geosphere (version 1.5-10)

distGeo: Distance on an ellipsoid (the geodesic)

Description

Highly accurate estimate of the shortest distance between two points on an ellipsoid (default is WGS84 ellipsoid). The shortest path between two points on an ellipsoid is called the geodesic.

Usage

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

Arguments

p1

longitude/latitude of point(s). Can be a vector of two numbers, a matrix of 2 columns (first column is longitude, second column 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

Vector of distances in 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. Also see the refEllipsoids function.

	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

C.F.F. Karney, 2013. Algorithms for geodesics, J. Geodesy 87: 43-55. https://dx.doi.org/10.1007/s00190-012-0578-z. Addenda: http://geographiclib.sf.net/geod-addenda.html. Also see http://geographiclib.sourceforge.net/

See Also

distCosine, distHaversine, distVincentySphere, distVincentyEllipsoid, distMeeus

Examples

# NOT RUN {
distGeo(c(0,0),c(90,90))
# }