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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
      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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