## 2 Literature Review
### Uses of BIM and Augmented Reality (AR) in Engineering  
AR is a technology that calculates the position and angle of a camera image in real-time and adds a corresponding image [34]. It enables real-world and virtual-world information to be integrated and allows for interactions in real-time [35]. [PERSON] [36] defines AR as a link between a real scene and virtual elements, where the virtual elements are 3D objects. Generally, AR output devices are used to connect the real world with virtual objects. Among them, handheld displays such as smartphones and pads are mobile, but have limited processing volume; head-mounted displays provide a good sense of immersion, but have limited use conditions because they require a lot of effort to place holograms accurately in real-world space [37] and their prices are higher than handheld displays [38]. Accordingly, the equipment needs to be selected according to the actual needs.  
In recent years, the advantages of 3D visualization and immersive experiences have led to the increasing use of AR in the architecture, engineering, and construction field [39]. The Laboratory for Interactive Visualization in Engineering (LIVE) at the University of Michigan has been engaged in AR research with applications related to construction operations planning, inspection, safety, and education [40]. Due to its feature of rapid visualization, some researchers applied AR to post-earthquake building models or information visualization [41; 42]. Others combined AR with other technologies such as close-range photogrammetry surveying techniques, remote sensing (RS) technology, etc., to assess building damage [43; 44]. In addition, most studies combine AR and BIM, which is beneficial to the integration of BIM information with sites, and facilitate communication and collaboration. AR could represent the site extension of the BIM concept and approach and maximize the potentials of BIM in the construction site [45]. Integrating BIM and AR realized architectural visualization in four stages of building life cycle [46]. In the design stage, it assisted in building design [47]. In the construction stage, BIM and AR have been used to monitor construction progress to promote project progress [48], visualize the physical context of each construction activity or task in real-time [49], and develop a mobile BIM-AR system with cloud storage to improve the efficiency of information retrieval during construction [50]. In the operation and maintenance stage, users combine AR and BIM to manage the quality of structural components [45], consolidate, optimize, and visualize data and models [51], and guide the maintenance processes of facilities to improve operational efficiency [52; 53]. Most of the current research on BIM and AR is focused on new construction, and there is a lack of systematic research on their application to earthquake-damaged buildings. The post-earthquake restoration of buildings is often performed in a complex environment. Owing to the loss of building-related materials after earthquake damage, the internal damage is unclear in some buildings, and in view of the possibility of modifying the retrofitting plan during the construction process, 2D drawings alone cannot meet the design and construction requirements. Therefore, the introduction of BIM and AR can solve these problems.