Loading ...
Sorry, an error occurred while loading the content.

RE: [ai-geostats] modelling trend and kriging type

Expand Messages
  • Els Verfaillie
    Dear AI-list, in which context KED is mostly used? I have found examples of this methodology in the context of soil science and climatology: Bourennane, H.,
    Message 1 of 10 , Jul 1, 2005
    View Source
    • 0 Attachment
      Dear AI-list,

      in which context KED is mostly used? I have found examples of this methodology in the context of soil science and climatology:


      Bourennane, H., King, D. and Couturier, A., 2000. Comparison of kriging with external drift and simple linear regression for predicting soil horizon thickness with different sample densities: Geoderma, v. 97, p. 255-271.

      Bourennane, H. and King, D., 2003. Using multiple external drifts to estimate a soil variable: Geoderma, v. 114, p. 1-18.

      Goovaerts, P., 1999. Using elevation to aid the geostatistical mapping of rainfall erosivity: Catena, v. 34, p. 227-242.

      Hudson, G. and Wackernagel, H., 1994. Mapping temperature using kriging with external drift: theory and an example from Scotland: International Journal of Climatology, v. 14, p. 77-91.

      Martinez-Cob, A. and Cuenca, R.H., 1992. Influence of elevation on regional evapotranspiration using multivariate geostatistics for various climatic regimes in Oregon. Journal of Hydrology 136, 353–380.


      Are there other interesting references for this methodology in the same or other application fields?

      Best wishes,
      ___________________________________________________

      Els Verfaillie, PhD student
      Renard Centre of Marine Geology - Ghent University
      Krijgslaan 281-S8
      B-9000 Gent - Belgium
      tel: +32-9-2644573 fax: +32-9-2644967
      e-mail: Els.Verfaillie@...
      http://www.rcmg.ugent.be/
      ___________________________________________________


      -----Original Message-----
      From: Pierre Goovaerts [mailto:Goovaerts@...]
      Sent: donderdag 30 juni 2005 16:54
      To: Recep kantarci; ai-geostats@...
      Subject: RE: [ai-geostats] modelling trend and kriging type


      To add to the excellent comments by Edzer and Gregoire,

      1. Universal kriging = kriging with a trend. The second terminology has been proposed by Andre
      Journel who felt that the term "universal" was vague and misleadingly "ambitious".

      2. Kriging with an external drift (KED) is mathematically the same as universal kriging (UK). Secondary variables
      are simply replacing the spatial coordinates used in UK.

      3. Regression kriging denotes all the techniques where the trend is modeled outside the kriging algorithm.
      There are various methods that can be used to model that trend, ranging from linear regression
      to neural networks. Kriging is used to interpolate the residuals. In practice these techniques have more
      flexibility than universal kriging in term of modeling the trend: multiple variables either categorical or
      continuous can be incorporated easily and many sofwtare are available for this trend modeling.
      The only limitation is that the trend is modeled globally (i.e. the regression coefficients are constant
      in space) while in KED the coefficients are reestimated within each search window.

      Cheers,

      Pierre


      Pierre Goovaerts

      Chief Scientist at Biomedware

      516 North State Street

      Ann Arbor, MI 48104

      Voice: (734) 913-1098
      Fax: (734) 913-2201

      http://home.comcast.net/~goovaerts/

      -----Original Message-----
      From: Recep kantarci [mailto:recep_kantarci_1978@...]
      Sent: Thu 6/30/2005 9:38 AM
      To: ai-geostats@...
      Cc:
      Subject: [ai-geostats] modelling trend and kriging type


      Dear ai-geostats members

      When the data used has a trend, it is needed to model trend and in this case there exists various types of kriging to apply (universal kriging, kriging with a trend, regression kriging etc).
      If this is the case, does one should use the same type of kriging or different depending on modeling the trend using coordinates of target variable or using other (namely, secondary or auxillary) variables such as elevation or topography ? That is , are there a dinstinction depending on the type of variables to model the trend while kriging?

