Thanks Markus!
On 19/02/2010 11:52, Markus Metz wrote:
You can try the overhauled v.surf.bspline module. You would need to
svn up to get the new version, available in grass64 and higher.
I was browsing the source code but did not see it
http://trac.osgeo.org/grass/browser/grass/branches/releasebranch_6_4/vector
http://trac.osgeo.org/grass/browser/grass/trunk/vector
Am I looking at the wrong spot?
I will probably get it in the next grasswin standalone installer, but I
also need source code to update an heritage cygwin/grass version.
run v.surf.bspline with the -e flag first to get estimated mean
distance between points. If your points are not completely but almost
regularly spaced, multiply the estimated distance by 1.5 and use that
value for sin and sie.
This is great fine-tuning get me up and running -- thanks.
BTW, method=bicubic gives much nicer results than method=bilinear.
I think it is slower, isn't it? Not sure how much slower, though.
To conserve the range of the original data, use a low lambda_i value
somewhere between 0.01 and 0.1.
I would be really interested if it works for you!
I will let you know. Thanks again,
Luigi
Markus M
Luigi Ponti wrote:
Hello,
I have a grid of (almost) regularly spaced vector points from which I
would like to get a continuous raster surface. I say "almost"
regularly spaced, because the grid is almost square in that the
position of points derives from a netCDF grid with a different
projection than the current GRASS location. One cell of this
non-aligned grid covers several raster cells at the current region
resolution.
So far I have been using a v.surf.idw approach but I am not sure
whether that is appropriate. An exact interpolator would be best, but
at least I want conserve the range of the original data.
According the the GRASS book (p. 228), my options would be v.surf.idw
and v.surf.rst but the latter does not conserve data range, I think.
Another idea would be to use bilinear interpolation.
Any hints very welcome and thanks for your attention if you got so far,
Luigi
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