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

Re: AI-GEOSTATS: indicator kriging with a trend

Expand Messages
  • Pierre Goovaerts
    Hi Marius, There are different ways to deal with a trend, which depends whether it is considered as global (i.e. over the entire area) or local (i.e. within
    Message 1 of 2 , Dec 17, 2002
    • 0 Attachment
      Hi Marius,

      There are different ways to deal with a trend, which
      depends whether it is considered as global (i.e.
      over the entire area) or local (i.e. within the
      search window used for kriging). Universal kriging
      is a way to deal with local trends, that is the mean
      is not assumed to be constant within the search window
      but modeled as a linear combination of functions of
      spatial coordinates.
      For global trends, you can either (1) ignore it if the
      search window is not too large with respect to the
      extent of the trend and use ordinary kriging,
      or (2) model it as a function of spatial coordinates
      and perform kriging on the residuals, or (3) use
      UK with a very large search window (could not be
      implemented if the data density is too high).

      The public-domain code ik3d from Gslib would allow you
      to implement the aforementioned options.

      Regards,

      Pierre Goovaerts
      <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

      Dr. Pierre Goovaerts
      Consultant in (Geo)statistics
      and Senior Chief Scientist with Biomedware Inc.
      710 Ridgemont Lane
      Ann Arbor, Michigan, 48103-1535, U.S.A.

      E-mail: goovaert@...
      Phone: (734) 668-9900
      Fax: (734) 668-7788
      http://alumni.engin.umich.edu/~goovaert/

      <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

      On Tue, 17 Dec 2002, Marius Gilbert wrote:

      > Dear colleagues,
      >
      > I have a set of presence/absence spatial data (1,0) representing the
      > locations of site infested/uninfested trees by a tree pest. The
      > distribution of infested sites (1) presents a strong trend toward the
      > south (infested sites are much more abundant in the south). All
      > semivariance estimators (variogram, std variogram, correlogram) are thus
      > biased by this trend. I would like to estimate the infestation probability
      > using kriging, but wonder how I should adress this. I have considered the
      > following options:
      >
      > a) Indicator kriging: Can IK account for spatial trend ? If so, how ?
      > (any indication regarding software package would be appreciated)
      >
      > b) Universal kriging of binary data: would this be a valid way to estimate
      > infestation probability ? If not, what would be the caveats of using such
      > approach ?
      >
      > Any help would be greatly appreciated and will be summarized to the list.
      >
      > Have a good day,
      >
      > Marius Gilbert
      >
      >
      >
      >
      > --------------------------------------------------
      > Dr. Marius Gilbert
      > Collaborateur Scientifique FNRS
      > Laboratoire de biologie animale et cellulaire
      > Universite Libre de Bruxelles CP 160/12
      > 50, av F.D. Roosevelt 1050, Bruxelles BELGIUM
      > http://lubies.ulb.ac.be
      > ---------------------------------------------------
      >
      >
      >
      > --
      > * 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
      >


      --
      * 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.