      Best regards
      Recep


      _____

      Yahoo! kullaniyor musunuz?
      Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi korunma Yahoo! Postada
      http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>


      --
      No virus found in this incoming message.
      Checked by AVG Anti-Virus.
      Version: 7.0.322 / Virus Database: 267.8.2/29 - Release Date: 27/06/2005

      --
      No virus found in this outgoing message.
      Checked by AVG Anti-Virus.
      Version: 7.0.322 / Virus Database: 267.8.2/29 - Release Date: 27/06/2005
    • ABREU Carlos Eduardo
      Dear Els A good reference on geostats in the oil industry is the excelent book from Olivier Dubrule Geostatistics for Seismic Data Integration in Earth
      Message 2 of 10 , Jul 1, 2005
      View Source
      • 0 Attachment
        Dear Els

        A good reference on geostats in the oil industry is the excelent book from
        Olivier Dubrule "Geostatistics for Seismic Data Integration in Earth
        Models", where you will also find KDE aplications.

        Actually, it is the reference book of a 1 day course offered by SEG (Society
        of Exploration GEophysicists)/EAGE (European Association og Geoscientists
        and Engineers).
        http://www.eage.org/index.php?Menu_Code=DISCDetails&EVS_Id=45&ActiveMenu=57&
        Opendivs=s13,s15


        Sincerely

        Carlos Eduardo ABreu

        -----Message d'origine-----
        De : Els Verfaillie [mailto:els.verfaillie@...]
        Envoyé : vendredi 1 juillet 2005 10:55
        À : Pierre Goovaerts; Recep kantarci; ai-geostats@...
        Objet : RE: [ai-geostats] modelling trend and kriging type


        Dear AI-list,

        in which context KED is mostly used? I have found examples of this
        methodology in the context of soil science and climatology:


        Bourennane, H., King, D. and Couturier, A., 2000. Comparison of kriging with
        external drift and simple linear regression for predicting soil horizon
        thickness with different sample densities: Geoderma, v. 97, p. 255-271.

        Bourennane, H. and King, D., 2003. Using multiple external drifts to
        estimate a soil variable: Geoderma, v. 114, p. 1-18.

        Goovaerts, P., 1999. Using elevation to aid the geostatistical mapping of
        rainfall erosivity: Catena, v. 34, p. 227-242.

        Hudson, G. and Wackernagel, H., 1994. Mapping temperature using kriging with
        external drift: theory and an example from Scotland: International Journal
        of Climatology, v. 14, p. 77-91.

        Martinez-Cob, A. and Cuenca, R.H., 1992. Influence of elevation on regional
        evapotranspiration using multivariate geostatistics for various climatic
        regimes in Oregon. Journal of Hydrology 136, 353–380.


        Are there other interesting references for this methodology in the same or
        other application fields?

        Best wishes,
        ___________________________________________________

        Els Verfaillie, PhD student
        Renard Centre of Marine Geology - Ghent University
        Krijgslaan 281-S8
        B-9000 Gent - Belgium
        tel: +32-9-2644573 fax: +32-9-2644967
        e-mail: Els.Verfaillie@...
        http://www.rcmg.ugent.be/
        ___________________________________________________


        -----Original Message-----
        From: Pierre Goovaerts [mailto:Goovaerts@...]
        Sent: donderdag 30 juni 2005 16:54
        To: Recep kantarci; ai-geostats@...
        Subject: RE: [ai-geostats] modelling trend and kriging type


        To add to the excellent comments by Edzer and Gregoire,

        1. Universal kriging = kriging with a trend. The second terminology has been
        proposed by Andre
        Journel who felt that the term "universal" was vague and misleadingly
        "ambitious".

        2. Kriging with an external drift (KED) is mathematically the same as
        universal kriging (UK). Secondary variables
        are simply replacing the spatial coordinates used in UK.

        3. Regression kriging denotes all the techniques where the trend is modeled
        outside the kriging algorithm.
        There are various methods that can be used to model that trend, ranging from
        linear regression
        to neural networks. Kriging is used to interpolate the residuals. In
        practice these techniques have more
        flexibility than universal kriging in term of modeling the trend: multiple
        variables either categorical or
        continuous can be incorporated easily and many sofwtare are available for
        this trend modeling.
        The only limitation is that the trend is modeled globally (i.e. the
        regression coefficients are constant
        in space) while in KED the coefficients are reestimated within each search
        window.

