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GEOSTATS: Variowin - GSTAT conversion??

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  • Peter Schlesinger
    Greetings, I am a newcomer to this list, indeed to geostatistics, but I couldn t find this question in the FAQ. My colleagues and I have several hundred dates
    Message 1 of 1 , May 27, 1999
      Greetings,
      I am a newcomer to this list, indeed to geostatistics, but I couldn't
      find this question in the FAQ. My colleagues and I have several hundred
      dates of both potential evapotranspiration and precipitation data as
      well as soil profiles that we are attempting to krige. We purchased
      several intro-to-geostatistics-texts, the VARIOWIN book/software, and
      have created variogram models for each of our datasets. We plan to krige
      our data using GSTAT 2.0. However, we're having a couple difficulties
      with the conversion. The following is a sample variowin model
      (jun97pet.mod):

      The variogram model (for the same data) in VARIOWIN looks like the
      following:
      MODEL PARAMETERS
      Measure of spatial continuity: Variogram
      Variable(s): PET
      EXPERIMENTAL VARIOGRAMS
      Direction: 50 - Tolerance: 30 - MaxBW.: N/A
      Direction: 0 - Tolerance: 30 - MaxBW.: N/A
      Gamma(h): 1.058 + 3.404 Gauss.18 (h)
      Dir.(1): 50 | anis.(1): 1000
      IGF: 5.3989e-02
      A priori covariance: 4.5763e+00 A priori correlation: 1e+00
      MODEL PARAMETERS TO BE INCLUDED IN A GSLIB PARAMETER FILE
      1 1.058 :nst, nugget
      3 10.392304 3.404 40 1000 :it, aa, cc, ang1, anis

      When I translate this model to use in a GSTAT command file, I have used
      the following (contents of jun97pet.cmd):

      data(jun97pet):'jun97pet.eas', x=1, y=2, v=3;
      mask: 'samask';
      variogram(jun97pet): 1.058 Nug (0) + 3.404 Gau (18,40,1000);
      predictions(jun97pet): 'jun97_pr';
      output: 'jun97prd.eas';

      When the above command file is run in GSTAT, it crashes with the
      following report to the screen:

      C:\GSTAT>gstat jun97pet.cmd
      gstat 2.0i (February 1999) for Win32
      Copyright (C) 1992, 1999 Edzer J. Pebesma
      parsing anis(40,0,0,1000,1), error on 1000
      gstat: variable outside valid range: this value should be in <0..1]

      Is this because GSTAT is expecting an anisotropy correction as a ratio
      between 0..1 and we
      are supplying something else? How do we calculate the correct value from
      our model (above)?

      Also, we think that there are directional issues between the two
      softwares VARIOWIN and GSTAT. We understand that Zero degrees in
      Variowin is 90 degrees in GSTAT, 5 degrees in Variowin is 85 in GSTAT,
      and so on. Are we correct in our assumption?

      Is there anything missing from our GSTAT command file that we can
      correctly gain from our VARIOWIN model to aid in our kriging, and ought
      to use? Thanks in advance for any help you can offer.

      Regards,

      Peter Schlesinger

      --
      Peter Schlesinger
      GIS & Remote Sensing Laboratory
      Woods Hole Research Center
      PO Box 296, 13 Church Street
      Woods Hole, MA 02543
      (508)540-9900, ext 118
      (508)540-9700, fax
      email: pschles@...
      WWW: www.whrc.org


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