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  • Cathy Schloeder & Mike Jacobs
    Hi to all, This is my scenario followed by several questions since I am new to the world of geostats, variograms, and kriging. I collected soil samples at 46
    Message 1 of 1 , Dec 2, 1997
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      Hi to all,

      This is my scenario followed by several questions since I am new to the
      world of geostats, variograms, and kriging. I collected soil samples at 46
      sites on a valley floor and wish to interpolate to 130 sites in order to
      determine the distribution of each soil property on the landscape. Each
      property will be analyzed individually. So far I have worked using S+,
      attempting each step of the variogram and kriging processes. These are my
      questions:

      (1) Some of the data needs transformation due to skewness, etc. When I
      apply an omnidirectional to the transformed data 7 of the properties appear
      to be spatially autocorrelated versus 5 when the data are not transformed.
      Is it appropriate for me to be transforming my data based on (a) some
      properties do exhibit spat. auto. following transformation and (b)
      information posted in ai-geostats-FAQ states that a bias is introduced when
      using transformed data in kriging?

      (2) My sample size is too small to consider looking for anisotropic affects,
      or directional trends - what is recommended in this instance to check for
      (a) possibility of stationarity and/or (b) remove the affect of a potential
      trend, or at this sample size I should not worry about these?

      (3) Is there anything out there that would guide me in the interpretation of
      the y-axis of the semivariogram results - that is, the semivariance values
      that are computed for each property? Some of property results are low while
      others are high, my guess somewhat a function of scale of measurement, but
      (a) how much and (b) at what point would they indicate that even if there is
      spat. autocorr. the variances are too high in general to consider using the
      results for the kriging process - or is this a worthy question?

      Thats enough for now - thanks, Cathy
      Cathy Schloeder
      Utah State University
      Dept. Fisheries and Wildlife
      UMC 5210
      Logan, UT 84322-5210
      Telephone: 801-797-1346
      Fax: 801-797-1871

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