        Cheers,

        Pierre


        Pierre Goovaerts

        Chief Scientist at Biomedware

        516 North State Street

        Ann Arbor, MI 48104

        Voice: (734) 913-1098
        Fax: (734) 913-2201

        http://home.comcast.net/~goovaerts/

        -----Original Message-----
        From: Recep kantarci [mailto:recep_kantarci_1978@...]
        Sent: Thu 6/30/2005 9:38 AM
        To: ai-geostats@...
        Cc:
        Subject: [ai-geostats] modelling trend and kriging type


        Dear ai-geostats members

        When the data used has a trend, it is needed to model trend and in
        this case there exists various types of kriging to apply (universal kriging,
        kriging with a trend, regression kriging etc).
        If this is the case, does one should use the same type of kriging or
        different depending on modeling the trend using coordinates of target
        variable or using other (namely, secondary or auxillary) variables such as
        elevation or topography ? That is , are there a dinstinction depending on
        the type of variables to model the trend while kriging?

        Best regards
        Recep


        _____

        Yahoo! kullaniyor musunuz?
        Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi korunma
        Yahoo! Postada
        http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>


        --
        No virus found in this incoming message.
        Checked by AVG Anti-Virus.
        Version: 7.0.322 / Virus Database: 267.8.2/29 - Release Date: 27/06/2005

        --
        No virus found in this outgoing message.
        Checked by AVG Anti-Virus.
        Version: 7.0.322 / Virus Database: 267.8.2/29 - Release Date: 27/06/2005




        __________________________

        Ce message (et toutes ses pièces jointes éventuelles) est confidentiel et établi à l'intention exclusive de ses destinataires. Toute utilisation de ce message non conforme à sa destination, toute diffusion ou toute publication, totale ou partielle, est interdite, sauf autorisation expresse. L'IFP décline toute responsabilité au titre de ce message.

        This message and any attachments (the message) are confidential and intended solely for the addressees. Any unauthorised use or dissemination is prohibited. IFP should not be liable for this message.

        Visitez notre site Web / Visit our web site : http://www.ifp.fr
        __________________________
      • PCollier@xstrata.com.au
        Hi all I may know this already, but what are the symptoms of data with a trend? What is the difference between a dataset with a trend and a non-stationary
        Message 3 of 10 , Jul 6, 2005
        View Source
        • 0 Attachment
          RE: [ai-geostats] modelling trend and kriging type

          Hi all

          I may know this already, but what are the symptoms of data with a trend?  What is the difference between a dataset with a trend and a non-stationary dataset?

          Cheers


          Perry Collier

          Senior Mine Geologist
          Ernest Henry Mine  
          Xstrata Copper Australia
          Ph (07) 4769 4527
          Fx (07) 4769 4555
          E-mail PCollier@...
          Web http://www.xstrata.com
           
          PO Box 527
          Cloncurry QLD 4824
          Australia
           
          "Light travels faster than sound. That is why some people appear bright
          until you hear them speak"




          -----Original Message-----
          From: Pierre Goovaerts [mailto:Goovaerts@...]
          Sent: Friday, 1 July 2005 12:54 AM
          To: Recep kantarci; ai-geostats@...
          Subject: RE: [ai-geostats] modelling trend and kriging type


          To add to the excellent comments by Edzer and Gregoire,
           
          1. Universal kriging = kriging with a trend. The second terminology has been proposed by Andre
          Journel who felt that the term "universal" was vague and misleadingly "ambitious".
           
          2. Kriging with an external drift (KED) is mathematically the same as universal kriging (UK). Secondary variables
          are simply replacing the spatial coordinates used in UK.
           
          3. Regression kriging denotes all the techniques where the trend is modeled outside the kriging algorithm.
          There are various methods that can be used to model that trend, ranging from linear regression
          to neural networks. Kriging is used to interpolate the residuals. In practice these techniques have more
          flexibility than universal kriging in term of modeling the trend: multiple variables either categorical or
          continuous can be incorporated  easily and many sofwtare are available for this trend modeling.
          The only limitation is that the trend is modeled globally (i.e. the regression coefficients are constant
          in space) while in KED the coefficients are reestimated within each search window.
           
