antipode: Antipodes

In geosphere: Spherical Trigonometry

Description

Compute an antipode, or check whether two points are antipodes. Antipodes are places on Earth that are diametrically opposite to one another; and could be connected by a straight line through the centre of the Earth.

Antipodal points are connected by an infinite number of great circles (e.g. the meridians connecting the poles), and can therefore not be used in some great circle based computations.

Usage

antipode(p)
antipodal(p1, p2, tol=1e-9)

Arguments

p	Longitude/latitude of a single point, in degrees; can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object
p1	as above
p2	as above
tol	tolerance for equality

Value

antipodal points or a logical value (TRUE if antipodal)

Author(s)

Robert Hijmans

References

http://en.wikipedia.org/wiki/Antipodes

Examples

antipode(rbind(c(5,52), c(-120,37), c(-60,0), c(0,70)))
antipodal(c(0,0), c(180,0))

Example output

     [,1] [,2]
[1,] -175  -52
[2,]   60  -37
[3,]  120    0
[4,] -180  -70
[1] TRUE

geosphere documentation built on May 2, 2019, 5:16 p.m.