2.2.3. Centreline Separation Visualisation Tool

Within the trails, an essential task of an approach ATCO was to set and monitor the separation between aircraft on centreline and final approach. In addition, distance markers (scale) were available on modern primary displays, which allowed a quite fast and reliable estimation of the distances between approaching with subdivision in a nautical mile. For a much more finely graduated distance display, the final approach distance indicator centreline Separation Visualisation Tool (CSVT) was developed (Figure 6). Located in separate windows for each centreline, the aircraft which were currently on final approach approach were represented by defined symbols with callsigns. In addition, the current distances between the aircraft were displayed in NM. In this way, the alphanumeric display enabled the ATCO not only to monitor the current distances, but also to immediately detect any changes in their tendency and to intervene with guidance in the event of imminent separation violations.

**Figure 6.** The CSVT. The symbols mark the positions of aircraft (triangle), ghosts (square) and TargetWindows (semicircle). The labels' colours represent the aircraft's weight classes (yellow: medium; green: heavy), and the white numbers between the labels indicate the current separation between them.

In addition to actual aircraft, labels for ghosts (squares) and TargetWindows' positions (semicircles) were also displayed, allowing approach ATCOs to estimate how large the separation would be after turning over Base or LMP and before reaching the final approach. Different colours for the weight classes of aircraft allowed more precise differentiation.
