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

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

as above

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

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: rlll{ 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.

Examples

Run this code

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)

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