          Cheers,
           
          Pierre
           

          Pierre Goovaerts

          Chief Scientist at Biomedware

          516 North State Street

          Ann Arbor, MI 48104

          Voice: (734) 913-1098
          Fax: (734) 913-2201

          http://home.comcast.net/~goovaerts/

                  -----Original Message-----
                  From: Recep kantarci [mailto:recep_kantarci_1978@...]
                  Sent: Thu 6/30/2005 9:38 AM
                  To: ai-geostats@...
                  Cc:
                  Subject: [ai-geostats] modelling trend and kriging type
                 
                 
                  Dear ai-geostats members
                  
                  When the data used has a trend, it is needed to model trend and in this case there exists various types of kriging to apply (universal kriging, kriging with a trend, regression kriging etc).

                  If this is the case, does one should use the same type of kriging or different depending on modeling the trend using coordinates of target variable or using other (namely, secondary or auxillary) variables such as elevation or topography ? That is , are there a dinstinction depending on the type of variables to model the trend while kriging?

                  
                  Best regards
                  Recep

                 
            _____ 

                  Yahoo! kullaniyor musunuz?
                  Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi korunma Yahoo! Posta’da
                  http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>

          **********************************************************************

          The information contained in this e-mail is confidential and is

          intended only for the use of the addressee(s).

          If you receive this e-mail in error, any use, distribution or

          copying of this e-mail is not permitted. You are requested to

          forward unwanted e-mail and address any problems to the

          Xstrata Queensland Support Centre.

          Support Centre e-mail: supportcentre@...

          Support Centre phone: Australia 1800 500 646

          International +61 2 9034 3710

          **********************************************************************

        • Isobel Clark
          Perry Your basic semi-variogram graph has a parabola added to it. Shoots off upwards (usually) at some distance. If the distance is large (past the range of
          Message 4 of 10 , Jul 7, 2005
          View Source
          • 0 Attachment
            Perry
             
            Your basic semi-variogram graph has a parabola added to it. Shoots off upwards (usually) at some distance. If the distance is large (past the range of influence) you can ignore it. See some of our  mid-80s papers on the Wolfcamp data which lots of people use as a teaching set now. Or read my free tutorial at http://geoecosse.bizland.com/softwares (kriging with trend).
             
            Isobel

            PCollier@... wrote:

            Hi all

            I may know this already, but what are the symptoms of data with a trend?  What is the difference between a dataset with a trend and a non-stationary dataset?

            Cheers


            Perry Collier

            Senior Mine Geologist
            Ernest Henry Mine  
            Xstrata Copper Australia
            Ph (07) 4769 4527
            Fx (07) 4769 4555
            E-mail PCollier@...
            Web http://www.xstrata.com
             
            PO Box 527
            Cloncurry QLD 4824
            Australia
             
            "Light travels faster than sound. That is why some people appear bright
            until you hear them speak"




            -----Original Message-----
            From: Pierre Goovaerts [mailto:Goovaerts@...]
            Sent: Friday, 1 July 2005 12:54 AM
            To: Recep kantarci; ai-geostats@...
            Subject: RE: [ai-geostats] modelling trend and kriging type


            To add to the excellent comments by Edzer and Gregoire,
             
            1. Universal kriging = kriging with a trend. The second terminology has been proposed by Andre
            Journel who felt that the term "universal" was vague and misleadingly "ambitious".
             
            2. Kriging with an external drift (KED) is mathematically the same as universal kriging (UK). Secondary variables
            are simply replacing the spatial coordinates used in UK.
             
            3. Regression kriging denotes all the techniques where the trend is modeled outside the kriging algorithm.
            There are various methods that can be used to model that trend, ranging from linear regression
            to neural networks. Kriging is used to interpolate the residuals. In practice these techniques have more
            flexibility than universal kriging in term of modeling the trend: multiple variables either categorical or
            continuous can be incorporated  easily and many sofwtare are available for this trend modeling.
            The only limitation is that the trend is modeled globally (i.e. the regression coefficients are constant
            in space) while in KED the coefficients are reestimated within each search window.
             
