# The Ocean-Going Autonomous Ship--Challenges and Threats
## 2 Navigational Equipment and Related Challenges
### Route Following and Basic Equipment  
The full autonomy of the ships (level 4-5 and equivalents) is certainly a long-term perspective. Initially these objects will be closely supervised, undoubtedly with elements of remote control. Navigational tasks in this context seem to be solved, because already today the degree of automation of navigation means that many manned vessels operate in autopilot mode from one waypoint to the next, ensuring the movement on the planned trajectory. This is ensured by connecting the GPS (Global Positioning System) receiver with autopilot and gyro-compass. The task is quite easy, because each new position determined by the GPS receiver is the basis for calculating a new bearing to the next waypoint. This information is passed to the autopilot as a new course to the target, and compared with the current course, which gives the basis for calculating the correction to the rudder/thruster. As a rule, this happens every second, so in the realities of ships it can be assumed that the process is smooth (analog). However, it should be noted that there is also a connection between the GPS receiver and the gyro-compass (Figure 1)--to correct the speed deviation to the gyrocompass, information on the ship's latitude and its speed should be provided. These quantities can be obtained from the GPS receiver, however the speed can also be obtained from the log. In fact, the network of navigation data is more complex. Its still simplified version is shown in Figure 2. It should be noted that this is just one option of the technology dependency scheme. Also, \begin{table}
\begin{tabular}{c c} \hline
**Level** & **Description** \\ \hline M & Manually operated function. \\ \hline DS & System decision supported function. \\ \hline \multirow{2}{*}{DSE} & System decision supported function with conditional system execution capabilities \\  & (human in the loop, required acknowledgement by human before execution). \\ \hline \multirow{2}{*}{SC} & Self-controlled function (the system will execute the operation, but the human is able to override the action. Sometimes referred to as ’human on the loop’. \\ \hline \multirow{2}{*}{A} & Autonomous function (the system will execute the function, normally without the possibility for a human to intervene on the functional level). \\ \hline \end{tabular}
\end{table} 
Table 4: MASS Levels of Control according to the Class Guideline for Autonomous and remotely operated ships by DNV GL. Reproduced with the permission from the authors of ‘Autonomous and remotely operated ships’, published by DNVGL-CG, Edition September 2018 [12] (p. 51). Figure 1: The diagram of information flow for the implementation of route following. one block of this scheme does not need to represent one particular device on the vessel, rather the technology, utilized for a particular purpose. It is clear here that a GPS and gyro-compass (or more general Global Navigation Satellite Systems (GNSS) and the heading device) are essential for the operation of all navigation systems. In the context of an autonomous vessel monitoring, it is worth noting that these data sources have a constant impact on satellite communication, which will most probably be the major communication method. The position of the ship and its course are the basis for setting the antenna of the communication system towards the satellite. The satellite-tracking functions of the satellite communication terminal use not only raw GNSS and heading data, but augment it with inertial motion units (IMU) and process the positioning information using the algorithms based on Kalman filtering to ensure the proper satellite tracking. Therefore, the lack of GNSS position input will not cause the malfunction of the satellite communication immediately, but the accuracy of the tracking solution will decrease with time.