AP_AHRS: rename DCM members to clarify EAS vs TAS

libraries/AP_AHRS/AP_AHRS.cpp

@@ -346,9 +346,9 @@ void AP_AHRS::update_state(void)
     state.primary_core = _get_primary_core_index();
     state.wind_estimate_ok = _wind_estimate(state.wind_estimate);
     state.EAS2TAS = AP_AHRS_Backend::get_EAS2TAS();
-    state.airspeed_ok = _airspeed_estimate(state.airspeed, state.airspeed_estimate_type);
-    state.airspeed_true_ok = _airspeed_estimate_true(state.airspeed_true);
-    state.airspeed_vec_ok = _airspeed_vector_true(state.airspeed_vec);
+    state.airspeed_ok = _airspeed_EAS(state.airspeed, state.airspeed_estimate_type);
+    state.airspeed_true_ok = _airspeed_TAS(state.airspeed_true);
+    state.airspeed_vec_ok = _airspeed_TAS(state.airspeed_vec);
     state.quat_ok = _get_quaternion(state.quat);
     state.secondary_attitude_ok = _get_secondary_attitude(state.secondary_attitude);
     state.secondary_quat_ok = _get_secondary_quaternion(state.secondary_quat);
@@ -931,7 +931,7 @@ bool AP_AHRS::_should_use_airspeed_sensor(uint8_t airspeed_index) const
 
 // return an airspeed estimate if available. return true
 // if we have an estimate
-bool AP_AHRS::_airspeed_estimate(float &airspeed_ret, AirspeedEstimateType &airspeed_estimate_type) const
+bool AP_AHRS::_airspeed_EAS(float &airspeed_ret, AirspeedEstimateType &airspeed_estimate_type) const
 {
 #if AP_AHRS_DCM_ENABLED || (AP_AIRSPEED_ENABLED && AP_GPS_ENABLED)
     const uint8_t idx = get_active_airspeed_index();
@@ -970,20 +970,20 @@ bool AP_AHRS::_airspeed_estimate(float &airspeed_ret, AirspeedEstimateType &airs
 #if AP_AHRS_DCM_ENABLED
     case EKFType::DCM:
         airspeed_estimate_type = AirspeedEstimateType::DCM_SYNTHETIC;
-        return dcm.airspeed_estimate(idx, airspeed_ret);
+        return dcm.airspeed_EAS(idx, airspeed_ret);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
         airspeed_estimate_type = AirspeedEstimateType::SIM;
-        return sim.airspeed_estimate(airspeed_ret);
+        return sim.airspeed_EAS(airspeed_ret);
 #endif
 
 #if HAL_NAVEKF2_AVAILABLE
     case EKFType::TWO:
 #if AP_AHRS_DCM_ENABLED
         airspeed_estimate_type = AirspeedEstimateType::DCM_SYNTHETIC;
-        return dcm.airspeed_estimate(idx, airspeed_ret);
+        return dcm.airspeed_EAS(idx, airspeed_ret);
 #else
         return false;
 #endif
@@ -999,7 +999,7 @@ bool AP_AHRS::_airspeed_estimate(float &airspeed_ret, AirspeedEstimateType &airs
     case EKFType::EXTERNAL:
 #if AP_AHRS_DCM_ENABLED
         airspeed_estimate_type = AirspeedEstimateType::DCM_SYNTHETIC;
-        return dcm.airspeed_estimate(idx, airspeed_ret);
+        return dcm.airspeed_EAS(idx, airspeed_ret);
 #else
         return false;
 #endif
@@ -1027,18 +1027,18 @@ bool AP_AHRS::_airspeed_estimate(float &airspeed_ret, AirspeedEstimateType &airs
 #if AP_AHRS_DCM_ENABLED
     // fallback to DCM
     airspeed_estimate_type = AirspeedEstimateType::DCM_SYNTHETIC;
-    return dcm.airspeed_estimate(idx, airspeed_ret);
+    return dcm.airspeed_EAS(idx, airspeed_ret);
 #endif
 
     return false;
 }
 
-bool AP_AHRS::_airspeed_estimate_true(float &airspeed_ret) const
+bool AP_AHRS::_airspeed_TAS(float &airspeed_ret) const
 {
     switch (active_EKF_type()) {
 #if AP_AHRS_DCM_ENABLED
     case EKFType::DCM:
-        return dcm.airspeed_estimate_true(airspeed_ret);
+        return dcm.airspeed_TAS(airspeed_ret);
 #endif
 #if HAL_NAVEKF2_AVAILABLE
     case EKFType::TWO:
@@ -1064,7 +1064,7 @@ bool AP_AHRS::_airspeed_estimate_true(float &airspeed_ret) const
 
