Hi, The main difference between SOCK and TOCK is that, in the standardized form, only one unbiasedness constraint is imposed, i.e. the sum of all primary and secondary data weights is one, while in the traditional version a separate constraint is applied for each variable, i.e. sum of primary data weights is one and the sum of secondary data weights is zero for each secondary variable. The traditional constraints lead to larger and more frequent negative weights for the secondary variables. The difference between SOCK and TOCK estimates is expected to increase as differences between the variance of primary and secondary variables increases. The different types of cokriging are described and compared in the following paper: Goovaerts, P. 1998. Ordinary cokriging revisited. Mathematical Geology, 30(1): 21-42.
Cheers, Pierre Pierre Goovaerts Chief Scientist at BioMedware 516 North State Street Ann Arbor, MI 48104 Voice: (734) 913-1098 (ext. 8) Fax: (734) 913-2201 http://home.comcast.net/~goovaerts/ -----Original Message----- From: Adrián Martínez Vargas [mailto:[EMAIL PROTECTED] Sent: Wed 1/4/2006 12:53 PM To: Behrang Kushavand; ai-geostats@unil.ch Cc: Subject: Re: [ai-geostats] Traditional OCK or Standardize OCK? In the definition of the cross variogram you can see that it is not adimentional (depend of units >> Km, %, ppm, etc.), you can avoid this effect using standardize Ordinary Co-Kriging. Adrian -----Original Message----- From: "Behrang Kushavand" <[EMAIL PROTECTED]> To: <ai-geostats@unil.ch> Date: Wed, 4 Jan 2006 19:55:01 +0330 Subject: [ai-geostats] Traditional OCK or Standardize OCK? > Dear All, > > > > Is it true that estimation variance of standardize Ordinary Co-Kriging > (SOCK) is always equal or smaller than Traditional Ordinary Co-Kriging > (TOCK)? > > What is the advantage of TOCK to SOCK (I think it is about negative > weights) and are there any criteria to choice TOCK or SOCK? > > > > Thanks > > Behrang > > ____________________________________________________________________________________________ Participe en el V Congreso Internacional de Educación Superior "Universidad 2006". La Habana, Cuba, del 13 al 17 de Febrero del 2006 http://www.universidad2006.cu _____________________________________ Instituto Superior Minero Metalúrgico de Moa Dr. Antonio Núñez Jiménez http://www.ismm.edu.cu
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