5.2.7.4 Video update rate

The fidelity of the image presented to the ATCO/AFISO also depends on the video update rate (also known as ‘frame rate’), defined as the number of times per second the video is updated. The video update rate primarily affects the following operational aspects of the presented image: the appearance of moving objects (such as aircraft or vehicles), i.e. if a smooth and regular impression to the human eye is provided; the capability to perceive and monitor flashing/rotating objects (such as runway guard lights (RGL), aircraft strobe lights, emergency vehicle lights or rotating propellers/rotors); and the ability to perceive acceleration/deceleration/direction changes (i.e. turns) of moving objects. The appropriate video update rate, including its variation in time, should be determined by the local safety assessment, taking into account the operational context, in order to ensure an adequate presentation of moving objects to the ATCO/AFISO, as well as an adequate presentation of flashing/rotating objects, e.g. flashing lights. It is acknowledged that defining a recommended video update rate is complex due to the capabilities and nature of the human eye, the influence of motion blur and due to inherent dependency of many system parameters (e.g. jitter, contrast, video compression, bandwidth and codex). It is further acknowledged that the video update will likely be a compromise against image resolution in order to optimise bandwidth consumption; where the image resolution will influence the capability to detect and recognise objects, the video update rate will influence the factors listed above (appearance of moving objects, ability to perceive acceleration/deceleration/direction changes of moving objects, capability to perceive and monitor flashing/rotating objects). The video update rate is therefore recommended to be evaluated and defined for each implementation, taking into account the specificities of the local operational needs and conditions. Note: For further considerations related to video update rate, refer to EUROCAE ED-240A [19] Change 1 (Section 4.2.2). Note: Recommendations on minimum video update rates can be found in SESAR publications [23] (REQ-06.09.03-OSED-VC03.1104) & [24] (REQ-12.04.07-TS-0110.0006). Further to this, an empirical study published in 2018 on video update rate [42] is publicly available.