hexagonal grid

[Nancy Greeley]

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