## 4 Field Experiment
### Verification of Proposed Image Processing Method  
To validate the applicability and effectiveness of the proposed method, target objects inside the climbing formwork covered with a safety net were selected. The four objects were safety signs, personal protective equipment worn by workers, climbing formwork ladders, and work platforms, which are essential equipment to ensure the safety of workers. Regarding identification of the safety signs, the original and improved images were compared, as shown in Figure 12. The Korean text on the safety signs was regarding the dismantling of the bolt of the climbing formwork. A typical accident that occurs in climbing formworks is when workers arbitrarily disassemble the connection bolt before the lifting hook is fastened to the climbing formwork, causing the workers to fall. The red circle mark shown in Figure 12 indicates that the dismantling of connection bolts 1 and 2 \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **GSD (cm/pixel)** & **RMSE (cm)** \\ \hline Value & 0.49 & 1.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Quantitative evaluation metrics of 3D modeling quality. Figure 11: The climbing formwork and shooting points are considered: (**a**) Photo of considered climbing formwork; (**b**) Shooting point. is prohibited before fastening the lifting hook to the climbing formwork. In the original image, it was difficult to recognize the attachment state of the safety sign and text owing to the construction safety net (Figure 12a). However, the application of the proposed image processing technology leads to an enhancement in the image contrast, thereby improving the visibility of the installation status of safety signs, ultimately achieving observable levels (Figure 12b). Using the proposed image processing method, the installation state and contents of the safety signs can be clearly observed. Workers must wear hard hats as personal protective equipment (PPE) during construction work to ensure safety in the event of an accident. At construction sites, managers, including those who are responsible for safety, should ensure that workers wear hard hats. Monitoring all areas of large construction sites is difficult because certain workers work without PPE, such as hard hats. In particular, it is challenging to monitor whether PPE is worn by workers on climbing formworks using UAVs, primarily owing to the presence of construction safety nets. It is difficult to determine the number of workers wearing hard hats, as shown by the red circle in Figure 13a. However, in the image improved by the proposed image processing method, the identification of internal work was enhanced. As shown in Figure 13b, it is evident that the two workers were wearing yellow hard hats. Using the proposed method combined with UAVs, construction managers do not need to directly access the climbing formwork to inspect the compliance of workers with safety and protective equipment. A more effective means of safety management is anticipated because the workers can be easily monitored from outside the climbing formwork. Figure 12: Identification of the attachment state and content of the safety sign; (**a**) Original image; (**b**) After improvement. Figure 13: Inspection of workers wearing hard hats: (**a**) Original image; (**b**) After improvement. According to regulations, a ladder should be installed on the climbing formwork to facilitate the movement of workers between floors. However, its usability may be compromised owing to inadequate installation conditions, such as poor installation quality and failure to adhere to proper installation intervals. The installation status of the ladders is challenging to observe, despite using UAVs to capture the footage outside the climbing formwork, as indicated by the red square box (Figure 14a). However, when the proposed image processing technology was utilized, installation of the two blue ladders connecting the layers of the climbing formwork became evident (Figure 14b).