This page illustrates the geodesic routines available in
GeographicLib.
The C++ code has been converted to Javascript so the calculations
are carried out on the client. The algorithms are considerably
more accurate than Vincenty's method, and offer more functionality
(an inverse method which never fails to converge, differential
properties of the geodesic, and the area under a geodesic). The
algorithms are derived in
This page just provides a basic interface. Enter latitudes,
longitudes, and azimuths as degrees and distances as meters using
spaces or commas as separators. (Angles may be entered as decimal
degrees or as degrees, minutes, and seconds, e.g. -20.51125,
20°30′40.5″S, S20d30'40.5", or
-20:30:40.5.) The results are accurate to about
15 nanometers (or 0.1 m2 per vertex for
areas). A slicker page where the geodesics are incorporated into
Google Maps is given here.