**2.3 Required information**

Once a spill occurs, the oil will spread quickly on the water surface to form oil layers such as slicks, films, and sheens. To alleviate the severity of oil spills and promptly react to such incidents, it is crucial to have oil-spill monitoring systems that enable an effective contingency plan [51]. A rapid response time and a quick intervention allow dictating the best actions to deal with oil spills. Therefore, monitoring systems must perform several functionalities and provide valuable information to contain the damage [52].

1.Functionality #1: Oil-spill detection

The most important part during oil spills is to detect oil slicks. It is important to locate them and to determine how large the spread is. This necessary information allows oil spill mapping for both tactical and strategic countermeasures.

2.Functionality #2: Oil-thickness estimation

The thickness distribution of spilled oil is another critical information for spill containment. Using the knowledge about the oil thickness, an estimation of the total volume spilled can be performed so that adequate tools are used in cleanup operations.

3.Functionality #3: Oil classification

Classifying the oil type is also important during spill containment. Based on this information, the authorities estimate the environmental damage in the shortand long term to take appropriate response activities.

4.Functionality #4: Oil-spill tracking

Since the spill can spread quickly within a few hours, an effective contingency plan demands the ability to track the spill over time. Tracking provides timely and valuable information to anticipate possible damage scenarios, predict the trajectory using additional input from weather forecasts, and assist in cleanup operations.
