AP_NavEKF3: integrate Source for alt

libraries/AP_NavEKF3/AP_NavEKF3.cpp

@@ -189,13 +189,7 @@ const AP_Param::GroupInfo NavEKF3::var_info[] = {
 
     // Height measurement parameters
 
-    // @Param: ALT_SOURCE
-    // @DisplayName: Primary altitude sensor source
-    // @Description: Primary height sensor used by the EKF. If a sensor other than Baro is selected and becomes unavailable, then the Baro sensor will be used as a fallback. NOTE: the EK3_RNG_USE_HGT parameter can be used to switch to range-finder when close to the ground in conjunction with EK3_ALT_SOURCE = 0 or 2 (Baro or GPS). NOTE: Setting EK3_ALT_SOURCE = 4 uses external nav system data only if data is also being used for horizontal position
-    // @Values: 0:Use Baro, 1:Use Range Finder, 2:Use GPS, 3:Use Range Beacon, 4:Use External Nav
-    // @User: Advanced
-    // @RebootRequired: True
-    AP_GROUPINFO("ALT_SOURCE", 9, NavEKF3, _altSource, 0),
+    // 9 was ALT_SOURCE
 
     // @Param: ALT_M_NSE
     // @DisplayName: Altitude measurement noise (m)

libraries/AP_NavEKF3/AP_NavEKF3.h

@@ -460,7 +460,6 @@ private:
     AP_Int8  _flowDelay_ms;         // effective average delay of optical flow measurements rel to IMU (msec)
     AP_Int16  _rngInnovGate;        // Percentage number of standard deviations applied to range finder innovation consistency check
     AP_Float _maxFlowRate;          // Maximum flow rate magnitude that will be accepted by the filter
-    AP_Int8 _altSource;             // Primary alt source. 0 = Baro, 1 = range finder, 2 = GPS, 3 = range beacons, 4 = external nav
     AP_Float _rngNoise;             // Range finder noise : m
     AP_Int8 _gpsCheck;              // Bitmask controlling which preflight GPS checks are bypassed
     AP_Int8 _imuMask;               // Bitmask of IMUs to instantiate EKF3 for

libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp

@@ -600,7 +600,7 @@ void  NavEKF3_core::updateFilterStatus(void)
     bool filterHealthy = healthy() && tiltAlignComplete && (yawAlignComplete || (!use_compass() && (PV_AidingMode != AID_ABSOLUTE)));
 
     // If GPS height usage is specified, height is considered to be inaccurate until the GPS passes all checks
-    bool hgtNotAccurate = (frontend->_altSource == 2) && !validOrigin;
+    bool hgtNotAccurate = (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::GPS) && !validOrigin;
 
     // set individual flags
     filterStatus.flags.attitude = !stateStruct.quat.is_nan() && filterHealthy;   // attitude valid (we need a better check)

libraries/AP_NavEKF3/AP_NavEKF3_Measurements.cpp

@@ -765,11 +765,11 @@ void NavEKF3_core::correctEkfOriginHeight()
 
     // calculate the variance of our a-priori estimate of the ekf origin height
     float deltaTime = constrain_float(0.001f * (imuDataDelayed.time_ms - lastOriginHgtTime_ms), 0.0f, 1.0f);
-    if (activeHgtSource == HGT_SOURCE_BARO) {
+    if (activeHgtSource == AP_NavEKF_Source::SourceZ::BARO) {
         // Use the baro drift rate
         const float baroDriftRate = 0.05f;
         ekfOriginHgtVar += sq(baroDriftRate * deltaTime);
-    } else if (activeHgtSource == HGT_SOURCE_RNG) {
+    } else if (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER) {
         // use the worse case expected terrain gradient and vehicle horizontal speed
         const float maxTerrGrad = 0.25f;
         ekfOriginHgtVar += sq(maxTerrGrad * norm(stateStruct.velocity.x , stateStruct.velocity.y) * deltaTime);

