Re: [postgis-users] simplifying (homogenize) a polygon
Hi Denis, In your example, I don't understand how the parts of your multipolygons can be adjacent. Are they valid ? Do you have a visual example ? Thank you Nicolas On 21 November 2013 07:32, Denis Rouzaud denis.rouz...@gmail.com wrote: Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
Thanks for the explanation. You could correct the multipolygons in one step, by using the st_buildArea function, that merges a linework of linestrings, preserving holes. To extract polygons boundaries as linestring, st_boundary() is very handy: The bad_multipg table contains invalid multipolygons with adjacent parts (http://imgur.com/MP6Cy4f) select gid, st_buildArea(st_boundary(geom)) from bad_multipg group by gid; Gives: http://imgur.com/RqlowFI Nicolas On 21 November 2013 13:50, Denis Rouzaud denis.rouz...@gmail.com wrote: Hi Nicolas, I edit my multi polygons in QGIS, and you're right the geometry becomes invalid if some parts have adjacent segments. In a simple case, I would have a multi polygons with 3 parts with 2 parts adjacent. http://imgur.com/zvxPFeR Although the geometry is invalid, my intention is to make it valid, and therefore merge the two parts, which is impossible in QGIS - AFAIK. So my intention was to save the geometry as this, and make it valid by a command. I could achieve this with a function: CREATE OR REPLACE FUNCTION distribution.simplemultipoly(geom geometry) RETURNS geometry AS $BODY$ DECLARE num_geom integer; BEGIN SELECT ST_NumGeometries(geom) into num_geom; SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geom,n FROM generate_series(1,num_geom) n INTO geom; RETURN geom; END; $BODY$ LANGUAGE plpgsql; But I wondered if there was a more direct way. Cheers, Denis On 21. 11. 13 12:42, Nicolas Ribot wrote: Hi Denis, In your example, I don't understand how the parts of your multipolygons can be adjacent. Are they valid ? Do you have a visual example ? Thank you Nicolas On 21 November 2013 07:32, Denis Rouzaud denis.rouz...@gmail.com wrote: Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
wow, thanks a lot! indeed, much much nicer! thanks again, Denis On 21. 11. 13 15:47, Nicolas Ribot wrote: Thanks for the explanation. You could correct the multipolygons in one step, by using the st_buildArea function, that merges a linework of linestrings, preserving holes. To extract polygons boundaries as linestring, st_boundary() is very handy: The bad_multipg table contains invalid multipolygons with adjacent parts (http://imgur.com/MP6Cy4f) select gid, st_buildArea(st_boundary(geom)) from bad_multipg group by gid; Gives: http://imgur.com/RqlowFI Nicolas On 21 November 2013 13:50, Denis Rouzaud denis.rouz...@gmail.com wrote: Hi Nicolas, I edit my multi polygons in QGIS, and you're right the geometry becomes invalid if some parts have adjacent segments. In a simple case, I would have a multi polygons with 3 parts with 2 parts adjacent. http://imgur.com/zvxPFeR Although the geometry is invalid, my intention is to make it valid, and therefore merge the two parts, which is impossible in QGIS - AFAIK. So my intention was to save the geometry as this, and make it valid by a command. I could achieve this with a function: CREATE OR REPLACE FUNCTION distribution.simplemultipoly(geom geometry) RETURNS geometry AS $BODY$ DECLARE num_geom integer; BEGIN SELECT ST_NumGeometries(geom) into num_geom; SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geom,n FROM generate_series(1,num_geom) n INTO geom; RETURN geom; END; $BODY$ LANGUAGE plpgsql; But I wondered if there was a more direct way. Cheers, Denis On 21. 11. 13 12:42, Nicolas Ribot wrote: Hi Denis, In your example, I don't understand how the parts of your multipolygons can be adjacent. Are they valid ? Do you have a visual example ? Thank you Nicolas On 21 November 2013 07:32, Denis Rouzaud denis.rouz...@gmail.com wrote: Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
