AP_AHRS: added a getter function to get active source set once the ekf3 filter is started

libraries/AP_AHRS/AP_AHRS.cpp

@@ -3148,6 +3148,16 @@ void AP_AHRS::set_posvelyaw_source_set(uint8_t source_set_idx)
 #endif
 }
 
+//returns active source set used, 0=primary, 1=secondary, 2=tertiary
+uint8_t AP_AHRS::get_posvelyaw_source_set() const
+{
+#if HAL_NAVEKF3_AVAILABLE
+    return EKF3.get_active_source_set();
+#else
+    return 0;
+#endif   
+}
+
 void AP_AHRS::Log_Write()
 {
 #if HAL_NAVEKF2_AVAILABLE

libraries/AP_AHRS/AP_AHRS.h

@@ -360,6 +360,9 @@ public:
     // set position, velocity and yaw sources to either 0=primary, 1=secondary, 2=tertiary
     void set_posvelyaw_source_set(uint8_t source_set_idx);
 
+    //returns index of active source set used, 0=primary, 1=secondary, 2=tertiary
+    uint8_t get_posvelyaw_source_set() const;
+
     void Log_Write();
 
     // check if non-compass sensor is providing yaw.  Allows compass pre-arm checks to be bypassed