[postgis-devel] FW: [postgis-users] how to identify the_geom thatcause:RelateOperation called withLWGEOMCOLLECTION type

Obe, Regina robe.dnd at cityofboston.gov
Wed Dec 10 04:49:22 PST 2008


Do you guys consider this to be a bug?  It is sort of, but not sure if anything can be done about it.  I presume it would go under GEOS not PostGIS.  Anyrate it seems to me that if a geometry is valid -  ST_Centroid should not be returning an empty geometry collection except when given an Empty Geometry Collection.  Am I wrong in that assumption?
 
 

________________________________

From: Obe, Regina 
Sent: Wednesday, December 10, 2008 7:42 AM
To: 'PostGIS Users Discussion'
Subject: RE: [postgis-users] how to identify the_geom thatcause:RelateOperation called withLWGEOMCOLLECTION type


Fred and Ghislain,
 
Thanks - yes that's because of the rounding that happens in ST_GeomFromText -- the ST_GeomFromText is rounding the last couple of digits so the text rep isn't actually what the geometry is so its probably something like
 
796579.5624334065668  or some such thing.  Looking at this in OpenJump, the polygon is practically a line so borders on being almost invalid.
 
So I guess its some sort of rounding issue that before it gets to ST_Centroid its not invalid because the 2 mid points are technically not the same, but once it gets into ST_Centroid some rounding happens that makes it equivalent to an invalid geometry (basically a polygon with 3 points).
 
Well I'm able to recreate this result in "POSTGIS="1.3.5SVN" GEOS="3.1.0-CAPI-1.5.0" PROJ="Rel. 4.6.0, 21 Dec 2007"
 
I suppose the workaround for now would be to ignore anything where the area is close to 0 or centroid is empty or use ST_SnapToGrid to get rid of those extra digits in your geometry.
 
http://postgis.refractions.net/documentation/manual-svn/ST_SnapToGrid.html
 
None of which is terribly appealing.
 
 
Thanks,
Regina
 

________________________________

From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Fred Lehodey
Sent: Wednesday, December 10, 2008 5:28 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] how to identify the_geom thatcause:RelateOperation called withLWGEOMCOLLECTION type


Hi,
just a note:

inserting the same geometry :

INSERT INTO bug (gid, the_geom) VALUES (
1  , '0103000020BE6B0000010000000400000081F178483F4F2841D730212506D33C418045F71F474F2841D706623902D33C417E45F71F474F2841D806623902D33C4181F178483F4F2841D730212506D33C41'
);

and 

INSERT INTO bug (gid, the_geom) VALUES (2,st_geomfromtext('POLYGON((
796575.641547725 1889030.1450377,
796579.562433407 1889026.22415202,
796579.562433406 1889026.22415202,
796575.641547725 1889030.1450377))',-1))

then :
SELECT gid, st_area(the_geom), astext(centroid(the_geom)), isvalid(the_geom)
FROM bug

returns:

1; 0.0001220703125;"GEOMETRYCOLLECTION EMPTY";t
2; 0.0001220703125;"POINT(796578.255471513 1889027.53111391)";t

!!

Fred.





On Wed, Dec 10, 2008 at 9:06 AM, Ghislain Geniaux <geniaux at avignon.inra.fr> wrote:


	Exact,
	 that's the problem :
	
	scot3=# SELECT gid, the_geom
	scot3-# FROM bd_dispo_final
	scot3-# WHERE isempty(centroid(the_geom));
	 gid  |                                                                             the_geom
	-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------
	 16435 | 0103000020BE6B0000010000000400000081F178483F4F2841D730212506D33C418045F71F474F2841D706623902D33C417E45F71F474F2841D806623902D33C4181F178483F4F2841D730212506D33C41
	(1 row)
	
	
	Here, you will find  the ouput of  pg_dump to study this geometrry. Thanks again.
	
	
	
	--
	-- PostgreSQL database dump
	--
	
	SET client_encoding = 'SQL_ASCII';
	SET standard_conforming_strings = off;
	SET check_function_bodies = false;
	SET client_min_messages = warning;
	SET escape_string_warning = off;
	
	SET search_path = public, pg_catalog;
	
	SET default_tablespace = '';
	
	SET default_with_oids = false;
	
	--
	-- Name: bug; Type: TABLE; Schema: public; Owner: postgres; Tablespace:--
	
	CREATE TABLE bug (
	   gid integer,
	   the_geom geometry
	);
	
	
	ALTER TABLE public.bug OWNER TO postgres;
	
	--
	-- Data for Name: bug; Type: TABLE DATA; Schema: public; Owner: postgres
	--
	
	COPY bug (gid, the_geom) FROM stdin;
	16435   0103000020BE6B0000010000000400000081F178483F4F2841D730212506D33C418045F71F474F2841D706623902D33C417E45F71F474F2841D806623902D33C4181F178483F4F2841D730212506D33C41
	\.
	
	
	--
	-- PostgreSQL database dump complete
	--
	
	
	Le 9 déc. 08 à 13:04, Obe, Regina a écrit : 




		Ghislain,
		
		The only time I have seen this kind of behavior is when centroid returns an empty geometry collection.  In those cases its because the geometry is invalid.
		
		Although none of your geometries are invalid, it could be a bug in either the centroid code or isvalid check that may or may not be fixed in 3.0.3+ of GEOS.
		
		
		Can you do the following
		
		SELECT gid, the_geom
		FROM ZS2C
		WHERE isempty(centroid(the_geom))
		
		
		and send us as an attatched file with one of those geometries.  We can cross check with GEOS 3.0.3 or 3.1 to see if the issue still remains.
		
