[postgis-users] Raster geomval return integer

[Bborie Park]

Only GDAL trunk (to become 1.9) provides the floating point support.
I don't believe the floating point support will be backported to 1.8
as it is a new function to GDAL.

-bborie

On Thu, Oct 27, 2011 at 8:11 AM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca> wrote:
> 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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-- 
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
bkpark at ucdavis.edu