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RE: AI-GEOSTATS: I'm new

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  • Gregoire Dubois
    Hi Guido, As Pierre wrote, I have put some material on the web site of AI-GEOSTATS: 1) Frequently Asked Questions (See FAQs) 2) Links to papers published
    Message 1 of 5 , Mar 30, 2004
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      Hi Guido,

      As Pierre wrote, I have put some material on the web site of
      AI-GEOSTATS:

      1) Frequently Asked Questions (See FAQs)

      2) Links to papers published online (mainly conference proceedings but I
      linked only those I found of a good quality). You could also check
      www.scirus.com : you will get for free hundreds of recent peer reviewed
      paper for free in a pdf format.

      3) Software. All software for geostatistics have a similar architecture.
      Try Geoeas & Variowin (free) until you become confident with words like
      semivariogram, covariance, kriging, block kriging. There if
      unfortunately no manual for Variowin. I will ask Yvan Pannatier (the
      author of Variowin) if there is any way to get an electronic copy of his
      book (out of print since a few years) or of the help file that I can put
      on the ai-geostats web site. There is nothing else available now and it
      is much needed. I think this is the best way to have an idea on what the
      whole is about. The software mentioned above can be downloaded for free
      and there are plenty of other tools for more advanced geostatistics.

      4) Last but not least, the archives of ai-geostats (see web site for
      links) are a goldmine thanks to the kings and queens of geostatistics
      who constantly gave all these years the best support one would dream
      about.

      Welcome to ai-geostats and good luck !

      Gregoire



      -----Original Message-----
      From: ai-geostats-list@... [mailto:ai-geostats-list@...] On
      Behalf Of guidichi@...
      Sent: 30 March 2004 20:49
      To: ai-geostats@...
      Subject: AI-GEOSTATS: I'm new
      Importance: High


      Hello list,
      My name is Guido Sagasti. I'm from Rosario City (Argentina) and I'm
      studying Statistics at the university. My english isn't the best, as
      you'll see or you can see now. I'm here because I'm interested in
      Spatial Statistics (Geostatistics, autoregresive models, spatial
      interpolation, etc.). I'm not read a lot about the subject and don't
      have a lot of material about it (It's not developed here - we don't have
      spatial statistics at University but the statistic and mathematical
      formation is very strong and I think I can handle with it) I want to
      know if there is material for principiants in the subject in the
      internet. In spite of my poor experience about spatial statistics, I'm
      100% aviable for everyone.

      Thanks
      Guido Sagasti.


      --------
      E-mail y acceso a Internet UltraVeloz totalmente GRATIS en Buenos Aires,
      Rosario, Cordoba, Mendoza, La Plata y Pilar http://www.Argentina.com
      Nro. de acceso 5078-5000 Usuario: Argentina Password: Argentina




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    • Mark Dowdall
      Hello This is a newbie question but I have been all over the Faqs and cannot find an answer. Any help is appreciated and a summary of answers will be posted.
      Message 2 of 5 , Mar 31, 2004
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        Hello

        This is a newbie question but I have been all over the Faqs and cannot
        find an answer.

        Any help is appreciated and a summary of answers will be posted.

        I have a set of data that was taken over a particular area. I have
        kriged and contoured and am happy with the results.

        But I need to demonstrate, within the bounds of the
        study/analysis/assumptions, that the number of samples taken was
        sufficient to describe the area.

        So my plan was to demonstrate that for a cetain number of samples the
        variance in the estimates had reached a value that could not be reduced
        efefctively by increasing sample number.

        And I thought this could be done by eliminating at random a point (so I
        have x-1 data points), kriging the remainder with the chosen parameters
        and checking the relevant parameters. (x is the number of actual
        samples)

        Then eliminating two points at random (x-2), repeating and so on.
        Eventually only 1 point being left.

        But.....if I eliminate the first point at random, does it matter which
        point is eliminated? Or in the first instance (x-1 points) should I do
        the process for all possible samples and take an average of the
        estimation uncertainty?

        I am using GEOEAS and this could take a long time as all possible
        permutations of for example x-20 could be quite large.

        I did download Explostat which has a feature that sems to do this
        automatically but the manual is not great and the software is a little
        impenetrable.

        If anyone can shed light on this I would be most grateful.

