ABSTRACT: Automatic Radar with Plotting Aids is the basic means of preventing collisions at sea for many years. However, the use of the radar on a moving vessel requires image stabilization, which has been at least for the last 50 years solved by coupling with the gyrocompass and the log. In the present century, the widespread use of Global Navigation Satellite System receivers has led to the common practice of interconnecting this receiver with many other systems on ships. This is often also the case for radar, although GNSS gives information about movement related to the ground, whereas the International Maritime Organization recommends using parameters relating to water. The mandatory and widespread equipping ships with the Automatic Identification System means that this system is increasingly used in the process of collision avoidance, but also with the use of ground-referenced data. The aim of the paper is to investigate whether this is acceptable and what are the limits of this practice. This question becomes increasingly important in the context of the growing number of unmanned vessels. Not all, especially small autonomous surface vehicles will be equipped with radar and may also use AIS transmissions in collision avoidance algorithms. Studies have shown that this may pose a risk of collision. At low ship speeds, if the current speed exceeds 5 knots and the direction of the current significantly deviates from the course of one of the ships, there is a risk that the planned maneuver will not be carried out. This may mean that the closest approach distance will be significantly different from the planned one.

KEYWORDS: Safety at Sea, Automatic Identification System (AIS), Collision Avoidance, Operational Use of ECDIS, GNSS, International Regulations for Preventing Collisions at Sea, Radar Navigation, Autonomous Ships

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