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AI-GEOSTATS: comment on previous email: Project proposal - flood risk

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  • Eric Delmelle
    Dear all This does not relate directly to the previous email. One of the questions that strike my interest across the many emails on the use of kriging and DEM
    Message 1 of 2 , Feb 10, 2004
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      Dear all
      This does not relate directly to the previous email.
      One of the questions that strike my interest across the many emails on the
      use of kriging and DEM is its legitimate use. It seems to me that when the
      elevation set is greatly varying (with huge difference of altitude at
      specific locations) that this will automatically influence the covariogram.
      Especially in mountain areas, huge altitude differences can occur at small
      lag distances, leading to hign semivariance values at very short distances.
      Did anyone come across some litterature on this issue?
      Regards, --ERic Delmelle.



      -----Original Message-----
      From: ai-geostats-list@... [mailto:ai-geostats-list@...]On
      Behalf Of Norrie, Gordon
      Sent: Tuesday, February 10, 2004 8:02 AM
      To: ai-geostats@...
      Subject: AI-GEOSTATS: Project proposal - flood risk


      Dear List Members,

      I am just writing a quick mail to ask if anyone is aware of a paper by
      Kyriakidis, P., Shortridge, A, and Goodchild, M.F. published in the
      International Journal for Geographical Information Science in 1999. That
      paper which related to use of simple co-kriging in the production of high
      accuracy hard elevation reference surface DEM from the conflation of two
      data sets, one high accuracy, comprising of a number of spot elevation
      points at relatively sparse locations, and a lower accuracy elevation data
      set, but which has a far denser coverage of the study area (about 200 times
      the amount of data as the hard spot elevation data).

      That study focused upon an area which consisted of greatly varying terrain
      and elevation, but I am seeking to apply that methodology to two data sets
      which are located in a flood plain and the immediate surrounds at a town in
      East Sussex, which has suffered badly as a result of flooding. The aim is
      to use high accuracy DGPS surveying points to work out elevation at a number
      of points in and around the floodplain. That is to act as the 'hard data'
      and is to be conflated with a set of lower accuracy IfSAR data, with a
      resolution of 5m. The idea is to produce a number of different hard
      elevation reference surfaces, which are to represent an increased accuracy
      in terms of the DEM, and over which either a flood innundation model can be
      run, or a simple flooding alrgorithm run in software such as Erdas Imagine.
      This would provide a form of stochastic modelling, providing a number of
      flood footprints. Using MasterMap data from the OS, I am seeking to assign
      risk in terms of percentage likelihood a property object is flooded, based
      upon the number of flood footprints that the property falls into.

      If someone is aware of this paper, my main question is to ask whether you
      think the project is feasible, or whether you can think of any problems,
      bearing in mind the significant difference in the nature of the datasets
      used by the authors of the paper, and that proposed to be used by myself ?
      Any advice or comments would be greatly appreciated.

      Many thanks for your time.

      Best regards,

      Gordon Norrie

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