RhumbSolve (version 1.49) performs rhumb line calculations for an arbitrary ellipsoid of revolution. The path with a constant heading between two points on the ellipsoid at (lat1, lon1) and (lat2, lon2) is called the rhumb line (or loxodrome); its length is s12 and the rhumb line has a forward azimuth azi12 along its length. NOTE: the rhumb line is not the shortest path between two points; that is the geodesic and it is calculated by GeodSolve.
There are two standard rhumb line problems:
16.776 -3.009 16d47' -3d1' W3°0'34" N16°46'33" 3:0:34W 16:46:33NAzimuths are given in degrees clockwise from north. The distance s12 is in meters.
The additional quantity computed is:
The ellipsoid is specified by its equatorial radius, a, and its flattening, f = (a − b)/a, where b is the polar semi-axis. The default values for these parameters correspond to the WGS84 ellipsoid. The method is accurate for −99 ≤ f ≤ 0.99 (corresponding to 0.01 ≤ b/a ≤ 100). Note that f is negative for a prolate ellipsoid (b > a) and that it can be entered as a fraction, e.g., 1/297.
RhumbSolve is accurate to about 15 nanometers (for the WGS84 ellipsoid) and gives solutions for the inverse problem for any pair of points. The longitude becomes indeterminate when a rhumb line passes through a pole, and this tool reports NaNs (not a number) for lon2 and S12 in this case.
RhumbSolve, which is a simple wrapper of the GeographicLib::Rhumb class, is one of the utilities provided with GeographicLib. See also the section of the GeographicLib documentation on Rhumb lines and the Wikipedia page, Rhumb line.