[GRASS-user] Re: [GRASSLIST:1173] Downscaling DEMs (need some feedback)

[Wolfgang]

Downscaling is quite difficult, much depends on our area you are in. I 
was resmpling some SRTM data to 15 meter resolution and it was not that 
easy.

But have a look at r.bilinear or r.resamp.rst all parameters depend 
quite much on your topology and sometimes I found it it quite helpful 
not to do it in one step ( at least for r.resamp.rst). But I'm 
absolutely not a guru in this field. Just try it out on a small region.

Cheers
Wolfgang

Jonathan Greenberg schrieb:
> I'd like to resample a 30m DEM to 4m for use in the ATCOR3 topographic
> correction software package.  The issue that always pops up when doing
> downscaling like this is that the resultant "higher res" DEM contains the
> "ghosts" of the 30m pixels (e.g. it creates squares in the landscape).  My
> question is, what (if any) are the best ways to "get rid" of these effects?
> Does GRASS (or other packages) have any tools to deal with this?  It seems
> that the major issue is that a basic raster resampler treats the DEM as a
> flat surface of equal elevation, but treating it as a grid of points, where
> the center of each cell = the elevation, would be more appropriate (and
> then, for each cell that is not the centroid of a DEM cell, the value is
> some distance weighted function of the 4 elevation values which will
> surround it).  Thoughts?
> 
> --j
> 
> --
> 
> Jonathan A. Greenberg, PhD
> NASA Postdoctoral Researcher
> NASA Ames Research Center
> MS 242-4
> Moffett Field, CA 94035-1000
> Phone: 415-794-5043
> AIM: jgrn3007
> MSN: jgrn3007 at hotmail.com
> 
> 
>