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GEOSTATS: Hexagonal Grids in ARC/INFO

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  • William L. Osburn
    Thanks to those who pointed the way - Here is the summation The QUESTION ... The SUMMARY From: jutsonph@tec.irlgov.ie (Philip Jutson) You can generate a
    Message 1 of 1 , Mar 28, 1997
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      Thanks to those who pointed the way - Here is the summation

      The QUESTION

      >I am interested in utilizing a stratified hexagonal polygon grid to
      >define a ground water sampling network. In our shop we utilize ARC/INFO
      >for our GIS work. However, none of the GIS gurus I've talked to know of
      >a way to generate such a grid. Does anyone have a reference to
      >hexagonal grid generation in ARC/INFO?

      The SUMMARY

      From: jutsonph@... (Philip Jutson)

      You can generate a regular 'grid' of hexagons using the aml program I
      have
      included and a little bit of work. This program creates a file that the
      arc
      command GENERATE can use to create a point coverage (don't forget to
      build
      topology). You can then use the arc command THIESSEN to create
      hexagonal
      polygons. The only problem is that the edge polygons are not regular in
      shape.

      Notes: The AML can be obtained from Philip Jutson. It AML & technique
      works just fine
      thank you (see the RESULTS at the end).

      From: dstewart@... (David J. Stewart)

      In the past our lab has been in contact with ESRI, and they have
      provided us with a number of amls which we modified and extended to
      eventually produce a polygon coverage containing series of
      equal-sized, hexagons covering the area of interest. They worked,
      sort of, but were extremely cranky and sloooow...
      The research described in Pulliam, et al 1992 (Ecol. Appl.
      2:165-177) uses this technique but doesn't say much about it.

      Since then I've written several C programs that are called from
      entirely new amls which work much more efficiently, taking hours
      rather than days (or failing) to produce a 3ha cell size grid of
      a 780 sq km study area. (The time required to generate the lattice
      seems to be exponentially related to the number of cells. Still
      not efficient from a computer science perspective, but tractable.)
      The first research using the new programs will be presented at
      Forest Service conference in May.

      So the answer is -- yes, if what you want is a polygon coverage
      of adjacent, hexagonal polygons with few attributes beyond cell#,
      row, column, and neighbor list. I have other amls which will
      establish relates to other polygon coverages, by which attributes
      can be transferred.

      Note: More discussion was included and I'll send it to anyone who wants
      it.

      The RESULT

      Our local GIS staff had build series of amls for me that generated a
      point coverage and
      a variable rectangular (or square) grid coverage - then overlayed the
      two and gave
      output so I could determine what grid cells the points were in. In this
      way I could
      build a stratified square or rectangular sampling scheme. This
      generalized aml was also
      needed for ground water modelers, etc. Thus it was made as generalized
      as possible.

      The GIS programer decided to incorporate Philip Jutson's aml to build a
      hexagonal grid.
      The existing amls can overlay and draw the resulting point and hexagonal
      grid coverages.
      A few more tweaks and we'll have the output portion. Unfortunally, he
      had to leave for
      two weeks of Military Reserve duty!

      We'll have the resulting menu-driven aml system - square, rectangular,
      or hexagonal
      polygon and point generation and then coverage comparision done in 4
      weeks. All
      depending on what fires have to be put out when he gets back.

      If anyone wants the final aml system contract Chris Oman at
      cso@.... Ask
      him for a copy of Osburn's Grid and Point AML.

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