# Abnormal Ship Behavior Detection Based on AIS Data
## 4 Results and Discussion
### Experimental Results for Real Datasets
#### 4.2.2 Detection of Abnormal Ship Behavior Based on Thematic Attributes
By 3:00 a.m. on 30 October 2021, its end-hovering state began to continue, so its instantaneous speed and the amount of change in the steering angle showed an increase, as shown in the test results. Its position at the end hovering had  
Figure 15: Spatial distribution of abnormal ship behavior detection scores based on thematic attributes. (**a**) The spatial distribution of the detection score for abnormal ship behavior with the thematic attribute of the instantaneous speed over ground. (**b**) The spatial distribution of the detection score for abnormal ship behavior with the thematic attribute as the variation of the course over ground. (**c**) The spatial distribution of the detection score for abnormal ship behavior with the thematic attribute as the average speed. (**d**) The spatial distribution of the detection score for abnormal ship behavior with the thematic attribute as the mean acceleration. a higher abnormal score. At the same time, an abnormal condition for the spatial position attribute in this time period was detected for the ship. The variation of that characteristic of the travel topic and the geographic map status of the high point of the abnormal score are shown in Figure 17.  
We selected the vessel with the MMSI number 412,328,140 from 9 November 2021 to 10 November 2021 for the combined subject characteristics of the average speed and average acceleration of the test results. The ship was scheduled to sail from Xihoumen port to Bayuquan port. Through the experiment, we found that the ship appeared as an abnormal point with a high abnormal score during the course of navigation. We drew the average velocity and average acceleration of the segment for each feature after 0-1 normalization, and we could directly observe a significant peak point. It was found from that map that the location of the high abnormal score was near the Shandong Peninsula, at which point it was completing the turning task. The data records show that it took 120 s to complete  
Figure 16: Spatial distribution of abnormal ship behavior detection scores based on combined thematic attributes. (**a**) The spatial distribution of the anomaly detection results when the combined thematic attribute features were the speed over ground and the variation of the course over ground. (**b**) The spatial distribution of the anomaly detection results when the combined thematic attribute features were the average velocity and average acceleration. Figure 14.0 The thematic attribute set is the schematic diagram of abnormal ship point detection with instantaneous features. (**a**) The change over time after normalization of the two thematic attributes. (**b**) The realistic mapping of the high anomaly score points in (**a**) in the geographic environment. the turning task in the time period from 3:52 p.m. on 10 November 2021 to 3:54 p.m. on 10 November 2021. The linear distance between the points was 2299 m, and the instantaneous speed changed from 7.1 to 6.2. According to the actual geographical situation, it can be considered that the sudden drop in speed caused by the turning task was in line with the actual situation. The spatial location of the high anomaly score point in the geographic environment is shown in Figure 14.1