better comments for control state message

msg/control_state.msg

@@ -6,9 +6,9 @@ float32 z_acc			# Z acceleration in body frame
 float32 x_vel			# X velocity in body frame
 float32 y_vel			# Y velocity in body frame
 float32 z_vel			# Z velocity in body frame
-float32 x_pos			# X position in local frame
-float32 y_pos			# Y position in local frame
-float32 z_pos			# z position in local frame
+float32 x_pos			# X position in local earth frame
+float32 y_pos			# Y position in local earth frame
+float32 z_pos			# z position in local earth frame
 float32 airspeed		# Airspeed, estimated
 bool airspeed_valid		# False: Non-finite values or non-updating sensor
 float32[3] vel_variance	# Variance in body velocity estimate
@@ -17,4 +17,4 @@ float32[4] q 			# Attitude Quaternion
 float32 roll_rate		# Roll body angular rate (rad/s, x forward/y right/z down)
 float32 pitch_rate		# Pitch body angular rate (rad/s, x forward/y right/z down)
 float32 yaw_rate		# Yaw body angular rate (rad/s, x forward/y right/z down)
-float32 horz_acc_mag		# Magnitude of the horizontal acceleration
+float32 horz_acc_mag	# low pass filtered magnitude of the horizontal acceleration