Loading ...
Sorry, an error occurred while loading the content.

AI-GEOSTATS: Dealing with Universal Kriging

Expand Messages
  • Rubens Caldeira Monteiro
    Dear all, We are trying to apply Universal Kriging to “High Plains” Aquifer in Kansas (OLEA, 1999) for land surface elevation (LSE), using its 317 data
    Message 1 of 3 , Apr 9, 2002
    • 0 Attachment
      Dear all,

      We are trying to apply Universal Kriging to “High Plains” Aquifer in
      Kansas (OLEA, 1999) for land surface elevation (LSE), using its 317 data
      points. The purpose of this application is just for didactic ends.
      Our first step was to filter a prominent 1st degree drift. The way we
      did it was using Surfer 8.0 (Golden Software) and obtaining the
      residuals, in such way that summing the residuals by the 1st degree
      trend we obtain the original data.
      Obviously the values of this new variable (residuals of LSE, i.e., RLSE)
      are much lower than the original one.
      Calculating the experimental variogram, modeling it and kriging the
      variable is possible to obtain the RLSE (residuals of land surface
      elevation) map. Summing this map to the drift (calculated in a
      deterministic way) we obtain a map that we suppose that represents a map
      for the original variable (LSE).
      But what about the standard deviation?
      We did a little test and it seems that the standard deviation map for
      the residuals (RLSE) represents the std. dev. map for the original
      variable (LSE).

      Is this a correct conclusion and procedure? If we have less data, will
      it work? If we use a 2nd degree drift the standard deviation could be
      wrong?

      Thanks for your attention,

      Rubens

      ==========================
      Rubens Caldeira Monteiro
      # ICQ 106157533
      São Paulo State University at Rio Claro - UNESP/Rio Claro
      – PhD candidate on Geosciences & Environmental Sci.
      São Paulo University at Piracicaba - ESALQ-USP/Piracicaba
      – Undergrad. on Environmental Management
      University of North Carolina at Chapel Hill - UNC-CH
      URL: <http://www.unc.edu/~rubenscm/CASEhome.html>
      http://www.unc.edu/~rubenscm/CASEhome.html



      [Non-text portions of this message have been removed]
    • Isobel Clark
      Rubens Your approach has been long used in hydrology and similar fields with much success. The problem with the standard deviation is that it does not include
      Message 2 of 3 , Apr 9, 2002
      • 0 Attachment
        Rubens

        Your approach has been long used in hydrology and
        similar fields with much success.

        The problem with the standard deviation is that it
        does not include the the 'error' on the estimation of
        the true drift. To get a composite error you would
        either have to

        (a) add your kriging variance to some sort of
        classical regression variance to get a composite one;

        (b) use a Universal Kriging (or generalised
        covariance) approach to estimate the surface with the
        drift included.

        In our experience, your estimated surface will not
        change but your kriging variances will increase
        slightly.

        Isobel Clark

        __________________________________________________
        Do You Yahoo!?
        Everything you'll ever need on one web page
        from News and Sport to Email and Music Charts
        http://uk.my.yahoo.com

        --
        * 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.
        * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
        * Support to the list is provided at http://www.ai-geostats.org
      • Isobel Clark
        Alessandro Thanks for the contribution. If Universal Kriging is applied, there is no need for simulation or multi-indicator approaches to get a standard error,
        Message 3 of 3 , Apr 10, 2002
        • 0 Attachment
          Alessandro

          Thanks for the contribution.

          If Universal Kriging is applied, there is no need for
          simulation or multi-indicator approaches to get a
          standard error, it comes with the solution.

          Isobel

          __________________________________________________
          Do You Yahoo!?
          Everything you'll ever need on one web page
          from News and Sport to Email and Music Charts
          http://uk.my.yahoo.com

          --
          * 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.
          * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
          * Support to the list is provided at http://www.ai-geostats.org
        Your message has been successfully submitted and would be delivered to recipients shortly.