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GEOSTATS: interpolation

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  • Cathy Schloeder & Mike Jacobs
    My latest question: If you did not have spatially autocorrelated data, and wanted to interpolate soil property data over a large landscape, using 46 sites to
    Message 1 of 4 , Dec 2, 1997
      My latest question:

      If you did not have spatially autocorrelated data, and wanted to interpolate
      soil property data over a large landscape, using 46 sites to interpolate to
      176 sites, what method would you use, why, and what are possible bio-geo
      factors to consider in making the selection. The grid is oriented ne-sw, on
      a relatively level plain, with a mountain range run its length on the west,
      presumably contributing something colluvially. Thanks for feedback!

      Cathy
      Cathy Schloeder
      Utah State University
      Dept. Fisheries and Wildlife
      UMC 5210
      Logan, UT 84322-5210
      Telephone: 801-797-1346
      Fax: 801-797-1871

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    • c_vhagen@igkw2.agric.za
      hi i would like to find out the best method for interpolating rainfall and temperature data. the weather stations are randomly spread over an area of approx. 8
      Message 2 of 4 , Apr 1, 1998
        hi

        i would like to find out the best method for interpolating rainfall
        and temperature data. the weather stations are randomly spread over
        an area of approx. 8 million hectares. there are approx. 200 temp
        stations and approx 1000 rainfall stations. i have tried inverse
        distance weighting with 4 nearest neighbours for temp and 8 for
        rainfall, both using a 300m grid size. i am using arcview spatial
        analyst software.

        any help is appreciated.
        craig email: c_vhagen@...
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      • Donald Myers
        Tha is a non-sequitur, given only a finite amount of data and no state equations you have a non-unique problem. First of all one has to ask what does best
        Message 3 of 4 , Apr 1, 1998
          Tha is a non-sequitur, given only a finite amount of data and no state
          equations you have a non-unique problem. First of all one has to ask what
          does "best" mean? Again this is non-unique.

          There are quite a number of papers that have compared different
          methods/algorithms/implementations of algorithms/applications of algorithms
          for rainfall and temperature data but in general one can only conclude that
          for a particular data set one method or algorithm seemed to work best.

          You mentioned using arcview spatial software and inverse distance weighting
          with a specific choice of the search neighborhood. The results can be
          sensitive to not only the choice of the search neighborhood but also the
          choice of the exponent. See for example, Kane et al, Computers and
          Geosciences, 1982.

          If one uses kriging, i.e., a variant of kriging (simple, ordinary,
          universal, indicator, etc) then one still has to estimate and model the
          variogram as well as to choose the search neighborhood parameters. Unless
          the elevation is approximately constant over your region of interest you
          may need to incorporate that effect either by cokriging or by using an
          external drift.

          Differences in results from using different methods/algorithms may be
          considerably affected (or not) by the pattern of data locations.

          Do you want point interpolations or do you want average rainfall over
          specific subregions? Kriging will allow you to directly do the latter but
          IWD does not.

          Note that the thin plate spline and smoothing spline are both special cases
          of kriging.

          My suggestion is to search the literature more completely for papers that
          have applied different methods and try to match the specifics of one of
          those instances to your problem.

          Donald Myers
          Department of Mathematics
          University of Arizona
          Tucson, AZ 85721

          http://www.u.arizona.edu/~donaldm

          At 12:24 PM 4/1/98 +0000, you wrote:
          >hi
          >
          >i would like to find out the best method for interpolating rainfall
          >and temperature data. the weather stations are randomly spread over
          >an area of approx. 8 million hectares. there are approx. 200 temp
          >stations and approx 1000 rainfall stations. i have tried inverse
          >distance weighting with 4 nearest neighbours for temp and 8 for
          >rainfall, both using a 300m grid size. i am using arcview spatial
          >analyst software.
          >
          >any help is appreciated.
          >craig email: c_vhagen@...
          >--
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          >of any useful responses to your questions.
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          >"unsubscribe ai-geostats" in the message body.
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          >

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        • Yoshiro Nagao
          I have a few questions on ArcView Spatial Analyst. (Sorry for not answering to your question.) ... Can ArcView Spatial output interpolated values for several
          Message 4 of 4 , Apr 1, 1998
            I have a few questions on ArcView Spatial Analyst.
            (Sorry for not answering to your question.)

            c_vhagen@... sama said:
            >rainfall, both using a 300m grid size. i am using arcview spatial
            >analyst software.

            Can ArcView Spatial output interpolated values for
            several points which are listed in a table.

            I mean,

            You specify points for which you want interpolated values as follows:

            long. lat.
            8.5 135.2
            9.2 135.7
            10.3 136.0


            Then ArcView Spatial would output interpolated values to the above points
            into a file:

            long. lat. interpolated value
            8.5 135.2 23
            9.2 135.7 24
            10.3 136.0 25

            Or do you need to click each the above points on the map to see the interpolated
            values?

            How about other interpolation softwares?

            Nagao Yoshiro
            International Centre for Medical Research
            Kobe University
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