Sorry, an error occurred while loading the content.

## GEOSTATS: covariance VS. Variogram.

Expand Messages
• Hi all To all of you asking for summery of answers, I am out of the country right now and will be back after ISPRS congress 7/23, sorry for the delay, I
Message 1 of 2 , Jun 26 1:52 PM
Hi all

To all of you asking for summery of answers, I am out of the country right
now and will be back after ISPRS congress 7/23, sorry for the delay, I
promise to post all the answers and my interpretation when I come back.

Thanks.

Yaron A. Felus.
Research associate.
The Ohio-State University.
Department of Civil and Environmental Engineering and Geodetic.

>I was wandering about section 5.3 of the Geostatistics FAQ.
>( http://curie.ei.jrc.it/faq/sc_general.html )
>Which says that it is sometimes advantageous to use the covariance over the
>Variogram.
>
>I have a few references that prove the opposite of this fact for example:
>
>Cressie A.C. Noel. and Grondona O. Martin (1992); A comparison of Variogram
>Estimation with Covariogram Estimation, In The art of statistical Science
>Edited by K.V. Mardia Jhon pp:191-208, Wiley & Sons Ltd.
>
>and also in
>
>Cressie N.A.C. (1993) Statistics for spatial data. New York Wiley.
>
>Cressie and Grondona (1992) proves that variogram estimation is to be
>preferred to covariogram estimation; the main reasons for that are:
>1. In the Kriging process where we estimate the mean of the process and
>then predict the random process both the variogram estimator and
>covariogram estimator are biased. However the variogram bias is of smaller
>order.
>2. If our data has trend contamination then it has �disastrous effect� on
>attempts to estimate the covariogram while on the variogram it has a �small
>upward shift�.
>
>Does anybody have a reference (or reason) which supports this statement
>that the covariance has any advantage over the Variogram ?
>

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com

--
*To post a message to the list, send it to ai-geostats@....
*As a general service to list users, please remember to post a summary
of any useful responses to your questions.
*To unsubscribe, send email to majordomo@... with no subject and
"unsubscribe ai-geostats" in the message body.
DO NOT SEND Subscribe/Unsubscribe requests to the list!
Your message has been successfully submitted and would be delivered to recipients shortly.