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AI-GEOSTATS: Cross variogram

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  • Digby Millikan
    Hello everyone, The forumlea which I have obtained for the cross variogram is; gamma(h)=1/2N(h) SUMi,j(vi-vj)(ui-uj) Is it correct then that the product of
    Message 1 of 2 , Mar 13, 2003
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      Hello everyone,
      The forumlea which I have obtained for the cross variogram is;

      gamma(h)=1/2N(h) SUMi,j(vi-vj)(ui-uj)

      Is it correct then that the product of the differences can be negative in
      cases.

      Digby

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    • Isobel Clark
      Digby That is the traditional cross semi-variogram as discussed in Matheron s original work. Now also known as a co-located cross semi-variogram. There is a
      Message 2 of 2 , Mar 14, 2003
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        Digby

        That is the 'traditional' cross semi-variogram as
        discussed in Matheron's original work. Now also known
        as a co-located cross semi-variogram.

        There is a non-co-located cross semi-variogram which
        goes something like:

        gamma(h)=1/2N(h) SUMi,j(vi-uj)^2

        which is always positive. However, you probably have
        to standardise u and v to get meaningful results
        (which you can't really do with skewed data).

        Noel Cressie has shown in a paper in Math Geol that a
        semi-variogram calculated on logarithms is the same
        generically as a general relative semi-variogram.

        I should think that conclusion probably holds for
        cross semi-variograms too. Calculating on logarithms
        is computationally simpler than calculating a relative
        semi-variogram.

        Isobel Clark
        http://uk.geocities.com/drisobelclark

        --- Digby Millikan <digbym@...> wrote: >
        Hello everyone,
        > The forumlea which I have obtained for the cross
        > variogram is;
        >
        > gamma(h)=1/2N(h) SUMi,j(vi-vj)(ui-uj)
        >
        > Is it correct then that the product of the
        > differences can be negative in
        > cases.
        >
        > Digby


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