            Cheers,
             
            Pierre
             

            Pierre Goovaerts

            Chief Scientist at Biomedware

            516 North State Street

            Ann Arbor, MI 48104

            Voice: (734) 913-1098
            Fax: (734) 913-2201

            http://home.comcast.net/~goovaerts/

                    -----Original Message-----
                    From: Recep kantarci [mailto:recep_kantarci_1978@...]
                    Sent: Thu 6/30/2005 9:38 AM
                    To: ai-geostats@...
                    Cc:
                    Subject: [ai-geostats] modelling trend and kriging type
                   
                   
                    Dear ai-geostats members
                    
                    When the data used has a trend, it is needed to model trend and in this case there exists various types of kriging to apply (universal kriging, kriging with a trend, regression kriging etc).

                    If this is the case, does one should use the same type of kriging or different depending on modeling the trend using coordinates of target variable or using other (namely, secondary or auxillary) variables such as elevation or topography ? That is , are there a dinstinction depending on the type of variables to model the trend while kriging?

                    
                    Best regards
                    Recep

                   
              _____ 

                    Yahoo! kullaniyor musunuz?
                    Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi korunma Yahoo! Posta’da
                    http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>

            **********************************************************************

            The information contained in this e-mail is confidential and is

            intended only for the use of the addressee(s).

            If you receive this e-mail in error, any use, distribution or

            copying of this e-mail is not permitted. You are requested to

            forward unwanted e-mail and address any problems to the

            Xstrata Queensland Support Centre.

            Support Centre e-mail: supportcentre@...

            Support Centre phone: Australia 1800 500 646

            International +61 2 9034 3710

            **********************************************************************

            * By using the ai-geostats mailing list you agree to follow its rules
            ( see http://www.ai-geostats.org/help_ai-geostats.htm )

            * To unsubscribe to ai-geostats, send the following in the subject or in the body (plain text format) of an email message to sympa@...

            Signoff ai-geostats
          • Gregoire Dubois
            Hi Perry, I am curious to see how others will reply to your second question on the difference between a dataset with a trend and one that is non-stationary! My
            Message 5 of 10 , Jul 7, 2005
            View Source
            • 0 Attachment
              Hi Perry,

              I am curious to see how others will reply to your second question on the
              difference between a dataset with a trend and one that is
              non-stationary! My reply may sound provocative: you can always remove a
              trend when you recognize that there is one. Moving from non-stationarity
              to stationarity, on the other hand, can be infinitely more complex (e.g.
              moving to non-Euclidean space)

              :)


              For what concerns the detection of trends, have a look at the variogram:
              a quadratic/exp. increase usually means that there is a trend. Get rid
              of the presumed trend and check the variogram of the residuals which
              should clearly show a change of structure (if you had a trend
              obviously). Quicker might be to use a moving windows strategy to plot
              local averages and check if you see any structure (be careful that the
              "structure" is not simply an anisotropy of your variable). You could
              have a look into the old archives of AI-GEOSTATS. There have been very
              nice replies from Donald Myers (see his publications) in the past on
              these issues. see http://groups.yahoo.com/group/ai-geostats/

              Regards

              GD



              -----Original Message-----
              From: PCollier@... [mailto:PCollier@...]
              Sent: 07 July 2005 03:49
              To: ai-geostats@...
              Subject: RE: [ai-geostats] modelling trend and kriging type


              Hi all
              I may know this already, but what are the symptoms of data with a trend?
              What is the difference between a dataset with a trend and a
              non-stationary dataset?
              Cheers


              Perry Collier
              Senior Mine Geologist
              Ernest Henry Mine
              Xstrata Copper Australia
              Ph (07) 4769 4527
              Fx (07) 4769 4555
              E-mail PCollier@...
              Web http://www.xstrata.com

              PO Box 527
              Cloncurry QLD 4824
              Australia

              "Light travels faster than sound. That is why some people appear bright
              until you hear them speak"




              -----Original Message-----
              From: Pierre Goovaerts [mailto:Goovaerts@...]
              Sent: Friday, 1 July 2005 12:54 AM
              To: Recep kantarci; ai-geostats@...
              Subject: RE: [ai-geostats] modelling trend and kriging type


              To add to the excellent comments by Edzer and Gregoire,

              1. Universal kriging = kriging with a trend. The second terminology has
              been proposed by Andre
              Journel who felt that the term "universal" was vague and misleadingly
              "ambitious".

