## 7 Discussion  
One of the major AR characteristics is the combination of real and virtual objects in a real environment [29; 30]. The combination show a strong resemblance to that of building system maintenance, which constitutes the completion a complicated task by applying knowledge of various levels and representative forms. The diversity of mechanical equipment in building system maintenance requires hands-on experience and a thorough comprehension of the appropriate operation manuals in order to perform maintenance jobs at real sites. In addition to BIM, a task normally has to be carried out with support or resources from different fields, which possess the diverse characteristics of as-built reality, facility management, operational instruction, and working environments that could either be difficult to access or have complicated cross-space layouts throughout the entire building.  
Maintenance in dark or low lumen conditions is frequently encountered on working sites where safety is paramount. Safe routes and procedures should be clearly indicated with the lighting function  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Items** & **N** & **Mean** & **SD** \\ \hline Overall average & 1–16 & 15 & 1.74 & 0.40 \\ System usefulness & 1–6 & 15 & 1.42 & 0.30 \\ Information quality & 7–12 & 15 & 1.90 & 0.38 \\ Interface quality & 13–15 & 15 & 2.00 & 0.83 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The scores of the four items of the Post-Study System Usability Questionnaire (PSSUQ).  
Figure 8: The average score for all topics in the PSSUQ.  
clearly connected to operational signage. BARMS provides a route clear of unanticipated obstacles and an adaptable orientation for optimal nearby viewing angle. A BARMS-enabled smartphone becomes very helpful, with its easy mobility and embedded flashlight. The region of interest, lit by the smartphone flashlight, can now be connected to the entire system for a better understanding of the possibly affected components. An AR system, which can be very beneficial in working outdoors at night or in similar dark indoor situations, can now achieve an accurate level of reality that combines with the overall scope of the setting by using a commonly available illumination function. Consequently, work difficultly is significantly reduced, especially in cases involving an unfamiliar space.  
BARMS provided a straightforward indication of the valve location with a clear and simple maintenance animation to lessen the workload of the testers and increase operational efficiency. The integration of virtual building component information and on-site maintenance, in reality, is critical for as-built facility management tasks. Although the BIM 3D model and its attributes contribute to complete facility information, which can be accessed by maintenance workers from cloud computing services, the real piping layout and its exact penetration points are very challenging to verify from both sides of walls. The piping layout and penetration point can now be confirmed from both sides of walls, with piping geometries facilitated and integrated with both information and reality.  
Many researchers engaged in AR face the problem of poor geo-referencing [12]. Although visual tracking usually achieves the best results with low frequency motion, it is likely to fail with rapid camera movement [31]. Although BARMS can provide mediated information to assist with geometry and information mapping, drifting (0-20 cm) occurs at the far end of a pipe beginning when approximately 16.5 m away from the starting reference point. This deviation can also increase when workers approach the maintenance location from a greater distance. Currently, an auxiliary application that runs at a lower hierarchical position is used to eliminate drift at the distant location, next to the end of the pipe.