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

[elliott]

It is just one SRTM3 tile which is 1201 x 1201.  The data is used by 
scientific codes to determine the elevation at a given latitude and 
longitude.

On 10/12/2011 2:35 PM, Nordgren, Bryce wrote:
> I'd be interested to know the size of the raster tile (width x height) which took 1/2 hour to retrieve all the info.
>
> On the other hand, the usage paradigm for raster is to use the utility functions, because this is what is fast. Plpgsql is not compiled, so it'll be slow to iterate over all the pixels. What are you trying to do with the data once you get it? Can you accomplish the same thing by making an "expression" and using ST_MapAlgebra?
>
> Bryce
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of elliott
> Sent: Wednesday, October 12, 2011 2:05 PM
> 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?
>
> Thanks!
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