“…In the Cartesian coordinate system, it is assumed that its origin is the position of the own vessel, (X, Y) denotes the coordinates corresponding to the relative position of the target vessel, V o denotes the true velocity of the own vessel, V t denotes the true velocity of the target vessel, V r denotes the relative velocity of the target vessel with respect to the own vessel, and V rx , V ry denote the components of V r . Based on this assumption, we can obtain the DCPA, TCPA, D, and K as follows [20,21]:…”