[postgis-users] Raster/vector intersections with PostGIS WKT Raster

[George Silva]

Congratulations on the great job done!

George

On Tue, Jun 29, 2010 at 12:55 PM, Nicolas Ribot <nicolas.ribot at gmail.com>wrote:

> Waoo !
> Real nice.
>
> Thank you for this work.
>
> Nicolas
>
> On 29 June 2010 17:29, Pierre Racine <Pierre.Racine at sbf.ulaval.ca> wrote:
> > Hi everybody,
> >
> > I'm pleased to announce that you can now do intersections between rasters
> and geometries very much like you used to do geometry/geometry intersections
> in PostGIS. For this, PostGIS WKT Raster introduces two new functions to
> PostGIS: ST_Intersects(geometry, raster, band) and ST_Intersection(geometry,
> raster, band).
> >
> > As its geometry/geometry sister, ST_Intersects(geometry, raster, band)
> returns TRUE if the withvalue area of a raster or a raster tile (nodata
> value are ignored) intersects a geometry and ST_Intersection(geometry,
> raster, band) returns the geometry/value set of geometries representing the
> intersection between the geometry and each polygonized group of pixel
> sharing a same value from the raster and its associated value. Example:
> >
> > SELECT polyid,
> >       (ST_Intersection(the_geom, rast)).geom,
> >       (ST_Intersection(the_geom, rast)).val
> > FROM my_polygons, srtm_tiled
> > WHERE ST_Intersects(rast, the_geom)
> >
> > or, a bit more complex, but much faster and returning the same result:
> >
> > SELECT polyid, (gv).geom, (gv).val
> > FROM (SELECT polyid, ST_Intersection(the_geom, rast, 1) AS gv
> >     FROM my_polygons, srtm_tiled
> >     WHERE ST_Intersects(rast, the_geom)) foo
> >
> > These functions works with any kind of geometry so you can intersect any
> road, river, polygons or point layer with your favorite elevation or land
> cover raster of any resolution and any size. You can also load any number of
> raster in the database with one command line to constitute a unique table
> raster coverage of any shape (no matter if your group of raster do not form
> a rectangular coverage).
> >
> > You will find a complete tutorial on how to use those two new functions
> here: http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01. A reference
> is available here:
> http://postgis.refractions.net/documentation/manual-svn/RT_reference.htmland chapter 13 of "PostGIS in Action" is also a very good introduction to
> WKT Raster.
> >
> > Compilation and installation info are available in the project home page:
> http://trac.osgeo.org/postgis/wiki/WKTRaster
> >
> > These features are the result of two years of collaboration between many
> people and companies interested in bringing raster into PostGIS. I would
> like to thanks particularly Steve Cumming who initially made all this
> possible, Sandro Santilli who wrote the base code, Mateusz Loskot who wrote
> the Python loader, Jorge Arevalo who wrote the GDAL driver and
> ST_DumpAsPolygons(), Regina and Leo Obe who are doing so many things and
> believed in the project from the beginning by adding a chapter about WKT
> Raster in "PostGIS in Action" and also David Zwarg who wrote most of the
> setter functions.
> >
> > This is the first step toward a first complete raster/vector analysis and
> manipulation SQL API. We hope to make of PostGIS with WKT Raster the most
> powerful and complete GIS analysis and manipulation high level language ever
> (!!!). WKT Raster should normally be totally integrated into PostGIS in
> PostGIS release 2.0. Upcoming functions should include ST_Reclass, ST_Clip,
> ST_AsRaster, ST_Resample.
> >
> > Let us know your need and your experience with WKT Raster.
> >
> > Thanks,
> >
> > Pierre Racine
> >
> > _______________________________________________
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> > postgis-users at postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
> >
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>



-- 
George R. C. Silva

Desenvolvimento em GIS
http://blog.geoprocessamento.net
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