 // return estimate of true airspeed vector in body frame in m/s
 // returns false if estimate is unavailable
-bool AP_AHRS::_airspeed_vector_true(Vector3f &vec) const
+bool AP_AHRS::_airspeed_TAS(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
 #if AP_AHRS_DCM_ENABLED
@@ -1126,14 +1126,14 @@ bool AP_AHRS::airspeed_health_data(float &innovation, float &innovationVariance,
     return false;
 }
 
-// return a synthetic airspeed estimate (one derived from sensors
+// return a synthetic EAS estimate (one derived from sensors
 // other than an actual airspeed sensor), if available. return
 // true if we have a synthetic airspeed.  ret will not be modified
 // on failure.
 bool AP_AHRS::synthetic_airspeed(float &ret) const
 {
 #if AP_AHRS_DCM_ENABLED
-    return dcm.synthetic_airspeed(ret);
+    return dcm.synthetic_airspeed_EAS(ret);
 #endif
     return false;
 }

libraries/AP_AHRS/AP_AHRS.h

@@ -152,7 +152,7 @@ class AP_AHRS {
     // get air density / sea level density - decreases as altitude climbs
     float get_air_density_ratio(void) const;
 
-    // return an airspeed estimate if available. return true
+    // return an (equivalent) airspeed estimate if available. return true
     // if we have an estimate
     bool airspeed_estimate(float &airspeed_ret) const;
 
@@ -195,7 +195,7 @@ class AP_AHRS {
         return AP_AHRS_Backend::airspeed_sensor_enabled(airspeed_index);
     }
 
-    // return a synthetic airspeed estimate (one derived from sensors
+    // return a synthetic (equivalent) airspeed estimate (one derived from sensors
     // other than an actual airspeed sensor), if available. return
     // true if we have a synthetic airspeed.  ret will not be modified
     // on failure.
@@ -873,7 +873,7 @@ class AP_AHRS {
 
     // return an airspeed estimate if available. return true
     // if we have an estimate
-    bool _airspeed_estimate(float &airspeed_ret, AirspeedEstimateType &status) const;
+    bool _airspeed_EAS(float &airspeed_ret, AirspeedEstimateType &status) const;
 
     // return secondary attitude solution if available, as eulers in radians
     bool _get_secondary_attitude(Vector3f &eulers) const;
@@ -892,11 +892,11 @@ class AP_AHRS {
 
     // return a true airspeed estimate (navigation airspeed) if
     // available. return true if we have an estimate
-    bool _airspeed_estimate_true(float &airspeed_ret) const;
+    bool _airspeed_TAS(float &airspeed_ret) const;
 
     // return estimate of true airspeed vector in body frame in m/s
     // returns false if estimate is unavailable
-    bool _airspeed_vector_true(Vector3f &vec) const;
+    bool _airspeed_TAS(Vector3f &vec) const;
 
     // return the quaternion defining the rotation from NED to XYZ (body) axes
     bool _get_quaternion(Quaternion &quat) const WARN_IF_UNUSED;

libraries/AP_AHRS/AP_AHRS_Backend.h

@@ -135,13 +135,13 @@ class AP_AHRS_Backend
 
     // return an airspeed estimate if available. return true
     // if we have an estimate
-    virtual bool airspeed_estimate(float &airspeed_ret) const WARN_IF_UNUSED { return false; }
-    virtual bool airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const { return false; }
+    virtual bool airspeed_EAS(float &airspeed_ret) const WARN_IF_UNUSED { return false; }
+    virtual bool airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const { return false; }
 
     // return a true airspeed estimate (navigation airspeed) if
     // available. return true if we have an estimate
-    bool airspeed_estimate_true(float &airspeed_ret) const WARN_IF_UNUSED {
-        if (!airspeed_estimate(airspeed_ret)) {
+    bool airspeed_TAS(float &airspeed_ret) const WARN_IF_UNUSED {
+        if (!airspeed_EAS(airspeed_ret)) {
             return false;
         }
         airspeed_ret *= get_EAS2TAS();
@@ -156,6 +156,7 @@ class AP_AHRS_Backend
 
     // get apparent to true airspeed ratio
     static float get_EAS2TAS(void);
+    static float get_TAS2EAS(void) { return 1.0/get_EAS2TAS(); }
 
     // return true if airspeed comes from an airspeed sensor, as
     // opposed to an IMU estimate

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -724,16 +724,16 @@ AP_AHRS_DCM::drift_correction(float deltat)
             return;
         }
 
