[OSM-dev] multipolygon relation and non-closed ways
sly (sylvain letuffe)
liste at letuffe.org
Sun Oct 14 14:48:08 BST 2012
Le samedi 13 octobre 2012 21:49:21, Frederik Ramm a écrit :
> (Frankly I am surprised
> that you thought the list was necessary, as I believed everything to be
> explained properly already.)
I'm not surprised, I've been asking for a while what validity means in the
context of multipolygon relations in OSM (on tagging list), especially in
strange border cases, but I'm still missing answers.
I also guess that since changes on the wiki are recurrent about that, I'm not
the only one unsure about what is and what isn't valid.
But maybe I failed to reach the good list, and dev is better suited for that
as the answer is far from trivial, and is indeded more complex that you seam
to imply (+include some GIS background needs).
But nothing is ever too late isn't it ?
I'll come back later with examples as a graphic is far easier to understand
than fix font ASCII art
As a starting point for the shorter definition of what validity is, I suggest
referring to the OGC standard this way :
'''
A multipolygon relation in OSM is considered valid if it can be used, without
discarding nodes or ways or part of ways to build a valid geometry as define
by the OGC Simple Feature standard
(http://www.opengeospatial.org/standards/sfs)
with the notable exception of touching inner rings (see below).
'''
--
sly (sylvain letuffe)
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