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   *    notice, this list of conditions and the following disclaimer.
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   ****************************************************************************/
  
  /**
   * @file EKF2.cpp
   * Implementation of the attitude and position estimator.
   *
   * @author Roman Bapst
   */
  
  #pragma once
  
  #include "EKF2Selector.hpp"
  
  #include <float.h>
  
  #include <containers/LockGuard.hpp>
  #include <drivers/drv_hrt.h>
  #include <lib/ecl/EKF/ekf.h>
  #include <lib/mathlib/mathlib.h>
  #include <lib/perf/perf_counter.h>
  #include <px4_platform_common/defines.h>
  #include <px4_platform_common/module.h>
  #include <px4_platform_common/module_params.h>
  #include <px4_platform_common/posix.h>
  #include <px4_platform_common/px4_work_queue/ScheduledWorkItem.hpp>
  #include <px4_platform_common/time.h>
  #include <uORB/Publication.hpp>
  #include <uORB/PublicationMulti.hpp>
  #include <uORB/Subscription.hpp>
  #include <uORB/SubscriptionCallback.hpp>
  #include <uORB/SubscriptionMultiArray.hpp>
  #include <uORB/topics/airspeed.h>
  #include <uORB/topics/distance_sensor.h>
  #include <uORB/topics/ekf2_timestamps.h>
  #include <uORB/topics/ekf_gps_drift.h>
  #include <uORB/topics/estimator_innovations.h>
  #include <uORB/topics/estimator_optical_flow_vel.h>
  #include <uORB/topics/estimator_sensor_bias.h>
  #include <uORB/topics/estimator_states.h>
  #include <uORB/topics/estimator_status.h>
  #include <uORB/topics/estimator_status_flags.h>
  #include <uORB/topics/landing_target_pose.h>
  #include <uORB/topics/optical_flow.h>
  #include <uORB/topics/parameter_update.h>
  #include <uORB/topics/sensor_combined.h>
  #include <uORB/topics/sensor_selection.h>
  #include <uORB/topics/vehicle_air_data.h>
  #include <uORB/topics/vehicle_attitude.h>
  #include <uORB/topics/vehicle_global_position.h>
  #include <uORB/topics/vehicle_gps_position.h>
  #include <uORB/topics/vehicle_imu.h>
  #include <uORB/topics/vehicle_land_detected.h>
  #include <uORB/topics/vehicle_local_position.h>
  #include <uORB/topics/vehicle_magnetometer.h>
  #include <uORB/topics/vehicle_odometry.h>
  #include <uORB/topics/vehicle_status.h>
  #include <uORB/topics/wind_estimate.h>
  #include <uORB/topics/yaw_estimator_status.h>
  
  #include "Utility/PreFlightChecker.hpp"
  
  extern pthread_mutex_t ekf2_module_mutex;
  
  class EKF2 final : public ModuleParams, public px4::ScheduledWorkItem
  {
  public:
  	EKF2() = delete;
  	EKF2(int instance, const px4::wq_config_t &config, int imu, int mag, bool replay_mode);
  	~EKF2() override;
  
  	/** @see ModuleBase */
  	static int task_spawn(int argc, char *argv[]);
  
  	/** @see ModuleBase */
  	static int custom_command(int argc, char *argv[]);
  
  	/** @see ModuleBase */
  	static int print_usage(const char *reason = nullptr);
  
  	int print_status();
  
  	bool should_exit() const { return _task_should_exit.load(); }
  
  	void request_stop() { _task_should_exit.store(true); }
  
  	static void lock_module() { pthread_mutex_lock(&ekf2_module_mutex); }
  	static bool trylock_module() { return (pthread_mutex_trylock(&ekf2_module_mutex) == 0); }
  	static void unlock_module() { pthread_mutex_unlock(&ekf2_module_mutex); }
  
  private:
  	void Run() override;
  
  	template<typename Param>
  	void update_mag_bias(Param &mag_bias_param, int axis_index);
  
