gcMaxLat: Highest latitude on a great circle

In geosphere: Spherical Trigonometry

Description

What is northern most point that will be reached when following a great circle? Computed with Clairaut's formula. The southern most point is the antipode of the northern-most point. This does not seem to be very precise; and you could use optimization instead to find this point (see examples)

Usage

gcMaxLat(p1, p2)

Arguments

p1	longitude/latitude of point(s). Can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object
p2	as above

Value

A matrix with coordinates (longitude/latitude)

Author(s)

Ed Williams, Chris Veness, Robert Hijmans

References

http://www.edwilliams.org/ftp/avsig/avform.txt

http://www.movable-type.co.uk/scripts/latlong.html

See Also

gcLat, gcLon

Examples

gcMaxLat(c(5,52), c(-120,37))

# Another way to get there:
f <- function(lon){gcLat(c(5,52), c(-120,37), lon)}
optimize(f, interval=c(-180, 180), maximum=TRUE)

Example output

           lon      lat
[1,] -49.82544 65.76869
$maximum
[1] -49.82544

$objective
[1] 65.76869

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