VehicleOdometry.msg - clarify frames

msg/VehicleOdometry.msg

@@ -3,17 +3,21 @@ uint64 timestamp		# time since system start (microseconds)
 uint64 timestamp_sample
 
 uint8 POSE_FRAME_UNKNOWN = 0
-uint8 POSE_FRAME_NED     = 1 # NED earth-fixed frame
-uint8 POSE_FRAME_FRD     = 2 # FRD world-fixed frame, arbitrary heading reference
+uint8 POSE_FRAME_NED     = 1 # NED earth-fixed frame. Origin X, Y, Z, is position of IMU at EFK startup.
+uint8 POSE_FRAME_FRD     = 2 # FRD world-fixed frame. 
+                             # Origin and heading (X) fixed to arbitrary values at EKF startup. Z is down.
 uint8 pose_frame            # Position and orientation frame of reference
 
 float32[3] position         # Position in meters. Frame of reference defined by local_frame. NaN if invalid/unknown
 float32[4] q                # Quaternion rotation from FRD body frame to reference frame. First value NaN if invalid/unknown
 
 uint8 VELOCITY_FRAME_UNKNOWN  = 0
-uint8 VELOCITY_FRAME_NED      = 1 # NED earth-fixed frame
-uint8 VELOCITY_FRAME_FRD      = 2 # FRD world-fixed frame, arbitrary heading reference
-uint8 VELOCITY_FRAME_BODY_FRD = 3 # FRD body-fixed frame
+uint8 VELOCITY_FRAME_NED      = 1 # NED earth-fixed frame. Origin X, Y, Z, is position of IMU at EFK startup.
+uint8 VELOCITY_FRAME_FRD      = 2 # FRD world-fixed frame.
+                                  #  Origin X, Y, Z, is position of IMU at EFK startup. Z is down.
+uint8 VELOCITY_FRAME_BODY_FRD = 3 # FRD body-fixed frame.
+                                  # Origin travels with vehicle.
+                                  # Frame X, Y, Z is aligned to vehicle Front Right Down.
 uint8 velocity_frame        # Reference frame of the velocity data
 
 float32[3] velocity         # Velocity in meters/sec. Frame of reference defined by velocity_frame variable. NaN if invalid/unknown