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Re: GEOSTATS: Kriging query

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  • srahman@lgc.com
    ... I m ... valley, the . ... me to ... Since the valley is U-shaped, I am sure the valley wouldn t take too kindly to being treated as a flat surface, being a
    Message 1 of 2 , Mar 4, 1998
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      Fran Taylor wrote:

      > I was wondering if anyone has happened to have tried kriging of valleys.
      > trying to create a surface of a u-shaped valley using kriging.
      > An obvious observation (but none-the-less important) is that being a
      valley, the .
      > surface is not flat, either in long-profile or cross-section, which leads
      me to
      > ask, does this matter? should I account for drift, and do I do this using

      > universal kriging?

      Since the valley is U-shaped, I am sure the valley wouldn't take too kindly
      to being treated as a flat surface, being a valley and all. Either krige
      a limited search neighborhood or do a full universal kriging using, say,
      a polynomial drift of order 2 to describe the valley's trend. Use the early
      lag behavior for the variogram, ignoring the drift, or find a flat lying
      where the drift component is not likely to have much of an effect on the
      variogram. Have a look at the results -- does the valley still look like a
      just like all normal valleys? Such a shape should be retained because for
      a valley it makes sense.

      >A further question (if anyone is still reading this), I want to account
      for the
      >fact that the spatial variation over the valley surface is different in
      >different dirrections (ie is anisotrpic) I want to krig in the direction
      of the
      >long profile of the valley and in the direction of cross-section, can I do
      >without accounting for the drift (mentioned above). Would accounting for
      >anisotropy, cancel out the need to remove any drift that there might be in
      >data as a result of glacier valleys not being flat?

      Anisotropies account for the different ranges in different directions.
      are just that, trends -- an entirely different beast all together. You can
      a drift in the cross-sectional direction, but still get more or less the
      same range
      as the perpendicular direction.



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