## 3 AROS Overview  
### AROS Overview and Functions  
Figure 1 provides an overview of AROS. AROS has been developed to be deployed to handle the needs of safety and quality inspections for infrastructure projects. AROS allows inspections to be performed directly in the field, as well as remotely from the site office. For \"field inspection,\" AROS provides a series of functions and user interfaces customized for direct use by site inspectors. \"Remote inspection\" provides a set of functions for off-site management that enables continuous inspections despite restrictions, such as weather or site inaccessibility. Specifically, point clouds acquired through laser scans and virtual models are projected side-by-side, allowing inspections between as-built and as-planned models.  
Table 3 shows the main functions of AROS and their examples. These functions were developed based on surveys and interviews with site management experts [14] and included (1) checklist provisions via BIM model projection, (2) BIM element marker, (3) dimension measurement, (4) progress monitoring, (5) BIM model viewer, and (6) BIM  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Game Engine** & **Unity 3D** & **Unreal Engine** \\ \hline Programming language & C\# & C++ \\ Developer community (versatility) & Large & Small \\  & Suitable for rapid development of & Realistic graphics and performance, \\ Strengths & cross-platform apps, & low programming difficulty \\  & Short 3D model production period & High development difficulty \\ Weaknesses & Not open source & High development difficulty \\ BIM to AR integration tool & Reflect & Datasmith \\ OS for BIM to AR integration tool & Windows OS, Mac OS, Android, iOS & Windows OS \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of Unity 3D and Unreal engine (Adapted from Ref. [34]).  
Figure 1: Site management process using AROS.  
model and LiDAR analysis. The last function was developed exclusively for off-site inspections, whereas the other functions can be used for both field and remote inspections.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Function** & **Description** & **Examples of the Operation Screen** \\ \hline
1 & Checklist provisions via BIM model projection & Project BIM-based AR model that stores information on checklist and inspection results when selecting individual elements \\
2 & BIM element marker & Remark elements that have inspection issues or are insufficiently inspected and display elements with colors \\
3 & Dimension measurement & Provide an AR-based measurement tool to measure and detect the length of elements \\
4 & Progress monitoring & Project models by data for comparison of plans and current progress \\
5 & BIM model viewer & Instantly examine the designed BIM models on the screen \\
6 & BIM model and LiDAR analysis & Simultaneously project the point cloud data collected with LiDAR and BIM-based AR model in the same environment \\ \hline \hline \end{tabular}
\end{table}
Table 3: Main functions of AR on-site (AROS).  
Field inspections, the focus of this study, are conducted using a pre-entered checklist in AROS. The inspector checks and marks the individual elements using functions (1) through (5) and notates elements with safety or quality issues. These results are first saved in the virtual model in AROS, then subsequently updated in the original BIM model. This was achieved by encoding a conversion script in Dynamo to save the data in a JSON file format. Saving the information directly in the BIM model allows (1) sharing of the inspection results by all project stakeholders and (2) redisplaying the results in the subsequent inspection runs. AROS displays marked elements in red to ensure that inspectors can check whether related issues have been resolved.