I need to calculate to azimuth between two points. I'm using Projnet and GeographicLib to get the azimuth. So I have a UTM projection map then I need Projnet to get Lat/Lon coordinates because GeographicLib uses Lat/Lon to calculate this azimuth. Ok I get the angle but now my question is if I need to reproject this azimuth to my UTM projection map???
The azimuth of the geodesic, returned by GeographicLib, is with respect to due north (clockwise is positive). To get the corresponding azimuth in the UTM plane (with respect to grid north) subtract the meridian convergence for the projection. (The meridian convergence is the bearing of the grid north measured clockwise from true north.) GeographicLib can return the meridian convergence; I don't know about Projnet.