# Analyzing the Economic Performance of a TLS-Based Structural Safety Diagnosis Process
## 3 Results
### Economic Performance Analysis  
#### 3.4.1 Service Cost (SC) and Waiting Cost (WC)  
In this study, the service cost (SC) required for structural safety diagnosis projects and the waiting cost (WC) due to process delays or overtime work were defined. According to interviews conducted with the case company (Company A), an additional payment equiva  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multicolumn{2}{c}{**Project A**} & \multicolumn{2}{c}{**Project B**} & \multicolumn{2}{c}{**Project C**} \\ \cline{2-7}  & **As-Is** & **To-Be** & **As-Is** & **To-Be** & **As-Is** & **To-Be** \\ \hline Queue analysis model & M/M/1 & M/D/1 & M/M/1 & M/D/1 & M/M/1 & M/D/1 \\ Investigation period & 40 & 14 & 80 & 55 & 154 & 66 \\ required & 489.77 & & 59.09 & & & 15.59 \\ \(\mu\) & 538.75 & 1538.29 & 65 & 94.55 & 17.81 & 41.56 \\ \(\rho\) & 0.91 & 0.32 & 0.91 & 0.62 & 0.88 & 0.38 \\ \(1-\rho\) & 0.09 & 0.68 & 0.09 & 0.38 & 0.12 & 0.62 \\ \(L\) & 10 & 0.47 & 10 & 1.15 & 7.02 & 0.49 \\ \(L_{q}\) & 9.1 & 0.15 & 9.09 & 0.52 & 6.15 & 0.11 \\ W & 0.02 & 0.001 & 0.169 & 0.019 & 0.45 & 0.031 \\ \(W_{q}\) & 0.018 & 0.0003 & 0.154 & 0.009 & 0.394 & 0.007 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of queue analysis results between visual inspection and TLS-based methods.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multicolumn{2}{c}{**Project A**} & \multicolumn{2}{c}{**Project B**} & \multicolumn{2}{c}{**Project C**} \\ \cline{2-7}  & **As-Is** & **To-Be** & **As-Is** & **To-Be** & **As-Is** & **To-Be** \\ \hline \(P_{0}\) & 0.091 & 0.682 & 0.091 & 0.375 & 0.125 & 0.625 \\ \(P(W>1\) h, 0.125) & 0.002 & 0.000 & 0.478 & 0.012 & 0.758 & 0.039 \\ \(P\big{(}W_{q}>1\) h, 0.125\big{)} & 0.002 & 0.000 & 0.434 & 0.007 & 0.662 & 0.015 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Timeout probability with visual inspection and TLS-based 3D scanning reverse modeling methods.  
lent to 50% of the daily labor cost is required for 3 h of overtime work beyond the standard 8 h workday. Based on this, the calculated _SC_ and _WC_ showed the following differences.  
In Project A, the visual inspection method involved a daily labor cost of KRW 1,172,789 (one professional engineer, two senior engineers, and one junior engineer). The waiting cost (_WC_) was calculated as approximately KRW 195,465. Conversely, using the TLS-based 3D scanning reverse modeling method, the daily labor cost decreased to KRW 890,244 (one professional engineer, one senior engineer, and one junior engineer), significantly lowering the waiting cost to approximately KRW 148,374 per hour.  
In Project B, the visual inspection method had a daily labor cost of KRW 2,865,329, with the waiting cost calculated at KRW 477,555 per hour. In contrast, the TLS-based 3D scanning reverse modeling method reduced the daily labor cost to KRW 1,735,149 and significantly decreased the waiting cost to KRW 289,192 per hour.  
Similarly, for Project C, the visual inspection method's daily labor cost was KRW 2,865,329, with a waiting cost of KRW 477,555 per hour. However, the TLS-based 3D scanning reverse modeling method reduced the daily labor cost by nearly half, to KRW 1,452,604, resulting in a substantial reduction in the waiting cost to approximately KRW 242,101 per hour.  
Detailed comparisons of service costs (_SC_) and waiting costs (_WC_) for each project are provided in Table 6.  
Consequently, transitioning to the TLS-based 3D scanning reverse modeling approach demonstrates clear advantages in reducing overall project costs. This method not only lowers daily labor costs but also significantly reduces additional expenses associated with overtime work or project delays compared to the visual inspection method.