[GRASS-user] shifted surfaces - bug in interpolation modules?

[Carlos "Guâno" Grohmann]

Dear list,

After running some tests to compare different interpolation methods
(kriging in R, IDW, RST, nnbathy and bsplines), I realized that the
surfaces produced by GRASS presented a shift to southwest, when
compared with the surface made with R or ArcGIS. I know that the
surface that came from R is in the right place, I compared it with the
original SRTM data.

here are some images:


http://www.igc.usp.br/pessoais/guano/temp/srtm_original.jpg
http://www.igc.usp.br/pessoais/guano/temp/srtm_kriging.jpg
http://www.igc.usp.br/pessoais/guano/temp/srtm_IDW.jpg
http://www.igc.usp.br/pessoais/guano/temp/srtm_RST.jpg
http://www.igc.usp.br/pessoais/guano/temp/srtm_nnbathy.jpg
http://www.igc.usp.br/pessoais/guano/temp/srtm_bspline.jpg
http://www.igc.usp.br/pessoais/guano/temp/profiles.jpg
http://www.igc.usp.br/pessoais/guano/temp/profiles2.jpg


What do you guys think about this?

BTW, bspline needs some work, it's not patching the sub-regions right.


Carlos




-- 
+-----------------------------------------------------------+
              Carlos Henrique Grohmann - Guano
  Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
Linux User #89721  - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
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