Geodesic projections for an ellipsoid by Charles Karney

Four map projections based on geodesics (map projections, geodesics, azimuthal equidistant)

cassini_fwd(lat0, lon0, lat, lon, ellipsoid)

cassini_inv(lat0, lon0, x, y, ellipsoid)

eqdazim_fwd(lat0, lon0, lat, lon, ellipsoid)