<div>Hello,everyone,</div>
<div>If you say that my geometry is invalid, it means that GeosEnvelop return a invalid geometry. I use the </div>
<div>GeosEnvelop("LINE(1 3,1 6)") and it return the geometry like</div>
<div>GEOSGeom g2 = "POLYGON ((1 3, 1 3, 1 6, 1 6, 1 3))".</div>
<div>After I use the GEOSUnion, it give me result like "GEOMETRYCOLLECTION EMPTY". Does anyone can </div>
<div>tell me how to do that?<br></div>
<div class="gmail_quote">2009/4/14 <span dir="ltr"><<a href="mailto:geos-devel-request@lists.osgeo.org">geos-devel-request@lists.osgeo.org</a>></span><br>
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<br>When replying, please edit your Subject line so it is more specific<br>than "Re: Contents of geos-devel digest..."<br><br><br>Today's Topics:<br><br> 1. question about GEOSUnion? (LiN YongHeng)<br> 2. RE: question about GEOSUnion? (Obe, Regina)<br>
3. Re: question about GEOSUnion? (Mateusz Loskot)<br><br><br>----------------------------------------------------------------------<br><br>Message: 1<br>Date: Mon, 13 Apr 2009 09:17:11 +0800<br>From: LiN YongHeng <<a href="mailto:bicealyh@gmail.com">bicealyh@gmail.com</a>><br>
Subject: [geos-devel] question about GEOSUnion?<br>To: <a href="mailto:geos-devel@lists.osgeo.org">geos-devel@lists.osgeo.org</a><br>Message-ID:<br> <<a href="mailto:11e4f1140904121817o3acb3f0eo5c0203551d6b9cdc@mail.gmail.com">11e4f1140904121817o3acb3f0eo5c0203551d6b9cdc@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="iso-8859-1"<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>
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<br>------------------------------<br><br>Message: 2<br>Date: Mon, 13 Apr 2009 01:32:38 -0400<br>From: "Obe, Regina" <<a href="mailto:robe.dnd@cityofboston.gov">robe.dnd@cityofboston.gov</a>><br>Subject: RE: [geos-devel] question about GEOSUnion?<br>
To: "GEOS Development List" <<a href="mailto:geos-devel@lists.osgeo.org">geos-devel@lists.osgeo.org</a>><br>Message-ID:<br> <53F9CF533E1AA14EA1F8C5C08ABC08D204D7F27F@ZDND.DND.boston.cob><br>Content-Type: text/plain; charset="iso-8859-1"<br>
<br>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: <a href="mailto:geos-devel-bounces@lists.osgeo.org">geos-devel-bounces@lists.osgeo.org</a> on behalf of LiN YongHeng<br>Sent: Sun 4/12/2009 9:17 PM<br>
To: <a href="mailto:geos-devel@lists.osgeo.org">geos-devel@lists.osgeo.org</a><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><br><br>-----------------------------------------<br>The substance of this message, including any attachments, may be<br>confidential, legally privileged and/or exempt from disclosure<br>
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<br>------------------------------<br><br>Message: 3<br>Date: Mon, 13 Apr 2009 10:16:41 +0100<br>From: Mateusz Loskot <<a href="mailto:mateusz@loskot.net">mateusz@loskot.net</a>><br>Subject: Re: [geos-devel] question about GEOSUnion?<br>
To: GEOS Development List <<a href="mailto:geos-devel@lists.osgeo.org">geos-devel@lists.osgeo.org</a>><br>Message-ID: <<a href="mailto:49E302F9.2000008@loskot.net">49E302F9.2000008@loskot.net</a>><br>Content-Type: text/plain; charset=ISO-8859-1<br>
<br>LiN YongHeng wrote:<br>> Hello everyone, I have a question about GEOSUnion(). I give value to<br>> g1 and g2 like below: GEOSGeom g1 = "POLYGON ((1 3, 1 3, 1 6, 1 6,<br>> 1 3))" and GEOSGeom g2 = "POLYGON ((1 3, 1 3, 1 6, 1 6, 1 3))"<br>
> , but if I make union operation like GEOSGeom g3 = GEOSUnion(g1, g2),<br>> it give me result like "GEOMETRYCOLLECTION EMPTY". Does anyone can<br>> tell me why?<br><br>LiN YongHeng,<br><br>In order to be able to use GEOS or PostGIS, you need to read and<br>
understand some basic informations included in the OGC Simple Feature<br>Specification<br><br><a href="http://www.opengeospatial.org/standards/sfs" target="_blank">http://www.opengeospatial.org/standards/sfs</a><br><br>Otherwise, you will be hit the wall when you try to use every function.<br>
<br>Best regards,<br>--<br>Mateusz Loskot, <a href="http://mateusz.loskot.net/" target="_blank">http://mateusz.loskot.net</a><br>Charter Member of OSGeo, <a href="http://osgeo.org/" target="_blank">http://osgeo.org</a><br>
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<br>End of geos-devel Digest, Vol 78, Issue 10<br>******************************************<br></blockquote></div><br>