Interdependencies between evaluation of collision risks and performance of shipborne PNT data provision

摘要

The highest priority for safe ship navigation is the avoidance of collisions and groundings. For this purpose, the concept of ship domain has been introduced to describe the surrounding effective, waters which should be kept clear of other ships and obstacles. In the last decades, a large variety of ship domains have been developed differing in the applied method of their determination as well as in the modelled shape, size, and safety areas. However, a ship domain should be adjusted in real time to enable a reliable evaluation of collision risks by the officers of the watch. Until today in discussions about modelling and utilization of ship domains, it has been mostly unnoticed that the performance of vessel's position (P), navigation (N), and timing data (T) ultimately determines the accuracy and integrity of indicated ship domain. This paper addresses this question, and starts with a comprehensive analysis of AIS data to prove the violation of ship domains in the maritime practice. A simulation system has been developed to enable, for the first time, investigation into the extent inaccuracies in PNT data result to a faulty evaluation of collision risks. The simulation results have shown that there is a non-negligible risk of not detecting a collision, if inaccuracies of sensor data remain unnoticed.