[GRASS5] r.surf.idw: int or decimal

[Michael Ash]

Just to orient the question, here is the set-up: 
Region: approximately 50 million cells
Mask: approximately 11 million cells contiguous cells 
Input raster map: approximately 2 million cells, all within
the mask

r.surf.idw fills in the additional 11 million cells of the
mask (2 milllion cells in the input and 9 million more to
make up the mask).  I am using using npoints=12, the
default, after some trial and error.

My questions are:

(1) Is this an appropriate way to fill in the missing cells?
The output seems plausible to me, but since I am new to both
GIS and grass, I wanted to ask if my approach is
appropriate.

(2) The output raster map from r.surf.idw seems to have only
integer values.  Can I get decimal values if I multiply all
of the values in the input map by, say, 100, use r.surf.idw,
and then divide all the values by 100?

Best,

Michael Ash

Michael Ash, Assistant Professor 
  of Economics and Public Policy         
Department of Economics and CPPA
University of Massachusetts
Amherst, MA 01003        
Tel 413-545-6329 Fax 413-545-2921
Email mash at econs.umass.edu
http://www-unix.oit.umass.edu/~maash