[postgis-users] Raster + Geometry Intersection

[Ed Linde]

Hi,

I noticed that the OSM data is using srid = 900913. So I reloaded the tif
files as the same srid, yet
no luck with the intersection query! :(
*ALTER TABLE public.planet_osm_line ADD COLUMN way
geometry(LineString,900913);
*
Cheers,
Ed
On Mon, Feb 27, 2012 at 3:25 PM, Ed Linde <edolinde at gmail.com> wrote:

> Hi Pierre,
> I used --> */root/postgis-svn/raster/loader/raster2pgsql -s 4326 -t 50x50
> -I *.tif public.srtm_tiled > elev.sql*
> for the loading. The switch in args did not make a difference
> unfortunately! :(
> I am pretty sure that the OSM roads geometry used SRID = 4326, and I think
> the arguments I have
> used to get in the tif files with the -s option also is right.
> One warning I got while loading was (maybe it makes sense to you?) :
>
> */root/postgis-svn/raster/loader/raster2pgsql -s 4326 -t 50x50 -I *.tif
> public.srtm_tiled > elev.sql
> *Processing 1/4: srtm_38_01.tif
> Processing 2/4: srtm_38_02.tif
> *WARNING: Different geotransform matrices found in the set of rasters
> being converted to PostGIS raster
> *Processing 3/4: srtm_39_01.tif
> Processing 4/4: srtm_39_02.tif
>
> I tried loading the rasters and the roads in qgis, but it didn't manage to
> show them together, so I am not sure why its
> not aligning. I am sure its some sort of alignment issue, but do not see
> where its wrong. I am getting the SRTM files
> from http://gis-lab.info/data/srtm-tif/
> And the OSM road was just the map for Denmark on OSM -->
> http://download.geofabrik.de/osm/europe/
>
> Is it possible for you to intersect these? I understand you are the author
> of the postgis tutorial that I am trying to follow
> to achieve the same...hence I ask. :)
>
> Cheers,
> Ed
>
>
>
> On Mon, Feb 27, 2012 at 2:58 PM, Pierre Racine <
> Pierre.Racine at sbf.ulaval.ca> wrote:
>
>>
>>
>> > -----Original Message-----
>> > From: postgis-users-bounces at postgis.refractions.net [mailto:
>> postgis-users-
>> > bounces at postgis.refractions.net] On Behalf Of Ed Linde
>> > Sent: Monday, February 27, 2012 7:21 AM
>> > To: postgis-users at postgis.refractions.net
>> > Subject: [postgis-users] Raster + Geometry Intersection
>> >
>> > Hi,
>> > I am trying to compute elevations for a road network that I have
>> downloaded
>> > and installed into my pg database using osm2pgsql. I also have loaded
>> SRTM tif
>> > files and they are stored as type RASTER in my table.
>> > I am now trying to compute an intersection between the SRTM rasters and
>> the
>> > OSM road geometries... with no luck! :( I am following this tutorial -->
>> > http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01
>> > but I think it might be slightly outdated.
>>
>> The base queries to do the intersection are still valid. Only the
>> uploading changed. And not much.
>>
>> >  SELECT o.osm_id,
>> >         ST_Intersection(s.rast, o.way)
>> >  FROM planet_osm_line o,
>> >       srtm_tiled s
>> >  WHERE ST_Intersects(s.rast, o.way);
>> >
>> > way type -->   way geometry(LineString,900913)
>> >
>> > CREATE TABLE public.srtm_tiled
>> > (
>> >   rid integer NOT NULL DEFAULT nextval('srtm_tiled_rid_seq'::regclass),
>> >   rast raster,
>> >   CONSTRAINT srtm_tiled_pkey PRIMARY KEY (rid)
>> > )
>> > WITH (
>> >   OIDS=FALSE
>> > );
>> >
>> > performing the above query returns no rows. So I am not sure what is
>> wrong.. or
>> > if I am doing this query correctly. Is the SRID set differently in the
>> raster and
>> > geometry?
>>
>> You should do ST_Intersection(o.way , s.rast) instead of
>> ST_Intersection(s.rast, o.way). The first operates in the vector world and
>> the second in the raster world. Let me know if that makes a difference in
>> terms of results.
>>
>> Are the SRIDs identical? Did you make sure that the raster were loaded
>> properly by displaying values with ST_Value() or ST_DumpAsPolygons() or
>> simply displaying the raster in QGIS? Does the raster align with the roads
>> properly?
>>
>> > I also loaded the tif files using the tutorial, but I used the C
>> version not the
>> > python loader because I understand its been deprecated.
>>
>> Should not make any difference.
>>
>> Pierre
>> _______________________________________________
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>>
>
>
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