On 14 Apr 2014 04:21, "Juan Pablo Caram" <jpca...@gmail.com> wrote:
>
> Hi Mike,
> I understand the basic concept of a union and resulting type, but how can
the union of polygons result in anything but polygons?
> Thanks,
> JP

For example, given the range of incomplete coordinates in your example, the
two polygons appear to be disjoint, thus the result is GEOMETRYCOLLECTION
EMPTY. Is there any specific example where a polygon overlap was expected?
Sometimes invalid geometries muddle with these algorithms that may yield
unexpected results.

-Mike
Hi Mike,
I understand the basic concept of a union and resulting type, but how can
the union of polygons result in anything but polygons?
Thanks,
JP


On Sun, Apr 13, 2014 at 5:56 AM, Mike Toews <mwto...@gmail.com> wrote:

> On 13 April 2014 16:56, Juan Pablo Caram <jpca...@gmail.com> wrote:
> > Hi,
> > Is this at all possible? The GeometryCollection has a LineString!
>
> Sure, this is possible. A union can return any type of geometry, from
> GEOMETRYCOLLECTION EMPTY to POINT to anything else. If the result is a
> LINESTRING, then the union of the two geometries share a boundary. If
> it is in a GEOMETRYCOLLECTION, then there is a mixture of types in the
> same result, such as POINT and POLYGON parts. All these are possible,
> and not so strange when you look at them drawn out.
>
> -Mike
> _______________________________________________
> Community mailing list
> Community@lists.gispython.org
> http://lists.gispython.org/mailman/listinfo/community
>


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