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

AI-GEOSTATS: Negative variances

Expand Messages
  • Kevin Lowe Rfn
    Hi all I have been experimenting with various kriging methods in estimating Witwatersrand gold grades (South Africa) using Datamine software. I found that
    Message 1 of 2 , Nov 1, 2001
    • 0 Attachment
      Hi all

      I have been experimenting with various kriging methods in estimating
      Witwatersrand gold grades (South Africa) using Datamine software. I found
      that using lognormal ordinary kriging has resulted in negative variances in
      some blocks.

      My question is why does this happen and what is the significance of it?

      Kevin Lowe
      e-mail KLowe@...

      --
      * 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
      Kevin There is something badly wrong with your software. With ordinary kriging, it is not possible to get negative variances. With lognormal kriging, it is not
      Message 2 of 2 , Nov 2, 2001
      • 0 Attachment
        Kevin

        There is something badly wrong with your software.

        With ordinary kriging, it is not possible to get
        negative variances.

        With lognormal kriging, it is not possible to get
        negative varianse or negative estimates unless you are
        using a large additive constant.

        Isobel Clark
        http://uk.geocities.com/drisobelclark

        --- Kevin Lowe Rfn <KLowe@...> wrote: > Hi
        all
        >
        > I have been experimenting with various kriging
        > methods in estimating
        > Witwatersrand gold grades (South Africa) using
        > Datamine software. I found
        > that using lognormal ordinary kriging has resulted
        > in negative variances in
        > some blocks.
        >
        > My question is why does this happen and what is the
        > significance of it?
        >
        > Kevin Lowe
        > e-mail KLowe@...
        >
        > --
        > * 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

        ____________________________________________________________
        Nokia Game is on again.
        Go to http://uk.yahoo.com/nokiagame/ and join the new
        all media adventure before November 3rd.

        --
        * 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.