  	void PublishAttitude(const hrt_abstime &timestamp);
  	void PublishEkfDriftMetrics(const hrt_abstime &timestamp);
  	void PublishGlobalPosition(const hrt_abstime &timestamp);
  	void PublishInnovations(const hrt_abstime &timestamp, const imuSample &imu);
  	void PublishInnovationTestRatios(const hrt_abstime &timestamp);
  	void PublishInnovationVariances(const hrt_abstime &timestamp);
  	void PublishLocalPosition(const hrt_abstime &timestamp);
  	void PublishOdometry(const hrt_abstime &timestamp, const imuSample &imu);
  	void PublishOdometryAligned(const hrt_abstime &timestamp, const vehicle_odometry_s &ev_odom);
  	void PublishOpticalFlowVel(const hrt_abstime &timestamp, const optical_flow_s &optical_flow);
  	void PublishSensorBias(const hrt_abstime &timestamp);
  	void PublishStates(const hrt_abstime &timestamp);
  	void PublishStatus(const hrt_abstime &timestamp);
  	void PublishStatusFlags(const hrt_abstime &timestamp);
  	void PublishWindEstimate(const hrt_abstime &timestamp);
  	void PublishYawEstimatorStatus(const hrt_abstime &timestamp);
  
  	void UpdateAirspeedSample(ekf2_timestamps_s &ekf2_timestamps);
  	void UpdateAuxVelSample(ekf2_timestamps_s &ekf2_timestamps);
  	void UpdateBaroSample(ekf2_timestamps_s &ekf2_timestamps);
  	bool UpdateExtVisionSample(ekf2_timestamps_s &ekf2_timestamps, vehicle_odometry_s &ev_odom);
  	bool UpdateFlowSample(ekf2_timestamps_s &ekf2_timestamps, optical_flow_s &optical_flow);
  	void UpdateGpsSample(ekf2_timestamps_s &ekf2_timestamps);
  	void UpdateMagSample(ekf2_timestamps_s &ekf2_timestamps);
  	void UpdateRangeSample(ekf2_timestamps_s &ekf2_timestamps);
  
  	void UpdateMagCalibration(const hrt_abstime &timestamp);
  
  	/*
  	 * Calculate filtered WGS84 height from estimated AMSL height
  	 */
  	float filter_altitude_ellipsoid(float amsl_hgt);
  
  	static constexpr float sq(float x) { return x * x; };
  
  	const bool _replay_mode{false};			///< true when we use replay data from a log
  	const bool _multi_mode;
  	const int _instance;
  
  	px4::atomic_bool _task_should_exit{false};
  
  	// time slip monitoring
  	uint64_t _integrated_time_us = 0;	///< integral of gyro delta time from start (uSec)
  	uint64_t _start_time_us = 0;		///< system time at EKF start (uSec)
  	int64_t _last_time_slip_us = 0;		///< Last time slip (uSec)
  
  	perf_counter_t _ecl_ekf_update_perf{perf_alloc(PC_ELAPSED, MODULE_NAME": ECL update")};
  	perf_counter_t _ecl_ekf_update_full_perf{perf_alloc(PC_ELAPSED, MODULE_NAME": ECL full update")};
  
  	// Initialise time stamps used to send sensor data to the EKF and for logging
  	uint8_t _invalid_mag_id_count = 0;	///< number of times an invalid magnetomer device ID has been detected
  
  	// Used to check, save and use learned magnetometer biases
  	hrt_abstime _last_magcal_us = 0;	///< last time the EKF was operating a mode that estimates magnetomer biases (uSec)
  	hrt_abstime _total_cal_time_us = 0;	///< accumulated calibration time since the last save
  
  	Vector3f _last_valid_mag_cal{};	///< last valid XYZ magnetometer bias estimates (Gauss)
  	Vector3f _last_valid_variance{};	///< variances for the last valid magnetometer XYZ bias estimates (Gauss**2)
  	bool _valid_cal_available{false};	///< true when an unsaved valid calibration for the XYZ magnetometer bias is available
  
  	// Used to control saving of mag declination to be used on next startup
  	bool _mag_decl_saved = false;	///< true when the magnetic declination has been saved
  
  	bool _had_valid_terrain{false};			///< true if at any time there was a valid terrain estimate
  
  	uint64_t _gps_time_usec{0};
  	int32_t _gps_alttitude_ellipsoid{0};			///< altitude in 1E-3 meters (millimeters) above ellipsoid
  	uint64_t _gps_alttitude_ellipsoid_previous_timestamp{0}; ///< storage for previous timestamp to compute dt
  	float   _wgs84_hgt_offset = 0;  ///< height offset between AMSL and WGS84
  
  	uint8_t _imu_calibration_count{0};
  
  	uint32_t _device_id_accel{0};
  	uint32_t _device_id_baro{0};
  	uint32_t _device_id_gyro{0};
  	uint32_t _device_id_mag{0};
  
