There are two strategies to convert a table composed of many geometries to a raster coverage:
1) ST_AsRaster each geometries, ST_Union them and then ST_Tile them. 2) Use ST_ExtractToRaster() from the PostGIS Add-ons. I plan to blog about this as soon as I get 400 times 5 minutes... Pierre > -----Original Message----- > From: [email protected] [mailto:postgis-users- > [email protected]] On Behalf Of georgew > Sent: Thursday, April 17, 2014 7:25 AM > To: [email protected] > Subject: [postgis-users] Postgis raster tutorial > > As a new raster user I have found it extremely difficult to come to grips > with the task of creating a raster table with postgis, in particular from an > existing vector table, a task which is really trivial when done with some > existing s/w packages ( i.e. SAGA, GRASS etc..). Most of the examples I > could find were based on the use of raster2pgsql which implies the prior > existence of a raster file created with an external package, not on using > postgis native capabilities to create such a raster. If you already have a > raster file, postgis has no problem creating a table from it, but what if > you don't? Should you be forced to use one of the external packages? > The postgis manual has a total of two (2) examples on how to create a > raster > table with st_asraster, although there are ten (10) different variants. My > point is not a criticism of postgis raster, at the contrary, a suggestion > that it could be much more useful if properly explained to users not > familiar with it. In other words a good postgis raster tutorial would go a > long way to convince users to at least try postgis raster by itself without > recourse to external packages (except perhaps for the visualisation of the > rasters). Specifically, how to create with postgis a raster table from a > vector table, how to extract values from one of the vector attributes and > store them in the raster, resulting in a raster identical to what would have > been created with raster2pgsql. I, with my ignorance of the topic, have not > been able to do that yet. > If such a tutorial has already appeared somewhere I would be delighted to > be > pointed in that direction. > Many thanks > > > > > -- > View this message in context: http://postgis.17.x6.nabble.com/Postgis- > raster-tutorial-tp5006124.html > Sent from the PostGIS - User mailing list archive at Nabble.com. > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
