[GRASS-user] Proper Use of r.random and v.surf.rst

GRASS GRASS user
1

   Trying to follow the GRASS Book (page 292ff) to resample my 10m DEM to 5m
resolution using generation of random points and RST spline interpolation I
fail to get usable results.

   The input DEM has about 5000 cols and 5500 rows; a huge number of cells.
After waiting a long time for processing with 1 million plus points and
learning that 2G of RAM are insuffient for that many points, I settled on
100,000 points. The command used was:

r.random in=aberDEM n=100000 vector_out=aber10rand --o

   When that finished I invoked:

v.surf.rst in=aber10rand elev=elev10rand.def --o

using the defaults for v.surf.rst.

   When it finally finishes and I display elev10rand.def I get broad
horizontal color bands, from blue on the top to dark brown on the bottom.

   What have I done incorrectly?

Rich

2

On Tue, 9 Feb 2010, Rich Shepard wrote:

When that finished I invoked:
v.surf.rst in=aber10rand elev=elev10rand.def --o

   Think I found my error: not restting the resolution to 5m prior to running
the module. It's working away now on what I hope is the proper use.

Rich

3

On Tue, 9 Feb 2010, Rich Shepard wrote:

Trying to follow the GRASS Book (page 292ff) to resample my 10m DEM to 5m
resolution using generation of random points and RST spline interpolation I
fail to get usable results.

   My latest attempt (which ran most of the night) did not produce the
desired results. I've dropped the attempt for lack of time.

Rich