New collision alarm algorithm using obstacle zone by target (OZT)

In recent years, introduction of AISs (Automatic Ship Identification System) enables automatic collection of target ships' information. In addition, the performance standard of INS (Integrated Navigation System) has been established in IMO (International Maritime Organization) to realize modernized navigation to enhance navigation safety and to reduce workload of watch officers and its introduction has been promoted in many countries.However, these advanced support systems creates new problems. The increase in alarms has been raised as an issue of the increase in burden to watch officers. According to a field study on alarms in the bridge, 30% of alarms were collision alarms.To reduce the frequency of the collision alarms, some countermeasures are required such as optimal tuning of CPA (the closest point of approach) thresholds for CPA based collision alarms or a new algorithm for other collision alarms. In this paper, an algorithm for collision alarm using OZT (Obstacle zone by target) is introduced and is evaluated its reduction rate using recorded AIS traffic data.