[postgis-users] Retrieving Data from PostGIS Raster using ST_Value

Pierre Racine Pierre.Racine at sbf.ulaval.ca
Wed Oct 12 17:34:34 PDT 2011

If you want to get all the values for every pixel do:

SELECT (ST_DumpAsPolyogns(rast)).val
FROM your table

Can I ask why you want to do that? Normally people want to extract values intersecting with a polygon or a point.

You can also get the histogram of the raster using ST_Histogram().

From: postgis-users-bounces at postgis.refractions.net [postgis-users-bounces at postgis.refractions.net] On Behalf Of elliott [elliott at cpi.com]
Sent: Wednesday, October 12, 2011 9:04 AM
To: PostGIS Users Discussion
Subject: [postgis-users] Retrieving Data from PostGIS Raster using ST_Value

Hello Everyone,

I am very new to using PostGIS Raster.  I need to retrieve data fields
from a tile loaded into the database.  Using ST_Height and ST_Width, I
get the number of rows and columns and iterate over these using the
ST_Value to retrieve the data.  This is extremely slow taking 1/2 hour
to get all of the data required.  Is there a faster way to accomplish this?

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