		Thanks,
		Regina
		-----Original Message-----
		From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Ghislain Geniaux
		Sent: Monday, December 08, 2008 1:29 PM
		To: PostGIS Users Discussion
		Subject: Re: [postgis-users] how to identify the_geom that cause:RelateOperation called withLWGEOMCOLLECTION type
		
		On Linux  :
		
		POSTGIS="1.3.1" GEOS="3.0.0-CAPI-1.4.1" PROJ="Rel. 4.6.0, 21 Dec
		2007" USE_STATS
		(1 row)
		
		On Macos
		
		 POSTGIS="1.2.1" GEOS="3.0.0-CAPI-1.4.1" PROJ="Rel. 4.6.0, 21 Dec
		2007" USE_STATS
		(1 row)
		
		same result with the two platform and postgis version.
		
		Thanks.
		
		Le 8 déc. 08 à 17:53, Paragon Corporation a écrit :
		
		

			What does
			
			SELECT postgis_full_version();
			
			Return
			
			Thanks,
			Regina
			-----Original Message-----
			From: postgis-users-bounces at postgis.refractions.net
			[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
			Ghislain
			Geniaux
			Sent: Monday, December 08, 2008 11:03 AM
			To: PostGIS Users Discussion
			Subject: Re: [postgis-users] how to identify the_geom that cause
			:RelateOperation called withLWGEOMCOLLECTION type
			
			I've no collection. It's looks like a bug.
			
			Moreover my table is very large wiht more than 500 000 geometry and i
			found no solution to identy the wrong geom.
			
			Here you can see the query, with the same result on different
			plateform (LINUX DEBIAN, MACOS, with GEOS 3)
			
			otm=# select distinct geometrytype(the_geom) from ZS2c;
			 geometrytype
			--------------
			 MULTIPOLYGON
			(1 row)
			
			otm=# select distinct geometrytype(the_geom) from bd_dispo_finalc ;
			 geometrytype
			--------------
			 MULTIPOLYGON
			 POLYGON
			(2 rows)
			
			otm=# create table info_nonvoue1 as
			otm-# select b.id_parc, z.niv from bd_dispo_finalc as b, ZS2c as z
			otm-# where z.niv=1 and intersects(centroid(b.the_geom),z.the_geom)
			and b.the_geom && z.the_geom and isvalid(b.the_geom) and isvalid
			(z.the_geom);
			ERROR:  Relate Operation called with a LWGEOMCOLLECTION type.  This
			is unsupported
			otm=#
			
			
			
			Le 8 déc. 08 à 13:32, Obe, Regina a écrit :
			
			

				Many of the GEOS relation functions do not work with collections.
				
				You must have a geometry collection in there somewhere or its a bug.
				Also which relation function were you trying?
				
				To figure out the type of your geometries, run
				
				SELECT *
				FROM sometable
				WHERE GeometryType(the_geom) = 'GEOMETRYCOLLECTION'
				
				
				
				
				-----Original Message-----
				From: postgis-users-bounces at postgis.refractions.net
				[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
				Nicolas Ribot
				Sent: Monday, December 08, 2008 6:22 AM
				To: PostGIS Users Discussion
				Subject: Re: [postgis-users] how to identify the_geom that cause :
				RelateOperation called withLWGEOMCOLLECTION type
				
				

					I have an error with some geometry that cause : "ERROR Relate
					

				Operation
				

					called withLWGEOMCOLLECTION type".
					All the geometries seem clean (valid, non empty, closed, only
					POLYGON,
					

				..)
				

					My question : how to get information of which geometry cause the
					

				problem ?
				

					Is there a way  to have information about the geometry during
					postgis
					

				is
				

					working on a  SQL query ?
					Thanks.
					
					


				Hi Ghislain,
				
				What the query that failed looks like ?
				The message is telling that one geometry has an invalid type.
				In your query, you could try to ask for ST_GeometryType(geometry) and
				a geometry identifier to see which geometry has the wrong type.
				If you perform a spatial operation, it is possible that
				geometryCollection is produced.
				You could maybe split your query into smaller block to see where such
				collections are generated.
				
				Nicolas
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			INRA SAD Ecodéveloppement
			Site Agroparc
			Domaine St Paul
			84914 Avignon Cedex 9
			
			Tél : 04 32 72 25 64
			Fax : 04 32 72 25 62
			
			
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		------------------------------------------
		Geniaux Ghislain
		INRA SAD Ecodéveloppement
		Site Agroparc
		Domaine St Paul
		84914 Avignon Cedex 9
		
		Tél : 04 32 72 25 64
		Fax : 04 32 72 25 62
		
		
		_______________________________________________
		postgis-users mailing list
		postgis-users at postgis.refractions.net
		http://postgis.refractions.net/mailman/listinfo/postgis-users
		-----------------------------------------
		The substance of this message, including any attachments, may be
		confidential, legally privileged and/or exempt from disclosure
		pursuant to Massachusetts law. It is intended
		solely for the addressee. If you received this in error, please
		contact the sender and delete the material from any computer.
		_______________________________________________
		postgis-users mailing list
		postgis-users at postgis.refractions.net
		http://postgis.refractions.net/mailman/listinfo/postgis-users
		




	------------------------------------------
	Geniaux Ghislain
	INRA SAD Ecodéveloppement
	Site Agroparc
	Domaine St Paul
	84914 Avignon Cedex 9
	
	Tél : 04 32 72 25 64
	Fax : 04 32 72 25 62
	
	
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