Obstacle Zone Research Articles

Radars are already used for collision avoidance during more than 50 years. During this period many proposal for collision avoidance by using radar have been made, and the experience of their use have been gained. However the effectiveness of these proposals for collision avoidance is not enough, especially in congested water. The Automatic Identification System (AIS) will be equipped all ships of 300 gross tonnage and upwards engaged on international voyages. The AIS is expected to be very useful for collision avoidance. Even if AIS is used, it is necessary to consider the effect of predicted error of ship's position on the evaluation of collision risk. In this paper an approach to improve the evaluation and expression of collision risk is shown. This method is able to show the obstacle zone by target (OZT), considered an estimated error of ship's speed, and it will be useful for collision avoidance in congested water. Expression of OZT shown in this paper will be easy to trace the origin target of OZT and to check the fault information transmitted by the target.