35th Street Corvallis, Oregon 97333 Carr, Daniel B., Ralph Kahn, Kevin Sahr, and Anthony R. Olsen. The acronym ISEA stands for icosahedral Snyder equal area. The impetus for the global grid system came from what many would call an unusual perspective - survey sampling.
ISEA grids are simple in concept.
Begin with a Snyder Equal Area projection to a regular icosahedron inscribed in a sphere. In each of the 20 equilateral triangle faces of the icosahedron inscribe a hexagon by dividing each triangle edge into thirds. Then project the hexagon back onto the sphere using the Inverse Snyder Icosahedral equal area projection. This yields a coarse-resolution equal area grid called the resolution 1 grid. To form higher resolution grids, tessellate each equilateral triangle in the planar view with more hexagons and use the inverse projection back to the sphere.