geosphere (version 1.5-10)

distMeeus: 'Meeus' great circle distance

Description

The shortest distance between two points on an ellipsoid (the 'geodetic'), according to the 'Meeus' method. distGeo should be more accurate.

Usage

distMeeus(p1, p2, a=6378137, f=1/298.257223563)

Arguments

p1

longitude/latitude of point(s), in degrees 1; 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; or missing, in which case the sequential distance between the points in p1 is computed

a

numeric. Major (equatorial) radius of the ellipsoid. The default value is for WGS84

f

numeric. Ellipsoid flattening. The default value is for WGS84

Value

Distance value in the same units as parameter a of the ellipsoid (default is meters)

Details

Parameters from the WGS84 ellipsoid are used by default. It is the best available global ellipsoid, but for some areas other ellipsoids could be preferable, or even necessary if you work with a printed map that refers to that ellipsoid. Here are parameters for some commonly used ellipsoids:

	ellipsoid	a	f
	WGS84	6378137	1/298.257223563
	GRS80	6378137	1/298.257222101
	GRS67	6378160	1/298.25
	Airy 1830	6377563.396	1/299.3249646
	Bessel 1841	6377397.155	1/299.1528434
	Clarke 1880	6378249.145	1/293.465
	Clarke 1866	6378206.4	1/294.9786982
	International 1924	6378388	1/297
	Krasovsky 1940	6378245	1/298.2997381

more info: http://en.wikipedia.org/wiki/Reference_ellipsoid

References

Meeus, J., 1999 (2nd edition). Astronomical algoritms. Willman-Bell, 477p.

See Also

distGeo, distVincentyEllipsoid, distVincentySphere, distHaversine, distCosine

Examples

# NOT RUN {
distMeeus(c(0,0),c(90,90))
# on a 'Clarke 1880' ellipsoid
distMeeus(c(0,0),c(90,90), a=6378249.145, f=1/293.465)
# }