# Rapid Target Extraction in LiDAR Sensing and Its Application in Rocket Launch Phase Measurement
## 3 LiDAR Target Detection Experiment
### Experimental Verification of Rocket Launch Phase  
To further validate the practicality of the point cloud target extraction method, an outdoor rocket launch segment detection experiment was conducted, as referenced in the literature [25]. The LiDAR measurement device was deployed at a position 450 m away from the rocket at a launch site. Due to the relatively long distance, exceeding the detection range of the radar used in the preliminary experiments, the LeiShen Intelligent MS06-C hybrid solid-state LiDAR was employed to acquire effective point cloud data. The specific parameters of the LiDAR system are provided in the Table 3 below:  
The specific field setup is shown in the Figure 10 below: \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Laser band & 1550 nm \\ Detection range & 2000 m \\ Precision value & \(\pm\)3–20 cm \\ H/V view angle & 90\({}^{\circ}\)/30\({}^{\circ}\) \\ Frame rate & 5 fps \\ Angle resolution & 0.39\({}^{\circ}\)\(\times\) 0.2\({}^{\circ}\) \\ Total line number & 150 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: MS06-C Radar performance parameters. Figure 10: Rocket point cloud measurement test scene diagram. During the rocket launch, data were collected by the LiDAR at a frequency of 5 Hz. The surface of the rocket is primarily white, and due to the characteristics of laser signal emission and reception, the LiDAR scans white objects with the highest reflectance. Leveraging this property, the scatter plot was constructed using reflectance values, with the reflectance of the rocket's corresponding region enhanced. This enhancement allows the rocket's point cloud to be clearly highlighted in the scatter plot. In this experiment, point cloud data from the rocket launch segment was collected. Given the limited field of view of the LiDAR, a total of 23 frames were acquired. The collected point cloud data were then processed using the target extraction method proposed in this paper, with the results presented in Figure 11.  
The results of processing the rocket launch experimental data indicate that the target extraction method proposed in this paper effectively isolates the point cloud corresponding to the target rocket. While the LiDAR used in this experiment has a long measurement range, its angular resolution is not as high as that of the LiDAR used in the near-field experiments, resulting in fewer target rocket point clouds being collected. The LiDAR collected around 17,000 points per frame. By applying a filtering method, most of the background point clouds can be removed, and the point cloud containing the rocket can be extracted. The extraction of the rocket's target point cloud took 138 ms, and the 3D data of the rocket target was accurately extracted. This further validates the effectiveness and practicality of the proposed method for extracting targets at long distances. After performing target extraction on each frame of the rocket launch segment's point cloud data, the centroid coordinates of the rocket's 3D point cloud were calculated. The trajectory of the rocket's centroid in 3D coordinates is shown in Figure 12, where the values along the X and Z axes represent the displacement relative to the initial position. The experimental results show that the rocket gradually shifted in one direction during the launch phase. At the moment the rocket moved away from the launch tower, the X and Z displacements were 0.2159 m and 0.1911 m, respectively. This result aligns with data from other optical measurement devices at the launch site, further confirming the feasibility of the proposed point cloud target extraction method. Additionally, the results provide reliable data support for trajectory measurement during the rocket launch process, enhancing the efficiency of data processing and analysis for launch control and improving the safety of the rocket launch. Figure 11: (**a**) Rocket raw point cloud map; (**b**) cylindrical projection diagram; (**c**) 2D grayscale image; (**d**) rocket point cloud target; and (**e**) rocket 3D point cloud.