msgs: extra clarifications in descriptions. (#24846)

msg/FixedWingLateralGuidanceStatus.msg

@@ -3,7 +3,7 @@
 
 uint64 timestamp                # time since system start (microseconds)
 
-float32 course_setpoint         # [rad] [-pi, pi] Bearing angle. Same as course over ground setpoint, w.r.t. North.
+float32 course_setpoint         # [rad] [-pi, pi] Desired direction of travel over ground w.r.t (true) North. Set by guidance law
 float32 lateral_acceleration_ff # [m/s^2] [FRD] lateral acceleration demand only for maintaining curvature
 float32 bearing_feas            # [0,1] bearing feasibility
 float32 bearing_feas_on_track   # [0,1] on-track bearing feasibility

msg/versioned/FixedWingLateralSetpoint.msg

@@ -6,6 +6,6 @@ uint32 MESSAGE_VERSION = 0
 
 uint64 timestamp                        # time since system start (microseconds)
 
-float32 course 				# [rad] [-pi, pi] Course over ground setpoint, w.r.t. North. NAN if not controlled directly.
-float32 airspeed_direction    		# [rad] [-pi, pi] Angle projected to ground of desired airspeed vector, w.r.t. North. NAN if not controlled directly, used as feedforward if course setpoint is finite.
+float32 course 				# [rad] [-pi, pi] Desired direction of travel over ground w.r.t (true) North. NAN if not controlled directly.
+float32 airspeed_direction    		# [rad] [-pi, pi] Desired horizontal angle of airspeed vector w.r.t. (true) North. Same as vehicle heading if in the absence of sideslip. NAN if not controlled directly, used as feedforward if course setpoint is finite.
 float32 lateral_acceleration 		# [m/s^2] [FRD] Lateral acceleration setpoint. NAN if not controlled directly, used as feedforward if either course setpoint or airspeed_direction is finite.

msg/versioned/FixedWingLongitudinalSetpoint.msg

@@ -1,13 +1,14 @@
 # Fixed Wing Longitudinal Setpoint message
 # Used by the fw_lateral_longitudinal_control module
-# If not both pitch_direct and throttle_direct are finite, then either altitude or height_rate must be finite.
+# If pitch_direct and throttle_direct are not both finite, then the controller relies on altitude/height_rate and equivalent_airspeed to control vertical motion.
+# If both altitude and height_rate are NAN, the controller maintains the current altitude.
 
 uint32 MESSAGE_VERSION = 0
 
 uint64 timestamp                        # time since system start (microseconds)
 
 float32 altitude  			# [m] Altitude setpoint AMSL, not controlled directly if NAN or if height_rate is finite
-float32 height_rate 			# [m/s] NAN if not controlled directly
-float32 equivalent_airspeed 		# [m/s] NAN if system default should be used
-float32 pitch_direct 			# [rad] [FRD] NAN if not controlled, overrides total energy controller
+float32 height_rate 			# [m/s] [ENU] Scalar height rate setpoint. NAN if not controlled directly
+float32 equivalent_airspeed 		# [m/s] [0, inf] Scalar equivalent airspeed setpoint. NAN if system default should be used
+float32 pitch_direct 			# [rad] [-pi, pi] [FRD] NAN if not controlled, overrides total energy controller
 float32 throttle_direct 		# [0,1] NAN if not controlled, overrides total energy controller

msg/versioned/LongitudinalControlConfiguration.msg

@@ -6,12 +6,12 @@ uint32 MESSAGE_VERSION = 0
 
 uint64 timestamp                        # time since system start (microseconds)
 
-float32 pitch_min   			# [rad]
-float32 pitch_max   			# [rad]
-float32 throttle_min 			# [0,1]
-float32 throttle_max 			# [0,1]
-float32 climb_rate_target 		# [m/s] target climbrate used to change altitude. Not used if height_rate is directly set in FixedWingLongitudinalSetpoint.
-float32 sink_rate_target 		# [m/s] target sinkrate used to change altitude. Not used if height_rate is directly set in FixedWingLongitudinalSetpoint.
+float32 pitch_min   			# [rad][-pi, pi] defaults to FW_P_LIM_MIN if NAN.
+float32 pitch_max   			# [rad][-pi, pi] defaults to FW_P_LIM_MAX if NAN.
+float32 throttle_min 			# [0,1] deaults to FW_THR_MIN if NAN.
+float32 throttle_max 			# [0,1] defaults to FW_THR_MAX if NAN.
+float32 climb_rate_target 		# [m/s] target climbrate to change altitude. Defaults to FW_T_CLIMB_MAX if NAN. Not used if height_rate is directly set in FixedWingLongitudinalSetpoint.
+float32 sink_rate_target 		# [m/s] target sinkrate to change altitude. Defaults to FW_T_SINK_MAX if NAN. Not used if height_rate is directly set in FixedWingLongitudinalSetpoint.
 float32 speed_weight 			# [0,2], 0=pitch controls altitude only, 2=pitch controls airspeed only
 bool enforce_low_height_condition 	# if true, total energy controller will use lower altitude control time constant
 bool disable_underspeed_protection 	# if true, underspeed handling is disabled in the total energy controller