Copter: log EKF height reset

ArduCopter/defines.h

@@ -325,6 +325,7 @@ enum FlipState {
 #define DATA_MOTORS_INTERLOCK_ENABLED       57
 #define DATA_ROTOR_RUNUP_COMPLETE           58  // Heli only
 #define DATA_ROTOR_SPEED_BELOW_CRITICAL     59  // Heli only
+#define DATA_EKF_ALT_RESET                  60
 
 // Centi-degrees to radians
 #define DEGX100 5729.57795f

ArduCopter/motors.cpp

@@ -156,6 +156,7 @@ bool Copter::init_arm_motors(bool arming_from_gcs)
     if (ap.home_state == HOME_UNSET) {
         // Reset EKF altitude if home hasn't been set yet (we use EKF altitude as substitute for alt above home)
         ahrs.get_NavEKF().resetHeightDatum();
+        Log_Write_Event(DATA_EKF_ALT_RESET);
     } else if (ap.home_state == HOME_SET_NOT_LOCKED) {
         // Reset home position if it has already been set before (but not locked)
         set_home_to_current_location();