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1515RE: AI-GEOSTATS: testing sample number

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  • Mark Dowdall
    Mar 31, 2004
    • 0 Attachment
      Hello

      This is a newbie question but I have been all over the Faqs and cannot
      find an answer.

      Any help is appreciated and a summary of answers will be posted.

      I have a set of data that was taken over a particular area. I have
      kriged and contoured and am happy with the results.

      But I need to demonstrate, within the bounds of the
      study/analysis/assumptions, that the number of samples taken was
      sufficient to describe the area.

      So my plan was to demonstrate that for a cetain number of samples the
      variance in the estimates had reached a value that could not be reduced
      efefctively by increasing sample number.

      And I thought this could be done by eliminating at random a point (so I
      have x-1 data points), kriging the remainder with the chosen parameters
      and checking the relevant parameters. (x is the number of actual
      samples)

      Then eliminating two points at random (x-2), repeating and so on.
      Eventually only 1 point being left.

      But.....if I eliminate the first point at random, does it matter which
      point is eliminated? Or in the first instance (x-1 points) should I do
      the process for all possible samples and take an average of the
      estimation uncertainty?

      I am using GEOEAS and this could take a long time as all possible
      permutations of for example x-20 could be quite large.

      I did download Explostat which has a feature that sems to do this
      automatically but the manual is not great and the software is a little
      impenetrable.

      If anyone can shed light on this I would be most grateful.

      Thanks in advance

      M.dowdall

      Ie.



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