ekf2: fix comments about primary height sources

Having the xxx_hgt flag set only means that the sensor is fused for
altitude/height aiding. It's not necessarily the height reference.

msg/EstimatorStatus.msg

@@ -27,9 +27,9 @@ uint8 CS_MAG_3D = 5		# 5 - true if 3-axis magnetometer measurement are being fus
 uint8 CS_MAG_DEC = 6		# 6 - true if synthetic magnetic declination measurements are being fused
 uint8 CS_IN_AIR = 7		# 7 - true when thought to be airborne
 uint8 CS_WIND = 8		# 8 - true when wind velocity is being estimated
-uint8 CS_BARO_HGT = 9		# 9 - true when baro height is being fused as a primary height reference
-uint8 CS_RNG_HGT = 10		# 10 - true when range finder height is being fused as a primary height reference
-uint8 CS_GPS_HGT = 11		# 11 - true when GPS height is being fused as a primary height reference
+uint8 CS_BARO_HGT = 9		# 9 - true when baro data is being fused
+uint8 CS_RNG_HGT = 10		# 10 - true when range finder data is being fused for height aiding
+uint8 CS_GPS_HGT = 11		# 11 - true when GPS altitude is being fused
 uint8 CS_EV_POS = 12		# 12 - true when local position data from external vision is being fused
 uint8 CS_EV_YAW = 13		# 13 - true when yaw data from external vision measurements is being fused
 uint8 CS_EV_HGT = 14		# 14 - true when height data from external vision measurements is being fused

msg/EstimatorStatusFlags.msg

@@ -13,9 +13,9 @@ bool cs_mag_3d                #  5 - true if 3-axis magnetometer measurement fus
 bool cs_mag_dec               #  6 - true if synthetic magnetic declination measurements fusion is intended
 bool cs_in_air                #  7 - true when the vehicle is airborne
 bool cs_wind                  #  8 - true when wind velocity is being estimated
-bool cs_baro_hgt              #  9 - true when baro height is being fused as a primary height reference
-bool cs_rng_hgt               # 10 - true when range finder height is being fused as a primary height reference
-bool cs_gps_hgt               # 11 - true when GPS height is being fused as a primary height reference
+bool cs_baro_hgt              #  9 - true when baro data is being fused
+bool cs_rng_hgt               # 10 - true when range finder data is being fused for height aiding
+bool cs_gps_hgt               # 11 - true when GPS altitude is being fused
 bool cs_ev_pos                # 12 - true when local position data fusion from external vision is intended
 bool cs_ev_yaw                # 13 - true when yaw data from external vision measurements fusion is intended
 bool cs_ev_hgt                # 14 - true when height data from external vision measurements is being fused

src/modules/ekf2/EKF/aid_sources/range_finder/range_height_control.cpp

@@ -78,7 +78,7 @@ void Ekf::controlRangeHaglFusion(const imuSample &imu_sample)
 			}
 
 		} else {
-			// If we are supposed to be using range finder data as the primary height sensor, have bad range measurements
+			// If we are supposed to be using range finder data but have bad range measurements
 			// and are on the ground, then synthesise a measurement at the expected on ground value
 			if (!_control_status.flags.in_air
 			    && _range_sensor.isRegularlySendingData()

src/modules/ekf2/EKF/common.h

@@ -573,10 +573,10 @@ union filter_control_status_u {
 		uint64_t mag_dec                 : 1; ///< 6 - true if synthetic magnetic declination measurements fusion is intended
 		uint64_t in_air                  : 1; ///< 7 - true when the vehicle is airborne
 		uint64_t wind                    : 1; ///< 8 - true when wind velocity is being estimated
-		uint64_t baro_hgt                : 1; ///< 9 - true when baro height is being fused as a primary height reference
+		uint64_t baro_hgt                : 1; ///< 9 - true when baro data is being fused
 uint64_t rng_hgt                 :
-		1; ///< 10 - true when range finder height is being fused as a primary height reference
-		uint64_t gps_hgt                 : 1; ///< 11 - true when GPS height is being fused as a primary height reference
+		1; ///< 10 - true when range finder data is being fused for height aiding
+		uint64_t gps_hgt                 : 1; ///< 11 - true when GPS altitude is being fused
 		uint64_t ev_pos                  : 1; ///< 12 - true when local position data fusion from external vision is intended
 		uint64_t ev_yaw                  : 1; ///< 13 - true when yaw data from external vision measurements fusion is intended
 		uint64_t ev_hgt                  : 1; ///< 14 - true when height data from external vision measurements is being fused

src/modules/ekf2/EKF/ekf_helper.cpp

@@ -345,7 +345,6 @@ void Ekf::get_ekf_ctrl_limits(float *vxy_max, float *vz_max, float *hagl_min, fl
 	// TODO : calculate visual odometry limits
 	const bool relying_on_rangefinder = isOnlyActiveSourceOfVerticalPositionAiding(_control_status.flags.rng_hgt);
 
-	// Keep within range sensor limit when using rangefinder as primary height source
 	if (relying_on_rangefinder) {
 		*hagl_min = rangefinder_hagl_min;
 		*hagl_max = rangefinder_hagl_max;