Copter: reset ahrs gyro drift after gyro calibration

ArduCopter/GCS_Mavlink.pde

@@ -1113,6 +1113,8 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
             if (packet.param1 == 1) {
                 // gyro offset calibration
                 ins.init_gyro();
+                // reset ahrs gyro bias
+                ahrs.reset_gyro_drift();
                 result = MAV_RESULT_ACCEPTED;
             }
             if (packet.param3 == 1) {

ArduCopter/system.pde

@@ -320,6 +320,11 @@ static void startup_ground(bool force_gyro_cal)
     report_ins();
  #endif
 
+    // reset ahrs gyro bias
+    if (force_gyro_cal) {
+        ahrs.reset_gyro_drift();
+    }
+
     // setup fast AHRS gains to get right attitude
     ahrs.set_fast_gains(true);