libraries/AP_NavEKF3/AP_NavEKF3_OptFlowFusion.cpp

@@ -32,7 +32,7 @@ void NavEKF3_core::SelectFlowFusion()
     // Check if the optical flow data is still valid
     flowDataValid = ((imuSampleTime_ms - flowValidMeaTime_ms) < 1000);
     // check is the terrain offset estimate is still valid - if we are using range finder as the main height reference, the ground is assumed to be at 0
-    gndOffsetValid = ((imuSampleTime_ms - gndHgtValidTime_ms) < 5000) || (activeHgtSource == HGT_SOURCE_RNG);
+    gndOffsetValid = ((imuSampleTime_ms - gndHgtValidTime_ms) < 5000) || (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER);
     // Perform tilt check
     bool tiltOK = (prevTnb.c.z > frontend->DCM33FlowMin);
     // Constrain measurements to zero if takeoff is not detected and the height above ground
@@ -80,7 +80,7 @@ void NavEKF3_core::EstimateTerrainOffset()
     || velHorizSq < 25.0f 
     || (MAX(ofDataDelayed.flowRadXY[0],ofDataDelayed.flowRadXY[1]) > frontend->_maxFlowRate));
 
-    if ((!rangeDataToFuse && cantFuseFlowData) || (activeHgtSource == HGT_SOURCE_RNG)) {
+    if ((!rangeDataToFuse && cantFuseFlowData) || (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER)) {
         // skip update
         inhibitGndState = true;
     } else {

libraries/AP_NavEKF3/AP_NavEKF3_Outputs.cpp

@@ -128,7 +128,7 @@ bool NavEKF3_core::getHeightControlLimit(float &height) const
         }
         height = MAX(float(_rng->max_distance_cm_orient(ROTATION_PITCH_270)) * 0.007f - 1.0f, 1.0f);
         // If we are are not using the range finder as the height reference, then compensate for the difference between terrain and EKF origin
-        if (frontend->_altSource != 1) {
+        if (frontend->_sources.getPosZSource() != AP_NavEKF_Source::SourceZ::RANGEFINDER) {
             height -= terrainState;
         }
         return true;
@@ -635,7 +635,7 @@ void NavEKF3_core::send_status_report(mavlink_channel_t chan) const
     // height estimation or optical flow operation. This prevents false alarms at the GCS if a
     // range finder is fitted for other applications
     float temp;
-    if (((frontend->_useRngSwHgt > 0) && activeHgtSource == HGT_SOURCE_RNG) || (PV_AidingMode == AID_RELATIVE && flowDataValid)) {
+    if (((frontend->_useRngSwHgt > 0) && activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER) || (PV_AidingMode == AID_RELATIVE && flowDataValid)) {
         temp = sqrtf(auxRngTestRatio);
     } else {
         temp = 0.0f;

libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp

@@ -247,7 +247,7 @@ void NavEKF3_core::ResetHeight(void)
     // Check that GPS vertical velocity data is available and can be used
     if (inFlight && !gpsNotAvailable && (frontend->_sources.getVelZSource() == AP_NavEKF_Source::SourceZ::GPS) && !frontend->inhibitGpsVertVelUse) {
         stateStruct.velocity.z =  gpsDataNew.vel.z;
-    } else if (inFlight && useExtNavVel && (activeHgtSource == HGT_SOURCE_EXTNAV)) {
+    } else if (inFlight && useExtNavVel && (activeHgtSource == AP_NavEKF_Source::SourceZ::EXTNAV)) {
         stateStruct.velocity.z = extNavVelDelayed.vel.z;
     } else if (onGround) {
         stateStruct.velocity.z = 0.0f;
@@ -275,7 +275,7 @@ void NavEKF3_core::ResetHeight(void)
 // Return true if the height datum reset has been performed
 bool NavEKF3_core::resetHeightDatum(void)
 {
-    if (activeHgtSource == HGT_SOURCE_RNG || !onGround) {
+    if (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER || !onGround) {
         // only allow resets when on the ground.
         // If using using rangefinder for height then never perform a
         // reset of the height datum
@@ -489,7 +489,7 @@ void NavEKF3_core::SelectVelPosFusion()
         ResetPositionNE(gpsDataDelayed.pos.x, gpsDataDelayed.pos.y);
 
