# UAV Application for Typhoon Damage Assessment in Construction Sites
## 4 Case Study and Process Design  
### Image Collection at the Construction Site  
In this study, the Xiamen Electronic City project under construction was used as the case to collect images of the construction site. Xiamen Electronic City- International Innovation Center project is located in Jimei District, Xiamen City, Fujian, China, with a total area of 103,200 m\({}^{2}\) and a total construction area of about 570,000 m\({}^{2}\) (as shown in Figure 4). In this study, the construction risk analysis was carried out by building 3D and 2D models of the construction site, and the real-time image data acquisition of the construction site was carried out by UAV to verify the feasibility of the plan. The experiment used the DJI PHANTOM4 PRO V2.0. The specific parameters of the UAV and its load sensor are shown in Table 9. The point cloud model of the construction site was established based on the site image captured by the UAV. The pixel position information on the image of the construction site could be transformed into the position information of the construction site surface so that the point cloud model of the construction site could be established in reverse.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Aircraft**} & \multicolumn{2}{c}{**Vision Sensing System**} \\ \hline Weight & 1375 g & Visual system & Front, Back, and Lower \\  & & & Vision Systems \\ \hline Maximum ascent speed & Sport mode: 6 m/s & & Front: 10 HZ \\  & Position mode: 5 m/s & & Back: 10 HZ \\  & & & Lower: 20 HZ \\ \hline Maximum horizontal speed & Sport mode: 72 km/h & & \\  & Attitude Mode: 58 km/h & & Textured surfaces, Adequate \\  & Position mode: 50 km/h & & lighting (\textgreater{}15 lux) \\ \hline Maximum altitude speed & 6000 m & & **Camera** \\ \hline Maximum withstand wind speed & 10 m/s & Image sensor & 1 in CMOS, \\  & & & Effective Pixels 20 million \\ \hline Maximum flight time & 30 min & & **PTZ** \\ \hline Working temperature & 0 \({}^{\circ}\)C-40 \({}^{\circ}\)C & Stable system & 3 axes \\ \hline Satellite positioning module & GPS/GLONASS & Controllable rotation range & Pitch: \(-90^{\circ}\)\(\sim\)+\(30^{\circ}\) \\ \hline \multicolumn{2}{c}{**Infrared Perception System**} & \multicolumn{2}{c}{**APP image transfer**} \\ \hline Obstacle perception range & 0.2–7 m & Mobile devices & DJI go4 \\ \hline Measurement frequency & 10 HZ & Real-time image transfer & 720P@30 fps \\  & & 1080@30 fps \\ \hline \hline \end{tabular}
\end{table}
Table 9: Main parameters of UAV and payload sensor.  
Figure 4: Xiamen Electronic City project under construction.  
The weather on the experimental date was sunny, and the wind was less than level 4. In this experiment, the flight altitude of the UAV was set to 120 m, and the resolution of the converted image was guaranteed to meet the subsequent identification and detection work during the flight shooting at a speed of 2 m/s. Refer to the pix4d manual for general image acquisition mode requirements, and use regular grid mode to acquire images with at least 75% frontal overlap and 60% side overlap. The camera was kept at a constant height above the subject as much as possible. The images of the construction site captured by the UAV were then sorted, and the size of the obtained image was finally determined to be 1920*1088 through image conversion and screening, and the image acquisition result is shown in Figure 5.