[postgis-users] Raster + Geometry Intersection

Ed Linde edolinde at gmail.com
Mon Feb 27 06:59:43 PST 2012


ok, just to get this right.. :) , you are suggesting I keep my OSM as is
(id: 900913). Load in the tif rasters as srid (4326) and then "reproject"
the OSM road geometry to srid = 4326 right? So it matches the srid of my
raster! I ask because you said to reproject to 900913 in your mail.

Cheers,
Ed

On Mon, Feb 27, 2012 at 3:53 PM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca>wrote:

> > I checked the srids of the geometry and the rasters and they are both
> now set to
> > --> 900913!
>
> But you loaded the raster with -s 900913. Right? That does not make the
> raster coordinates to be transformed. You actually corrupted your rasters.
> You have to load them in their proper srid (4326) and reproject them
> afterward (or reproject the geometries) to 900913. I would go with
> reprojecting the geometries.
>
> > I was using qgis and I think I made a mistake because I think the tif
> files on disk
> > are using srid = 4326, while the postgis layer I added was using 900913
> for osm.
> > I have never used OpenJump.. is it possible to view both my raster and
> road
> > geometries from postgis on to qgis? Or you recommend installing OpenJump?
>
> I do. It's still the best/stable tool to work both raster and vectors. You
> can't display raster but you can display their extent and their
> vectorization (with ST_DumpAsPolygon()) as in the tutorial.
>
> > Also, do I still need to do some sort of reprojection on the geometries?
> Is the
> > SRID of 900913 reported for my rasters...reliable information?
>
> Again, the loader do not reproject. It just assign the srid you tell him.
> You have to reproject at some point (before or after loading, before or
> while intersecting).
>
> Pierre
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