[postgis-users] Raster geomval return integer

[Pierre Racine]

Could you give it a try?

> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
> bounces at postgis.refractions.net] On Behalf Of Andreas Forø Tollefsen
> Sent: Thursday, October 27, 2011 11:00 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] Raster geomval return integer
> 
> Hi, I have 1.8.1
> "POSTGIS="2.0.0SVN" GEOS="3.3.1-CAPI-1.7.1" PROJ="Rel. 4.7.1, 23 September
> 2009" GDAL="GDAL 1.8.1, released 2011/07/09" LIBXML="2.7.8"
> USE_STATS"
> Should i update to latest subversion?
> 
> Andreas
> 
> 2011/10/27 Pierre Racine <Pierre.Racine at sbf.ulaval.ca>:
> > Ticket 650 was fixed in PostGIS and in the GDAL trunk. The ticket says "New
> GDAL polygonize function implemented in GDAL release 22476 (
> http://trac.osgeo.org/gdal/changeset/22476). Please, update your GDAL copy
> to a release"
> >
> > What version of libgdal do you have?
> >
> >> -----Original Message-----
> >> From: postgis-users-bounces at postgis.refractions.net
> >> [mailto:postgis-users- bounces at postgis.refractions.net] On Behalf Of
> >> Andreas Forø Tollefsen
> >> Sent: Thursday, October 27, 2011 7:59 AM
> >> To: PostGIS Users Discussion
> >> Subject: Re: [postgis-users] Raster geomval return integer
> >>
> >> Replying to my own post.
> >>
> >> Just to confirm my belief I used the raster calculator in QGIS and
> >> calculated 'rast*100'.
> >> Then imported it to postgis and ran the query again:
> >>
> >> SELECT gid,(foo.geomval).val,
> >> CAST(SUM(ST_Area((foo.geomval).geom)) AS decimal(8,5)) as area,
> >> CAST(SUM(ST_Area((foo.geomval).geom))/0.25*100 AS decimal(6,3)) as
> >> percentarea FROM (SELECT p.gid,
> >> ST_Intersection(ST_SetSRID(p.cell,4326),
> >> ST_SetSRID(r.rast,4326), 1) AS geomval FROM mountain r, priogrid_land
> >> p WHERE ST_Intersects(ST_SetSRID(p.cell,4326),
> >> ST_SetSRID(r.rast,4326),1)) AS foo WHERE gid = 183230 AND
> >> (foo.geomval).val >= 0 GROUP BY gid, (foo.geomval).val ORDER BY gid;
> >>
> >> Result:
> >> 183230;74;0.00000;0.000
> >> 183230;33;0.00694;2.778
> >> 183230;80;0.00000;0.000
> >> 183230;16;0.00694;2.778
> >> 183230;9;0.00694;2.778
> >> 183230;100;0.04167;16.666
> >> 183230;73;0.00694;2.778
> >> 183230;89;0.00694;2.778
> >> 183230;71;0.00694;2.777
> >> 183230;22;0.00694;2.778
> >> 183230;35;0.00000;0.000
> >> 183230;48;0.00000;0.000
> >> 183230;59;0.00694;2.778
> >> 183230;0;0.13889;55.555
> >> 183230;12;0.00000;0.000
> >> 183230;6;0.00694;2.778
> >> 183230;1;0.00695;2.778
> >>
> >> I can of course do this with any raster including a decimal pixel
> >> value, but I really would like to not have to.
> >>
> >> Any ideas?
> >>
> >> Andreas
> >>
> >>
> >> 2011/10/27 Andreas Forø Tollefsen <andreasft at gmail.com>:
> >> > Hi all,
> >> >
> >> > I have been working on this issue previously, but now we have
> >> > updated to rev 8001 and the ticket 650 is fixed.
> >> > Hence, I wanted to see if I can calculate the average pixelvalue
> >> > within my grid cells (.5x.5 decimal degrees).
> >> >
> >> > However, I now experience that any value above 0 becomes 1, and i
> >> > do not get the actual averaged value.
> >> > I also tested to group by the polygonized pixel value, and this
> >> > revealed that everything other than 0 is 1.
> >> > According to my raster this is not correct, since I have many other
> >> > values within the cells borders (see jpg).
> >> >
> >> > I have tried to use the ST_Value(rast,
> >> > ST_SetSRID(ST_Point(lat,long)) and this give me the correct pixel values.
> >> > However, I do not understand what is giving me integer values using
> >> > the query below.
> >> >
> >> > Any ideas on what is wrong with my query?
> >> >
> >> > Query:
> >> > SELECT gid,CAST(((foo.geomval).val) AS decimal(8,6)) AS mntval,
> >> > CAST(SUM(ST_Area((foo.geomval).geom)) AS decimal(8,5)) as area,
> >> > CAST(SUM(ST_Area((foo.geomval).geom))/0.25*100 AS decimal(6,3)) as
> >> > percentarea FROM (SELECT p.gid,
> >> > ST_Intersection(ST_SetSRID(r.rast,4326),
> >> > ST_SetSRID(p.cell,4326)) AS geomval FROM mountain r, priogrid_land
> >> > p WHERE ST_Intersects(ST_SetSRID(p.cell,4326),
> >> > ST_SetSRID(r.rast,4326))) AS foo WHERE gid = 183230 AND
> >> > (foo.geomval).val >= 0 GROUP BY gid, (foo.geomval).val ORDER BY
> >> > gid;
> >> >
> >> > Result:
> >> > 183230;1.000000;0.06945;27.778
> >> > 183230;0.000000;0.18055;72.222
> >> >
> >> >
> >> > Best,
> >> > Andreas
> >> >
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