| distMeeus {geosphere} | R Documentation |
'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 |
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: https://en.wikipedia.org/wiki/Reference_ellipsoid
Value
Distance value in the same units as parameter a of the ellipsoid (default is meters)
Note
This algorithm is also used in the spDists function in the sp package
Author(s)
Robert Hijmans, based on a script by Stephen R. Schmitt
References
Meeus, J., 1999 (2nd edition). Astronomical algoritms. Willman-Bell, 477p.
See Also
distGeo, distVincentyEllipsoid, distVincentySphere, distHaversine, distCosine
Examples
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)