If you want to do “field-effect calculations” or care about preservation of shapes you probably want a conformal grid. If you want to trade off area vs. shape d

If you want to do “field-effect calculations” or care about preservation of shapes you probably want a conformal grid. If you want to trade off area vs. shape distortion, it’s probably better to pick a projection which tries to optimize distance errors. Using a gnomonic projection for each icosahedron triangle is probably not the best choice for pretty much any application, though it has the advantage of being less work to implement. There are lots of reasonable choices for high-level grid shapes, e.g. http://www.lib.ncep.noaa.gov/ncepofficenotes/files/on467.pdf http://www.lib.ncep.noaa.gov/ncepofficenotes/files/on467.pdf For human comprehensibility of coordinates I would recommend instead starting with an octahedron as the basic geometric skeleton.