longitude/latitude of point(s), in degrees; 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. Should be of same length of p1, or a single point (or vice versa when p1 is a single point
Value
A pair of coordinates (longitude/latitude)
Details
Just as the initial bearing may vary from the final bearing, the midpoint may not be located half-way between latitudes/longitudes; the midpoint between 35N,45E and 35N,135E is around 45N,90E.