[geos-devel] question about GEOSUnion?

[Obe, Regina]

LiN YongHeng,

your geometry is invalid since first you don't have enough points to form a polygon after you remove the dupes and second you have self intersections.  Therefore the union is undefined at best.

Hope that helps,
Regina


-----Original Message-----
From: geos-devel-bounces at lists.osgeo.org on behalf of LiN YongHeng
Sent: Sun 4/12/2009 9:17 PM
To: geos-devel at lists.osgeo.org
Subject: [geos-devel] question about GEOSUnion?
 
Hello everyone,
I have a question about GEOSUnion().
I give value to g1 and g2 like below:
GEOSGeom g1 = "POLYGON ((1  3, 1  3, 1  6, 1  6, 1 3))"  and GEOSGeom g2 =
"POLYGON ((1  3, 1  3, 1  6, 1  6, 1 3))"  , but if I make union operation
like GEOSGeom g3 =
GEOSUnion(g1, g2), it give me result like "GEOMETRYCOLLECTION EMPTY".
Does anyone can tell me why?



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