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AI-GEOSTATS: Re: cokriging/GSLIB list of responses

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  • jozebel amayllo
    I am sending the answers I got. Thanks Maria Morales and Julian Ortiz! Joz Jozebel, there are two programs of gslib library to use for collocated cokriging:
    Message 1 of 1 , Jan 19, 2004
      I am sending the answers I got. Thanks Maria Morales and Julian Ortiz!
      Joz

      Jozebel,

      there are two programs of gslib library to use for collocated cokriging: cokb3d and newcokb3d.
      cokb3d uses collocated cokriging using the linear model of coregionalization (lmc).
      newcokb3d uses collocated cokriging using the lmc and also has the option for using markov models (mm1 and mm2).
      when entering the number of variables, if using the collocated option you have to use only the primary. the secondary is then entered as a separate file, in which the secondary variable is entered in each location where the primary will be estimated (the covariate file).

      in the kriging types, you can choose simple kriging, ordinary cokriging and ordinary cokriging traditional.
      when traditional ordinary cokriging is used, the weights of the primary data are forced to sum one and the weights of the secondary data are forced to sum zero. this causes problems sometimes (see Ordinary Cokriging Revisited, P. Goovaerts, Mathematical Geology, Vol. 30. No. 1, 1998). then, the ordinary cokriging constraints the sum of the weights to one. there is a rescaling of the cokriging estimator. so, you need to enter the mean of the primary and secondary variables when the option 1 (ordinary cokriging) is chosen.

      in the case of the newcokb3d, you then enter the variogram models, depending of the model you chose for modeling the coregionalization (lmc, mm1 or mm2).

      hope this helps,

      Maria

      -----------------------------------------------
      Maria N. Morales
      Mining Engineering Department
      Federal University of Rio Grande do Sul
      Porto Alegre, Brazil
      +55 +51 33163357
      Fax +55 +51 32864343

      Hello,

      It is not implemented in the version that comes with the book, and I am
      not sure if it has been implemented in the newer versions available at
      www.gslib.com (I don't think so...)

      In any case, you would need your scattered primary variable in 2 or 3D.
      Additionally, you would need a secondary variable that must be
      exhaustive (informed in every node of the grid you are considering) and
      the correlation coefficient between the two variables.

      Those are the key parameters. Look at the help in www.gslib.com and if
      you can, get the book:

      Deutsch, C.V. and Journel, A.G., GSLIB: Geostatistical Software Library
      and User�s Guide. Oxford University Press, New York, 2nd edition, 1998.

      Regards,

      Juli�n.

      Juli�n Ortiz C., Ph. D.
      Assistant Professor
      Mining Engineering Department
      University of Chile

      web: www.ualberta.ca/~jmo1
      phone: +56 2 678.4585
      fax: +56 2 672.3504


      ----- Original Message -----
      From: jozebel amayllo
      To: ai-geostats@...
      Sent: Friday, January 09, 2004 4:18 PM
      Subject: AI-GEOSTATS: cokriging


      I�m trying to use gslib for colocated cokriging. Can someone help me about how to use?

      Thanks for any help on this.

      Joz





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