diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp
index 34dc0dfd66..335e76e9b9 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp
@@ -210,7 +210,7 @@ void NavEKF3_core::setAidingMode()
             // GPS aiding is the preferred option unless excluded by the user
             if (readyToUseGPS() || readyToUseRangeBeacon() || readyToUseExtNav()) {
                 PV_AidingMode = AID_ABSOLUTE;
-            } else if ((readyToUseOptFlow()  && (frontend->_flowUse == FLOW_USE_NAV)) || readyToUseBodyOdm()) {
+            } else if (readyToUseOptFlow() || readyToUseBodyOdm()) {
                 PV_AidingMode = AID_RELATIVE;
             }
             break;
@@ -434,6 +434,15 @@ bool NavEKF3_core::useRngFinder(void) const
 // return true if the filter is ready to start using optical flow measurements
 bool NavEKF3_core::readyToUseOptFlow(void) const
 {
+    // ensure flow is used for navigation and not terrain alt estimation
+    if (frontend->_flowUse != FLOW_USE_NAV) {
+        return false;
+    }
+
+    if (frontend->_sources.getVelXYSource() != AP_NavEKF_Source::SourceXY::OPTFLOW) {
+        return false;
+    }
+
     // We need stable roll/pitch angles and gyro bias estimates but do not need the yaw angle aligned to use optical flow
     return (imuSampleTime_ms - flowMeaTime_ms < 200) && tiltAlignComplete && delAngBiasLearned;
 }
@@ -441,6 +450,11 @@ bool NavEKF3_core::readyToUseOptFlow(void) const
 // return true if the filter is ready to start using body frame odometry measurements
 bool NavEKF3_core::readyToUseBodyOdm(void) const
 {
+    if ((frontend->_sources.getVelXYSource() != AP_NavEKF_Source::SourceXY::EXTNAV) &&
+        (frontend->_sources.getVelXYSource() != AP_NavEKF_Source::SourceXY::WHEEL_ENCODER)) {
+        return false;
+    }
+
     // Check for fresh visual odometry data that meets the accuracy required for alignment
     bool visoDataGood = (imuSampleTime_ms - bodyOdmMeasTime_ms < 200) && (bodyOdmDataNew.velErr < 1.0f);
 
@@ -467,12 +481,20 @@ bool NavEKF3_core::readyToUseGPS(void) const
 // return true if the filter to be ready to use the beacon range measurements
 bool NavEKF3_core::readyToUseRangeBeacon(void) const
 {
+    if (frontend->_sources.getPosXYSource() != AP_NavEKF_Source::SourceXY::BEACON) {
+        return false;
+    }
+
     return tiltAlignComplete && yawAlignComplete && delAngBiasLearned && rngBcnAlignmentCompleted && rngBcnDataToFuse;
 }
 
 // return true if the filter is ready to use external nav data
 bool NavEKF3_core::readyToUseExtNav(void) const
 {
+    if (frontend->_sources.getPosXYSource() != AP_NavEKF_Source::SourceXY::EXTNAV) {
+        return false;
+    }
+
     return tiltAlignComplete && extNavDataToFuse;
 }
 
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_core.h b/libraries/AP_NavEKF3/AP_NavEKF3_core.h
index a18a1cbc2c..78ac19919f 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_core.h
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_core.h
@@ -817,7 +817,7 @@ private:
     // Calculate weighting that is applied to IMU1 accel data to blend data from IMU's 1 and 2
     void calcIMU_Weighting(float K1, float K2);
 
-    // return true if the filter is ready to start using optical flow measurements
+    // return true if the filter is ready to start using optical flow measurements for position and velocity estimation
     bool readyToUseOptFlow(void) const;
 
     // return true if the filter is ready to start using body frame odometry measurements