Get the final direction (bearing) when arriving at p2 after starting from p1 and following the shortest path on an ellipsoid (following a geodetic) or on a sphere (following a great circle).
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
a
major (equatorial) radius of the ellipsoid. The default value is for WGS84
f
ellipsoid flattening. The default value is for WGS84
sphere
logical. If TRUE, the bearing is computed for a sphere, instead of for an ellipsoid
Value
A vector of directions (bearings) in degrees
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/