# Fuzzy Logic in Selection of Maritime Search and Rescue Units
## 4 Case Study
### Procedure Description  
The method consists of the following stages: collection of information about vessels available in the vicinity of distress, conducting the modelling of the decision-maker's preferences and carrying out a computational experiment. _Stage 1: Data gathering_  
A group of civilian ships which could possibly be employed in the SAR action has been identified in the vicinity of the distress by means of the Automatic Identification System (AIS). The data for the simulation are inserted in Table 2. The values for length, beam, draught and speed are numerical. Information on vessel type and navigational status is presented in descriptive form. In the original, all data are coded in accordance with NMEA (National Marine Electronics Association) 0183/2000 standard. _Stage 2: Modelling the preferences_  
Preferences represent the expert's (decision-maker's, SAR coordinator's) opinion on the vessel's parameters which are the most useful in a SAR operation of a certain profile. The modelling of preferences consists primarily in determining the set of criteria and the weights of the individual criteria. Furthermore, the type of preference function, the direction of preference and the thresholds were defined. This step was carried out in the form of an expert study. A group of three experts defined the action profile and the criteria for assessing vessels: speed, draught, vessel type, navigation status, observation height, medical equipment. The AIS system allows the first four parameters to be determined almost immediately. The other two require extended investigation. The expert group proposes to use a new criterion \"quality\". This criterion will be established by fuzzing out the criteria of observation height and medical supplies. Details are given in Table 3. An explanation regarding the criteria choice is placed below. The operational speed of the ship has a significant impact on the effect of the action. In the case of the hypothermia risk, quick action and rapid implementation can increase the chances of saving the survivor's life. Criterion is maximised. The criterion is the most important (weighting 0.275). The draught of a ship can be important for two reasons. The first is the presence of shallows or other underwater hazards (e.g., wrecks, rocks). Which may increase the risk of the vessel. The second is the ability to carry out search patterns. When searching for a single person in the water, manoeuvrability and a small circulation radius will matter. Search tracks will be laid out at close distances. Vessels with large draught may experience problems. The criterion is minimised. The criterion is the least important (weighting 0.125). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Vessel 1** & **Vessel 2** & **Vessel 3** & **Vessel 4** & **Vessel 5** \\ \hline Length over & & & & & \\ all (LOA) & 84 m & 250 m & 144 m & 120 m & 67 m \\ \hline Beam (B) & 12 m & 44 m & 23 m & 11 m & 10 m \\ \hline Draught (T) & 4.7 m & 7.7 m & 6.4 m & 5.2 m & 3.2 m \\ \hline Navigational & underway & underway & underway & underway & & underway \\ Status & using engine & using engine & using engine & & using engine \\ \hline Type & general cargo & passenger & general cargo & general cargo & military \\ vessel & vessel & vessel & vessel & vessel & \\ \hline Speed & 15 km & 19 km & 14 km & 18 km & 12 km \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Ships parameters provided by AIS. Navigation status affects response time. Ships underway are ready for immediate action. Ships busy with work may require an extended response time. Ships in a particular state may not be fit to undertake any task and are usually the least preferred by the coordinator. The criterion shall be evaluated qualitatively. The criterion is minimised. The weighting of the criterion is significant (0.225). The criterion of the type of vessel provides information about how the vessel is operated.