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Luigi,<br><br>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.<br><br><br>Pablo Torres Carreira
<br><br><br><br>> Date: Fri, 19 Feb 2010 11:52:43 +0100<br>> From: markus.metz.giswork@googlemail.com<br>> To: lponti@infinito.it<br>> Subject: Re: [GRASS-user] Raster surface from regularly spaced points<br>> CC: grass-user@lists.osgeo.org<br>> <br>> You can try the overhauled v.surf.bspline module. You would need to svn <br>> up to get the new version, available in grass64 and higher.<br>> <br>> run v.surf.bspline with the -e flag first to get estimated mean distance <br>> between points. If your points are not completely but almost regularly <br>> spaced, multiply the estimated distance by 1.5 and use that value for <br>> sin and sie.<br>> <br>> BTW, method=bicubic gives much nicer results than method=bilinear.<br>> <br>> To conserve the range of the original data, use a low lambda_i value <br>> somewhere between 0.01 and 0.1.<br>> <br>> I would be really interested if it works for you!<br>> <br>> Markus M<br>> <br>> <br>> <br>> Luigi Ponti wrote:<br>> > Hello,<br>> ><br>> > I have a grid of (almost) regularly spaced vector points from which I <br>> > would like to get a continuous raster surface. I say "almost" <br>> > regularly spaced, because the grid is almost square in that the <br>> > position of points derives from a netCDF grid with a different <br>> > projection than the current GRASS location. One cell of this <br>> > non-aligned grid covers several raster cells at the current region <br>> > resolution.<br>> ><br>> > So far I have been using a v.surf.idw approach but I am not sure <br>> > whether that is appropriate. An exact interpolator would be best, but <br>> > at least I want conserve the range of the original data.<br>> ><br>> > According the the GRASS book (p. 228), my options would be v.surf.idw <br>> > and v.surf.rst but the latter does not conserve data range, I think. <br>> > Another idea would be to use bilinear interpolation.<br>> ><br>> > Any hints very welcome and thanks for your attention if you got so far,<br>> ><br>> > Luigi<br>> ><br>> > _______________________________________________<br>> > grass-user mailing list<br>> > grass-user@lists.osgeo.org<br>> > http://lists.osgeo.org/mailman/listinfo/grass-user<br>> ><br>> _______________________________________________<br>> grass-user mailing list<br>> grass-user@lists.osgeo.org<br>> http://lists.osgeo.org/mailman/listinfo/grass-user<br> <br /><hr />Quer comprar na Internet com segurança? <a href='http://go.microsoft.com/?linkid=9707132' target='_new'>Instale grátis o Internet Explorer 8.</a></body>
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