5.2 Visual surveillance system

A visual surveillance system constitutes the core element of remote provision of ATS to aerodromes and typically consists of two main operational parts: the ‘visual presentation’ replacing the OTW view of a conventional tower and the ‘binocular functionality’ emulating traditional binoculars, both further described below. A visual surveillance system includes a number of integrated elements, including sensors, data transmission links, data processing systems and situation displays. Regardless of the technical solution/design, it is crucial that the visual surveillance system fulfils the regulatory requirements and the operational needs that exist on the service provision. These regulatory requirements and operational needs as well as some functional requirements/considerations are described and discussed in sections 5.2.3, 5.2.4, 5.2.5 and 5.2.7 below. It is acknowledged that the human vision sensing system is very sophisticated and that it may not be feasible to precisely replicate the ATCO/AFISO visual performance that could be obtained via direct OTW visual observation. Note: The visual performance obtained by the means of a visual surveillance system may in some circumstances and to some extent improve the OTW visual observation. Fully replicating the visual performance obtained via direct OTW visual observation is also not key to the implementation of remote aerodrome ATS. Instead, it is fundamental to define operational visual performance requirements — corresponding to the specific operational context — and ensuring that they can be supported by the visual surveillance system. A process for the definition and the verification of requirements is described in the EUROCAE ‘ED-240A Change 1’ MASPS document [19]. Based on the discussion in Sections 5.2.3, 5.2.4 and 5.2.5 below, the ATS provider may use the process described by ‘ED-240A Change 1’, or equivalent, to define the local operational visual performance requirements (termed ‘Area-of-Interest and Object-of Interest Requirements’ (AOREQ) and ‘Tracking-of-Interest Requirements’ (ToIREQ) by ED-240A Change 1). An extensive work to define a set of baseline operational visual performance requirements has been performed in the framework of the SESAR JU programme. As a support to remote aerodrome implementers, these requirements are presented in Appendix 5. They can be seen as example requirements and may be used by an ATS provider/implementer as a starting point when defining their own local operational visual requirements, tailored to the specific operational needs and the specific operational context of the particular implementation. It is recommended that the visual surveillance system is operationally validated against the perceived total image quality, and not only against individual system parameters. The general operator’s acceptance process described in EUROCAE ‘ED-240A Change 1’ MASPS document serves as the first verification of the performance of the visual surveillance system under reference (i.e. optimal) conditions. However, it is furthermore recommended that the performance of the visual surveillance system is operationally validated in various visual conditions (e.g. dawn, daylight, dusk, darkness and different visibility conditions), not only as a variation in time but also as a variation in the presented view of the aerodrome and its vicinity at one point in time — as light conditions are likely to differ across the view. It may be beneficial to apply a ‘scenario/use case’ approach when both defining and validating operational visual performance requirements. For instance, a scenario could be: ‘Detect an aircraft of a certain type/size at 5 NM final, recognise the aircraft at some stage to be able to give a landing clearance, be able to see/follow the aircraft during its complete landing from detection to landing, roll-out, taxiing off the runway and until taxiing to apron (leaving the manoeuvring area)’. Adopting such validation approach will help to understand the operational benefits and shortcomings of a specific implementation case. If shortcomings are identified, they could be managed either by improving the technical system or by implementing appropriate operational procedures and mitigation means. It is assumed that the visual surveillance system is primarily based on a visible spectrum camera/sensor solution where cameras capture the image at the aerodrome and the image is relayed to the ATCO’s/AFISO’s screens, possibly enhanced by cameras/sensors from the non-visible spectrum, such as thermal, infrared etc. As regards differentiation between ATC and AFIS provision with respect to visual surveillance systems, no significant differences affecting the implementation of remote aerodrome ATS at a certain aerodrome have been identified. Instead, it is rather the traffic volume/density and operational complexity (as opposed to the type of service, ATC/AFIS, provided) that should be considered when defining the exact operational and functional/technical requirements on the visual presentation and the binocular functionality. For recommendations related to interoperability, integrity and system availability regarding a visual surveillance system, refer to EUROCAE ED-240A Change 1 [19].