[Tagging] type=bounday

[Minh Nguyen]

Vào lúc 13:19 2022-03-28, Colin Smale đã viết:
> 
>> On 03/28/2022 9:31 PM Minh Nguyen <minh at nguyen.cincinnati.oh.us> wrote:
>>
>>   
>> Vào lúc 10:04 2022-03-25, David Marchal via Tagging đã viết:
>>> Multipolygons were considered but boundary was preferred because such
>>> areas are often subject to a separate set of laws, akin to a protected
>>> area, but less strict, so it was more akin to a boundaried area than to
>>> a simple multipolygon.
>>>
>>> That being said, as you said, this changes almost nothing for mapping.
>>
>> Boundary relations can indicate the capital (admin_centre) or cultural
>> center (label) of an administrative area.
> 
> Since when has the "label" indicated the cultural centre? AFAIK it's a hint for the renderer, useful when the geometry of the area is such that classic placement algorithms such as centroid would pick a bad place.

You're right, this is precisely what the documentation on the wiki said 
from 2017 to 2020. Still, the algorithmically determined place can be 
"bad" not only because of a topological edge case but also because of a 
city's lopsided development pattern.

I wrote "cultural center" as shorthand for whatever is widely accepted 
as the centerpoint of the city settlement, irrespective of the bizarre 
shape that its boundary might take. Depending on the city, it can also 
be described as a "downtown", "commercial center", "town square", "town 
hall", "origin of the street grid", etc. Basically, it's wherever the 
place=* POI would be located -- and thus where the renderer would place 
the label anyways.

As far as I can tell, this has long been the primary manner in which the 
label role is used on city boundaries in the United States. However, I 
wouldn't be surprised if it's used differently in other places, since 
the role became popular organically.

The important thing is to distinguish it from admin_centre, which is 
specifically about the capital. The label place=* POI is a different 
representation of the same place as the boundary, whereas the 
admin_centre place=* POI is a different place altogether.

-- 
minh at nguyen.cincinnati.oh.us