Hi Nicolas, I edit my multi polygons in QGIS, and you're right the geometry becomes invalid if some parts have adjacent segments. In a simple case, I would have a multi polygons with 3 parts with 2 parts adjacent. http://imgur.com/zvxPFeR Although the geometry is invalid, my intention is to make it valid, and therefore merge the two parts, which is impossible in QGIS - AFAIK. So my intention was to save the geometry as this, and make it valid by a command. I could achieve this with a function: CREATE OR REPLACE FUNCTION distribution.simplemultipoly(geom geometry) RETURNS geometry AS $BODY$ DECLARE num_geom integer; BEGIN SELECT ST_NumGeometries(geom) into num_geom; SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geom,n FROM generate_series(1,num_geom) n INTO geom; RETURN geom; END; $BODY$ LANGUAGE plpgsql; But I wondered if there was a more direct way. Cheers, Denis On 21. 11. 13 12:42, Nicolas Ribot wrote: Hi Denis, In your example, I don't understand how the parts of your multipolygons can be adjacent. Are they valid ? Do you have a visual example ? Thank you Nicolas On 21 November 2013 07:32, Denis Rouzaud denis.rouz...@gmail.com wrote: Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
You welcome. In fact, thanks to you: I used to extract multipolygons boundaries with such queries (!!): st_exteriorRing((st_dumpRings( (st_dump(geom)).geom )).geom) as geom until your use case makes me remember st_boundary function :) Nicolas On 21 November 2013 15:51, Denis Rouzaud denis.rouz...@gmail.com wrote: wow, thanks a lot! indeed, much much nicer! thanks again, Denis On 21. 11. 13 15:47, Nicolas Ribot wrote: Thanks for the explanation. You could correct the multipolygons in one step, by using the st_buildArea function, that merges a linework of linestrings, preserving holes. To extract polygons boundaries as linestring, st_boundary() is very handy: The bad_multipg table contains invalid multipolygons with adjacent parts (http://imgur.com/MP6Cy4f) select gid, st_buildArea(st_boundary(geom)) from bad_multipg group by gid; Gives: http://imgur.com/RqlowFI Nicolas On 21 November 2013 13:50, Denis Rouzaud denis.rouz...@gmail.com wrote: Hi Nicolas, I edit my multi polygons in QGIS, and you're right the geometry becomes invalid if some parts have adjacent segments. In a simple case, I would have a multi polygons with 3 parts with 2 parts adjacent. http://imgur.com/zvxPFeR Although the geometry is invalid, my intention is to make it valid, and therefore merge the two parts, which is impossible in QGIS - AFAIK. So my intention was to save the geometry as this, and make it valid by a command. I could achieve this with a function: CREATE OR REPLACE FUNCTION distribution.simplemultipoly(geom geometry) RETURNS geometry AS $BODY$ DECLARE num_geom integer; BEGIN SELECT ST_NumGeometries(geom) into num_geom; SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geom,n FROM generate_series(1,num_geom) n INTO geom; RETURN geom; END; $BODY$ LANGUAGE plpgsql; But I wondered if there was a more direct way. Cheers, Denis On 21. 11. 13 12:42, Nicolas Ribot wrote: Hi Denis, In your example, I don't understand how the parts of your multipolygons can be adjacent. Are they valid ? Do you have a visual example ? Thank you Nicolas On 21 November 2013 07:32, Denis Rouzaud denis.rouz...@gmail.com wrote: Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
[postgis-users] simplifying (homogenize) a polygon
Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
Re: [postgis-users] simplifying (homogenize) a polygon
Hello Rémi, I was hoping a simplest request without enabling topology but thanks anyway! Cheers, Denis On 20. 11. 13 18:26, Rémi Cura wrote: From what I understand of your needs, Postigs topology was designed for this. Cheers, Rémi-C 2013/11/20 Denis Rouzaud denis.rouz...@gmail.com mailto:denis.rouz...@gmail.com Hi all, I am drawing some multipolygons in QGIS and sometimes, I have parts of them which are adjacent and I'd like to homogenize them to have less parts and no adjacent parts. I could do this with a quite complex method: 1. get the number of parts Z: SELECT ST_NumGeometries(geometry) FROMmytable WHERE id=123; 2. do the simplification using ST_CollectionHomogenize: SELECT ST_Multi(ST_CollectionHomogenize(ST_Union(ST_GeometryN(geometry,n FROM mytable CROSS JOIN generate_series(1,Z) n WHERE id = 123; 3. update manually the result in the table (copy paste). Does someone has something more straightforward??? Thanks a lot! Best regards, Denis ___ postgis-users mailing list postgis-users@lists.osgeo.org mailto:postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users ___ postgis-users mailing list postgis-users@lists.osgeo.org http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
