[postgis-users] Raster geomval return integer

[Andreas Forø Tollefsen]

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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