              2. Kriging with an external drift (KED) is mathematically the same as
              universal kriging (UK). Secondary variables
              are simply replacing the spatial coordinates used in UK.

              3. Regression kriging denotes all the techniques where the trend is
              modeled outside the kriging algorithm.
              There are various methods that can be used to model that trend, ranging
              from linear regression
              to neural networks. Kriging is used to interpolate the residuals. In
              practice these techniques have more
              flexibility than universal kriging in term of modeling the trend:
              multiple variables either categorical or
              continuous can be incorporated easily and many sofwtare are available
              for this trend modeling.
              The only limitation is that the trend is modeled globally (i.e. the
              regression coefficients are constant
              in space) while in KED the coefficients are reestimated within each
              search window.

              Cheers,

              Pierre

              Pierre Goovaerts
              Chief Scientist at Biomedware
              516 North State Street
              Ann Arbor, MI 48104
              Voice: (734) 913-1098
              Fax: (734) 913-2201
              http://home.comcast.net/~goovaerts/
              -----Original Message-----
              From: Recep kantarci [mailto:recep_kantarci_1978@...]
              Sent: Thu 6/30/2005 9:38 AM
              To: ai-geostats@...
              Cc:
              Subject: [ai-geostats] modelling trend and kriging type


              Dear ai-geostats members

              When the data used has a trend, it is needed to model trend and
              in this case there exists various types of kriging to apply (universal
              kriging, kriging with a trend, regression kriging etc).
              If this is the case, does one should use the same type of
              kriging or different depending on modeling the trend using coordinates
              of target variable or using other (namely, secondary or auxillary)
              variables such as elevation or topography ? That is , are there a
              dinstinction depending on the type of variables to model the trend while
              kriging?

              Best regards
              Recep

              _____
              Yahoo! kullaniyor musunuz?
              Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi
              korunma Yahoo! Posta'da
              http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>
              **********************************************************************
              The information contained in this e-mail is confidential and is
              intended only for the use of the addressee(s).
              If you receive this e-mail in error, any use, distribution or
              copying of this e-mail is not permitted. You are requested to
              forward unwanted e-mail and address any problems to the
              Xstrata Queensland Support Centre.
              Support Centre e-mail: supportcentre@...
              Support Centre phone: Australia 1800 500 646
              International +61 2 9034 3710
              **********************************************************************
            • sebastiano.trevisani@unipd.it
              Dear Perry Collier I`m interested in the second question: what is the difference between a dataset with a trend and a non-stationary dataset? Without clearly
              Message 6 of 10 , Jul 8, 2005
              View Source
              • 0 Attachment
                Dear Perry Collier
                I`m interested in the second question: what is the difference between a dataset
                with a trend and a non-stationary dataset?
                Without clearly pointing out about which kind of stationarity we are talking
                (second order, intrinsic or generalized intrinsic), we need stationarity
                (well !!! togheter with ergodicity) for some statistical index (in this case a
                index about spatial variability) to perform inference. From my perspective the
                dualism trend-residual makes possible always (or not?) to explain non
                stationarity in spatial variability in term of presence of a trend: this trend
                could be global as well as local: it is only a matter of scale.The point is: we
                have reasons or so many data to use a complex trend model?

                In particular this question makes me to think to a point. Very often people who
                use Universal Kriging do this:
                1) detrend data globally (same trend coefficients for all spatial domain)
                2) calculate a residual variogram
                3) perfom Uk with local search windows (inside which the trend coefficients are
                calculated i.e. the trend is filtered locally)
                This doesen`t seem to me correct: I think (maybe, if you have many data IRF-K
                approach works better) that you can not
                one time calculate trend globally and the other time locally: it could happen
                that globally you need a quadratic trend while locally a linear trend model is
                enough. What about that?

