hexagonal grid

Michael Camann camann at athena.cs.uga.edu
Mon Nov 2 16:13:25 EST 1992


> 
> What is the interest in hexagonal grids? GRASS doesn't use them.
> 
> Of course if you had a system that used hexagonal grids you could use
> a simple resampling to shift every other row one half cell to the right
> (or left) and that would create a hexagonal grid.
> 

I'm trying to tie a spatially-explicit model of insect population flux, 
movement, etc. to a real landscape via GIS.  Specifically, I'm modeling
southern pine beetle infestations in the Georgia piedmont forests.  Hexagonal
grids have several advantages in any model of dispersing animal populations:

1)  they permit six directions of movement rather than four,

2)  they fill the space completely, unlike octagons, etc, and,

3)  the center to center distance to any adjacent cell is the same, regardless
of direction, unlike rectangular grids where the diagonal distance is greater 
than the vertical or the horizontal distances.

One of our local GIS labs has worked out tools for converting ARC/INFO map
coverages into a hexagonal array, but I prefer to work with GRASS.  Any help
would be greatly appreciated.

Note that I'm not talking about just imposing a hexagonal vector pattern onto
raster images, but reclassifying the underlying raster map into an array of
hexagonal cells via some sort of transformation within each hexagon, 
e.g. "every pixel within the hexagon is set to the dominant class ocurring
within that hexagon".  I need to apply my transformations across the entire
map layer, hexagon by hexagon.  The biological model will then run on the
resulting "landscape" of hexagonal cells.  Actually, it will run on a land-
scape composed of many layers of such cells, representing the model parameters
distributed in space.

The capacity to produce these hexagonally transformed landscapes is very
important for modeling biological movement or dispersion.


	Michael Camann				camann at athena.cs.uga.edu
	Department of Entomology		office 	(706) 542-2640
	University of Georgia				(706) 542-2816
	Athens, GA  30602			fax	(706) 542-2272



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