         // If we are also using GPS as the height reference, reset the height
-        if (activeHgtSource == HGT_SOURCE_GPS) {
+        if (activeHgtSource == AP_NavEKF_Source::SourceZ::GPS) {
             ResetPositionD(-hgtMea);
         }
     }
@@ -499,7 +499,7 @@ void NavEKF3_core::SelectVelPosFusion()
         // mark a source reset as consumed
         pos_source_reset = false;
         ResetPositionNE(extNavDataDelayed.pos.x, extNavDataDelayed.pos.y);
-        if (activeHgtSource == HGT_SOURCE_EXTNAV) {
+        if (activeHgtSource == AP_NavEKF_Source::SourceZ::EXTNAV) {
             ResetPositionD(-hgtMea);
         }
     }
@@ -635,7 +635,7 @@ void NavEKF3_core::FuseVelPosNED()
         // if vertical GPS velocity data and an independent height source is being used, check to see if the GPS vertical velocity and altimeter
         // innovations have the same sign and are outside limits. If so, then it is likely aliasing is affecting
         // the accelerometers and we should disable the GPS and barometer innovation consistency checks.
-        if (useGpsVertVel && fuseVelData && (frontend->_altSource != 2)) {
+        if (useGpsVertVel && fuseVelData && (frontend->_sources.getPosZSource() != AP_NavEKF_Source::SourceZ::GPS)) {
             // calculate innovations for height and vertical GPS vel measurements
             const float hgtErr  = stateStruct.position.z - velPosObs[5];
             const float velDErr = stateStruct.velocity.z - velPosObs[2];
@@ -810,7 +810,7 @@ void NavEKF3_core::FuseVelPosNED()
                     const float gndMaxBaroErr = 4.0f;
                     const float gndBaroInnovFloor = -0.5f;
 
-                    if(expectGndEffectTouchdown && activeHgtSource == HGT_SOURCE_BARO) {
+                    if (expectGndEffectTouchdown && activeHgtSource == AP_NavEKF_Source::SourceZ::BARO) {
                         // when a touchdown is expected, floor the barometer innovation at gndBaroInnovFloor
                         // constrain the correction between 0 and gndBaroInnovFloor+gndMaxBaroErr
                         // this function looks like this:
@@ -970,13 +970,13 @@ void NavEKF3_core::selectHeightForFusion()
     bool rangeFinderDataIsFresh = (imuSampleTime_ms - rngValidMeaTime_ms < 500);
     const bool extNavDataIsFresh = (imuSampleTime_ms - extNavMeasTime_ms < 500);
     // select height source
-    if (extNavUsedForPos && (frontend->_altSource == 4)) {
+    if (extNavUsedForPos && (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::EXTNAV)) {
         // always use external navigation as the height source if using for position.
-        activeHgtSource = HGT_SOURCE_EXTNAV;
-    } else if ((frontend->_altSource == 1) && _rng && rangeFinderDataIsFresh) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::EXTNAV;
+    } else if ((frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::RANGEFINDER) && _rng && rangeFinderDataIsFresh) {
         // user has specified the range finder as a primary height source
-        activeHgtSource = HGT_SOURCE_RNG;
-    } else if ((frontend->_useRngSwHgt > 0) && ((frontend->_altSource == 0) || (frontend->_altSource == 2)) && _rng && rangeFinderDataIsFresh) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::RANGEFINDER;
+    } else if ((frontend->_useRngSwHgt > 0) && ((frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::BARO) || (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::GPS)) && _rng && rangeFinderDataIsFresh) {
         // determine if we are above or below the height switch region
         float rangeMaxUse = 1e-4f * (float)_rng->max_distance_cm_orient(ROTATION_PITCH_270) * (float)frontend->_useRngSwHgt;
         bool aboveUpperSwHgt = (terrainState - stateStruct.position.z) > rangeMaxUse;
@@ -1003,40 +1003,40 @@ void NavEKF3_core::selectHeightForFusion()
             * hysteresis to avoid rapid switching. Using range finder for height requires a consistent terrain height
             * which cannot be assumed if the vehicle is moving horizontally.
         */
-        if ((aboveUpperSwHgt || dontTrustTerrain) && (activeHgtSource == HGT_SOURCE_RNG)) {
+        if ((aboveUpperSwHgt || dontTrustTerrain) && (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER)) {
             // cannot trust terrain or range finder so stop using range finder height
-            if (frontend->_altSource == 0) {
-                activeHgtSource = HGT_SOURCE_BARO;
-            } else if (frontend->_altSource == 2) {
-                activeHgtSource = HGT_SOURCE_GPS;
+            if (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::BARO) {
+                activeHgtSource = AP_NavEKF_Source::SourceZ::BARO;
+            } else if (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::GPS) {
+                activeHgtSource = AP_NavEKF_Source::SourceZ::GPS;
             }
         } else if (belowLowerSwHgt && trustTerrain && (prevTnb.c.z >= 0.7f)) {
             // reliable terrain and range finder so start using range finder height
-            activeHgtSource = HGT_SOURCE_RNG;
+            activeHgtSource = AP_NavEKF_Source::SourceZ::RANGEFINDER;
         }
-    } else if (frontend->_altSource == 0) {
-        activeHgtSource = HGT_SOURCE_BARO;
-    } else if ((frontend->_altSource == 2) && ((imuSampleTime_ms - lastTimeGpsReceived_ms) < 500) && validOrigin && gpsAccuracyGood) {
-        activeHgtSource = HGT_SOURCE_GPS;
-    } else if ((frontend->_altSource == 3) && validOrigin && rngBcnGoodToAlign) {
-        activeHgtSource = HGT_SOURCE_BCN;
-    } else if ((frontend->_altSource == 4) && extNavDataIsFresh) {
-        activeHgtSource = HGT_SOURCE_EXTNAV;
+    } else if (frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::BARO) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::BARO;
+    } else if ((frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::GPS) && ((imuSampleTime_ms - lastTimeGpsReceived_ms) < 500) && validOrigin && gpsAccuracyGood) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::GPS;
+    } else if ((frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::BEACON) && validOrigin && rngBcnGoodToAlign) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::BEACON;
+    } else if ((frontend->_sources.getPosZSource() == AP_NavEKF_Source::SourceZ::EXTNAV) && extNavDataIsFresh) {
+        activeHgtSource = AP_NavEKF_Source::SourceZ::EXTNAV;
     }
 