                Sincerely,
                Sebastiano Trevisani



                At 03.48 07/07/2005, PCollier@... wrote:

                Hi all

                I may know this already, but what are the symptoms of data with a trend? What
                is the difference between a dataset with a trend and a non-stationary dataset?

                Cheers

                Perry Collier

                Senior Mine Geologist
                Ernest Henry Mine
                Xstrata Copper Australia
                Ph (07) 4769 4527
                Fx (07) 4769 4555
                E-mail PCollier@...
                Web http://www.xstrata.com

                PO Box 527
                Cloncurry QLD 4824
                Australia

                "Light travels faster than sound. That is why some people appear bright
                until you hear them speak"



                -----Original Message-----
                From: Pierre Goovaerts [mailto:Goovaerts@...]
                Sent: Friday, 1 July 2005 12:54 AM
                To: Recep kantarci; ai-geostats@...
                Subject: RE: [ai-geostats] modelling trend and kriging type

                To add to the excellent comments by Edzer and Gregoire,

                1. Universal kriging = kriging with a trend. The second terminology has been
                proposed by Andre
                Journel who felt that the term "universal" was vague and
                misleadingly "ambitious".

                2. Kriging with an external drift (KED) is mathematically the same as universal
                kriging (UK). Secondary variables
                are simply replacing the spatial coordinates used in UK.

                3. Regression kriging denotes all the techniques where the trend is modeled
                outside the kriging algorithm.
                There are various methods that can be used to model that trend, ranging from
                linear regression
                to neural networks. Kriging is used to interpolate the residuals. In practice
                these techniques have more
                flexibility than universal kriging in term of modeling the trend: multiple
                variables either categorical or
                continuous can be incorporated easily and many sofwtare are available for this
                trend modeling.
                The only limitation is that the trend is modeled globally (i.e. the regression
                coefficients are constant
                in space) while in KED the coefficients are reestimated within each search
                window.

                Cheers,

                Pierre


                Pierre Goovaerts

                Chief Scientist at Biomedware

                516 North State Street

                Ann Arbor, MI 48104

                Voice: (734) 913-1098
                Fax: (734) 913-2201

                http://home.comcast.net/~goovaerts/

                -----Original Message-----
                From: Recep kantarci [mailto:recep_kantarci_1978@...]
                Sent: Thu 6/30/2005 9:38 AM
                To: ai-geostats@...
                Cc:
                Subject: [ai-geostats] modelling trend and kriging type


                Dear ai-geostats members

                When the data used has a trend, it is needed to model trend and in this
                case there exists various types of kriging to apply (universal kriging, kriging
                with a trend, regression kriging etc).

                If this is the case, does one should use the same type of kriging or
                different depending on modeling the trend using coordinates of target variable
                or using other (namely, secondary or auxillary) variables such as elevation or
                topography ? That is , are there a dinstinction depending on the type of
                variables to model the trend while kriging?


                Best regards
                Recep


                _____

                Yahoo! kullaniyor musunuz?
                Istenmeyen postadan biktiniz mi? Istenmeyen postadan en iyi korunma
                Yahoo! Posta’da
                http://tr.mail.yahoo.com <http://tr.mail.yahoo.com/>

                **********************************************************************

                The information contained in this e-mail is confidential and is

                intended only for the use of the addressee(s).

                If you receive this e-mail in error, any use, distribution or

                copying of this e-mail is not permitted. You are requested to

                forward unwanted e-mail and address any problems to the

                Xstrata Queensland Support Centre.

                Support Centre e-mail: supportcentre@...

                Support Centre phone: Australia 1800 500 646

                International +61 2 9034 3710

                **********************************************************************
                * By using the ai-geostats mailing list you agree to follow its rules
                ( see http://www.ai-geostats.org/help_ai-geostats.htm )

                * To unsubscribe to ai-geostats, send the following in the subject or in the
                body (plain text format) of an email message to sympa@...

                Signoff ai-geostats


                -------------------------------------------------
                This mail sent through IMP: webmail.unipd.it
              Your message has been successfully submitted and would be delivered to recipients shortly.