diff --git a/code/perception/src/coordinate_transformation.py b/code/perception/src/coordinate_transformation.py
index b8c86f85..f65dc4cb 100755
--- a/code/perception/src/coordinate_transformation.py
+++ b/code/perception/src/coordinate_transformation.py
@@ -11,7 +11,7 @@
 from tf.transformations import euler_from_quaternion
 
 
-a = 6378137  # EARTH_RADIUS_EQUA in Pylot
+a = 6378137  # EARTH_RADIUS_EQUA in Pylot, used in geodetic_to_enu
 b = 6356752.3142
 f = (a - b) / a
 e_sq = f * (2 - f)