1) Make sure ST_SRID on the geometries and ST_SRID on the raster give the same result.
2) Use OpenJump to display vector queries from PostGIS and make sure everything align properly. Pierre > -----Original Message----- > From: postgis-users-boun...@postgis.refractions.net [mailto:postgis-users- > boun...@postgis.refractions.net] On Behalf Of Ed Linde > Sent: Monday, February 27, 2012 9:25 AM > To: PostGIS Users Discussion > Subject: Re: [postgis-users] Raster + Geometry Intersection > > Hi Pierre, > I used --> /root/postgis-svn/raster/loader/raster2pgsql -s 4326 -t 50x50 -I > *.tif > public.srtm_tiled > elev.sql for the loading. The switch in args did not make > a > difference unfortunately! :( I am pretty sure that the OSM roads geometry used > SRID = 4326, and I think the arguments I have used to get in the tif files > with the > -s option also is right. > One warning I got while loading was (maybe it makes sense to you?) : > > /root/postgis-svn/raster/loader/raster2pgsql -s 4326 -t 50x50 -I *.tif > public.srtm_tiled > elev.sql Processing 1/4: srtm_38_01.tif Processing 2/4: > srtm_38_02.tif > WARNING: Different geotransform matrices found in the set of rasters being > converted to PostGIS raster Processing 3/4: srtm_39_01.tif Processing 4/4: > srtm_39_02.tif > > I tried loading the rasters and the roads in qgis, but it didn't manage to > show > them together, so I am not sure why its not aligning. I am sure its some sort > of > alignment issue, but do not see where its wrong. I am getting the SRTM files > from http://gis-lab.info/data/srtm-tif/ > And the OSM road was just the map for Denmark on OSM --> > http://download.geofabrik.de/osm/europe/ > > Is it possible for you to intersect these? I understand you are the author of > the > postgis tutorial that I am trying to follow to achieve the same...hence I > ask. :) > > Cheers, > Ed > > > > On Mon, Feb 27, 2012 at 2:58 PM, Pierre Racine <pierre.rac...@sbf.ulaval.ca> > wrote: > > > > > > -----Original Message----- > > From: postgis-users-boun...@postgis.refractions.net [mailto:postgis- > users- > > boun...@postgis.refractions.net] On Behalf Of Ed Linde > > Sent: Monday, February 27, 2012 7:21 AM > > To: postgis-users@postgis.refractions.net > > Subject: [postgis-users] Raster + Geometry Intersection > > > > Hi, > > I am trying to compute elevations for a road network that I have > downloaded > > and installed into my pg database using osm2pgsql. I also have loaded > SRTM tif > > files and they are stored as type RASTER in my table. > > I am now trying to compute an intersection between the SRTM rasters > and the > > OSM road geometries... with no luck! :( I am following this tutorial > --> > > http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01 > > but I think it might be slightly outdated. > > > The base queries to do the intersection are still valid. Only the > uploading > changed. And not much. > > > > SELECT o.osm_id, > > ST_Intersection(s.rast, o.way) > > FROM planet_osm_line o, > > srtm_tiled s > > WHERE ST_Intersects(s.rast, o.way); > > > > way type --> way geometry(LineString,900913) > > > > CREATE TABLE public.srtm_tiled > > ( > > rid integer NOT NULL DEFAULT > nextval('srtm_tiled_rid_seq'::regclass), > > rast raster, > > CONSTRAINT srtm_tiled_pkey PRIMARY KEY (rid) > > ) > > WITH ( > > OIDS=FALSE > > ); > > > > performing the above query returns no rows. So I am not sure what is > wrong.. or > > if I am doing this query correctly. Is the SRID set differently in the > raster and > > geometry? > > > You should do ST_Intersection(o.way , s.rast) instead of > ST_Intersection(s.rast, o.way). The first operates in the vector world and the > second in the raster world. Let me know if that makes a difference in terms of > results. > > Are the SRIDs identical? Did you make sure that the raster were loaded > properly by displaying values with ST_Value() or ST_DumpAsPolygons() or simply > displaying the raster in QGIS? Does the raster align with the roads properly? > > > > I also loaded the tif files using the tutorial, but I used the C > version not > the > > python loader because I understand its been deprecated. > > > Should not make any difference. > > Pierre > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > > _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
