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Re: AI-GEOSTATS: 3D-kriging with soil data

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  • Med Bennett
    ... I would compute a vertical or downhole variogram to see if there if any significant spatial correlation in that direction. If so, you should attempt to
    Message 1 of 3 , Jun 7, 2001
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      At 01:03 PM 6/7/01 +0200, Markus Boehm wrote:
      >Dear all,
      >
      >how should soil data (~3300 profiles, ~150m average horizontal distance,
      >all about 1 meter deep with different thickness of horizons representing
      >type of soil, humus contents, ...) be kriged?
      >
      >I need all information of the different horizons to calculate the somewhat
      >like ground water infiltration rate.
      >
      >Does it make sense to use 3D-kriging methods? I think then there should a
      >modification of the z-coordinate be made. I mean stretching of the
      >z-coordinate. Does anyone know how to deal with the problem or some useful
      >textbook?
      >
      >Or would you prefer to do 2D-kriging for a number of depths (10cm,
      >20cm,...), so there's no need to modify the z-coordinate?
      >
      >
      >Regards,
      >Markus


      I would compute a vertical or "downhole" variogram to see if there if any
      significant spatial correlation in that direction. If so, you should
      attempt to use a 3D kriging method, as it would be wasteful not to use that
      information. You will have to use a very high value for anisotropy in the
      Z direction (on the order of 1000 probably) or else leave the depth units
      as cm and the horizontal units in m.


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    • Markus Boehm
      Dear List, sorry that you had to wait for this summary. I post the answers that I received in this Mail with the corresponding names and email addresses. The
      Message 2 of 3 , Jun 21, 2001
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        Dear List,

        sorry that you had to wait for this summary.

        I post the answers that I received in this Mail with the corresponding
        names and email addresses. The answers were help for us to decide to do
        kriging in 2-dimensional layers. However, so far do not have final results
        but it seems to work fine this way.
        Thanks to


        Rudi Dutter <R.Dutter@...>:
        (...
        I was involved in a geochemical analysis project at the peninsula Kola
        where we
        had less data than you have, and also a much smaller amount of values in
        the
        z-direction. Nevertheless the results are documented in
        C. Reiman et al. (1998): Environmental Geochemical Atlas of the Central
        Barents
        Region. Norges geologiske undersokelse (NGU), Geological Survey of Norway.

        We experienced with kriging in 2-dimensional layers, and the results are
        published. Only afterwards we started investigating the relations between
        the
        empirical structures between the layers. This seems to be very
        interesting,
        however, no result is published.

        I believe that 3d-kriging does not bring much, however, the comparisons
        between
        the structures of the layers are very challencing.
        ...)



        Denis Marcotte <Denis.Marcotte@...>:
        (...
        It is probably better to treat this kind of data as 2D, soil type by soil
        type. You can krige the thickness of each soil type and also the measured
        variables; this will allow you to reconstruct vertical sections
        everywhere. The data probably shows a complicated trend along the vertical
        profile which complicates seriously the 3D study.
        ...)



        Med Bennett <mbennett@...>:
        (...
        I would compute a vertical or "downhole" variogram to see if there if any
        significant spatial correlation in that direction. If so, you should
        attempt to use a 3D kriging method, as it would be wasteful not to use
        that
        information. You will have to use a very high value for anisotropy in the
        Z direction (on the order of 1000 probably) or else leave the depth units
        as cm and the horizontal units in m.
        ...)



        "Nel, Fanie" <fnel@...>:
        (...
        I would suggest that you only krig within a horizon , not across horizons.
        This assumes that the variables behave diffrently in each horizon. You
        will
        also have to estimate the width of each horizon.

        If a variable shows a different variograms vertically and horizontally you
        should do 3D kriging.
        ...)



        I hope there all who wrote to me listed above (there is some chaos in my
        Mailbox these days).

        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        Markus Böhm
        Groner Landstr. 45
        D-37081 Goettingen

        fon: +49 (0)551 / 5317388
        fax: +49 (0)180 / 01212 5 109 12 817
        mail: 1) mboehm@...-goettingen
        2) boehm.m@...
        url: http://www.stud.uni-goettingen.de/~mboehm

        On Thu, 7 Jun 2001, Markus Boehm wrote:

        > Dear all,
        >
        > how should soil data (~3300 profiles, ~150m average horizontal distance,
        > all about 1 meter deep with different thickness of horizons representing
        > type of soil, humus contents, ...) be kriged?
        >
        > I need all information of the different horizons to calculate the somewhat
        > like ground water infiltration rate.
        >
        > Does it make sense to use 3D-kriging methods? I think then there should a
        > modification of the z-coordinate be made. I mean stretching of the
        > z-coordinate. Does anyone know how to deal with the problem or some useful
        > textbook?
        >
        > Or would you prefer to do 2D-kriging for a number of depths (10cm,
        > 20cm,...), so there's no need to modify the z-coordinate?
        >
        >
        > Regards,
        > Markus
        >
        >
        > --
        > * To post a message to the list, send it to ai-geostats@...
        > * As a general service to the users, please remember to post a summary of any useful responses to your questions.
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        >


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