[postgis-users] PostGIS Raster efficient enough to get height given coords from a large DEM?

[Bborie Park]

On Sun, Dec 4, 2011 at 12:10 AM, Volkmar Herbst <volkmar.herbst at gmx.de> wrote:
> Yes, we also do use plr for kriging of soil data, which works very fast, but
> there are many different variants of it. It helps to know about geo
> statistics and get the right type and formula for the kriging. It is also
> possible to do the following steps:
> 1. create your grid (in plr)
> 2. calculate kriging (in plr)
> 3. create contours (in plr)
> 4. create contour polygons (I have done it in a postgis function but it
> should be also possible in plr)
> I abandoned the raster data type as kriging output to postgis as I could not
> create the postgis raster from the plr raster in an acceptable time. The
> ratser postgis function st_setvalue which works on each pixel takes too long
> and there seem to be no other way to set raster values programmatically,
> that’s why I switched to contours. We do need array to pixel value or so-
> see
> http://trac.osgeo.org/postgis/ticket/1228
> Hope that helps

Yes, you are correct about the significant performance issues with
calling ST_SetValue for each pixel of a raster.  This unfortunately
has to do with the deserialization and serialization that occurs every
time ST_SetValue is called.

Hopefully, I can get to it before the 2.0 code freeze but the outlook
doesn't look good.

-bborie

-- 
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
bkpark at ucdavis.edu