  	Vector3f _last_local_position_for_gpos{};
  
  	Vector3f _last_accel_bias{};
  	Vector3f _last_gyro_bias{};
  	Vector3f _last_mag_bias{};
  
  	uORB::Subscription _airdata_sub{ORB_ID(vehicle_air_data)};
  	uORB::Subscription _airspeed_sub{ORB_ID(airspeed)};
  	uORB::Subscription _distance_sensor_sub{ORB_ID(distance_sensor)};
  	uORB::Subscription _ev_odom_sub{ORB_ID(vehicle_visual_odometry)};
  	uORB::Subscription _landing_target_pose_sub{ORB_ID(landing_target_pose)};
  	uORB::Subscription _magnetometer_sub{ORB_ID(vehicle_magnetometer)};
  	uORB::Subscription _optical_flow_sub{ORB_ID(optical_flow)};
  	uORB::Subscription _parameter_update_sub{ORB_ID(parameter_update)};
  	uORB::Subscription _sensor_selection_sub{ORB_ID(sensor_selection)};
  	uORB::Subscription _status_sub{ORB_ID(vehicle_status)};
  	uORB::Subscription _vehicle_gps_position_sub{ORB_ID(vehicle_gps_position)};
  	uORB::Subscription _vehicle_land_detected_sub{ORB_ID(vehicle_land_detected)};
  
  	uORB::SubscriptionCallbackWorkItem _sensor_combined_sub{this, ORB_ID(sensor_combined)};
  	uORB::SubscriptionCallbackWorkItem _vehicle_imu_sub{this, ORB_ID(vehicle_imu)};
  
  	bool _callback_registered{false};
  	int _lockstep_component{-1};
  
  	bool _distance_sensor_selected{false}; // because we can have several distance sensor instances with different orientations
  	bool _armed{false};
  	bool _standby{false}; // standby arming state
  
  	hrt_abstime _last_status_flag_update{0};
  
  	uint32_t _filter_control_status{0};
  	uint32_t _filter_fault_status{0};
  	uint32_t _innov_check_fail_status{0};
  
  	uint32_t _filter_control_status_changes{0};
  	uint32_t _filter_fault_status_changes{0};
  	uint32_t _innov_check_fail_status_changes{0};
  
  	uORB::PublicationMulti<ekf2_timestamps_s>            _ekf2_timestamps_pub{ORB_ID(ekf2_timestamps)};
  	uORB::PublicationMulti<ekf_gps_drift_s>              _ekf_gps_drift_pub{ORB_ID(ekf_gps_drift)};
  	uORB::PublicationMulti<estimator_innovations_s>      _estimator_innovation_test_ratios_pub{ORB_ID(estimator_innovation_test_ratios)};
  	uORB::PublicationMulti<estimator_innovations_s>      _estimator_innovation_variances_pub{ORB_ID(estimator_innovation_variances)};
  	uORB::PublicationMulti<estimator_innovations_s>      _estimator_innovations_pub{ORB_ID(estimator_innovations)};
  	uORB::PublicationMulti<estimator_optical_flow_vel_s> _estimator_optical_flow_vel_pub{ORB_ID(estimator_optical_flow_vel)};
  	uORB::PublicationMulti<estimator_sensor_bias_s>      _estimator_sensor_bias_pub{ORB_ID(estimator_sensor_bias)};
  	uORB::PublicationMulti<estimator_states_s>           _estimator_states_pub{ORB_ID(estimator_states)};
  	uORB::PublicationMulti<estimator_status_s>           _estimator_status_pub{ORB_ID(estimator_status)};
  	uORB::PublicationMulti<estimator_status_flags_s>     _estimator_status_flags_pub{ORB_ID(estimator_status_flags)};
  	uORB::PublicationMulti<vehicle_odometry_s>           _estimator_visual_odometry_aligned_pub{ORB_ID(estimator_visual_odometry_aligned)};
  	uORB::PublicationMulti<yaw_estimator_status_s>       _yaw_est_pub{ORB_ID(yaw_estimator_status)};
  	uORB::PublicationMulti<wind_estimate_s>              _wind_pub{ORB_ID(wind_estimate)};
  
