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Re: AI-GEOSTATS: unconditional gaussian simulation using GSLIB

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  • Pierre Goovaerts
    Hello, The constraint that the sill must be one arises from the fact that the simulation is conducted in the normal space. Just standardize the semivariogram
    Message 1 of 1 , May 23, 2003
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      Hello,

      The constraint that the sill must be one arises from the
      fact that the simulation is conducted in the normal space.
      Just standardize the semivariogram model to a unit sill, perform
      the non conditional simulation, then rescale the simulated
      normal scores to the desired mean and variance.
      Note that the final distribution of simulated values will be normal.
      A non Gaussian reference distribution can also be specified
      in the sgsim parameter file if needed.

      Regards,

      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: goovaert@...
      Phone: (734) 668-9900
      Fax: (734) 668-7788
      http://alumni.engin.umich.edu/~goovaert/

      <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

      On Fri, 23 May 2003, #GAO SHAN# wrote:

      > Dear all:
      >
      > I am trying to generate an unconditional realization using SGSIM of
      > GSLIB.
      >
      > The mean and deviation of the result data should be: 30 and 7.1
      >
      > The spatial variation should follow a 3d spherical model with following
      >
      > Parameters:
      > Horizontal: a=30 c=50;
      > Vertical: a=3 c=50;
      >
      > My questions are:
      >
      > (1) What should I put in the parameter file for my variogram
      > The parameter file for SGSIM requires the sum of sill to be 1,
      > Should I standardize my variogram by setting cc=1?
      > Can anyone help me to figure out why this constraint is added?
      > I still can not figure out the difference between the "krige" subroutine
      > used in this simulation process and the "kt3d" kriging programs,
      > although there should be someone if different variogram parameters are
      > used.
      >
      >
      > (2) Because the specific mean and deviation value (rather than the
      > default values: mean:0 , deviation:1), is it enough just to change the
      > mean and deviation values of the random number generation in the SGSIM
      > subroutine.
      >
      > Thanks for the help.
      >
      > GaoShan
      >
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