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GEOSTATS: Kriging query

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  • Fran Taylor
    Hello I was wondering if anyone has happened to have tried kriging of valleys. I m trying to create a surface of a u-shaped valley using kriging. An obvious
    Message 1 of 2 , Feb 24 3:01 PM
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      Hello

      I was wondering if anyone has happened to have tried kriging of valleys. I'm
      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?

      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 this
      without accounting for the drift (mentioned above). Would accounting for the
      anisotropy, cancel out the need to remove any drift that there might be in the
      data as a result of glacier valleys not being flat?

      Cheers

      Fran Taylor



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      Frances M Taylor

      Department of Geography
      University of Edinburgh
      Drummond Street
      Edinburgh
      EH9 8XP

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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 2 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.
        I'm
        > 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
        with
        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
        surface
        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
        U
        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
        this
        >without accounting for the drift (mentioned above). Would accounting for
        the
        >anisotropy, cancel out the need to remove any drift that there might be in
        the
        >data as a result of glacier valleys not being flat?

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

        Regards,

        Syed


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