On Mar 18, 2008, at 2:39 PM, GRASS GIS wrote:
#99: r.resamp.interp fails for bicubic and bilinear interpolation
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Reporter: cmbarton | Owner: [email protected]
Type: defect | Status: new
Priority: critical | Milestone: 6.3.0
Component: default | Version: unspecified
Keywords: |
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I just found out that r.resamp.interp fails for both bicubic and
bilinear
interpolation. It makes maps with all NAN values. I used the new
NC data
set and produced a set of random elevation points (raster and
vector),
then tried to use these in r.resamp.interp.
Michael - unless you have at least on point per cell NAN is actually
a correct result.
r.resamp.interp is for resampling a raster map not for interpolating
from randomly distributed points.
Eg this is the example from the book - you go from 30m resolution to
10m resolution -
let me know if that does not work (then we are in trouble because
this worked so we may have a bug introduced somewhere).
g.region rast=elevation -p
r.resamp.interp elev_ned_30m out=elev_ned10m_bil meth=bilinear
r.resamp.interp elev_ned_30m out=elev_ned10m_bic meth=bicubic
Helena
The nearest neighbor routine
worked, but the others did not. I tried the original raster point
map and
also tried one that I converted to a CELL map. Neither gave usable
results. FWIW, I got the same result using r.bilinear.
I'm having a very difficult time putting together a class on
interpolation
using GRASS today. v.surf.bspline does not work, 2 of the 3
methods in
r.resamp.interp do not work. r.bilinear does not work. Pretty bad
press.
Michael
--
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