[postgis-users] raster extent and performance problem... anyone?
woklist at kyngchaos.com
Thu Aug 23 06:46:21 PDT 2012
I created a raster table for a large area of DEM data, with index and constraints, no overviews. When I run gdalinfo on the table, it takes about 15m to query to get the extents, which are then wrong.
Original 32bit float geotiffs = 27GiB (uncompressed), 84W, 36N to 71W, 45.5N (not complete coverage)
In PostGIS = 25GiB, 74W, 33.5N to 61W, 43N
There are 15936 records in the table, which matches the number of input TIFFs and the tile size I used (actually 22 more than the input), so it looks like all the data was imported.
It looks like the data was shifted 10 deg east and 2.5 deg south.
When I try to extract a region from that with gdal_translate, it takes the 15m to check the extants again, then extracts garbage.
I'm just getting started with PG rasters and don't know enough about the SQL needed to check within PG if everything is OK there or not (extents, extract some data to tif) or if it's a GDAL problem.
A GDAL vrt of the geotiffs processes quickly and reports the correct extents.
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
"Time is an illusion - lunchtime doubly so."
- Ford Prefect
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