Hi,
On 13.10.2012 21:35, Pedro Larroy wrote:
Thanks for the link. I have updated the wiki with requirements for
valid multipolygon relations:
http://wiki.openstreetmap.org/wiki/Relation:multipolygon#Valid_Multipolygon_conditions
I made a few changes to your list in the Wiki. (Frankly I am surprised
that you thought the list was necessary, as I believed everything to be
explained properly already.)
First of all, the "role" is not actually required to determine validity,
and I have removed your references of "... belonging to the same role".
The algorithm laid out on the multipolygon page takes care of any valid
multipolygon whatever the role; and algorithms relying on the role are
broken. The use of the inner/outer roles is recommended because it adds
redundancy and will often make it clearer what the mapper intended to
do, but these roles are not a condition for validity.
Also, the ways in a mutlipolygon relation do not have to form "a closed
chain" (your words) but "one or more closed chains".
You wrote that inner polygons "should" not overlap with outers; I
changed that to "must" because the polygon is invalid otherwise.
Also, your rule that no more than two unclosed ways may meet in a point
is not correct in the case of touching inner rings, where any even
number of unclosed ways might touch in one point.
Bye
Frederik
--
Frederik Ramm ## eMail [email protected] ## N49°00'09" E008°23'33"
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