[postgis-users] Using Postgis raster for water elevation

[Gabriel Vatin]

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