geodGc {oce}

Great-circle Segments Between Points on Earth

Description

Each pair in the longitude and latitude vectors is considered in turn. For long vectors, this may be slow.

Usage

geodGc(longitude, latitude, dmax)

Arguments

longitude

vector of longitudes, in degrees east

latitude

vector of latitudes, in degrees north

dmax

maximum angular separation to tolerate between sub-segments, in degrees.

Value

Data frame of longitude and latitude.

Author(s)

Dan Kelley, based on code from Clark Richards, in turn based on formulae provided by Ed Williams (see reference 1)].

References

1. ⁠http://williams.best.vwh.net/avform.htm#Intermediate⁠ (link worked for years but failed 2017-01-16).

See Also

Other functions relating to geodesy: geodDist(), geodXyInverse(), geodXy()

Examples

library(oce)
data(coastlineWorld)
mapPlot(coastlineWorld,
    type = "l",
    longitudelim = c(-80, 10), latitudelim = c(35, 80),
    projection = "+proj=merc"
)
# Great circle from New York to Paris (Lindberg's flight)
l <- geodGc(c(-73.94, 2.35), c(40.67, 48.86), 1)
mapLines(l$longitude, l$latitude, col = "red", lwd = 2)