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## [ai-geostats] simple kriging question

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• Hi everybody I have a little question about simple kriging (SK). I have put a pdf document on my website www.buffalo.edu/~delmelle/sk.pdf with the formula. In
Message 1 of 1 , Jan 26, 2005
Hi everybody

I have a little question about simple kriging (SK). I have put a pdf
document on my website www.buffalo.edu/~delmelle/sk.pdf with the formula.

In that formula, the estimate at a particular location is a function of
the observed values at neighboring locations and also a function of the
mean m over the study area. Normally, as we move away from existing
points, the mean m weights more in the formula. Furthermore, there is no
constraint about the weights, like in OK where they have to sum to 1.

Now here is the problem. Suppose that we work with probabilities (P(s)>0)
and that we know the mean over the area. The mean is positive.

Now, if I want to estimate the probability at a particular location and if
the sum of the weights is greater than one, the term [1- sum_{i=1}^{n}
w_{i} ] becomes negative.

Is it true that I may end up having a negative probability? I guess there
will be a counter effect from the first part of the equation and w_{i}
Z_{i} will be very large.

Any thoughts?

Thank you

Eric

**************************************
Eric Delmelle
Department of Geography
S.U.N.Y. at Buffalo
Buffalo, NY 14201
Phone: (716) 983-2038
URL: www.buffalo.edu/~delmelle
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