Hello Oriol,
Isobel gave good advice when she suggested to download Chapter 4 of her
Practical Geostatistics. This book taught me more than David's
Geostatistical Ore Reserve Estimation and Journel and Huijbregts's
Mining Geostatistics combined because of its many practical examples.
For example, look at Clark's hypothetical uranium data (see Clark and the
Kriging Game at http://www.ai-geostats.org/documents/JW_Merks/
) and find out what happens if the variance of the distance-weighted average
were to resurface after it went missing on Krige's watch at the Witwatersrand
gold reef complex in South Africa in the 1950s. You should also peruse http://en.wikipedia.org/wiki/Geostatistics
to find out why statistically astute thinking was lacking when pioneering
geostatisticians replaced the genuine variance of a single distance-weighted
average with the pseudo kriging variance ofsome set of kriged
estimates. Study Clark's hypothetical uranium data step-by-step as
outlined on the Geostatistics talk page. It is possible to make the
variance of the distance-weighted average vanish again by the condition that
thisvariance be replacedwith thekriging variance ofsome
set of kriged estimates if, and only if, the absolute difference between the
true variance and the Central Limit Theorem exceeds say 1% or
perhaps5%.Conditional switching between real variances and voodoo
variancesmay not be a bright idea so early in your career.
Kind regards,Jan W Merks
- Original Message -
From:
Isobel Clark
To: Oriol Falivene
Cc: ai-geostats@jrc.it
Sent: Wednesday, July 12, 2006 6:06
AM
Subject: AI-GEOSTATS: Re: generalize
kriging variance to average-based estimators different than
Oriol
Download for free, my old book Practical Geostatistics. Chapter 4 tells
you all about calculating the variance for any weighted average estimator.
Follow links from http://www.kriging.com
IsobelOriol Falivene [EMAIL PROTECTED]
wrote:
Dear
Colleagues,Im a PhD student working on interpolation of categorical
variables(like facies).I would like to know if its possible to
generalize the kriging varianceto other average-based estimators
different than kriging, such askriging with an areal trend, indicator
kriging or inverse distanceweighting?; if its possible could you send
me some references where Ican find that?.Thank you.Best
regardsOriol--__Oriol
Falivene[EMAIL PROTECTED]http://www.ub.es/ggactel. (+34)
93 4034028fax (+34) 93 4021340Fac. de Geologia,Univ. de
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