On 24 October 2013 01:31, BladeOfLight16 <[email protected]> wrote: > I was looking at this page today: > > http://postgis.refractions.net/docs/using_postgis_dbmanagement.html#OGC_Validity
FYI, the only official project site is postgis.net, so http://postgis.net/docs/manual-2.0/using_postgis_dbmanagement.html#OGC_Validity > This is a wonderfully simple explanation of what constitutes validity and > simplicity with regards to geometries. However, I noted that this page > doesn't seem to address problems with POLYGONs like when the exterior ring > is self intersecting. For example, this query: > > SELECT ST_IsValidDetail(ST_GeomFromText('POLYGON((0 1,1 1,1 0,-1 0,-1 -1,0 > -1,0 1))')); > > correctly yields > > (f,Self-intersection,010100000000000000000000000000000000000000) > > Maybe I'm missing something in the documentation, but I don't see anything > that directly indicates that this would be considered invalid. Maybe it's > assumed that this would not be considered a POLYGON at all since a POLYGON > must be simple? I'm not really sure. I think some kind of clarification is > in order regardless of what kind. It seems that polygon rings must adhere to > the simplicity requirements for line strings. Maybe that could be mentioned? It is described in words. I believe, these two make the whole picture: "a simple geometry is one that has no anomalous geometric points, such as self intersection" "boundary of a POLYGON may intersect at a POINT but only as a tangent" Best regards, -- Mateusz Loskot, http://mateusz.loskot.net _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
