diff --git a/sw/airborne/common_nav.h b/sw/airborne/common_nav.h
index 84018a022f..3047e5c111 100644
--- a/sw/airborne/common_nav.h
+++ b/sw/airborne/common_nav.h
@@ -18,7 +18,7 @@ struct point {
 #define WaypointY(_wp) (waypoints[_wp].y)
 #define WaypointAlt(_wp) (waypoints[_wp].a)
 
-extern void nav_move_waypoint(uint8_t wp_id, float ux, float uy, float alt);
+extern void nav_move_waypoint(uint8_t wp_id, float utm_east, float utm_north, float alt);
 
 extern const uint8_t nb_waypoint;
 extern struct point waypoints[];
@@ -65,9 +65,11 @@ void common_nav_periodic_task_4Hz(void);
 #define Or(x, y) ((x) || (y))
 #define Min(x,y) (x < y ? x : y)
 #define Max(x,y) (x > y ? x : y)
-#define NavBlockTime() (block_time)
 #define LessThan(_x, _y) ((_x) < (_y))
 
+/** Time in s since the entrance in the current block */
+#define NavBlockTime() (block_time)
+
 #define NavSetGroundReferenceHere() ({ nav_reset_reference(); nav_update_waypoints_alt(); FALSE; })
 
 #define NavSetWaypointHere(_wp) ({ \
diff --git a/sw/airborne/nav.h b/sw/airborne/nav.h
index 555bb0ceef..dfc20a22ce 100644
--- a/sw/airborne/nav.h
+++ b/sw/airborne/nav.h
@@ -103,6 +103,7 @@ extern void nav_circle_XY(float x, float y, float radius);
 #define NavCircleWaypoint(wp, radius) \
   nav_circle_XY(waypoints[wp].x, waypoints[wp].y, radius)
 
+/** Normalize a degree angle between 0 and 359 */
 #define NormCourse(x) { \
   while (x < 0) x += 360; \
   while (x >= 360) x -= 360; \
@@ -110,7 +111,10 @@ extern void nav_circle_XY(float x, float y, float radius);
 
 #define NavCircleCount() (fabs(nav_circle_radians) / (2*M_PI))
 #define NavCircleQdr() ({ float qdr = DegOfRad(M_PI_2 - nav_circle_trigo_qdr); NormCourse(qdr); qdr; })
+
+/** True if x (in degrees) is close to the current QDR (less than 10 degrees)*/
 #define NavQdrCloseTo(x) ({ float _course = x; NormCourse(_course); float circle_qdr = NavCircleQdr(); (Min(_course, 350) < circle_qdr && circle_qdr < _course+10); })
+
 #define NavCourseCloseTo(x) ({ float _course = x; NormCourse(_course); float deg = DegOfRad(estimator_hspeed_dir); (Min(_course, 350) < deg && deg < _course+10); })
 
 /*********** Navigation along a line *************************************/
diff --git a/sw/airborne/traffic_info.h b/sw/airborne/traffic_info.h
index dd3aaecee0..a4cbe031a3 100644
--- a/sw/airborne/traffic_info.h
+++ b/sw/airborne/traffic_info.h
@@ -34,8 +34,8 @@
 
 struct ac_info_ {
   uint8_t ac_id;
-  float east; /* m */
-  float north; /* m */
+  float east; /* m relative to nav_utm_east0 */
+  float north; /* m relative to nav_utm_north0 */
   float course; /* rad (CW) */
   float alt; /* m */
   float gspeed; /* m/s */