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GEOSTATS: weighted interpolation method

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  • Dubois Gregoire
    Greetings to all Arc/Users and or AI-geostatisticians, The IDW is an inverse distance weighted interpolation method. The problem here is the definition of the
    Message 1 of 2 , Feb 7, 1997
      Greetings to all Arc/Users and or AI-geostatisticians,

      The IDW is an inverse distance weighted interpolation method.
      The problem here is the definition of the distance.
      2 measurements of a variable X close together can be separated
      geographically by a hill which won't be taken into account during
      the interpolation,

      Therefore, if I use a DEM (for exemple) to add another weight to
      the interpolation function ( with cost distance functions like
      those proposed by ESRI for ARc/Info) I wouldn't be limited
      anymore to euclidian distances.


      The use of a "cost distance weight", a measure of the "effort" to reach
      2 points, could also be usefull for the variogram calculation.

      Well, these are things I'm trying out for the moment with a pollutant.


      Any suggestions on how to do it with/without Grid (Arc/Info) ?


      Thanks for any help,


      Best regards,


      Gregoire
      --
      Gregoire Dubois (PhD student) Tel. 39-332-78.99.44
      Joint Research Centre Fax. 39-332-78.54.66
      Environment Inst. TP 321 Email: gregoire.dubois@...
      I-21020 Ispra (Va), ITALY URL: http://java.ei.jrc.it/rem/gregoire/
      --
      *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.
    • John Kern
      Gregoire, Defining alternative metrics seems like a good idea on the face of it although a great deal of subjective input is needed and a sensible metric for
      Message 2 of 2 , Feb 9, 1997
        Gregoire,

        Defining alternative metrics seems like a good idea on the face of it
        although a great deal of subjective input is needed and a sensible metric
        for one variable may not be sensible for other measured or mapped variables
        available. This poses an interesting problem in which different metrics are
        integrated into a single cost function for interpolation. An alternative I
        try to employ if possible is to investigate linear/nonlinear regression /
        ancova relationships between the variable of interest and any other
        available covariates such as elevation, slope aspect, satelite image data,
        and on and on depending on the particular application. After partialling
        out large scale trends with categorical and continuous variables, the
        residual process is often independent or only weakly spatially correlated
        and predictions are made in a universal kriging type analysis where the
        design matrix contains more than just geographic coordinates or a single
        variable external drift. I do this in a MATLAB toolbox which I have been
        developing over the last year or so. However, this could be conducted in
        ARC by fitting regression models in S+, SAS, SPSS or your favorite
        statistical software package followed by ordinary kriging the residuals and
        adding. This can probably be done in GSLIB also without a great deal of
        trouble. Especially in the case of pollutants, I have found this approach
        especially useful for pollutants such as PCB or heavy metals.

        >Greetings to all Arc/Users and or AI-geostatisticians,
        >
        >The IDW is an inverse distance weighted interpolation method.
        >The problem here is the definition of the distance.
        >2 measurements of a variable X close together can be separated
        >geographically by a hill which won't be taken into account during
        >the interpolation,
        >
        >Therefore, if I use a DEM (for exemple) to add another weight to
        >the interpolation function ( with cost distance functions like
        >those proposed by ESRI for ARc/Info) I wouldn't be limited
        >anymore to euclidian distances.
        >
        >
        >The use of a "cost distance weight", a measure of the "effort" to reach
        >2 points, could also be usefull for the variogram calculation.
        >
        >Well, these are things I'm trying out for the moment with a pollutant.
        >
        >
        >Any suggestions on how to do it with/without Grid (Arc/Info) ?
        >
        >
        >Thanks for any help,
        >
        >
        >Best regards,
        >
        >
        >Gregoire
        >--
        >Gregoire Dubois (PhD student) Tel. 39-332-78.99.44
        >Joint Research Centre Fax. 39-332-78.54.66
        >Environment Inst. TP 321 Email: gregoire.dubois@...
        >I-21020 Ispra (Va), ITALY URL: http://java.ei.jrc.it/rem/gregoire/
        >--
        >*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 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.
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