     // Use Baro alt as a fallback if we lose range finder, GPS, external nav or Beacon
-    bool lostRngHgt = ((activeHgtSource == HGT_SOURCE_RNG) && !rangeFinderDataIsFresh);
-    bool lostGpsHgt = ((activeHgtSource == HGT_SOURCE_GPS) && ((imuSampleTime_ms - lastTimeGpsReceived_ms) > 2000));
-    bool lostExtNavHgt = ((activeHgtSource == HGT_SOURCE_EXTNAV) && !extNavDataIsFresh);
-    bool lostRngBcnHgt = ((activeHgtSource == HGT_SOURCE_BCN) && ((imuSampleTime_ms - rngBcnDataDelayed.time_ms) > 2000));
+    bool lostRngHgt = ((activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER) && !rangeFinderDataIsFresh);
+    bool lostGpsHgt = ((activeHgtSource == AP_NavEKF_Source::SourceZ::GPS) && ((imuSampleTime_ms - lastTimeGpsReceived_ms) > 2000));
+    bool lostExtNavHgt = ((activeHgtSource == AP_NavEKF_Source::SourceZ::EXTNAV) && !extNavDataIsFresh);
+    bool lostRngBcnHgt = ((activeHgtSource == AP_NavEKF_Source::SourceZ::BEACON) && ((imuSampleTime_ms - rngBcnDataDelayed.time_ms) > 2000));
     if (lostRngHgt || lostGpsHgt || lostExtNavHgt || lostRngBcnHgt) {
-        activeHgtSource = HGT_SOURCE_BARO;
+        activeHgtSource = AP_NavEKF_Source::SourceZ::BARO;
     }
 
