> I never read your book, but in all
> textbooks I have consulted so far
> the kriging system is derived
> in terms of covariances...
Simply because it is easier to follow the mathematics
that way.
In 1971, I and 16 other people were taught in a short
course at Fontainebleau given by Andre Journel and
Charles Huijbregts, completely in terms of the
semi-variogram with the covariance only being brought
in as a special case when you could ensure
stationarity of both mean and standard deviation.
Where these conditions are met, the two are
equivalent. For simple kriging, the mean has to be
stationary by definition but only the covariance of
the increments (differences) has to be stationary to
obtain a semi-variogram.
I have an original copy of Matheron's book and would
be pleased to allow anyone who can afford a return
fare to Johannesburg to look through it.
Please do not take offence so easily. We old timers
are good for some things, if only perspective. Maybe
you should read that book after all. I read yours (and
everyone else's) and recommend them where appropriate.
Isobel Clark
http://uk.geocities.com/drisobelclark
then,
> provided that unbiasedness conditions are
> included in the system (that is ORDINARY
> AND UNIVERSAL KRIGING cases) the system
> is expressed in terms of semivariograms.
>
> Instead of referring to Matheron's book,
> let's look at Chiles and Delfiner's 1999
> book, which should be close enough!
> On page 170, second paragraph
> from the bottom, I quote "There is
> no variogram analog to the simple kriging
> system (3.2) because then Z*-Z_0 is not
> an allowable linear combination".
>
> Next time, think twice before sending
> confusing e-mails that do not help
> readers who are trying to learn basic
> geostat concepts!
>
> Cheers,
>
> Pierre
>
> PS: If you find Matheron's work with a SIMPLE
> kriging system expressed in terms of variograms,
> keep it in a safe place.. it must be worth a
> fortune..
>
>
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
>
> ________ ________
> | \ / | Pierre Goovaerts
> |_ \ / _| Assistant professor
> __|________\/________|__ Dept of Civil &
> Environmental Engineering
> | | The University of
> Michigan
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> |________________________| Ann Arbor, Michigan,
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>
>
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
>
>
> On Tue, 22 May 2001, [iso-8859-1] Isobel Clark
> wrote:
>
> > > In fact, once the "pseudo-sill" A cancels out
> from
> > > the system of linear equations, the system is
> > > expressed in terms of semivariograms....
> > My point exactly and, if you don't do it, you
> don't
> > make silly assumptions.
> >
> > > I use to think in terms of covariances since
> > > it's more intuitive, and the simple kriging
> > > system can only be expressed in terms of
> > > covariances anyway...
> > That is just so much nonsense. Ordinary kriging
> and
> > simple kriging are derived on the basis of the
> > semi-variogram and are simply slight variations on
> one
> > another. If you don't trust my book, go back to
> your
> > original Matheron, please.
> >
> > Isobel
> >
> >
>
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