Hi, Thank you for the tips.
Well, I don't know why, but the st_clip function doesn't seem work fine. After clipping and dumping each pixel as point, some points follow tiles, others follow the geometry. Any idea why ? For now, to avoid the problem, I apply a St_ContainsProperly after the dump. [image: unnamed.png] Red : geometry Light blue : tiles Dark blue : pixels as points Thank you for your help ! Pierre Le ven. 15 juil. 2016 à 17:28, Pierre Racine <pierre.rac...@sbf.ulaval.ca> a écrit : > Sorry for the late answer. > > You have to vectorize them on the fly from within OpenJump: > > SELECT (ST_DumpAsPolygons(rast).* FROM yourrastertable; > > If your raster is very big and tiled, just vectorize the tiles you need: > > SELECT rid, rast::geometry FROM yourrastertable; > > Look at the rids and then: > > SELECT (ST_DumpAsPolygons(rast).* FROM yourrastertable > WHERE rid = x or rid = y > > Pierre > > > -----Original Message----- > > From: postgis-users [mailto:postgis-users-boun...@lists.osgeo.org] On > Behalf > > Of Pierre Bails > > Sent: Friday, June 24, 2016 12:32 PM > > To: PostGIS Users Discussion <postgis-users@lists.osgeo.org> > > Subject: Re: [postgis-users] Raster tile size impact results > > > > Hello, > > > > Unfortunatly, I don't find a way to print raster results in OpenJump. > Can you > > explain me how I can do it ? > > > > Thank you for your help ! > > > > Pierre > > > > Le lun. 20 juin 2016 à 16:16, Pierre Racine <pierre.rac...@sbf.ulaval.ca > > <mailto:pierre.rac...@sbf.ulaval.ca> > a écrit : > > > > > > I would try to understand, visually using OpenJump, how your tiles > are > > clipped in the two cases... I guess sometimes 1 pixel wide tiles get > clipped in a > > strange way. > > > > Pierre > > > > > -----Original Message----- > > > From: postgis-users [mailto: > postgis-users-boun...@lists.osgeo.org > > <mailto:postgis-users-boun...@lists.osgeo.org> ] On Behalf > > > Of Pierre Bails > > > Sent: Wednesday, June 15, 2016 11:41 AM > > > To: postgis-users@lists.osgeo.org <mailto:postgis- > > us...@lists.osgeo.org> > > > Subject: [postgis-users] Raster tile size impact results > > > > > > Hi all, > > > > > > I'm looking for get all pixel's value in a raster insert thanks > to > > raster2pgsql > > > intersect by a polygon. > > > Nevertheless, there are some things that I don't understand: > depends > > on tile > > > size, I don't have the same result... The error between 2 raster > is also > > correlate > > > to the pixel size (I assume it's due to the pixel number). > > > > > > Can you explain me how the tile size can influence the final > result ? > > > > > > Here is the query : > > > SELECT DISTINCT SUM((px).val) > > > FROM( > > > SELECT * > > > FROM mns INNER JOIN > > > > > > st_setsrid(st_geomfromgeojson('{"type":"Polygon","coordinates":[[[x,y],[x,y],[x > > > ,y] ]]}'), 4326) as geom on ST_Intersects(mns.rast, geom) > > > ) AS clip, ST_PixelAsCentroids (ST_Clip(clip.rast, clip.geom),1) > AS px; > > > > > > > > > DSM px size 70cm: > > > raster2pgsql -a -t 250x250 -s 4326 -F pathToDSM.tiff dsmTable > (result: > > 46 347 > > > 846) > > > > > > raster2pgsql -a -t 50x50 -s 4326 -F pathToDSM.tiff dsmTable : > 46 382 > > 873 > > > Difference: 35027 > > > > > > > > > DSM px size 20cm : > > > raster2pgsql -a -t 250x250 -s 4326 -F pathToDSM.tiff dsmTable : > 567 > > 505 888 > > > > > > raster2pgsql -a -t 50x50 -s 4326 -F pathToDSM.tiff dsmTable : > 596 > > 897 610 > > > Difference: 29 391 722 > > > > > > > > > If we considere 250x250's result as reference, there is a > difference of > > 0.07% in > > > the first case, and 5% in the second. If the polygon area > increases, the > > error rate > > > increases. > > > > > > Thank you, > > > > > > Pierre > > _______________________________________________ > > postgis-users mailing list > > postgis-users@lists.osgeo.org <mailto: > postgis-users@lists.osgeo.org> > > http://lists.osgeo.org/mailman/listinfo/postgis-users > > _______________________________________________ > postgis-users mailing list > postgis-users@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/postgis-users
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