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Re: [ai-geostats] 3D cross-variograms fittind

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  • seba
    Hi Luke Yes, as you suggest very often in geology the third dimension (say z) is more similar to a temporal dimension than to a spatial one. (Think for example
    Message 1 of 2 , Mar 1, 2006
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      Hi Luke
      Yes, as you suggest very often in geology the third dimension (say z) is
      more similar to a temporal dimension than to a spatial one.
      (Think for example to quaternary sedimentary deposits). So is it so a big
      deal to preform a 3d analisys? isn't it better to conduct
      a stratified 2D analysis?
      For this reason I`m glad if someone has some idea also only for 2D
      cross-variogram fitting.
      Bye
      Sebastiano



      At 12.19 01/03/2006, Luke Spadavecchia wrote:
      >Hi seba,
      >
      >I have found similar problems. What kind of 3D model are you trying to
      >fit? If it is a separable covariance model (of the product or product-sum)
      >variety, a good place to start is the modified GSLIB code that appeared in
      >the attached article. The code can be downloaded from the computers and
      >geosciences website. The code will compute the empirical semivariance
      >surface for you, but there is no fitting routine. I am about to embark on
      >a major programming task (when I get the time) to fit a variogram surface
      >to the output of GAMSURF, but in the meantime, I just fit my model in
      >Excel, or some other spreadsheet. I have attached an example for you:
      >although it is spatio-temporal, the same model is permissable in 3D space.
      >Any nested variograms permitted in 2D can be used for the separable
      >models. This is actually quite appealing, given the nature of the
      >covariance in the vertical may be different in functional form from the
      >horizontal covariance, since different processes may underlie the
      >autocorrelation.
      >
      >Hope that is helpful
      >
      >Luke
      >
      >
      >
      >
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