Hi Laure, One of the main culprits for negative cokriging weights is the ordinary cokriging constraint that the sum of the secondary weights must be zero. I found that the frequency and magnitude of negative cokriging weights greatly decreased when using a single constraint that primary and secondary data weights must sum to one (referred to as standardized cokriging in Gslib software). This issue is discussed in my book and in the following publication:
Goovaerts, P. 1998. Ordinary cokriging revisited. Mathematical Geology, 30(1): 21-42. Cheers, Pierre <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> Dr. Pierre Goovaerts President of PGeostat, LLC Chief Scientist with Biomedware Inc. 710 Ridgemont Lane Ann Arbor, Michigan, 48103-1535, U.S.A. E-mail: [EMAIL PROTECTED] Phone: (734) 668-9900 Fax: (734) 668-7788 http://alumni.engin.umich.edu/~goovaert/ <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> On Thu, 4 Sep 2003 [EMAIL PROTECTED] wrote: > Hi Mailinglist!!! > > I have got some problems with negative weight in my cokriging, they induce > negative grade. Have you got some advice or publication to help me.I hope > you can help me with some of your answers. > > Thank > > Laure > > > > Laure FONTAINE > Services des Réserves > COGEMA BUM/DT > tél: 33 1 39 26 32 05 > Fax: 33 1 39 26 27 31 > > > > -- > * To post a message to the list, send it to [EMAIL PROTECTED] > * As a general service to the users, please remember to post a summary of any useful > responses to your questions. > * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and > "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO > NOT SEND Subscribe/Unsubscribe requests to the list > * Support to the list is provided at http://www.ai-geostats.org > > -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org
