Yes. The result of that query is the value for the first pixel. If you're going to dump out all the values of all tiles, you're better off with something like ST_DumpValues instead...
http://postgis.net/docs/manual-2.1/RT_ST_DumpValues.html If you're scanning the whole MODIS scene(s), nothing beats the performance of directly going to the files. Since you're new, two bits of advice... 1. If your raster data is read-only, keep the raster data outside the database using out-db (raster2pgsql's -R flag) 2. There is no optimal tile size for storing data in-db as that is highly dependent on the source raster data (# of bands, pixel types of each band). For out-db though, I strongly recommend using the block size specified by the output of gdalinfo. The reason for this is that GDAL is used to get the data from the out-db raster. $ gdalinfo myraster.tif Driver: GTiff/GeoTIFF Files: myraster.tif Size is 1405, 621 Coordinate System is: GEOGCS["NAD83", DATUM["North_American_Datum_1983", SPHEROID["GRS 1980",6378137,298.2572221010002, AUTHORITY["EPSG","7019"]], AUTHORITY["EPSG","6269"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4269"]] Origin = (-125.020833333333329,49.937500000002032) Pixel Size = (0.041666666666670,-0.041666666666670) Metadata: AREA_OR_POINT=Area Image Structure Metadata: INTERLEAVE=BAND Corner Coordinates: Upper Left (-125.0208333, 49.9375000) (125d 1'15.00"W, 49d56'15.00"N) Lower Left (-125.0208333, 24.0625000) (125d 1'15.00"W, 24d 3'45.00"N) Upper Right ( -66.4791667, 49.9375000) ( 66d28'45.00"W, 49d56'15.00"N) Lower Right ( -66.4791667, 24.0625000) ( 66d28'45.00"W, 24d 3'45.00"N) Center ( -95.7500000, 37.0000000) ( 95d45' 0.00"W, 37d 0' 0.00"N) Band 1 *Block=1405x1* Type=Float32, ColorInterp=Gray Min=10.920 Max=49.370 Minimum=10.920, Maximum=49.370, Mean=29.345, StdDev=5.782 NoData Value=-9999 -bborie On Tue, Apr 21, 2015 at 9:18 AM, Albury, Carl -FS <[email protected]> wrote: > Hi > > I’m new to PostGIS so please bear with me. > > I’m working with MODIS data that I tiled using the auto tile switch in > raster2pgsql resulting in 13250 82x94 tiles. > > When I try to query for pixel values using ST_Value, such as: > > > > SELECT > > ST_Value(rast, 2, 1,1) -- multiband raster > > FROM > > MODIS_test; > > > > I get a value for each tile, not for each pixel (I assume the value is for > the first pixel in the tile?). > > If I want to query each pixel do I need to loop through each tile and have > a sub loop for each pixel in that tile? If so I can’t figure out the syntax > to designate the tiles vs pixels. > > > > Thanks very much, > > Carl > > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >
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