  	// publications with topic dependent on multi-mode
  	uORB::PublicationMulti<vehicle_attitude_s>           _attitude_pub;
  	uORB::PublicationMulti<vehicle_local_position_s>     _local_position_pub;
  	uORB::PublicationMulti<vehicle_global_position_s>    _global_position_pub;
  	uORB::PublicationMulti<vehicle_odometry_s>           _odometry_pub;
  
  	PreFlightChecker _preflt_checker;
  
  	Ekf _ekf;
  
  	parameters *_params;	///< pointer to ekf parameter struct (located in _ekf class instance)
  
  	DEFINE_PARAMETERS(
  		(ParamExtInt<px4::params::EKF2_MIN_OBS_DT>)
  		_param_ekf2_min_obs_dt,	///< Maximum time delay of any sensor used to increase buffer length to handle large timing jitter (mSec)
  		(ParamExtFloat<px4::params::EKF2_MAG_DELAY>)
  		_param_ekf2_mag_delay,	///< magnetometer measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_BARO_DELAY>)
  		_param_ekf2_baro_delay,	///< barometer height measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_GPS_DELAY>)
  		_param_ekf2_gps_delay,	///< GPS measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_OF_DELAY>)
  		_param_ekf2_of_delay,	///< optical flow measurement delay relative to the IMU (mSec) - this is to the middle of the optical flow integration interval
  		(ParamExtFloat<px4::params::EKF2_RNG_DELAY>)
  		_param_ekf2_rng_delay,	///< range finder measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_ASP_DELAY>)
  		_param_ekf2_asp_delay,	///< airspeed measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_EV_DELAY>)
  		_param_ekf2_ev_delay,	///< off-board vision measurement delay relative to the IMU (mSec)
  		(ParamExtFloat<px4::params::EKF2_AVEL_DELAY>)
  		_param_ekf2_avel_delay,	///< auxillary velocity measurement delay relative to the IMU (mSec)
  
  		(ParamExtFloat<px4::params::EKF2_GYR_NOISE>)
  		_param_ekf2_gyr_noise,	///< IMU angular rate noise used for covariance prediction (rad/sec)
  		(ParamExtFloat<px4::params::EKF2_ACC_NOISE>)
  		_param_ekf2_acc_noise,	///< IMU acceleration noise use for covariance prediction (m/sec**2)
  
  		// process noise
  		(ParamExtFloat<px4::params::EKF2_GYR_B_NOISE>)
  		_param_ekf2_gyr_b_noise,	///< process noise for IMU rate gyro bias prediction (rad/sec**2)
  		(ParamExtFloat<px4::params::EKF2_ACC_B_NOISE>)
  		_param_ekf2_acc_b_noise,///< process noise for IMU accelerometer bias prediction (m/sec**3)
  		(ParamExtFloat<px4::params::EKF2_MAG_E_NOISE>)
  		_param_ekf2_mag_e_noise,	///< process noise for earth magnetic field prediction (Gauss/sec)
  		(ParamExtFloat<px4::params::EKF2_MAG_B_NOISE>)
  		_param_ekf2_mag_b_noise,	///< process noise for body magnetic field prediction (Gauss/sec)
  		(ParamExtFloat<px4::params::EKF2_WIND_NOISE>)
  		_param_ekf2_wind_noise,	///< process noise for wind velocity prediction (m/sec**2)
  		(ParamExtFloat<px4::params::EKF2_TERR_NOISE>) _param_ekf2_terr_noise,	///< process noise for terrain offset (m/sec)
  		(ParamExtFloat<px4::params::EKF2_TERR_GRAD>)
  		_param_ekf2_terr_grad,	///< gradient of terrain used to estimate process noise due to changing position (m/m)
  
