# A System to Improve Port Navigation Safety and Its Use in Italian Harbours
## 3 Results
The system has been tried on several real cases by analyzing critical situations, providing satisfactory results in detecting hazardous areas; the examination of two accidents that occurred in the port of Livorno and Bari are described here. Figure 14: Detail of virtual traffic lights in the port of Livorno: (**a**) on 24 February 2020 at 02:20; (**b**) on 5 December 2020 at 12:10; thresholds equal to 11.5 and 12.5 m.  
As first, we describe the dynamic analysis of the bathymetry of the port of Livorno on 6 February 2021 (examination of an accident occurred in the past, so the bathymetry is updated by loading sea level values from a data storage): at 08:00 a container ship of 11.5 m through stranded while was entering the port (the sea level measured by the hydrometer was 0.15 m). Figure 16a shows virtual traffic lights at the entrance area of the port at that time: threshold levels are selected at 11.5 and 12.5 m; the mouse pointer indicates the approximate location (Easting 604,380, Northing 4,822,105, m) where the vessel grounded; as we can see, the red virtual traffic light indicates that this position was forbidden for that ship at that moment because its updated depth (11.15 m) was smaller than the ship draught. Figure 15: Detail of virtual traffic lights in the port of Bari on 24 July 2020: (**a**) at 17:30; (**b**) at 23:30; thresholds equal to 9 and 10 m.  
It is also worth noting that the position considered may not be forbidden for the same ship at another time (corresponding to different sea-level values, for example during a high tide), as well as the same position at the same time could be allowed for another vessel with smaller draught (which would result in different threshold levels). For example, Figure 16b shows virtual traffic lights at the same position for the same ship on 10 February 2021 at 07:40: the greater sea-level value (0.55 m) makes the updated depth equal to 11.55 m, then a little greater than the ship draught, so that position belongs to a yellow or warning area. Note that the increase of 0.40 m in sea level between the two situations is partially due to a decrease of 14.6 hPa in atmospheric pressure. As regards the port of Bari, on 12 July 2011 at about 10:00 a ship of 9 m draught struck the seabed at 8.45 m depth while approaching docks (the monitoring station was measuring: sea level \(-\)0.08 m); the dynamic analysis of the bathymetric map for this event had been  
Figure 16: Detail of virtual traffic lights in the port of Livorno: (**a**) on 6 February 2021 at 08:00; (**b**) on 10 February 2021 at 07:40; thresholds equal to 11.5 and 12.5 m.  
executed: the updating of the map has been performed by reading from the archive sea level measurements related to that day. Figure 17a shows virtual traffic lights of a detail of the port at that time: thresholds are chosen equal to 9 and 10 m, respectively. As we can see, particular circumstances occur and a few red pixels (pointed by the mouse arrow) stand out in the middle of the green background (Easting 656,142, Northing 4,555,857 m). This is approximately the position where the ship collided with the anchoring systems of some mooring buoys (structures on the sea floor consisting of metal cages containing concrete inside); the peculiarity of this situation consists in the fact that the danger was concentrated in a very limited area inside a much wider area allowed (for that ship). Figure 17: Detail of virtual traffic lights in the port of Bari: (**a**) on 12 July 2011 at 10:00; (**b**) on 21 March 2012 at 08:00; thresholds equal to 9 and 10 m.  
As we can see in Figure 17b at another time, for example, on 21 March 2012 at 08:00, during a low tide (sea level--0.59 m), the same position would be surrounded by a yellow area that that could make the danger better perceptible. Overall, the usefulness of this application is the capability of detecting potentially dangerous areas in certain locations, at certain times, and, above all, for a given ship.