PostGIS
Name
ST_SummaryStats — Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.
Synopsis
summarystats +`*`+ST_SummaryStats*(`raster `rast, boolean
exclude_nodata_value`)`;
summarystats +`*`+ST_SummaryStats*(`raster `rast, integer
nband, boolean exclude_nodata_value`)`;
Description
Returns summarystats consisting of count, sum,
mean, stddev, min, max for a given raster band of a raster or raster
coverage. If no band is specified nband defaults to 1.
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Changed: 3.1.0 ST_SummaryStats(rastertable, rastercolumn, …) variants are removed. Use ST_SummaryStatsAgg instead.
Availability: 2.0.0
Example: Single raster tile
SELECT rid, band, (stats).*
FROM (SELECT rid, band, ST_SummaryStats(rast, band) As stats
FROM dummy_rast CROSS JOIN generate_series(1,3) As band
WHERE rid=2) As foo;
rid | band | count | sum | mean | stddev | min | max
-----+------+-------+------+------------+-----------+-----+-----
2 | 1 | 23 | 5821 | 253.086957 | 1.248061 | 250 | 254
2 | 2 | 25 | 3682 | 147.28 | 59.862188 | 78 | 254
2 | 3 | 25 | 3290 | 131.6 | 61.647384 | 62 | 254Example: Summarize pixels that intersect buildings of interest
This example took 574ms on PostGIS windows 64-bit with all of Boston Buildings and aerial Tiles (tiles each 150x150 pixels ~ 134,000 tiles), ~102,000 building records
WITH
-- our features of interest
feat AS (SELECT gid As building_id, geom_26986 As geom FROM buildings AS b
WHERE gid IN(100, 103,150)
),
-- clip band 2 of raster tiles to boundaries of builds
-- then get stats for these clipped regions
b_stats AS
(SELECT building_id, (stats).*
FROM (SELECT building_id, ST_SummaryStats(ST_Clip(rast,2,geom)) As stats
FROM aerials.boston
INNER JOIN feat
ON ST_Intersects(feat.geom,rast)
) As foo
)
-- finally summarize stats
SELECT building_id, SUM(count) As num_pixels
, MIN(min) As min_pval
, MAX(max) As max_pval
, SUM(mean*count)/SUM(count) As avg_pval
FROM b_stats
WHERE count > 0
GROUP BY building_id
ORDER BY building_id;
building_id | num_pixels | min_pval | max_pval | avg_pval
-------------+------------+----------+----------+------------------
100 | 1090 | 1 | 255 | 61.0697247706422
103 | 655 | 7 | 182 | 70.5038167938931
150 | 895 | 2 | 252 | 185.642458100559Example: Raster coverage
-- stats for each band --
SELECT band, (stats).*
FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band) As stats
FROM generate_series(1,3) As band) As foo;
band | count | sum | mean | stddev | min | max
------+---------+--------+------------------+------------------+-----+-----
1 | 8450000 | 725799 | 82.7064349112426 | 45.6800222638537 | 0 | 255
2 | 8450000 | 700487 | 81.4197705325444 | 44.2161184161765 | 0 | 255
3 | 8450000 | 575943 | 74.682739408284 | 44.2143885481407 | 0 | 255
-- For a table -- will get better speed if set sampling to less than 100%
-- Here we set to 25% and get a much faster answer
SELECT band, (stats).*
FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band,true,0.25) As stats
FROM generate_series(1,3) As band) As foo;
band | count | sum | mean | stddev | min | max
------+---------+--------+------------------+------------------+-----+-----
1 | 2112500 | 180686 | 82.6890480473373 | 45.6961043857248 | 0 | 255
2 | 2112500 | 174571 | 81.448503668639 | 44.2252623171821 | 0 | 255
3 | 2112500 | 144364 | 74.6765884023669 | 44.2014869384578 | 0 | 255