  		(ParamExtFloat<px4::params::EKF2_GPS_V_NOISE>)
  		_param_ekf2_gps_v_noise,	///< minimum allowed observation noise for gps velocity fusion (m/sec)
  		(ParamExtFloat<px4::params::EKF2_GPS_P_NOISE>)
  		_param_ekf2_gps_p_noise,	///< minimum allowed observation noise for gps position fusion (m)
  		(ParamExtFloat<px4::params::EKF2_NOAID_NOISE>)
  		_param_ekf2_noaid_noise,	///< observation noise for non-aiding position fusion (m)
  		(ParamExtFloat<px4::params::EKF2_BARO_NOISE>)
  		_param_ekf2_baro_noise,	///< observation noise for barometric height fusion (m)
  		(ParamExtFloat<px4::params::EKF2_BARO_GATE>)
  		_param_ekf2_baro_gate,	///< barometric height innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_GND_EFF_DZ>)
  		_param_ekf2_gnd_eff_dz,	///< barometric deadzone range for negative innovations (m)
  		(ParamExtFloat<px4::params::EKF2_GND_MAX_HGT>)
  		_param_ekf2_gnd_max_hgt,	///< maximum height above the ground level for expected negative baro innovations (m)
  		(ParamExtFloat<px4::params::EKF2_GPS_P_GATE>)
  		_param_ekf2_gps_p_gate,	///< GPS horizontal position innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_GPS_V_GATE>)
  		_param_ekf2_gps_v_gate,	///< GPS velocity innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_TAS_GATE>)
  		_param_ekf2_tas_gate,	///< True Airspeed innovation consistency gate size (STD)
  
  		// control of magnetometer fusion
  		(ParamExtFloat<px4::params::EKF2_HEAD_NOISE>)
  		_param_ekf2_head_noise,	///< measurement noise used for simple heading fusion (rad)
  		(ParamExtFloat<px4::params::EKF2_MAG_NOISE>)
  		_param_ekf2_mag_noise,		///< measurement noise used for 3-axis magnetoemeter fusion (Gauss)
  		(ParamExtFloat<px4::params::EKF2_EAS_NOISE>)
  		_param_ekf2_eas_noise,		///< measurement noise used for airspeed fusion (m/sec)
  		(ParamExtFloat<px4::params::EKF2_BETA_GATE>)
  		_param_ekf2_beta_gate, ///< synthetic sideslip innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_BETA_NOISE>) _param_ekf2_beta_noise,	///< synthetic sideslip noise (rad)
  		(ParamExtFloat<px4::params::EKF2_MAG_DECL>) _param_ekf2_mag_decl,///< magnetic declination (degrees)
  		(ParamExtFloat<px4::params::EKF2_HDG_GATE>)
  		_param_ekf2_hdg_gate,///< heading fusion innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_MAG_GATE>)
  		_param_ekf2_mag_gate,	///< magnetometer fusion innovation consistency gate size (STD)
  		(ParamExtInt<px4::params::EKF2_DECL_TYPE>)
  		_param_ekf2_decl_type,	///< bitmask used to control the handling of declination data
  		(ParamExtInt<px4::params::EKF2_MAG_TYPE>)
  		_param_ekf2_mag_type,	///< integer used to specify the type of magnetometer fusion used
  		(ParamExtFloat<px4::params::EKF2_MAG_ACCLIM>)
  		_param_ekf2_mag_acclim,	///< integer used to specify the type of magnetometer fusion used
  		(ParamExtFloat<px4::params::EKF2_MAG_YAWLIM>)
  		_param_ekf2_mag_yawlim,	///< yaw rate threshold used by mode select logic (rad/sec)
  
  		(ParamExtInt<px4::params::EKF2_GPS_CHECK>)
  		_param_ekf2_gps_check,	///< bitmask used to control which GPS quality checks are used
  		(ParamExtFloat<px4::params::EKF2_REQ_EPH>) _param_ekf2_req_eph,	///< maximum acceptable horiz position error (m)
  		(ParamExtFloat<px4::params::EKF2_REQ_EPV>) _param_ekf2_req_epv,	///< maximum acceptable vert position error (m)
  		(ParamExtFloat<px4::params::EKF2_REQ_SACC>) _param_ekf2_req_sacc,	///< maximum acceptable speed error (m/s)
  		(ParamExtInt<px4::params::EKF2_REQ_NSATS>) _param_ekf2_req_nsats,	///< minimum acceptable satellite count
  		(ParamExtFloat<px4::params::EKF2_REQ_PDOP>)
  		_param_ekf2_req_pdop,	///< maximum acceptable position dilution of precision
  		(ParamExtFloat<px4::params::EKF2_REQ_HDRIFT>)
  		_param_ekf2_req_hdrift,	///< maximum acceptable horizontal drift speed (m/s)
  		(ParamExtFloat<px4::params::EKF2_REQ_VDRIFT>) _param_ekf2_req_vdrift,	///< maximum acceptable vertical drift speed (m/s)
  
