Improving stand-on ship's situational awareness by estimating the intention of the give-way ship

The lack of situational awareness is a major cause of ship collisions. Thus, enhancing the situational awareness of the stand-on ship is a key for navigational safety, where the intention estimation of the give-way ship is crucial. According to COLREGs, the stand-on ship is not allowed to take evasive actions until the give-way ship does not take proper actions timely. The stage that needs the stand-on ship to take actions plays as the second protective layer for the ship, which is named as 'Stand-on Ship as Second Line of Defense' (SLoD). A method to estimate the intention of the give-way ship and to trigger SLoD is proposed in this article. Four modules of the proposed method include: "data pre-processing" collects all traffic information and determines the ships' obligations; "action identification" pinpoints the turning points; "action uncertainty" generates a bounded reachable velocity considering the give-way ship's maneuverability; "conflict assessment" judges potential collision by using nonlinear velocity obstacle algorithm. Several typical encounter scenarios are simulated to demonstrate the feasibility of the proposed method. The results show that intention estimation of the give-way ship improves the situational awareness of the stand-on ship, which can support the stand-on ship to make collision avoidance decisions.