[GRASS-user] Raster surface from regularly spaced points

[Pablo Carreira]

Luigi,

In my works I get good results with v.surf.rst, but it needs a good calibration of the tension and smoothing parametes to conserve the data range. For that I select a small region of the data and then try many combinations.


Pablo Torres Carreira




> Date: Fri, 19 Feb 2010 11:52:43 +0100
> From: markus.metz.giswork at googlemail.com
> To: lponti at infinito.it
> Subject: Re: [GRASS-user] Raster surface from regularly spaced points
> CC: grass-user at lists.osgeo.org
> 
> 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.
> 
> 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.
> 
> BTW, method=bicubic gives much nicer results than method=bilinear.
> 
> 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!
> 
> 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
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user
> >
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
 		 	   		  
_________________________________________________________________
Você sabia que o Windows 7 inicia e desliga mais rápido? Clique e conheça mais.
http://www.microsoft.com/brasil/windows7/default.html?WT.mc_id=1539
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20100219/b4885835/attachment-0001.html