ISEA Based DGGs
Our extended community of DGG researchers
has developed a specification for equal area DGGs based on
the Icosahedral Snyder Equal Area (ISEA) projection. We can use
the list of DGG design choices given in
[Sahr, White, and Kimerling, 2003] to
define ISEA grids as Discrete Global Grid Systems with the
For common ISEA DGGs this site provides:
- Base polyhedron: The icosahedron.
- Orientation of polyhedron relative to earth: Place
one icosahedron vertex at
11.250E longitude, 58.282525590N latitude, and place an adjacent
vertex at an azimuth of 0.00 from the first vertex. This placement is
- Transformation from spherical to planar face: The Icosahedral Snyder Equal Area
projection (see Snyder, J.P. (1992), "An equal-area map projection for polyhedral
globes," Cartographica 29(1):10-21).
- Hierarchical spatial partitioning method: Hexagon, triangle, or diamond-based
grids. Of particular interest are aperture 3 and 4 hexagon grids and aperture 4 triangle
and diamond grids, where aperture is defined as the ratio of areas between cells in a
given DGG resolution and the next finer resolution.
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