A comprehensive model for assessing the risk of close approach between maritime autonomous surface ships and objects

The purpose of this study is to further develop the ship domain model based on an N-focal ellipse. The relevance of the study is determined by the need for a more rigorous and accurate description of the geometric shape of the ship domain, with the possibility of distinguishing between collision-avoidance tasks involving moving objects subject to the COLREGs and tasks involving other navigational hazards. The methods used include established elliptical ship domain models and the N-focal ellipse first proposed by D. C. Maxwell. A natural pairwise division of the foci is proposed: foci formalizing the vessel’s geometric dimensions and the accuracy of positioning systems; foci characterizing the current kinematic parameters of vessel motion; and foci accounting for the vessel’s maneuvering characteristics for planning collision-avoidance maneuvers in accordance with the COLREGs. Multipliers are introduced to adapt the geometry and boundaries of the N-focal ship domain to navigation conditions and to introduce the concept of the minimum required navigational safety margin. The results of the study are supported by graphical illustrations based on computer simulation results. It is expected that the application of the proposed ship domain model in the control systems of Maritime Autonomous Surface Ships (MASS) will enable navigational safety tasks to be addressed at a qualitatively new level, in close connection with traditional methods of navigational safety monitoring.