orthogproj {globe}

Orthogonal Projection

Description

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.

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.

Value

A vector (or matrix) giving the transformed coordinates of each point, with the first two coordinates giving the orthogonal projection.

Author(s)

Adrian Baddeley and Tom Lawrence

See Also

globeearth

Examples

 orthogproj(place("newyorkcity"), place("northpole"), c(1,0,0))