# Holographic Mixed Reality System for Air Traffic Control and Management
## 6 Flight Scenarios and User Tests  
The 3D scenery files and flight trajectories of Jeju Airport in the Republic of Korea were used in the flight tests. Eleven flights were included in the test. Two types of flight trajectories were simulated in our holographic mixed reality system: The first one was consisted of real flights in Jeju Airport; the second type of flight trajectory was created by the authors with the help of a flight simulator. The real flight trajectories were recorded and collected from an online source called FlightRadar24 [25], whereas the second type of flight was scenario-based and created with the help of the X-Plane 11 [26] software. There, a total of three scenario-based flight trajectories were undertaken, as described below:  
1. An emergency situation for an airplane occurred while landing at Jeju Airport due to the collision of a bird with the wind screen. After landing, the airplane stopped right in the middle of the runway. 2. An airplane was approaching the runway to take off and was blocked by the emergency that happened in scenario 1. Hence, this airplane returned to the gate. 3. There was another airplane that was supposed to land on the same runway after the airplane's takeoff discussed in scenario 2. Therefore, due to the blockage of the runway, this airplane was on hold and flying around the airport until it received the clearance signal to land. The flight data were retrieved as a CSV file for each flight trajectory. They mainly consisted of the longitude, latitude, altitude, speed and heading of the airplane with a timestamp for the whole flight trajectory. One of the main concerns in testing was to analyze the accurate mapping of the airplanes' location in mixed reality. In the flight tests, the flight trajectories were mapped accurately in the mixed reality view with respect to real world locations. As a result of very accurate mapping of the airplanes' location in mixed reality, air traffic controllers could easily rely on the proposed system to monitor the runways and the rest of the airfield. The outside view from the control tower was not required to monitor the airfield anymore. This would facilitate the air traffic controllers in controlling flights during bad weather. The 4D holographic view increased the interpretation power. Moreover, 3D spatial sound provided with the airplanes played a vital role in giving signals about an airplane's location in the mixed reality world. A controller could easily find the location of an airplane in the mixed reality world with the help of spatial sound. Another main purpose of testing was to analyze the ease of interaction with multiple interfaces using a single head-mounted see-through display. With the help of a holographic menu and voice commands, it was very comfortable to switch between multiple interfaces in no time. In emergency situations, it is necessary to timely convey a message to the air traffic controller about the emergency with all information on the flight. The main purpose for creating emergency scenarios in flight tests was to analyze the performance of the system in emergency situations. With the help of 3D spatial sound and the interface of the proposed system presented in Section 4.6, it sent the user an alarm about the emergency situation and location of the airplane at the right time. Due to safety reasons, it was difficult to evaluate the system's performance in the control tower with the real time air traffic. Hence, the pre-recorded as well as specially designed scenario-based flight trajectories were used to test the system in a controlled environment. For this testing, two experienced former air traffic controllers were invited who visualized flight trajectories and interacted with the system to assess the system's usability. The proposed system was deployed on Hololens and tested by two former air traffic controllers with an average age of 62 years. Due to their unfamiliarity with Hololens device, the authors demonstrated the way of using it and later executed the test.