     // if there is new baro data to fuse, calculate filtered baro data required by other processes
     if (baroDataToFuse) {
         // calculate offset to baro data that enables us to switch to Baro height use during operation
-        if  (activeHgtSource != HGT_SOURCE_BARO) {
+        if (activeHgtSource != AP_NavEKF_Source::SourceZ::BARO) {
             calcFiltBaroOffset();
         }
         // filtered baro data used to provide a reference for takeoff
@@ -1053,19 +1053,19 @@ void NavEKF3_core::selectHeightForFusion()
     // combined local NED position height and origin height remains consistent with the GPS altitude
     // This also enables the GPS height to be used as a backup height source
     if (gpsDataToFuse &&
-            (((frontend->_originHgtMode & (1 << 0)) && (activeHgtSource == HGT_SOURCE_BARO)) ||
-            ((frontend->_originHgtMode & (1 << 1)) && (activeHgtSource == HGT_SOURCE_RNG)))
+            (((frontend->_originHgtMode & (1 << 0)) && (activeHgtSource == AP_NavEKF_Source::SourceZ::BARO)) ||
+            ((frontend->_originHgtMode & (1 << 1)) && (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER)))
             ) {
             correctEkfOriginHeight();
     }
 
     // Select the height measurement source
-    if (extNavDataToFuse && (activeHgtSource == HGT_SOURCE_EXTNAV)) {
+    if (extNavDataToFuse && (activeHgtSource == AP_NavEKF_Source::SourceZ::EXTNAV)) {
         hgtMea = -extNavDataDelayed.pos.z;
         velPosObs[5] = -hgtMea;
         posDownObsNoise = sq(constrain_float(extNavDataDelayed.posErr, 0.1f, 10.0f));
         fuseHgtData = true;
-    } else if (rangeDataToFuse && (activeHgtSource == HGT_SOURCE_RNG)) {
+    } else if (rangeDataToFuse && (activeHgtSource == AP_NavEKF_Source::SourceZ::RANGEFINDER)) {
         // using range finder data
         // correct for tilt using a flat earth model
         if (prevTnb.c.z >= 0.7) {
@@ -1084,7 +1084,7 @@ void NavEKF3_core::selectHeightForFusion()
             // disable fusion if tilted too far
             fuseHgtData = false;
         }
-    } else if  (gpsDataToFuse && (activeHgtSource == HGT_SOURCE_GPS)) {
+    } else if (gpsDataToFuse && (activeHgtSource == AP_NavEKF_Source::SourceZ::GPS)) {
         // using GPS data
         hgtMea = gpsDataDelayed.hgt;
         velPosObs[5] = -hgtMea;
@@ -1096,7 +1096,7 @@ void NavEKF3_core::selectHeightForFusion()
         } else {
             posDownObsNoise = sq(constrain_float(1.5f * frontend->_gpsHorizPosNoise, 0.1f, 10.0f));
         }
-    } else if (baroDataToFuse && (activeHgtSource == HGT_SOURCE_BARO)) {
+    } else if (baroDataToFuse && (activeHgtSource == AP_NavEKF_Source::SourceZ::BARO)) {
         // using Baro data
         hgtMea = baroDataDelayed.hgt - baroHgtOffset;
         // enable fusion
@@ -1117,6 +1117,12 @@ void NavEKF3_core::selectHeightForFusion()
         fuseHgtData = false;
     }
 
+    // detect changes in source and reset height
+    if ((activeHgtSource != prevHgtSource) && fuseHgtData) {
+        prevHgtSource = activeHgtSource;
+        ResetPositionD(-hgtMea);
+    }
+
     // If we haven't fused height data for a while, then declare the height data as being timed out
     // set timeout period based on whether we have vertical GPS velocity available to constrain drift
     hgtRetryTime_ms = ((useGpsVertVel || useExtNavVel) && !velTimeout) ? frontend->hgtRetryTimeMode0_ms : frontend->hgtRetryTimeMode12_ms;

libraries/AP_NavEKF3/AP_NavEKF3_RngBcnFusion.cpp

@@ -54,7 +54,7 @@ void NavEKF3_core::FuseRngBcn()
     // health is set bad until test passed
     rngBcnHealth = false;
 
