Kevin, When was st_polygonize introduced? The docs say it was introduced in 1.0.0 RC1? I see it in my newere 1.3 databases. I don't see it in my 1.2.1 corrupted upgrade to 1.3. I suspect this is because of the long standing issue of the bug in upgrading aggregates with soft upgrade and I have had a db that has existed pre 1.0 and I forget the last time I did a complete upgrade on it. Thanks, Regina
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Kevin Neufeld Sent: Tuesday, September 18, 2007 3:43 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] UNION It sounds like you are after performing an overlay operation on two polygonal datasets. I would do something like: - extract all lines from your polygons - node the linework - re-polygonize the noded lines - transfer attributes from the original dataset to the newly formed polygons. http://postgis.refractions.net/support/wiki/index.php?ExamplesOverlayTab les Hope this helps, Kevin ------------- Kevin Neufeld Software Developer Refractions Research Inc. 300-1207 Douglas St. Victoria, B.C., V8W 2E7 Phone: (250) 383-3022 Email: [EMAIL PROTECTED] RAVI KUMAR wrote: Hi, a and b, are multiple tables derived from -2- shape files saved as POST-GIS data. Slide 1: 'a' this data as in the slide show has attributes, This is a square with polygons. 'b' as in the slide show is made up of 2 polygons with attributes which overlap 'a'. Slide 2: a and b are in UNION with the syntax below. But this is not the desired result. There are polygons overlapping other polygons, one below the other. Slide 3: 'abc' is a union of a and b, with desired result My further analysis with post GIS awaits HELP. Cheers Ravi Kumar "Obe, Regina" <[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]> wrote: Ravi, Is the graphic one record or multiple records? If multiple records - I'm afraid you may be asking 2 conflicting questions depending on your dataset so I'm not sure there is anything that can remedy that aside from treating them as two separate questions. I'm also afraid you are getting into territory I'm very weak. You may want to investigate use of st_boundary (which will give you a multilinestring of a polygon/multipolygon boundary and then apply buildarea to that). The below should get rid of some redundant overlapping polygons, but probably won't completely satisfy what you want to do. I'm also thinking you may want to be using intersection instead of geomunion for the inner part. But again depends what you are trying to answer. INSERT INTO abc(code, info, the_geom) SELECT newtb.code, newtb.info <http://newtb.info/> , multi(buffer(geomunion(distinct newtb.cgeom), 0.0)) as thenewgeom FROM ( SELECT a.code, b.info <http://b.info/> , intersection(a.geometry, b.geometry) as cgeom FROM a INNER JOIN b ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) UNION ALL SELECT a.code, null As info, a.geometry as cgeom FROM a LEFT JOIN b ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) WHERE b.geometry IS NULL UNION ALL SELECT null as code, b.info <http://b.info/> , b.geometry as cgeom FROM b LEFT JOIN a ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) WHERE a.geometry IS NULL ) AS newtb GROUP BY newtb.code, newtb.info <http://newtb.info/> Hope that helps, Regina ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of RAVI KUMAR Sent: Monday, September 17, 2007 9:04 AM To: postgis Subject: [postgis-users] UNION Hi Regina, giving the link to show actual how the UNION of polygons is not working as per expectation. Please see the clips in the link. CREATE TABLE abc(code smallint, info smallint) with oids; SELECT AddGeometryColumn('public', 'abc', 'the_geom', 4326, 'MULTIPOLYGON', 2); --The insert INSERT INTO abc(code, info, the_geom) SELECT newtb.code, newtb.info <http://newtb.info/> , geomunion(newtb.cgeom) as thenewgeom FROM ( SELECT a.code, b.info <http://b.info/> , geomunion(a.geometry, b.geometry) as cgeom FROM a INNER JOIN b ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) UNION ALL SELECT a.code, null As info, a.geometry as cgeom FROM a LEFT JOIN b ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) WHERE b.geometry IS NULL UNION ALL SELECT null as code, b.info <http://b.info/> , b.geometry as cgeom FROM b LEFT JOIN a ON a.geometry && b.geometry AND intersects(a.geometry, b.geometry) WHERE a.geometry IS NULL ) AS newtb GROUP BY newtb.code, newtb.info <http://newtb.info/> May be I should be using different syntax for such a result. http://www.kodakgallery.com/I.jsp?c=cjns10h3.8ovw4dsn&x=0&y=w3kbw0 <http://www.kodakgallery.com/I.jsp?c=cjns10h3.8ovw4dsn&x=0&y=w3kbw0> Ravi Kumar ________________________________ Catch up on fall's hot new shows <http://us.rd.yahoo.com/tv/mail/tagline/falltv/evt=47093/*http://tv.yaho o.com/collections/3658%20> on Yahoo! 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