Detection of hazardous encounters at the North sea from AIS data

In an initial study for the Dutch Ministry of Infrastructure and the Environment, MARIN has developed two approaches to detect near misses and other hazardous encounters at the North Sea from AIS data. One approach uses the progress of the Distance at Closest Point of Approach (DCPA) and Time to Closest Point of Approach (TCPA) during encounters, another estimates the normally maintained ship domains, and determines whether these domains are entered during encounters. Both approaches result in rankings of the encounters. The approaches were tested with one month of AIS data for a busy junction in a traffic separation scheme. Results showed that, although most relevant cases were highly ranked, also many normal encounters were ranked equally high. In the continuation of the study, criteria were refined for four distinct types of encounters: overtaking, head-on encounters, give-way ship crossing at bow, and give-way ship crossing at stern. Particularly for the crossing encounters, criteria for the CPA-TCPA relation largely reduced the number of candidate encounters, and many normal encounters could be disregarded. The improved approach was tested for one year of AIS data of two areas: the busy junction and a bigger area with more diverse encounters without traffic separation scheme. For this area 1.71% of 106297 recorded encounters was returned, of which 491 were crossings. For the junction 0.93% of 38358 encounters was returned, 107 of which crossings. Animations of these encounters give good impressions of the most extreme encounters occurring in the areas.