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

GEOSTATS: Geostatistical Software Conventions

Expand Messages
  • Tom Mueller
    Dear AI- GEOSTATS readers, Geostatistical programs differ in the way they parameterize semivariogram models and in the way they consider direction. As I tried
    Message 1 of 3 , Aug 27, 1998
    • 0 Attachment
      Dear AI- GEOSTATS readers,

      Geostatistical programs differ in the way they parameterize semivariogram
      models and in the way they consider direction. As I tried to understand
      these conventions, several people asked if I would share this information
      with the AI-GEOSTATS readership. If these issues are important to your
      work, please suggest modifications or additions (for other programs) and
      then I will update these notes. Gregoire has agreed to put them somewhere
      on the AI-GEOSTATS web page. Thanks.

      Sincerely,
      Tom Mueller

      muelle26@...
      http://www.msu.edu/user/muelle26/

      A summary of Some Geostatistical Software Conventions
      by Tom Mueller

      Exponential Model

      (1) semivariogram = c[1-exp(-h/a)] - SAS, Surfer, GSLIB(1992)
      (2) semivariogram = c[1-exp(-3h/a)] - GS+, Variowin, GSLIB(1998)

      If you use an exponential model to fit experimental semivariograms with
      Variowin, you must divide a (vw) by three to krig with Surfer.

      Gaussian Model

      (1) semivariogram = c[1-exp((-h/a)^2)] - SAS, Surfer, GSLIB (1992)
      (2) semivariogram = c[1-exp(-3(h/a)^2)] -Variowin, GS+
      (3) semivariogram = c[1-exp((-3h/a)^2)] - GSLIB (1998)

      If you use a Gaussian model to fit experimental semivariograms with
      Variowin, you must divide a (vw) by the square root of three to krig with
      Surfer or multiply a (vw) by the square root of three to krig with GSLIB
      (1998).

      Notes:
      h = the separation vector

      a = the range, practical range, effective range or range parameter

      GS+ uses exponential model #1 and Gaussian model #1 computationally (they
      refer to a as the range parameter) but you enter and read the range (not the
      range parameter) as defined as the distance at which the semivariogram
      reaches 95% of the sill. In other words, GS+ defines the range as 3 * a for
      the exponential model and sqrt (3) * a for the Gaussian model. (This is why
      above I have GS+ listed as using the second forms of the models above)
      Variowin refers to this as the practical range and GSLIB refers this to this
      as the effective range (but the ways in which Variowin and GSLIB calculate
      them are different).

      Comments on direction.

      Surfer and Variowin consider the East direction to be 0 degrees and
      direction to increases counterclockwise.

      GS+, GSLIB (1992, 1998), and SAS considers due North to be 0 degrees and
      direction to increase clockwise.



      --
      *To post a message to the list, send it to ai-geostats@....
      *As a general service to list users, please remember to post a summary
      of any useful responses to your questions.
      *To unsubscribe, send email to majordomo@... with no subject and
      "unsubscribe ai-geostats" in the message body.
      DO NOT SEND Subscribe/Unsubscribe requests to the list!
    • Jennifer Dungan
      A few additions/corrections to Tom s post about software conventions. I ve been using S+Spatialstats, and have added it to the appropriate lists below, with
      Message 2 of 3 , Aug 27, 1998
      • 0 Attachment
        A few additions/corrections to Tom's post about software conventions.
        I've been using S+Spatialstats, and have added it to the appropriate lists
        below, with the convention that "a" is the value typed in as the "range"
        in the variogram menu. Also, I think the negative sign is in the wrong
        place in two of the Gaussian models (see below).

        -Jennifer

        Jennifer Dungan | MS 242-4
        CSU - Monterey Bay | NASA Ames Research Center
        Tel: 650-604-3618 FAX: 650-604-4680 | Moffett Field, CA 94035-1000
        email: jdungan@... | USA
        URL: http://geo.arc.nasa.gov |

        On Thu, 27 Aug 1998, Tom Mueller wrote:

        > A summary of Some Geostatistical Software Conventions
        > by Tom Mueller
        >
        > Exponential Model
        >
        > (1) semivariogram=c[1-exp(-h/a)] - SAS, Surfer, GSLIB(1992)
        > (2) semivariogram=c[1-exp(-3h/a)] - GS+,Variowin,GSLIB(1998),S+

        > If you use an exponential model to fit experimental semivariograms with
        > Variowin, you must divide a (vw) by three to krig with Surfer.
        >
        > Gaussian Model
        >
        > (1) semivariogram = c[1-exp((-h/a)^2)] - SAS, Surfer, GSLIB(1992), S+

        should be c[1-exp(-(h/a)^2)]

        > (2) semivariogram = c[1-exp(-3(h/a)^2)] -Variowin, GS+
        > (3) semivariogram = c[1-exp((-3h/a)^2)] - GSLIB (1998)

        should be c[1-exp(-(3h/a)^2)]
        >

        --
        *To post a message to the list, send it to ai-geostats@....
        *As a general service to list users, please remember to post a summary
        of any useful responses to your questions.
        *To unsubscribe, send email to majordomo@... with no subject and
        "unsubscribe ai-geostats" in the message body.
        DO NOT SEND Subscribe/Unsubscribe requests to the list!
      • Tom Mueller
        Dear AI-GEOSTATS readers: Thanks to everyone who responded. I ve updated the original message and Gregoire has posted it on the AI-GEOSTATS web site,
        Message 3 of 3 , Aug 30, 1998
        • 0 Attachment
          Dear AI-GEOSTATS readers:

          Thanks to everyone who responded. I've updated the original message and
          Gregoire has posted it on the AI-GEOSTATS web site, specifically located at
          http://curie.ei.jrc.it/software/soft_convention.htm. As you will note, some
          new software has been added (GEOEAS and S+) but there are many programs that
          have not been included (XGAM, ESRI software, etc.). So please let us know
          and we will keep this list up to date.

          Thanks,
          Tom Mueller
          muelle26@...

          --
          *To post a message to the list, send it to ai-geostats@....
          *As a general service to list users, please remember to post a summary
          of any useful responses to your questions.
          *To unsubscribe, send email to majordomo@... with no subject and
          "unsubscribe ai-geostats" in the message body.
          DO NOT SEND Subscribe/Unsubscribe requests to the list!
        Your message has been successfully submitted and would be delivered to recipients shortly.