-        float airspeed = _last_airspeed;
+        float airspeed_TAS = _last_airspeed_TAS;
 #if AP_AIRSPEED_ENABLED
         if (airspeed_sensor_enabled()) {
-            airspeed = AP::airspeed()->get_airspeed();
+            airspeed_TAS = AP::airspeed()->get_airspeed();
         }
 #endif
 
         // use airspeed to estimate our ground velocity in
         // earth frame by subtracting the wind
-        velocity = _dcm_matrix.colx() * airspeed;
+        velocity = _dcm_matrix.colx() * airspeed_TAS;
 
         // add in wind estimate
         velocity += _wind;
@@ -762,7 +762,7 @@ AP_AHRS_DCM::drift_correction(float deltat)
 
         // take positive component in X direction. This mimics a pitot
         // tube
-        _last_airspeed = MAX(airspeed.x, 0);
+        _last_airspeed_TAS = MAX(airspeed.x, 0);
     }
 
     if (have_gps()) {
@@ -1084,31 +1084,31 @@ bool AP_AHRS_DCM::get_location(Location &loc) const
     return _have_position;
 }
 
-bool AP_AHRS_DCM::airspeed_estimate(float &airspeed_ret) const
+bool AP_AHRS_DCM::airspeed_EAS(float &airspeed_ret) const
 {
 #if AP_AIRSPEED_ENABLED
     const auto *airspeed = AP::airspeed();
     if (airspeed != nullptr) {
-        return airspeed_estimate(airspeed->get_primary(), airspeed_ret);
+        return airspeed_EAS(airspeed->get_primary(), airspeed_ret);
     }
 #endif
     // airspeed_estimate will also make this nullptr check and act
     // appropriately when we call it with a dummy sensor ID.
-    return airspeed_estimate(0, airspeed_ret);
+    return airspeed_EAS(0, airspeed_ret);
 }
 
-// return an airspeed estimate:
+// return an (equivalent) airspeed estimate:
 //  - from a real sensor if available
 //  - otherwise from a GPS-derived wind-triangle estimate (if GPS available)
 //  - otherwise from a cached wind-triangle estimate value (but returning false)
-bool AP_AHRS_DCM::airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const
+bool AP_AHRS_DCM::airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const
 {
-    // airspeed_ret: will always be filled-in by get_unconstrained_airspeed_estimate which fills in airspeed_ret in this order:
+    // airspeed_ret: will always be filled-in by get_unconstrained_airspeed_EAS which fills in airspeed_ret in this order:
     //               airspeed as filled-in by an enabled airspeed sensor
     //               if no airspeed sensor: airspeed estimated using the GPS speed & wind_speed_estimation
     //               Or if none of the above, fills-in using the previous airspeed estimate
     // Return false: if we are using the previous airspeed estimate
-    if (!get_unconstrained_airspeed_estimate(airspeed_index, airspeed_ret)) {
+    if (!get_unconstrained_airspeed_EAS(airspeed_index, airspeed_ret)) {
         return false;
     }
 
@@ -1127,12 +1127,12 @@ bool AP_AHRS_DCM::airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret)
     return true;
 }
 
-// airspeed_ret: will always be filled-in by get_unconstrained_airspeed_estimate which fills in airspeed_ret in this order:
+// airspeed_ret: will always be filled-in by get_unconstrained_airspeed_EAS which fills in airspeed_ret in this order:
 //               airspeed as filled-in by an enabled airspeed sensor
 //               if no airspeed sensor: airspeed estimated using the GPS speed & wind_speed_estimation
 //               Or if none of the above, fills-in using the previous airspeed estimate
 // Return false: if we are using the previous airspeed estimate
-bool AP_AHRS_DCM::get_unconstrained_airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const
+bool AP_AHRS_DCM::get_unconstrained_airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const
 {
 #if AP_AIRSPEED_ENABLED
     if (airspeed_sensor_enabled(airspeed_index)) {
@@ -1143,13 +1143,13 @@ bool AP_AHRS_DCM::get_unconstrained_airspeed_estimate(uint8_t airspeed_index, fl
 
     if (AP::ahrs().get_wind_estimation_enabled() && have_gps()) {
         // estimated via GPS speed and wind
-        airspeed_ret = _last_airspeed;
+        airspeed_ret = _last_airspeed_TAS;
         return true;
     }
 
     // Else give the last estimate, but return false.
     // This is used by the dead-reckoning code
-    airspeed_ret = _last_airspeed;
+    airspeed_ret = _last_airspeed_TAS;
     return false;
 }
 