        Thanks in advance

        M.dowdall

        Ie.



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      • Koen Hufkens
        ... I never used variowin but it seems quite nice, and more important free! Here is a introduction to variowin:
        Message 3 of 5 , Mar 31, 2004
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          > 3) Software. All software for geostatistics have a similar architecture.
          > Try Geoeas & Variowin (free) until you become confident with words like
          > semivariogram, covariance, kriging, block kriging. There if
          > unfortunately no manual for Variowin. I will ask Yvan Pannatier (the
          > author of Variowin) if there is any way to get an electronic copy of his
          > book (out of print since a few years) or of the help file that I can put
          > on the ai-geostats web site. There is nothing else available now and it
          > is much needed. I think this is the best way to have an idea on what the
          > whole is about. The software mentioned above can be downloaded for free
          > and there are plenty of other tools for more advanced geostatistics.

          I never used variowin but it seems quite nice, and more important free!

          Here is a introduction to variowin:

          http://sal.agecon.uiuc.edu/csiss/pdf/variowin.pdf

          There should be more on the net if you look for it, I think...

          If you need automatisation of certain procedures look into R and the
          following packages:

          -spatstat
          -geoR
          -sgeostat
          -spdep
          -gstat (can also be used as stand alone program)

          All this software is open sourced and freely available!

          It made my repetitive work very easy.

          Best regards,
          Koen

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        • Pierre Goovaerts
          Hi Mark, For each number of samples you wish to eliminate, you really need to repeat the sampling many times in order to account for sampling fluctuations in
          Message 4 of 5 , Mar 31, 2004
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            Hi Mark,

            For each number of samples you wish to eliminate,
            you really need to repeat the sampling many times in order
            to account for sampling fluctuations in the assessment
            of prediction performances.
            The procedure need to be automated and you won't avoid
            having to modify a program (i.e. Gslib kt3d whose source code
            is distributed freely) to implement the hundreds or thousands of
            run needed for a thorough analysis. Just as an illustration
            of the kind of fluctuations you can expect if you select
            randomly 100 subsets of the same size, look at the following
            paper that can be downloaded from my webpage:

            Saito, H. and P. Goovaerts. 2000. Geostatistical interpolation of
            positively skewed and censored data in a dioxin contaminated site.
            Environmental Science & Technology, vol.34, No.19: 4228-4235.

            Regards,

            Pierre

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

            Dr. Pierre Goovaerts
            President of PGeostat, LLC
            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 Wed, 31 Mar 2004, Mark Dowdall wrote:

            >
            >
            > Hello
            >
            > This is a newbie question but I have been all over the Faqs and cannot
            > find an answer.
            >
            > Any help is appreciated and a summary of answers will be posted.
            >
            > I have a set of data that was taken over a particular area. I have
            > kriged and contoured and am happy with the results.
            >
            > But I need to demonstrate, within the bounds of the
            > study/analysis/assumptions, that the number of samples taken was
            > sufficient to describe the area.
            >
            > So my plan was to demonstrate that for a cetain number of samples the
            > variance in the estimates had reached a value that could not be reduced
            > efefctively by increasing sample number.
            >
            > And I thought this could be done by eliminating at random a point (so I
            > have x-1 data points), kriging the remainder with the chosen parameters
            > and checking the relevant parameters. (x is the number of actual
            > samples)
            >
            > Then eliminating two points at random (x-2), repeating and so on.
            > Eventually only 1 point being left.
            >
            > But.....if I eliminate the first point at random, does it matter which
            > point is eliminated? Or in the first instance (x-1 points) should I do
            > the process for all possible samples and take an average of the
            > estimation uncertainty?
            >
            > I am using GEOEAS and this could take a long time as all possible
            > permutations of for example x-20 could be quite large.
            >
            > I did download Explostat which has a feature that sems to do this
            > automatically but the manual is not great and the software is a little
            > impenetrable.
            >
            > If anyone can shed light on this I would be most grateful.
            >
            > Thanks in advance
            >
            > M.dowdall
            >
            > Ie.
            >
            >
            >
            > --
            > * 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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            > "unsubscribe ai-geostats" followed by "end" on the next line in the
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            >
            >
            > --
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            > of any useful responses to your questions.
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            >
            >
            > --
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            >

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