# YOLOv8n-CBAM-EfficientNetV2 Model for Aircraft Wake Recognition
## 2 LiDAR RHI Scanning Detection  
The characteristics of wake vortices generated by an aircraft, including the intensity, shape, existence time, and location, can vary, depending on the specific aircraft type, background winds, and turbulence [23]. The spiral wake vortex structure may persist over the runway for some time and affect other aircraft, especially during takeoff or landing near the runway. First, the characteristics of the wake vortex are affected by the maximum weight and wingspan length of the aircraft at takeoff, and the strength and duration of the wake vortex will be significantly different for light aircraft compared with heavy aircraft. For example, the wake vortices produced by large aircraft such as Boeing 747s are stronger and last longer, while the wake vortices produced by smaller aircraft are relatively weaker. Secondly, weather conditions also have an important effect on the characteristics of wake vortices. For example, in strong wind conditions, wake vortices may dissipate quickly, while in stable weather conditions, such as no wind or inversion layers, wake vortices may remain suspended in the air for a longer period of time, increasing potential flight safety risks. In this context, LiDAR is a valuable tool for wind field and meteorological detection, as it offers high accuracy, high spatial resolution, and long-distance measurements [24].  
The Hong Kong International Airport is one of the largest airports in the world in terms of passenger traffic. The Leosphere Windcube200s LiDAR [25; 26; 27; 28] was employed for detection over the runway. Table 1 shows the main parameters. The LiDAR was situated at a vertical distance of approximately 1400 m from the south runway of the Hong KongInternational Airport. The RHI scanning method was employed to detect the wake vortices generated by departing aircraft. Figure 1 illustrates the distribution of LiDAR locations within the airport. During the RHI scanning, it is necessary to fix the azimuth angle of the LiDAR. The due north direction, that is, 0\({}^{\circ}\), was set as the reference direction. The adjusted azimuth angle was 340\({}^{\circ}\). The pitch angle of the LiDAR was continuously adjusted to scan the runway in both the vertical and horizontal planes, according to the pre-set angle range, and the LiDAR one-dimensional echo signal was then received. Figure 2 illustrates the RHI scanning process. The collected one-dimensional echo signals were processed to generate two-dimensional RHI scan images, which were used as the dataset for aircraft wake recognition. The processing details are described in Section 4.1. The dataset used in the aircraft wake identification is derived from 2D wind fields scanned by RHI from the Leosphere Windcube200s LiDAR at Hong Kong International Airport between 3 and 5 February 2019.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Radar wavelength & 1.54 \(\mu\)m \\ Pulse width & 200 ns \\ Pulse repetition rate & 20 kHz \\ Detection range & 1000 m–1785 m \\ Range gate width & 5 m \\ Angular resolution & 0.5\({}^{\circ}\) \\ Elevation & \(-\)0.125\({}^{\circ}\)–5\({}^{\circ}\) \\ Azimuth & 340\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: LiDAR Parameter Settings.  
Figure 1: The location of the LiDAR (circled in red) at the Hong Kong International Airport.