[postgis-users] Using Postgis raster for water elevation

Rémi Cura remi.cura at gmail.com
Wed May 27 06:31:14 PDT 2015


Map Algebra?
(custom function with a thresholding?)


2015-05-27 14:57 GMT+02:00 Gabriel Vatin <gabriel.vatin at kinaxia.fr>:

> Hello all,
> I'd like to have some feedbacks on an operation that should be possible
> with Postgis raster, but I can't find out how to do this.
> I have a whole raster of French DEM (elevation data) stored on PostGis,
> with tiled objects. That makes a table with some 14.000 rows of data:
> france_mnt (rid, rast, filename)
> With ST_Value(france_mnt.rast, geometry), I can retrieve the elevation of
> a given coordinates in the geometry object.
> I'd like to create a new raster, on the fly, with a maximum value of
> elevation, such as : all pixels with value < 10
> This could be used for mapping water elevation in a area, for instance.
> Anyone has already done this? I'll be happy to have some tips on the
> function to use.
> Thanks!
> Gabriel
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