@@ -1182,7 +1182,7 @@ Vector2f AP_AHRS_DCM::groundspeed_vector(void)
     Vector2f gndVelADS;
     Vector2f gndVelGPS;
     float airspeed = 0;
-    const bool gotAirspeed = airspeed_estimate_true(airspeed);
+    const bool gotAirspeed = airspeed_TAS(airspeed);
     const bool gotGPS = (AP::gps().status() >= AP_GPS::GPS_OK_FIX_2D);
     if (gotAirspeed) {
         const Vector2f airspeed_vector{_cos_yaw * airspeed, _sin_yaw * airspeed};

libraries/AP_AHRS/AP_AHRS_DCM.h

@@ -82,18 +82,18 @@ class AP_AHRS_DCM : public AP_AHRS_Backend {
 
     // return an airspeed estimate if available. return true
     // if we have an estimate
-    bool airspeed_estimate(float &airspeed_ret) const override;
+    bool airspeed_EAS(float &airspeed_ret) const override;
 
     // return an airspeed estimate if available. return true
     // if we have an estimate from a specific sensor index
-    bool airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const override;
+    bool airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const override;
 
-    // return a synthetic airspeed estimate (one derived from sensors
+    // return a synthetic EAS estimate (one derived from sensors
     // other than an actual airspeed sensor), if available. return
     // true if we have a synthetic airspeed.  ret will not be modified
     // on failure.
-    bool synthetic_airspeed(float &ret) const WARN_IF_UNUSED {
-        ret = _last_airspeed;
+    bool synthetic_airspeed_EAS(float &ret) const WARN_IF_UNUSED {
+        ret = _last_airspeed_TAS;
         return true;
     }
 
@@ -173,12 +173,12 @@ class AP_AHRS_DCM : public AP_AHRS_Backend {
     // DCM matrix from the eulers.  Called internally we may.
     void            reset(bool recover_eulers);
 
-    // airspeed_ret: will always be filled-in by get_unconstrained_airspeed_estimate which fills in airspeed_ret in this order:
+    // airspeed_ret: will always be filled-in by get_unconstrained_airspeed_EAS which fills in airspeed_ret in this order:
     //               airspeed as filled-in by an enabled airspeed sensor
     //               if no airspeed sensor: airspeed estimated using the GPS speed & wind_speed_estimation
     //               Or if none of the above, fills-in using the previous airspeed estimate
     // Return false: if we are using the previous airspeed estimate
-    bool get_unconstrained_airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const;
+    bool get_unconstrained_airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const;
 
     // primary representation of attitude of board used for all inertial calculations
     Matrix3f _dcm_matrix;
@@ -262,7 +262,7 @@ class AP_AHRS_DCM : public AP_AHRS_Backend {
     Vector3f _last_fuse;
     Vector3f _last_vel;
     uint32_t _last_wind_time;
-    float _last_airspeed;
+    float _last_airspeed_TAS;
     uint32_t _last_consistent_heading;
 
     // estimated wind in m/s

libraries/AP_AHRS/AP_AHRS_SIM.cpp

@@ -41,7 +41,7 @@ bool AP_AHRS_SIM::wind_estimate(Vector3f &wind) const
     return true;
 }
 
-bool AP_AHRS_SIM::airspeed_estimate(float &airspeed_ret) const
+bool AP_AHRS_SIM::airspeed_EAS(float &airspeed_ret) const
 {
     if (_sitl == nullptr) {
         return false;
@@ -52,9 +52,9 @@ bool AP_AHRS_SIM::airspeed_estimate(float &airspeed_ret) const
     return true;
 }
 
-bool AP_AHRS_SIM::airspeed_estimate(uint8_t index, float &airspeed_ret) const
+bool AP_AHRS_SIM::airspeed_EAS(uint8_t index, float &airspeed_ret) const
 {
-    return airspeed_estimate(airspeed_ret);
+    return airspeed_EAS(airspeed_ret);
 }
 
 bool AP_AHRS_SIM::get_quaternion(Quaternion &quat) const

libraries/AP_AHRS/AP_AHRS_SIM.h

@@ -68,11 +68,11 @@ class AP_AHRS_SIM : public AP_AHRS_Backend {
 
     // return an airspeed estimate if available. return true
     // if we have an estimate
-    bool airspeed_estimate(float &airspeed_ret) const override;
+    bool airspeed_EAS(float &airspeed_ret) const override;
 
     // return an airspeed estimate if available. return true
     // if we have an estimate from a specific sensor index
-    bool airspeed_estimate(uint8_t airspeed_index, float &airspeed_ret) const override;
+    bool airspeed_EAS(uint8_t airspeed_index, float &airspeed_ret) const override;
 
     // return a ground vector estimate in meters/second, in North/East order
     Vector2f groundspeed_vector() override;