[GRASS-user] [newbie] r.surf.idw only gives integer values

[Robert Pollak]

Hi,

I have imported an x,y,z DEM file (grid points with floating point 
location and height values) into GRASS 6.0.1, using the v.in.ascii 
command's GUI. The generated command was:

 > v.in.ascii input=DEM10.xyz output=v format=point fs=' ' x=1 y=2 z=3 
cat=0 -z -t

(I have used "create 3D file" and "Do not create table in points mode", 
although I did not grok their meaning from the manual.)


I have then taken the region from the vector map v and set the 
resolution corresponding to the DEM file contents:

 > g.region vect=v res=10

d.what.vect shows the correct z values, when v is displayed.


Then I generated an intermediate raster map (because I could not make 
v.surf.idw work, but that's another story):

 > v.to.rast input=v output=r use=z

(Data type DCELL and data range in r.info still look ok.)


When I now use "inverse distance weighed average interpolation" like this

 > g.region res=20 #target resolution
 > r.surf.idw input=r output=r_idw20

, the generated raster map gets the integer data type CELL! Why doesn't 
it generate floating point values, as generated by the interpolation 
formula?

(When I use r.resamp.rst instead, the resulting type is floating point 
(FCELL), as expected.)

-- Robert