# A Web-Based BIM-AR Quality Management System for Structural Elements
## 5 Discussion  
The results showed that the main weaknesses of the current QM practice (namely: poor management, poor understanding of the scope of quality, and poor communication between stakeholders) can be overcome, while the practice itself can be made more efficient and effective by exploiting the integrated use of BIM and AR technologies in a web-based collaborative system. The case study allowed identification of benefits in adopting the proposed framework. Figure 13 maps the possible outcomes of the proposed system while pursuing the objectives of budget, time, and quality of the construction project.  
On the other hand, during the development and testing of the proposed system, some limitations and barriers have been identified. One of the most important is the problem related to the correct positioning of the virtual model on the real environment. In fact, the accuracy of the positioning is not sufficient to rely on this system as a tool for the measurement of geometry, and therefore geometric measurements should still be done using traditional approaches. Furthermore, due to the nature of the construction sites and the dependency of the AR system on depth sensors, it could be difficult to superimpose the pins in the correct positions to achieve an AR experience with acceptable accuracy during the first tries. A possible solution could be the integration of both marker-based and marker-less  
Figure 12: Case study, shots of the failed inspection lots: wall concrete surface with honeycomb (left), wall cross-sectional geometry (center), hole in a slab (right).  
Figure 13: Benefit map of the proposed system.  
tracking systems in the AR platform. With a proper enhancement of the software, the indoor positioning could exploit, e.g., near-real-time photogrammetric techniques to guide the procedure.  
Occlusions create difficulties, as well. In AR, an object closer to the viewer obscures the view of objects further away along the line of sight, affecting the interpretation of the environment by the AR application in the case of complex models with lots of elements and details. Again, it the opinion of the authors that this could be managed by the AR platform at software level so that, on the basis of a more accurate positioning of the device, it could recognize the relative distance of objects and manage the overlaps between superimposed elements. Examples of these problems are shown in Figure 14.  
From this point of view, several different techniques aiming at improving the accuracy of the positioning during the AR experience are under investigation by the scientific community [39], due to the huge potential that such technology has in various fields of application.  
Another shortcoming of the proposed system for quality inspection is represented by the dependency on Internet access, which may cause problems when the signal is poor. Finally, there is the need to train people to use the system properly for safety reasons: in fact, working with mobile AR applications may cause the user to lose attention to the surrounding area, which could be very dangerous in a construction site and cause safety issues [40].