## AI-GEOSTATS: Cross variogram

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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
Message 1 of 2 , Mar 13, 2003
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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• 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
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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