1 files changed, 4 insertions, 0 deletions
diff --git a/common.h b/common.h
index 332e19a..2668d91 100644
--- a/common.h
+++ b/common.h
@@ -14,6 +14,10 @@
 #define degrees(RAD)  (180.0 / (double)M_PI * (RAD))
 #define haversin(X)   (fma(-0.5, cos(X), 0.5))
 
+#define geodetic(GEOCENTRIC)\
+	atan(tan(GEOCENTRIC) * (LIBTELLURIAN_EQUATORIAL_RADIUS * LIBTELLURIAN_EQUATORIAL_RADIUS /\
+	                        (LIBTELLURIAN_POLAR_RADIUS * LIBTELLURIAN_POLAR_RADIUS)))
+
 
 void libtellurian_vincenty_inverse__(double latitude1, double longitude1, double latitude2, double longitude2,
                                      double *distance_out, double *azimuth1_out, double *azimuth2_out);