[geos-devel] MULTI* and Invalid
mtnclimb at telus.net
Fri Jun 14 08:09:17 PDT 2013
The relevant section of the OGC SFS spec (99-049) is 2.1.11 MultiSurface:
"The boundaries of any two elements in a MultiSurface may intersect at
most at a finite number of points"
An intersection which is a line segment contains an infinite number of
points, so this is invalid.
On 6/14/2013 6:41 AM, Sandro Santilli wrote:
> On Fri, Jun 14, 2013 at 01:16:02PM +0200, Oliver Courtin wrote:
>> Below an example, throught PostGIS
>> with GEOS 3.3.5-CAPI-1.7.5:
>> SELECT ST_IsValidReason(
>> 'MULTIPOLYGON(((0 0,1 0,1 1,0 1,0 0)),((1 0,2 0,2 1,1 1,1 0)))'::geometry
>> Output: Self-intersection[1 0]
>> After looking in SFS and ISO 19107,
>> we didn't find at first sight
>> why such a geometry should be invalid.
>> Could you give us some light on it ?
> The two components have a lineal intersection.
> Puntal intersection would be considered valid
> (ie: moving vertex 1,1 to 1,1.5).
> IIRC there was a "single point" wording in the spec, but
> Martin will know more about this.
> geos-devel mailing list
> geos-devel at lists.osgeo.org
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2013.0.2904 / Virus Database: 3184/6359 - Release Date: 05/26/13
> Internal Virus Database is out of date.
More information about the geos-devel