diff --git a/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp b/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
index 7ce5592b55..34e7924431 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
+++ b/libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
@@ -345,7 +345,7 @@ void NavEKF2_core::SelectVelPosFusion()
     } else if (extNavDataToFuse && PV_AidingMode == AID_ABSOLUTE) {
         // This is a special case that uses and external nav system for position
         extNavUsedForPos = true;
-        activeHgtSource = HGT_SOURCE_EV;
+        activeHgtSource = HGT_SOURCE_EXTNAV;
         fuseVelData = false;
         fuseHgtData = true;
         fusePosData = true;
@@ -875,7 +875,7 @@ void NavEKF2_core::selectHeightForFusion()
     // select height source
     if (extNavUsedForPos) {
         // always use external vision as the height source if using for position.
-        activeHgtSource = HGT_SOURCE_EV;
+        activeHgtSource = HGT_SOURCE_EXTNAV;
     } else if (_rng && ((frontend->_useRngSwHgt > 0) && (frontend->_altSource == 1)) && (imuSampleTime_ms - rngValidMeaTime_ms < 500)) {
         if (frontend->_altSource == 1) {
             // always use range finder
@@ -922,7 +922,7 @@ void NavEKF2_core::selectHeightForFusion()
     // Use Baro alt as a fallback if we lose range finder, GPS or external nav
     bool lostRngHgt = ((activeHgtSource == HGT_SOURCE_RNG) && ((imuSampleTime_ms - rngValidMeaTime_ms) > 500));
     bool lostGpsHgt = ((activeHgtSource == HGT_SOURCE_GPS) && ((imuSampleTime_ms - lastTimeGpsReceived_ms) > 2000));
-    bool lostExtNavHgt = ((activeHgtSource == HGT_SOURCE_EV) && ((imuSampleTime_ms - extNavMeasTime_ms) > 2000));
+    bool lostExtNavHgt = ((activeHgtSource == HGT_SOURCE_EXTNAV) && ((imuSampleTime_ms - extNavMeasTime_ms) > 2000));
     if (lostRngHgt || lostGpsHgt || lostExtNavHgt) {
         activeHgtSource = HGT_SOURCE_BARO;
     }
@@ -954,7 +954,7 @@ void NavEKF2_core::selectHeightForFusion()
     }
 
     // Select the height measurement source
-    if (extNavDataToFuse && (activeHgtSource == HGT_SOURCE_EV)) {
+    if (extNavDataToFuse && (activeHgtSource == HGT_SOURCE_EXTNAV)) {
         hgtMea = -extNavDataDelayed.pos.z;
         posDownObsNoise = sq(constrain_float(extNavDataDelayed.posErr, 0.01f, 10.0f));
     } else if (rangeDataToFuse && (activeHgtSource == HGT_SOURCE_RNG)) {
diff --git a/libraries/AP_NavEKF2/AP_NavEKF2_core.h b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
index d8e3886d46..6c3e83baf5 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2_core.h
+++ b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
@@ -46,11 +46,11 @@
 #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_EV   4
+#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
 
 // target EKF update time step
 #define EKF_TARGET_DT 0.01f