generate grids on sphere
Arguments
- N
number of refinenemts
- lower
return also the lower hemishpere?
- ico
use triangulation based on icosahedron (req. rgl)? N is then takes as refinement steps, should be <5!
#' Two ways:
A) a decreasing radius ring of N points from equator to pole with alternating 2pi/N shift. Concentrates on the poles, useful for statitical estimation if the pole area is where things happen.
B) Triangulation by refining an icosahedron.
Returns latitude-longitude matrix. use ll2xyz or ll2ai for transformation.