[postgis-users] raster intersect with polygon resulting in false NULL value

Wed Aug 21 13:05:01 PDT 2013

Hailey,

Can you run a query such as the following and post the results? I had to do
a double-take for the ST_SummaryStatsAgg() function as I'm not familiar
with that function.

WITH foo AS (
SELECT * FROM zben_allwshds WHERE bid = 61
)
SELECT
a.rid,
 ST_SummaryStats(ST_Clip(a.rast,1, f.geom, true))
FROM aet_1 a
JOIN foo f
ON ST_Intersects(a.rast, f.geom)

I'm suspecting that ST_SummaryStatsAgg() is having an issue where one
tile's summary stats has NULL values being combined with the aggregate
summary stats.

-bborie

On Wed, Aug 21, 2013 at 12:26 PM, Hailey Eckstrand <
haileyeckstrand at gmail.com> wrote:

> Hello,
> I am trying perform aggregate statistics on a raster vector overlay with a
> polygon of 192 sub polys. Many of the resulting 192 mean values are
> correct.. however, I am encountering that one vector overlay mean is NULL
> which I know to be incorrect. The polygon and raster are in the same
> projection and when I look at them in QGIS they are overlaid correctly and
> I can see that the polygon is over top of ~30 raster cells that are all the
> value 3 (it is not over top of any NA values). One thing that is sort of
> fishy is that QGIS is reading the raster statistics and no data value
> incorrectly (values included below) compared to the base ascii raster
> gdalinfo which is included below.
>
> My query:
>
> select bid,(ST_SummaryStatsAgg(ST_Clip(rast,1, geom, true))).mean
> FROM aet_1,(select * from zben_allwshds where bid = 61) foo
> WHERE ST_Intersects(rast, geom)
> GROUP BY bid
> order by bid;
> NOTICE:  The two rasters provided have no intersection.  Returning no band
> raster
> CONTEXT:  PL/pgSQL function "st_clip" line 39 at assignment
> NOTICE:  Could not find raster band of index 1 when setting pixel value.
> Nodata value not set. Returning original raster
> CONTEXT:  PL/pgSQL function "st_clip" line 41 at assignment
> NOTICE:  Invalid band index (must use 1-based). Returning NULL
> CONTEXT:  PL/pgSQL function "raster_summarystatsstate" line 9 at assignment
> SQL function "raster_summarystatsstate" statement 1
>  bid | mean
> -----+------
>   61 |
>
>
> Query which returns all the Summary Stats (order of stats is count | sum |
> mean | stddev | min | max)
>
> select bid,(ST_SummaryStatsAgg(ST_Clip(rast,1, geom, true)))
> FROM aet_1,(select * from zben_allwshds where bid = 61) foo
> WHERE ST_Intersects(rast, geom)
> GROUP BY bid
> order by bid;
> NOTICE:  The two rasters provided have no intersection.  Returning no band
> raster
> CONTEXT:  PL/pgSQL function "st_clip" line 39 at assignment
> NOTICE:  Could not find raster band of index 1 when setting pixel value.
> Nodata value not set. Returning original raster
> CONTEXT:  PL/pgSQL function "st_clip" line 41 at assignment
> NOTICE:  Invalid band index (must use 1-based). Returning NULL
> CONTEXT:  PL/pgSQL function "raster_summarystatsstate" line 9 at assignment
> SQL function "raster_summarystatsstate" statement 1
>  bid | st_summarystatsagg
> -----+--------------------
>   61 | (,237,,,3,3)
>
>
>
> The raster was loaded into postgresql with the raster2pgsql tool:
>
