# Towards a Cyber-Physical Range for the Integrated Navigation System (INS) System (INS)
## 3 The Composition of the INS
### Connections and Dependencies  
The INS is based on showing information on the MFD, and the compulsory connections to the MFD vary according to allocated navigational tasks (e.g., collision avoidance, route planning). The required connections to the MFD should be determined according to specific navigational tasks, using resolution MSC.252(83). The INS requirements do not strip down the individual dependencies among the equipment, but may increase the number of connections. For instance, displaying MSI messages provided by NAVTEX is mandatory for the optional navigational task of \"status and data display\" [5]. Equipment are allowed to be connected to each other beyond the IMO requirements. Table 3 depicts the dependencies between individual components as per the IMO requirements. The symbols \(\bot\) and \(\bigtriangleup\) in the table stand for \"OR\". Some equipment may not be mandatory as per the IMO requirements. In these cases \"OR\" is used in the table. The symbol \(\oplus\) for the ECDIS means that the primary heading sensor is gyro-compass, but if the vessel is not fitted with gyro-compass, the ECDIS requires the THD. The symbol \(\rightarrow\) stands for \"depends\"; for example, the AIS depends on \"GPS\", \"ROTI\", and \"gyro-compass or THD\". \begin{table}
\begin{tabular}{l c c c c c}
**Equipment** & **\(\rightarrow\)** & **\(\bigtriangleup\)** & **\(\rightarrow\)** & **\(\bigtriangleup\)** \\ \hline AIS & & \(\rightarrow\) & \(\bigtriangleup\) & & \(\rightarrow\) & \(\oplus\) \\ \hline ECDIS & & \(\rightarrow\) & \(\bigtriangleup\) & & \(\rightarrow\) & \(\oplus\) \\ \hline Gyro Compass & & \(\rightarrow\) & & & \\ \hline HCS & & \(\bigtriangleup\) & \(\bot\) & & \(\bigtriangleup\) & \(\bot\) \\ \hline RADAR & \(\rightarrow\) & \(\rightarrow\) & \(\bigtriangleup\) & & \(\rightarrow\) & \(\bigtriangleup\) \\ \hline TCS & & \(\rightarrow\) & \(\rightarrow\) & & \(\rightarrow\) & \\ \hline THD & & \(\bigtriangleup\) & & \(\bigtriangleup\) & & \\ \end{tabular}
\end{table} 
Table 3: Individual dependencies among equipment. The IMO does not specify which sensor should be used by the THD to determine the true heading. However, the \"ISO 22090: Ships and marine technology--Transmitting heading devices (THDs)\" standard specifies the THD. This standard consists of three parts, namely 22090-1 Part: 1 Gyro-compasses, 22090-2 Part 2: Geomagnetic principles, and 22090-3 Part 3: GNSS principles. Part 1 directly mentions gyro-compass standards. Part 2 mentions the combination of magnetic compass and THD. Part 3 mentions the combination of GNSS (e.g., GPS, GLONASS, GALILEO) and THD. All three parts also in their Annexes clearly give equivalent requirements in ISO 22090 and IMO Resolution MSC.116(73). A reference to the gyro-compass is made in Resolution A.424(XI), which states that \"_Means should be provided for correcting the errors induced by speed and latitude_\" [69]. Even though it is not explicitly defined in the resolution, the gyro-compass depends on the GPS to correct the speed deviation. Moreover, a GPS provides information on the ship's latitude to the gyro-compass [108]. The AIS may have a long-range feature [47,109]. The long-range feature offers AIS information exchange capability via ship satellite-based communication systems at the out-of coverage range of base stations. If this feature is available and is desired to be activated, the AIS requires to be connected to the satellite-based communication system of the ship, such as the Immarsat-C and Medium Frequencies/High Frequencies (MF/HF) part of the Global Maritime Distress Safety System (GMDSS) [20,101]. According to the IMO, \"_The ship's position should be continuously monitored by a second independent position source_\" [59]. Therefore, with reference to the Track Control Unit, the second equipment may be a second GPS. Alert management is essential for the INS. All connected equipment to the INS should be part of the alert management. If the BNVAS is installed, it should be connected to the alert management.