[GRASS-user] Raster surface from regularly spaced points

[Markus Metz]

Luigi Ponti wrote:
>
> 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?
Nearly there ;-) It's part of the lidar tools in e.g. 
branches/releasebranch_6_4/vector/lidar but a generic surface 
interpolation tool. As such, it is in the GUI in Raster -> Interpolate 
surfaces -> Bilinear and bicubic from vector points.  You need to make 
distclean for the whole source code when compiling the new version 
(updated header).
>
>
>>
>> BTW, method=bicubic gives much nicer results than method=bilinear.
>
> I think it is slower, isn't it? Not sure how much slower, though.
A bit, but IMHO it's worth it. Still faster than v.surf.rst.


>>
>>
>>
>> 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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>>>
>>
>
>