-    if (activeHgtSource != HGT_SOURCE_BCN) {
+    if (activeHgtSource != AP_NavEKF_Source::SourceZ::BEACON) {
         // calculate the vertical offset from EKF datum to beacon datum
         CalcRangeBeaconPosDownOffset(R_BCN, stateStruct.position, false);
     } else {
@@ -96,7 +96,7 @@ void NavEKF3_core::FuseRngBcn()
         // are at the same height as the flight vehicle when calculating the observation derivatives
         // and Kalman gains
         // TODO  - less hacky way of achieving this, preferably using an alternative derivation
-        if (activeHgtSource != HGT_SOURCE_BCN) {
+        if (activeHgtSource != AP_NavEKF_Source::SourceZ::BEACON) {
             t2 = 0.0f;
         }
         H_BCN[9] = -t2*t9;
@@ -158,7 +158,7 @@ void NavEKF3_core::FuseRngBcn()
         }
 
         // only allow the range observations to modify the vertical states if we are using it as a height reference
-        if (activeHgtSource == HGT_SOURCE_BCN) {
+        if (activeHgtSource == AP_NavEKF_Source::SourceZ::BEACON) {
             Kfusion[6] = -t26*(P[6][7]*t4*t9+P[6][8]*t3*t9+P[6][9]*t2*t9);
             Kfusion[9] = -t26*(t10+P[9][7]*t4*t9+P[9][8]*t3*t9);
         } else {
@@ -324,7 +324,7 @@ void NavEKF3_core::FuseRngBcnStatic()
         }
 
         if (rngBcnAlignmentCompleted) {
-            if (activeHgtSource != HGT_SOURCE_BCN) {
+            if (activeHgtSource != AP_NavEKF_Source::SourceZ::BEACON) {
                 // We are using a different height reference for the main EKF so need to estimate a vertical
                 // position offset to be applied to the beacon system that minimises the range innovations
                 // The position estimate should be stable after 100 iterations so we use a simple dual
@@ -341,7 +341,7 @@ void NavEKF3_core::FuseRngBcnStatic()
 
             }
         } else {
-            if (activeHgtSource != HGT_SOURCE_BCN) {
+            if (activeHgtSource != AP_NavEKF_Source::SourceZ::BEACON) {
                 // The position estimate is not yet stable so we cannot run the 1-state EKF to estimate
                 // beacon system vertical position offset. Instead we initialise the dual hypothesis offset states
                 // using the beacon vertical position, vertical position estimate relative to the beacon origin

libraries/AP_NavEKF3/AP_NavEKF3_core.cpp

@@ -317,7 +317,8 @@ void NavEKF3_core::InitialiseVariables()
     delAngBiasLearned = false;
     memset(&filterStatus, 0, sizeof(filterStatus));
     gpsInhibit = false;
-    activeHgtSource = 0;
+    activeHgtSource = AP_NavEKF_Source::SourceZ::BARO;
+    prevHgtSource = activeHgtSource;
     memset(&rngMeasIndex, 0, sizeof(rngMeasIndex));
     memset(&storedRngMeasTime_ms, 0, sizeof(storedRngMeasTime_ms));
     memset(&storedRngMeas, 0, sizeof(storedRngMeas));

libraries/AP_NavEKF3/AP_NavEKF3_core.h

@@ -46,13 +46,6 @@
 #define MASK_GPS_VERT_SPD   (1<<6)
 #define MASK_GPS_HORIZ_SPD  (1<<7)
 
-// active height source
-#define HGT_SOURCE_BARO     0
-#define HGT_SOURCE_RNG      1
-#define HGT_SOURCE_GPS      2
-#define HGT_SOURCE_BCN      3
-#define HGT_SOURCE_EXTNAV   4
-
 #define earthRate 0.000072921f // earth rotation rate (rad/sec)
 
 // maximum allowed gyro bias (rad/sec)
@@ -1306,7 +1299,8 @@ private:
     } rngBcnFusionReport[4];
 
     // height source selection logic
-    uint8_t activeHgtSource;    // integer defining active height source
+    AP_NavEKF_Source::SourceZ activeHgtSource;  // active height source
+    AP_NavEKF_Source::SourceZ prevHgtSource;    // previous height source used to detect changes in source
 
     // Movement detector
     bool takeOffDetected;           // true when takeoff for optical flow navigation has been detected