hexagonal grid

[Michael Shapiro]

Not to mention that all this data is really projected data and the
neighboring cells really aren't the distance that the coordinate system
implies due to distortions or distances and areas due to the projection.
|
|In reply to:
|"What is the interest in hexagonal grids? GRASS doesn't use them."
|
|
|"...There has been a continuing interest in regular hexagonal cells
|as the basis of spatial data structures, in part becasue in a hexagonal
|tessellation of the plane, all neighboring cells are equidistant, unlike
|the situation in a raster of square cells (P.J. Burt, 1980,  "Tree 
|and pyramid structures for coding Hexagonally Sampled Binary Images."
|Computer Graphics and Image Processing, Vol 14, No 3, pp271-280.)"
|
|The book from which I extracted this quote then goes on to describe
|the 2 problems created by hex--- cells:  1) the cells cannot be 
|recursively subdivided into smaller cells of the same shape as the
|original cells, and 2) a hex--- made up of smaller hexagons will not
|be the same shape as those smaller hex---.  Also, "less important",
|3) a numbering system for a hex--- system is more compliex than that 
|of a square system = "at least a small additional overhead in system
|operations."
|
|The book this is all from:  Geographic Information Systems; an Introduction
|by Jeffrey Star and John Estes.  Very clearly written.  Good stuff for
|an intro to GIS.
|
|-See ya.
|Nancy
|
|


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Michael Shapiro                        U.S. Army CERL                  
email:   shapiro at amber.cecer.army.mil  Office of GRASS Integration
phone:   (217) 373-7277                P.O. Box 9005                   
fax:     (217) 373-7222                Champaign, Ill. 61826-9005
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