Orthographic projection
orthographic(r, proj.centre = cbind(phi = 0, lambda = 0), ...)
Latitude-longitude coordinates in a matrix with columns
labelled phi
(latitude) and lambda
(longitude)
Location of centre of projection as matrix with
column names phi
(elevation) and lambda
(longitude).
Arguments not used by this projection.n
Two-column matrix with columns labelled x
and
y
of locations of projection of coordinates on plane
http://en.wikipedia.org/wiki/Map_projection, http://mathworld.wolfram.com/OrthographicProjection.html