Hi Mark, Can you elaborate on what you mean by "resultant raster does not map to the reference raster"?
The output from ST_AsRaster should result in a raster with the same SRID, scale and skew as the reference raster. The output raster should also be aligned with the reference raster as tested by ST_SameAlignment. -bborie On 06/23/2012 11:04 PM, Mark Wynter wrote: > I can rasterise a vector layer, but I'm having trouble mapping it to a > reference raster. > > The reference raster, called dummy_rast is a 1x1 raster tile with a height > and width of 500pixels, each of 250m in size. I created using a pl/pgsql > function: > SELECT make_tiled_raster('public', 'dummy_rast', 576000, -3780000, 1, 1, 500, > 500, 250, -250); > The result is > > srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | > pixel_types | nodata_values > ------+---------+---------+-------------+-------------+-----------+-------------+--------------- > 3577 | 250 | -250 | 500 | 500 | 1 | {8BUI} > | {NULL} > > > I now wish to burn a vector layer onto this raster: > > CREATE TABLE viewshed_rast AS > WITH vt as (SELECT ST_Union(geometry) as geometry FROM viewshed_vectors) > SELECT rt.rid, ST_AsRaster(vt.geometry, rt.rast, '8BUI', 120, 100) as rast > FROM dummy_rast as rt, vt; > > The result is > srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | > pixel_types | nodata_values > ------+---------+---------+-------------+-------------+-----------+-------------+--------------- > 3577 | 250 | -250 | 67 | 38 | 1 | {8BUI} > | {100} > (1 row) > > I do not understand why the resultant raster does not map to the reference > raster? Refer screenshot attached showing the resultant layers in QGIS. > The upperleftx and upperlefty, and the block size of the resultant raster are > defined by the extent of the vector layer and not the reference raster. > > Is there something obvious I'm doing wrong? Thanks. > > > > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users -- Bborie Park Programmer Center for Vectorborne Diseases UC Davis 530-752-8380 bkp...@ucdavis.edu _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users