# Fuzzy Logic in Selection of Maritime Search and Rescue Units
## 3 Materials and Methods
### Vessel Selecton Criteria  
When selected for an SAR operation, ships should be assessed for their search or rescue capabilities. Depending on the profile of the operation, vessels can have different potential. The profile of an SAR operation is essential in the building of the set of criteria and modelling the decision-maker's preferences, as it determines the relation between the type of distress and the type of assistance required. Some examples of SAR operation profiles are: search and rescue of a single survivor in the water, search and rescue of a large group of survivors in the aftermath of an accident of a passenger vessel, search for a missing ship, etc. Since each profile has its own key features and parameters, there is no universal vessel equally suitable for all profiles. Therefore, the selection of vessels suitable for a particular SAR operation profile is necessary and aimed to boost effectiveness of the operation. In search operations (for survivors in the water, lifesaving craft, missing ships) the following features of the ship are of utmost importance:  
* Precise location capabilities (detection equipment)
* Effective observation capabilities (high observation altitude or detection equipment)
* Relatively high speed of the vessel
* Relatively large range of operation
* Manoeuvrability (ability to carry out search patterns)
* Seaworthiness
* Relatively short time to scene (depending on the current position of the vessel)
* Experience and training of the crew  
In rescue operations (recovery of survivors from the water, picking up persons from survival crafts or vessels in distress) the following features of the ship are of utmost importance:  
Figure 1: Level preference function—MCDA Promethee II. * Equipment for the recovery of survivors from the water
* Equipment for providing medical assistance
* Ability to accommodate a certain number of survivors
* Communications equipment
* Ability to participate in the operation  
The criteria referred to above are qualitative or quantitative. An example evaluation of the criteria is shown in Table 1. Levels of compliance with a certain criterion (defined in the form of a description or range of values) correspond to certain grades. The grading scale can be defined arbitrarily and should be adjusted to the nature of the criterion. When comparing ships, their parameters need to be collected and evaluation matrix needs to be created. The SAR coordinator faces the challenge of gathering data within a short time span. The priority is to select the most suitable vessels as soon as possible and commence the search and/or rescue without further delay. Part of the data can be downloaded from vessel traffic monitoring systems, such as, e.g., the commonly used Automatic Identification System (AIS). The AIS provides the vessel's position, type, navigational status (e.g., underway, anchored, fishing, disabled, etc. ), current speed and course, and technical parameters (length overall, beam, draught). Data downloaded from the AIS can be approximate, inaccurate, or incomplete. Moreover, the AIS does not provide information about the vessel's equipment, which is crucial for the examination of search and rescue capabilities. Therefore, evaluation of compliance with the criteria may be challenging. For example, the SAR coordinator may wish to evaluate the vessel's compliance with the qualitative criterion of time to distress on a three-point scale--high, medium, and low. The exact time to distress is unknown, while the estimated time to distress is within 40 to 60 min. The boundary between Level 1 and Level 2 is at the value of 50 min. Another example--the coordinator wants to evaluate compliance with the qualitative criterion of vessel's equipment for the recovery of survivors from the water on a three-point descriptive scale (full, medium, low compliance). Their knowledge in this respect is limited (e.g., the type of lifeboats and launching method are known, but there is no information about other lifesaving appliances available on-board the vessel).