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RE: [ai-geostats] std deviation when using SGSIM

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  • Julián Ortiz
    Hello, This may be due to conditioning data that lower the std. dev. of your realizations. If you want to fix this, you could use the program TRANS in GSLIB
    Message 1 of 3 , Jul 20, 2004
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      Hello,

      This may be due to conditioning data that lower the std. dev. of your
      realizations.
      If you want to fix this, you could use the program TRANS in GSLIB and refer
      to the
      paper:

      "Posterior Identification of Histograms Conditional to Local Data, by A. G.
      Journel and W. Xu,
      Mathematical Geology, 26(3):323-359, 1994.

      If you are doing unconditional simulation, the lower std. dev. may be due to
      the size of your
      field as compared to the range of your variogram.

      Best regards,

      Julián Ortiz C., Ph. D.
      Profesor Asistente
      Departamento de Ingeniería de Minas
      Universidad de Chile

      Fono: +56 2 678 4585
      Fax : +56 2 672 3504
      Web : www.ualberta.ca/~jmo1

      -----Mensaje original-----
      De: Oriol Falivene [mailto:ofaliven@...]
      Enviado el: martes, 20 de julio de 2004 4:00
      Para: ai-geostats@...
      Asunto: [ai-geostats] std deviation when using SGSIM


      Hello,

      We're using SGSIM from GSLIB to create gaussian fields of standard
      deivation = 1.
      We realize that the standard deviation is always underestimated, tipical
      obtianed values are betwee 0.7 and 0.9.
      How can I get the correct std. dev?

      Regards

      --



      ______________________________________

      Oriol Falivene
      ofaliven@...
      http://www.ub.es/ggac

      tel. (+34) 93 4021373
      fax (+34) 93 4021340

      Fac. de Geologia,
      Univ. de Barcelona
    • Oriol Falivene
      Thanks Julian, I was doing unconditional simulation and the ranges were to large. I ve made some tests and each range should be at least 1/10 the grid
      Message 2 of 3 , Jul 20, 2004
      • 0 Attachment
        Thanks Julian,

        I was doing unconditional simulation and the ranges were to large. I've made
        some tests and each range should be at least 1/10 the grid dimensions to obtain
        a good match of the standard deviation. There is any literature regarding this
        issue?

        Regards.

        Oriol

        Julián Ortiz wrote:

        > Hello,
        >
        > This may be due to conditioning data that lower the std. dev. of your
        > realizations.
        > If you want to fix this, you could use the program TRANS in GSLIB and refer
        > to the
        > paper:
        >
        > "Posterior Identification of Histograms Conditional to Local Data, by A. G.
        > Journel and W. Xu,
        > Mathematical Geology, 26(3):323-359, 1994.
        >
        > If you are doing unconditional simulation, the lower std. dev. may be due to
        > the size of your
        > field as compared to the range of your variogram.
        >
        > Best regards,
        >
        > Julián Ortiz C., Ph. D.
        > Profesor Asistente
        > Departamento de Ingeniería de Minas
        > Universidad de Chile
        >
        > Fono: +56 2 678 4585
        > Fax : +56 2 672 3504
        > Web : www.ualberta.ca/~jmo1
        >
        > -----Mensaje original-----
        > De: Oriol Falivene [mailto:ofaliven@...]
        > Enviado el: martes, 20 de julio de 2004 4:00
        > Para: ai-geostats@...
        > Asunto: [ai-geostats] std deviation when using SGSIM
        >
        > Hello,
        >
        > We're using SGSIM from GSLIB to create gaussian fields of standard
        > deivation = 1.
        > We realize that the standard deviation is always underestimated, tipical
        > obtianed values are betwee 0.7 and 0.9.
        > How can I get the correct std. dev?
        >
        > Regards
        >
        > --
        >
        > ______________________________________
        >
        > Oriol Falivene
        > ofaliven@...
        > http://www.ub.es/ggac
        >
        > tel. (+34) 93 4021373
        > fax (+34) 93 4021340
        >
        > Fac. de Geologia,
        > Univ. de Barcelona

        --



        ______________________________________

        Oriol Falivene
        ofaliven@...
        http://www.ub.es/ggac

        tel. (+34) 93 4021373
        fax (+34) 93 4021340

        Fac. de Geologia,
        Univ. de Barcelona
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