Effects of Lower Frame Rates in a Remote Tower Environment

In the field of aviation, Remote Tower is a current and fast-growing concept offering cost-efficient Air Traffic Services (ATS) for aerodromes. In its basics it relies on optical camera sensor, whose video images are relayed from the aerodrome to an ATS facility situated anywhere, to be displayed on a video panorama to provide ATS independent on the out-of-the-tower-window view. Bandwidth, often limited and costly, plays a crucial role in such a cost-efficient system. Reducing the Frame Rate (FR, expressed in fps) of the relayed video stream is one parameter to save bandwidth, but at the cost of video quality. Therefore, the present article evaluates how much FR can be reduced without compromising operational performance and human factor issues. In our study, seven Air Traffic Control Officers watched real air traffic videos, recorded by the Remote Tower field test platform at the German Aerospace Center (DLR e.V.) at Braunschweig-Wolfsburg Airport (BWE). In a passive shadow mode, they executed ATS relevant tasks in four different FR conditions (2 fps, 5 fps, 10 fps & 15 fps) to objectively measure their visual detection performance and subjectively assess their current physiological state and their perceived video quality and system operability. Study results have shown that by reducing the FR, neither the visual detection performance nor physiological state is impaired. Only the perceived video quality and the perceived system operability drop by reducing FR to 2 fps. The findings of this study will help to better adjust video parameters in bandwidth limited applications in general, and in particular to alleviate large scale deployment of Remote Towers in a safe and cost-efficient way.