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<TITLE>RE: [geos-devel] question about GEOSUnion?</TITLE>
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<P><FONT SIZE=2>LiN YongHeng,<BR>
<BR>
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.<BR>
<BR>
Hope that helps,<BR>
Regina<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: geos-devel-bounces@lists.osgeo.org on behalf of LiN YongHeng<BR>
Sent: Sun 4/12/2009 9:17 PM<BR>
To: geos-devel@lists.osgeo.org<BR>
Subject: [geos-devel] question about GEOSUnion?<BR>
<BR>
Hello everyone,<BR>
I have a question about GEOSUnion().<BR>
I give value to g1 and g2 like below:<BR>
GEOSGeom g1 = "POLYGON ((1 3, 1 3, 1 6, 1 6, 1 3))" and GEOSGeom g2 =<BR>
"POLYGON ((1 3, 1 3, 1 6, 1 6, 1 3))" , but if I make union operation<BR>
like GEOSGeom g3 =<BR>
GEOSUnion(g1, g2), it give me result like "GEOMETRYCOLLECTION EMPTY".<BR>
Does anyone can tell me why?<BR>
<BR>
</FONT>
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