Enhance the AIS data availability by screening and interpolation
The AIS broadcasts the ship's navigation data automatically and autonomously through VHF band. It plays an important role in collision avoidance and maritime situational awareness. However, in inland waterways, it is common that the AIS data-link was obstructed by the river bank and mountains, or sometimes the AIS was encountered with the electromagnetic interference. Consequently, the AIS dynamic data is often lost and mixed with inaccurate, which may lead to misjudgment of the traffic situation. To address this problem, a method was proposed to enhance the availability of AIS data in this paper. Firstly, according to the ships' maneuverability, a set of factors, such as the moving distance, speed, acceleration, and course change rate, were designed to screen the inaccurate AIS data. Then, the piecewise cubic Hermite interpolation and cubic spline interpolation were employed to restore the AIS data. A real AIS trajectory was introduced to validate the accuracy of the two interpolation methods, which proves that the cubic spline interpolation performance is better than piecewise cubic Hermite interpolation. Field experiments in Wuhan reach of Yangtze River show that the method proposed in this paper is highly effective. The accuracy of the location is 3.5m, the speed accuracy is 0.05m/s, and the course accuracy is up to 0.7 degrees, the AIS data can be accurately repaired.