other
>     for the gate, then combine them all into the aforementioned
>     multipolygon relation for the landuse.

This is consistent with the practice of mapping adjacent areas as 
multipolygons that share member ways [1], which is frowned upon in some 
regions. It's also similar to tagging the inner way of a building as a 
natural=grass or highway=pedestrian area=yes.

While overloading the multipolygon's outer or inner way technically 
avoids double-tagging a single element with two orthogonal feature tags, 
it doesn't really solve the inconvenience associated with 
double-tagging. Data consumers still have to synthesize an additional 
feature to separate the multipolygon from the non-multipolygon feature, 
since shared ways doesn't translate to formats like GeoJSON.

For those who prefer to map adjacent areas as connected ways or 
multipolygons that don't share members, it would be consistent to map 
the fence as a way that shares nodes with the landuse area.

[1] Method B described in 
https://wiki.openstreetmap.org/wiki/Multipolygon#Mapping_style.2C_best_practice

Vào lúc 23:28 2020-12-30, Peter Elderson đã viết:
 > +1 if the fence is truly the perimeter of the area.
 > I seldom find a fence placed exactly at the perimeter of the area. In
 > practice, the fence is almost always placed a variable distance inside
 > the area.

Perhaps this is true in a literal sense, but so often the term "landuse" 
implicitly includes anything that's rendered similarly to landuse in 
discussions like this. So far this thread has touched upon leisure=park 
and amenity=school, neither of which are landuse=* values but both of 
which may be fenced off.

Consider leisure=dog_park: except maybe at the entrance, the dog park's 
shape is defined by the fence that encloses it. Mapping the fence as a 
distinct way keeps data consumers from having to synthesize features, 
and connecting the fence to the dog park is a clean, less fragile 
alternative to lining up the nodes by eyeballing it.

Besides, if a landuse=residential area isn't hewing to a fence, it might 
be hewing to a barrier=curb or area:highway=residential still waiting to 
be mapped.

-- 
minh at nguyen.cincinnati.oh.us