  		// measurement source control
  		(ParamExtInt<px4::params::EKF2_AID_MASK>)
  		_param_ekf2_aid_mask,		///< bitmasked integer that selects which of the GPS and optical flow aiding sources will be used
  		(ParamExtInt<px4::params::EKF2_HGT_MODE>) _param_ekf2_hgt_mode,	///< selects the primary source for height data
  		(ParamExtInt<px4::params::EKF2_TERR_MASK>)
  		_param_ekf2_terr_mask, ///< bitmasked integer that selects which of range finder and optical flow aiding sources will be used for terrain estimation
  		(ParamExtInt<px4::params::EKF2_NOAID_TOUT>)
  		_param_ekf2_noaid_tout,	///< maximum lapsed time from last fusion of measurements that constrain drift before the EKF will report the horizontal nav solution invalid (uSec)
  
  		// range finder fusion
  		(ParamExtFloat<px4::params::EKF2_RNG_NOISE>)
  		_param_ekf2_rng_noise,	///< observation noise for range finder measurements (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_SFE>) _param_ekf2_rng_sfe, ///< scale factor from range to range noise (m/m)
  		(ParamExtFloat<px4::params::EKF2_RNG_GATE>)
  		_param_ekf2_rng_gate,	///< range finder fusion innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_MIN_RNG>) _param_ekf2_min_rng,	///< minimum valid value for range when on ground (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_PITCH>) _param_ekf2_rng_pitch,	///< range sensor pitch offset (rad)
  		(ParamExtInt<px4::params::EKF2_RNG_AID>)
  		_param_ekf2_rng_aid,		///< enables use of a range finder even if primary height source is not range finder
  		(ParamExtFloat<px4::params::EKF2_RNG_A_VMAX>)
  		_param_ekf2_rng_a_vmax,	///< maximum allowed horizontal velocity for range aid (m/s)
  		(ParamExtFloat<px4::params::EKF2_RNG_A_HMAX>)
  		_param_ekf2_rng_a_hmax,	///< maximum allowed absolute altitude (AGL) for range aid (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_A_IGATE>)
  		_param_ekf2_rng_a_igate,	///< gate size used for innovation consistency checks for range aid fusion (STD)
  
  		// vision estimate fusion
  		(ParamInt<px4::params::EKF2_EV_NOISE_MD>)
  		_param_ekf2_ev_noise_md,	///< determine source of vision observation noise
  		(ParamFloat<px4::params::EKF2_EVP_NOISE>)
  		_param_ekf2_evp_noise,	///< default position observation noise for exernal vision measurements (m)
  		(ParamFloat<px4::params::EKF2_EVV_NOISE>)
  		_param_ekf2_evv_noise,	///< default velocity observation noise for exernal vision measurements (m/s)
  		(ParamFloat<px4::params::EKF2_EVA_NOISE>)
  		_param_ekf2_eva_noise,	///< default angular observation noise for exernal vision measurements (rad)
  		(ParamExtFloat<px4::params::EKF2_EVV_GATE>)
  		_param_ekf2_evv_gate,	///< external vision velocity innovation consistency gate size (STD)
  		(ParamExtFloat<px4::params::EKF2_EVP_GATE>)
  		_param_ekf2_evp_gate,	///< external vision position innovation consistency gate size (STD)
  
