[postgis-users] Raster geomval return integer

[Pierre Racine]

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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