[postgis-users] Re: Polygonize questions

[Charlie Savage]

Thanks.  I need to do this so my column can be rendered by QGIS - it 
doesn't seem to handle geometry collections.

One other question, do the polygons returned by polgyonize follow the 
Right-hand-rule or would I have to run them through the ForceRHR 
function if I needed that?


Charlie


strk at refractions.net wrote:
> On Sat, Nov 12, 2005 at 03:04:36PM -0700, Charlie Savage wrote:
>> Couple of questions about polygonize.
>>
>> * Why does it return a GeometryCollection instead of a MultiPolygon?
> 
> Because it's really a collection of polygons, not a MultiPolygon.
> A MultiPolygon must meet certain constraints in order to be valid
> (polygons must not intersect) and Polygonize doesn't try to enforce
> this.
> 
>> * Is there a way to convert a GeometryCollection returned by polygonize 
>> to a MultiPolygon?  Is there any advantage to doing this?
> 
> Check out the dump() and collect() functions.
> 
> --strk;
> 
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