  		// optical flow fusion
  		(ParamExtFloat<px4::params::EKF2_OF_N_MIN>)
  		_param_ekf2_of_n_min,	///< best quality observation noise for optical flow LOS rate measurements (rad/sec)
  		(ParamExtFloat<px4::params::EKF2_OF_N_MAX>)
  		_param_ekf2_of_n_max,	///< worst quality observation noise for optical flow LOS rate measurements (rad/sec)
  		(ParamExtInt<px4::params::EKF2_OF_QMIN>)
  		_param_ekf2_of_qmin,	///< minimum acceptable quality integer from  the flow sensor
  		(ParamExtFloat<px4::params::EKF2_OF_GATE>)
  		_param_ekf2_of_gate,	///< optical flow fusion innovation consistency gate size (STD)
  
  		// sensor positions in body frame
  		(ParamExtFloat<px4::params::EKF2_IMU_POS_X>) _param_ekf2_imu_pos_x,		///< X position of IMU in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_IMU_POS_Y>) _param_ekf2_imu_pos_y,		///< Y position of IMU in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_IMU_POS_Z>) _param_ekf2_imu_pos_z,		///< Z position of IMU in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_GPS_POS_X>) _param_ekf2_gps_pos_x,		///< X position of GPS antenna in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_GPS_POS_Y>) _param_ekf2_gps_pos_y,		///< Y position of GPS antenna in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_GPS_POS_Z>) _param_ekf2_gps_pos_z,		///< Z position of GPS antenna in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_POS_X>) _param_ekf2_rng_pos_x,		///< X position of range finder in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_POS_Y>) _param_ekf2_rng_pos_y,		///< Y position of range finder in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_RNG_POS_Z>) _param_ekf2_rng_pos_z,		///< Z position of range finder in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_OF_POS_X>)
  		_param_ekf2_of_pos_x,	///< X position of optical flow sensor focal point in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_OF_POS_Y>)
  		_param_ekf2_of_pos_y,	///< Y position of optical flow sensor focal point in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_OF_POS_Z>)
  		_param_ekf2_of_pos_z,	///< Z position of optical flow sensor focal point in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_EV_POS_X>)
  		_param_ekf2_ev_pos_x,		///< X position of VI sensor focal point in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_EV_POS_Y>)
  		_param_ekf2_ev_pos_y,		///< Y position of VI sensor focal point in body frame (m)
  		(ParamExtFloat<px4::params::EKF2_EV_POS_Z>)
  		_param_ekf2_ev_pos_z,		///< Z position of VI sensor focal point in body frame (m)
  
  		// control of airspeed and sideslip fusion
  		(ParamFloat<px4::params::EKF2_ARSP_THR>)
  		_param_ekf2_arsp_thr, 	///< A value of zero will disabled airspeed fusion. Any positive value sets the minimum airspeed which will be used (m/sec)
  		(ParamInt<px4::params::EKF2_FUSE_BETA>)
  		_param_ekf2_fuse_beta,		///< Controls synthetic sideslip fusion, 0 disables, 1 enables
  
  		// output predictor filter time constants
  		(ParamExtFloat<px4::params::EKF2_TAU_VEL>)
  		_param_ekf2_tau_vel,		///< time constant used by the output velocity complementary filter (sec)
  		(ParamExtFloat<px4::params::EKF2_TAU_POS>)
  		_param_ekf2_tau_pos,		///< time constant used by the output position complementary filter (sec)
  
  		// IMU switch on bias parameters
  		(ParamExtFloat<px4::params::EKF2_GBIAS_INIT>)
  		_param_ekf2_gbias_init,	///< 1-sigma gyro bias uncertainty at switch on (rad/sec)
  		(ParamExtFloat<px4::params::EKF2_ABIAS_INIT>)
  		_param_ekf2_abias_init,	///< 1-sigma accelerometer bias uncertainty at switch on (m/sec**2)
  		(ParamExtFloat<px4::params::EKF2_ANGERR_INIT>)
  		_param_ekf2_angerr_init,	///< 1-sigma tilt error after initial alignment using gravity vector (rad)
  
