Gilles, Glad you could build WKT Raster and it's working fine.
In order "to extract cells having "value > n" and build a polygon from those" you would need ST_SelectByValue(raster, ‘expression’) which would return a raster containing only the selected pixels (the others being filled with NODATA values) and then ST_AsPolygon(raster) which will convert every group of contiguous pixel with same value to a polygon. These two functions are planned but unfortunately not implemented yet. If you can give a hand you are welcome. ST_AsPolygon(raster) is planned to be implemented very soon but not ST_SelectByValue(raster, ‘expression’). Pierre >-----Original Message----- >From: [email protected] [mailto:postgis-users- >[email protected]] On Behalf Of Gilles Bassière >Sent: 2 novembre 2009 18:34 >To: PostGIS Users Discussion >Subject: Re: [postgis-users] Unable to build WKT Raster > >Mateusz Loskot wrote: >> The WKT Raster README file available from >> http://trac.osgeo.org/postgis/browser/spike/wktraster/README >> says >> >> "latest 1.3.5 release won't work" >> > >I've seen this indeed but was confused by other sources of documentation. > >In the meantime, I've managed to build PostGIS 1.4 and WKT raster >against it. It seems to work fine except that "make install" try to copy >gdal2wktraster.py directly to postgresql bin dir, ignoring the custom >prefix. Anyway, I copied the file manually and wktraster is now all set up. > >I've been able to load an SRTM tile and fetch individual values using >st_value. What I'd like to do is to extract cells having "value > n" and >build a polygon from those. Is this the kind of query wkt raster is >intended to support? > >Regards > >-- >Gilles Bassière - MAKINA CORPUS >http://www.makina-corpus.com >_______________________________________________ >postgis-users mailing list >[email protected] >http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