> raster2pgsql -s 3005 -I -C -M aet_1.asc -F -t 100x100 public.aet_1 | psql
> -d NWBC
>
> gdalinfo of the loaded raster:
>
> gdalinfo aet_1.asc
> Driver: AAIGrid/Arc/Info ASCII Grid
> Files: aet_1.asc
>        aet_1.asc.aux.xml
> Size is 2331, 2895
>  Coordinate System is `'
> Origin = (173461.904000000009546,1929781.912000000011176)
> Pixel Size = (400.000000000000000,-400.000000000000000)
> Corner Coordinates:
> Upper Left  (  173461.904, 1929781.912)
> Lower Left  (  173461.904,  771781.912)
> Upper Right ( 1105861.904, 1929781.912)
> Lower Right ( 1105861.904,  771781.912)
> Center      (  639661.904, 1350781.912)
> Band 1 Block=2331x1 Type=Float32, ColorInterp=Undefined
>   Min=0.000 Max=9.000
>   Minimum=0.000, Maximum=9.000, Mean=1.955, StdDev=2.375
>   NoData Value=-9999
>   Metadata:
>     STATISTICS_MAXIMUM=9
>     STATISTICS_MEAN=1.9546895049572
>     STATISTICS_MINIMUM=0
>     STATISTICS_STDDEV=2.3747620319231
>
> Incorrect QGIS Raster Statistics:
>
> STATISTICS_MAXIMUM=1.2341209168929e+033
>
> STATISTICS_MEAN=5.9293249344197e+031
>
> STATISTICS_MINIMUM=-9999
>
> STATISTICS_STDDEV=2.4574481861697e+032
>
> NODATA VALUE= -32768
>
> PostGIS raster info:
>
>   rid serial NOT NULL,
>   rast raster,
>   filename text,
>   CONSTRAINT aet_1_pkey PRIMARY KEY (rid),
>   CONSTRAINT enforce_height_rast CHECK (st_height(rast) = 100),
>   CONSTRAINT enforce_max_extent_rast CHECK
> (st_coveredby(st_convexhull(rast),
> '0103000020BD0B000001000000050000001D5A643BAF2C0541FCA9F1D2EB7D27411D5A643BAF2C0541FED478E935723D41448B6CE7954B3141FED478E935723D41448B6CE7954B3141FCA9F1D2EB7D27411D5A643BAF2C0541FCA9F1D2EB7D2741'::geometry)),
>   CONSTRAINT enforce_nodata_values_rast CHECK
> (_raster_constraint_nodata_values(rast)::numeric(16,10)[] =
> '{-9999}'::numeric(16,10)[]),
>   CONSTRAINT enforce_num_bands_rast CHECK (st_numbands(rast) = 1),
>   CONSTRAINT enforce_out_db_rast CHECK (_raster_constraint_out_db(rast) =
> '{f}'::boolean[]),
>   CONSTRAINT enforce_pixel_types_rast CHECK
> (_raster_constraint_pixel_types(rast) = '{32BF}'::text[]),
>   CONSTRAINT enforce_same_alignment_rast CHECK (st_samealignment(rast,
> '0100000000000000000000794000000000000079C01D5A643BAF2C0541FED478E935723D4100000000000000000000000000000000BD0B000001000100'::raster)),
>   CONSTRAINT enforce_scalex_rast CHECK (st_scalex(rast)::numeric(16,10) =
> 400::numeric(16,10)),
>   CONSTRAINT enforce_scaley_rast CHECK (st_scaley(rast)::numeric(16,10) =
> (-400)::numeric(16,10)),
>   CONSTRAINT enforce_srid_rast CHECK (st_srid(rast) = 3005),
>   CONSTRAINT enforce_width_rast CHECK (st_width(rast) = 100)
>
>
>
> Install info:
>
> PostgreSQL Version 9.1
>
> postgis_full_version:
>  POSTGIS="2.0.1 r9979" GEOS="3.3.8-CAPI-1.7.8" PROJ="Rel. 4.8.0, 6 March
> 2012" GDAL="GDAL 1.9.2, released 2012/10/08" LIBXML="2.7.8" TOPOLOGY RASTER
> (1 row)
>
> QGIS version:
> 1.8.0-Lisboa
> Compiled against GDAL/OGR
> 1.9.2
> Running against GDAL/OGR
> 1.9.2
> GEOS Version
> 3.3.8
> PostgreSQL Client Version
> 8.3.10
>
>
> Sorry for all the extra information, I just don't know what people need to
> know to help. Thanks in advance!
>
> Hailey
>
>
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>
>
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