Get the initial bearing (direction; azimuth) to go from point p1 to point p2 (in longitude/latitude) following the shortest path on an ellipsoid (geodetic). Note that the bearing of travel changes continuously while going along the path. A route with constant bearing is a rhumb line (see bearingRhumb).
bearing(p1, p2, a=6378137, f=1/298.257223563)
longitude/latitude of point(s). 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. Can also be missing, in which case the bearing is computed going from the first point to the next and continuing along the following points
major (equatorial) radius of the ellipsoid. The default value is for WGS84
ellipsoid flattening. The default value is for WGS84