  		// EKF saved XYZ magnetometer bias values
  		(ParamFloat<px4::params::EKF2_MAGBIAS_X>) _param_ekf2_magbias_x,		///< X magnetometer bias (Gauss)
  		(ParamFloat<px4::params::EKF2_MAGBIAS_Y>) _param_ekf2_magbias_y,		///< Y magnetometer bias (Gauss)
  		(ParamFloat<px4::params::EKF2_MAGBIAS_Z>) _param_ekf2_magbias_z,		///< Z magnetometer bias (Gauss)
  		(ParamInt<px4::params::EKF2_MAGBIAS_ID>)
  		_param_ekf2_magbias_id,		///< ID of the magnetometer sensor used to learn the bias values
  		(ParamFloat<px4::params::EKF2_MAGB_VREF>)
  		_param_ekf2_magb_vref, ///< Assumed error variance of previously saved magnetometer bias estimates (Gauss**2)
  		(ParamFloat<px4::params::EKF2_MAGB_K>)
  		_param_ekf2_magb_k,	///< maximum fraction of the learned magnetometer bias that is saved at each disarm
  
  		// EKF accel bias learning control
  		(ParamExtFloat<px4::params::EKF2_ABL_LIM>) _param_ekf2_abl_lim,	///< Accelerometer bias learning limit (m/s**2)
  		(ParamExtFloat<px4::params::EKF2_ABL_ACCLIM>)
  		_param_ekf2_abl_acclim,	///< Maximum IMU accel magnitude that allows IMU bias learning (m/s**2)
  		(ParamExtFloat<px4::params::EKF2_ABL_GYRLIM>)
  		_param_ekf2_abl_gyrlim,	///< Maximum IMU gyro angular rate magnitude that allows IMU bias learning (m/s**2)
  		(ParamExtFloat<px4::params::EKF2_ABL_TAU>)
  		_param_ekf2_abl_tau,	///< Time constant used to inhibit IMU delta velocity bias learning (sec)
  
  		// Multi-rotor drag specific force fusion
  		(ParamExtFloat<px4::params::EKF2_DRAG_NOISE>)
  		_param_ekf2_drag_noise,	///< observation noise variance for drag specific force measurements (m/sec**2)**2
  		(ParamExtFloat<px4::params::EKF2_BCOEF_X>) _param_ekf2_bcoef_x,		///< ballistic coefficient along the X-axis (kg/m**2)
  		(ParamExtFloat<px4::params::EKF2_BCOEF_Y>) _param_ekf2_bcoef_y,		///< ballistic coefficient along the Y-axis (kg/m**2)
  
  		// Corrections for static pressure position error where Ps_error = Ps_meas - Ps_truth
  		// Coef = Ps_error / Pdynamic, where Pdynamic = 1/2 * density * TAS**2
  		(ParamExtFloat<px4::params::EKF2_ASPD_MAX>)
  		_param_ekf2_aspd_max,		///< upper limit on airspeed used for correction  (m/s**2)
  		(ParamExtFloat<px4::params::EKF2_PCOEF_XP>)
  		_param_ekf2_pcoef_xp,	///< static pressure position error coefficient along the positive X body axis
  		(ParamExtFloat<px4::params::EKF2_PCOEF_XN>)
  		_param_ekf2_pcoef_xn,	///< static pressure position error coefficient along the negative X body axis
  		(ParamExtFloat<px4::params::EKF2_PCOEF_YP>)
  		_param_ekf2_pcoef_yp,	///< static pressure position error coefficient along the positive Y body axis
  		(ParamExtFloat<px4::params::EKF2_PCOEF_YN>)
  		_param_ekf2_pcoef_yn,	///< static pressure position error coefficient along the negative Y body axis
  		(ParamExtFloat<px4::params::EKF2_PCOEF_Z>)
  		_param_ekf2_pcoef_z,	///< static pressure position error coefficient along the Z body axis
  
  		// Test used to determine if the vehicle is static or moving
  		(ParamExtFloat<px4::params::EKF2_MOVE_TEST>)
  		_param_ekf2_move_test,	///< scaling applied to IMU data thresholds used to determine if the vehicle is static or moving.
  
  		(ParamFloat<px4::params::EKF2_REQ_GPS_H>) _param_ekf2_req_gps_h, ///< Required GPS health time
  		(ParamExtInt<px4::params::EKF2_MAG_CHECK>) _param_ekf2_mag_check, ///< Mag field strength check
  
  		// Used by EKF-GSF experimental yaw estimator
  		(ParamExtFloat<px4::params::EKF2_GSF_TAS>)
  		_param_ekf2_gsf_tas_default	///< default value of true airspeed assumed during fixed wing operation
  
  	)
  };
  