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<TITLE>RE: [postgis-users] masking out part of a MULTILINESTRING</TITLE>
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<P><FONT SIZE=2>What a difference difference makes. Thanks for the help, strk. But I've got a related question now. Hope I haven't worn out my welcome.</FONT></P>
<P><FONT SIZE=2>The difference(the_geom,***) works beautifully when done as part of the DATA clause in a .map, but I'm ready to nuke the data directly in the table so that I won't have to mask out the unwanted area every time.</FONT></P>
<P><FONT SIZE=2>However, when I do that, I end up w/ a total of 3 different geometries:</FONT>
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<P><FONT SIZE=2>etopo2_bathy=# select distinct(GeometryType(difference(the_geom,GeometryFromText('BOX3D(-87 24,-79 31)'::box3d,-1)))) from etopo2_contours;</FONT></P>
<P><FONT SIZE=2> geometrytype </FONT>
<BR><FONT SIZE=2>--------------------</FONT>
<BR><FONT SIZE=2> GEOMETRYCOLLECTION</FONT>
<BR><FONT SIZE=2> LINESTRING</FONT>
<BR><FONT SIZE=2> MULTILINESTRING</FONT>
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<P><FONT SIZE=2>My original table has MULTILINESTRINGs and are bathymetry contours. Of course, when I try to do an update, I get constraint problems on the geometry type. I'm happy to drop the constraint if that's what I need to do. And masking doesn't seem to do the trick, either. I would have thought that a GEOMETRYCOLLECTION geometry type could handle it all, ach no.</FONT></P>
<P><FONT SIZE=2>Any ideas?</FONT>
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<P><FONT SIZE=2>Thanks.</FONT>
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<P><FONT SIZE=2>________________________________________</FONT>
<BR><FONT SIZE=2>From: Purvis, Charlton [<A HREF="mailto:cpurvis@asg.sc.edu">mailto:cpurvis@asg.sc.edu</A>] </FONT>
<BR><FONT SIZE=2>Sent: Wednesday, April 20, 2005 1:02 PM</FONT>
<BR><FONT SIZE=2>To: 'PostGIS Users Discussion'</FONT>
<BR><FONT SIZE=2>Subject: RE: [postgis-users] masking out part of a MULTILINESTRING</FONT>
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<P><FONT SIZE=2>> This should be difference(geom, box); </FONT>
<BR><FONT SIZE=2>> --strk; </FONT>
<BR><FONT SIZE=2>Genius! Works like a charm. Thanks. </FONT>
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