Project points from the unit sphere onto a plane orthogonal
to the viewing direction.
Usage
orthogproj(eye, top, loc)
Arguments
eye
Viewpoint. A vector of length 3 (or a list(lon,lat))
determining a position in space.
top
Top point. A location which will be projected onto the \(y\) axis.
Vector of length 3 (or a list(lon,lat))
determining a position in space.
loc
Vector of length 3, or matrix with 3 columns,
or list(lon,lat). The points on the sphere to be projected.
Value
A vector (or matrix) giving the transformed coordinates of each point,
with the first two coordinates giving the orthogonal projection.
Details
This function is used to obtain orthogonal projections of
points on the sphere, for use in plotting 3D views of the sphere.
Each point of loc is expressed
in an orthonormal coordinate system determined by the
arguments eye and top. The coordinate system is
such that the third (\(z\)) axis
passes through the eye of the viewer and the
centre of the sphere.