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UPDATE: The SQL below works fine. My problem was a newbie mistake in using the Python psycopg2 functions to execute it. So I think I should just delete this question.

ORIGINAL QUESTION: I have a large number of possibly overlapping rasters and need to be able to sample all those that intersect a point at that point. My first attempt was to create a single table containing all of the rasters, and query as such:

SELECT ST_Value(rast, 1, ST_MakePoint(-122.0, 38.0))
FROM table_name
WHERE ST_Intersects(rast, ST_MakePoint(-122.0, 38.0));

This returns a value for one raster, but not all of the intersecting rasters. It seems that a single raster coverage table is not designed to be used this way.

Is the proper approach to create separate tables, grouping together non-overlapping rasters?

What is the best strategy?

I am hoping to keep everything in a single table if possible. I am pretty new to PostGIS and SQL.

  • I would investigate by displaying the raster extents in QGIS or OpenJump. SELECT rid, rast::geometry FROM table_name – Pierre Racine Oct 5 '17 at 13:55
  • Thank you for your suggestion, Pierre. It prompted me to do more testing and discover my problem. – Geoffrey Ely Oct 5 '17 at 20:33

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