## 5 Discussion  
This study contributes to remote collaboration in the AEC industry by combining the potential of BIM and MR for remote collaboration. Remote collaboration in the construction industry is not sufficiently pioneered, thus challenging. We can find the reason in the unique characteristics of the construction project. In the case of the manufacturing industry, many of the same products are manufactured in a structured environment, such as a factory; however, construction products are unique and attached to the surface of the earth. Therefore, the environment around the site, which is usually unstructured, is very important in a construction project. Therefore, communicating the unstructured field situation is important for successful remote collaboration. This study used BIM and MR to communicate the on-site situation and confirmed the applicability of the developed remote collaboration system.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Question**} & \multicolumn{5}{c}{**Response**} \\ \cline{2-6}  & **Strongly Disagree** & **Disagree** & **Neutral** & **Agree** & **Strongly Agree** \\ \hline
1 & 0 & 0 & 1 & 1 & 8 \\
3 & 0 & 0 & 0 & 3 & 7 \\
4 & 0 & 0 & 0 & 2 & 8 \\
5 & 0 & 0 & 0 & 1 & 9 \\
6 & 0 & 0 & 1 & 3 & 6 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Survey Responses to MR2 CS’s Usability.  
Figure 9: Real-world view with a virtual window on laboratory wall: (**a**) Real-world view of the laboratory wall; (**b**) Real-world view with a virtual window.  
As mentioned previously, remote collaboration research has not been sufficiently conducted in the AEC industry because construction products are attached to the land. Therefore, the spatial alignment of BIM elements is essential for remote collaboration in a construction project. On the other hand, spatial alignment is not very important in the manufacturing industry because manufacturing is product-oriented and not heavily influenced by the surrounding environment. This study showed that the combination of BIM and MR could resolve this issue.  
As a result of the usability test of the developed system, testers' positive responses were obtained, but some challenging comments were also received. The FOS users have pointed out low sound and image quality. Furthermore, a few testers indicated that the sharpness of the object hologram is low, and the viewing angle is narrow. However, these issues will be resolved as hardware and software develop. We found that the field of view was narrow in the feedback of OMS users. The testers think it is not easy to grasp and understand the overall situation of the field because the field of view is narrow. Furthermore, comments were received that it would be desirable for an OMS user to manipulate the virtual BIM object directly.  
The proposed system can be used where remote collaboration is needed in the AEC industry. Especially it can be effectively used when the office manager monitors the construction site during the construction phase. The field operator can check whether the construction is proceeding as planned by wearing the FOS with receiving remote support from the office manager. The office manager can see the real-world image of the site and BIM objects superimposed without having to visit the site. For example, a project engineer at the site can monitor the artifacts such as steels and forms for quality control, while a senior manager or engineer can see the project engineer is viewing and giving instructions. This system also can be effectively utilized even in the design phase for a remodeling project. Since FOS users can manipulate virtual objects and share the MRC with remote office managers, it can be very helpful in decision-making.