# Collision Avoidance Behavior Mining Model Considering Encounter Scenarios
## 3 Results
### Comparative Analysis
(**b**) The course change of trajectory 2.  
different local features of the ship's trajectory points are obtained. The calculation results of the two trajectories are shown in Figures 13 and 14. Figure 13: Illustration of turning point identification for trajectory \(1\) using the proposed model. curvature value of the ship's trajectory points during the straight-line stabilization phase is consistently \(<C_{L}\), which aligns with the ship's motion and maneuvering characteristics. According to the fixed window rule in Section 2.2, when the absolute curvature of a trajectory point exceeds \(C_{L}\) and the turning factor \(\Delta k>6\), the previous \(\Delta k_{i-1}\) time points are considered to be the ship's turning points, and the curvature turning parameter \(R_{i}\) is recorded. Specifically, as shown in Figure 13b, the absolute curvature of the ship's trajectory gradually increases from 0 to 37.213083, and then it decreases back to nearly 0. This process corresponds to the ship's collision avoidance turning operation, where the ship turns first and then stabilizes. This segment of the trajectory contains 11 points with an absolute curvature greater than seven, which meets the fixed window selection criterion. The 11 th point prior to the current time is taken as the ship's turning point. Because the curvature is positive, the recovery factor \(R_{i}^{t}\) is +1, and this is set as the starting point of the variable window. According to the variable window selection criteria, the identification of whether there is course recovery behavior is performed in a time-sequenced manner to determine whether the identified turning points are collision avoidance turning points. The curvature-time variation of the course recovery trajectory segment is shown in Figure 13c. In this segment, the absolute curvature of the ship's trajectory gradually increases from 0 to 15.991441 and then decreases back to nearly 0. This pattern corresponds to the ship's recovery navigation turning operation, where the ship first turns and then stabilizes on the original heading. This segment of the trajectory contains nine points with absolute curvature greater than seven, which meets the fixed window selection criterion. The recovery factor \(R_{i}^{r}\) is \(-1\), and \(R_{i}^{t}+R_{i}^{r}=0\), which satisfies the variable window determination standard. Therefore, it can be concluded that the ship's trajectory exhibits course recovery behavior, and the turning point identified by the algorithm is a collision avoidance turning point. Due to the impact of wind, waves, and currents on the ship's trajectory, AIS data may experience fluctuations, leading to a sudden increase in trajectory curvature. However, through the fixed window selection rule established by the Curvature-Based Ship Collision Avoidance Behavior Recognition algorithm, the curvature values \(\Delta k\) of the fluctuating trajectory points are all \(<\)6. Moreover, according to the operational characteristics of ships, normal turning trajectories do not exhibit sudden changes, meaning that the absolute value of curvature does not spike. Therefore, this model effectively avoids interference from factors like wind, waves, and currents and successfully identifies the true earliest turning points. The results are shown in Figure 13d. Figure 14 shows the calculation result of trajectory 2. Figure 14a illustrates the overall curvature variation of the trajectory, where the curvature curve clearly reveals sections of collision avoidance and course recovery. As shown in Figure 14b, the vessel in trajectory 2 initially performed a left-turn maneuver, with the absolute value of curvature increasing to 18.134932, followed by a return to near 0. According to Figure 14c, after a period of straight sailing, the collision risk was resolved, prompting the vessel to execute a right-turn maneuver, with the absolute value of curvature rising to 70.684339, and the ship recovered its initial course. Alse, there are still segments affected by data interference in trajectory 2.