# Integrated Digital-Twin-Based Decision Support System for
## 4 Developing a DT Platform
### Digital Layer  
The digital layer is the backbone of the DT platform, serving as the integrative component that transforms raw data from the physical layer into actionable virtual representations [45; 46]. It is responsible for creating and managing high-fidelity virtual models of RMBs that support real-time visualization, tracking, analysis, and decision making. This layer integrates three key technologies: BIM, IoT, and GISs. Each of these components plays a unique and complementary role in ensuring the platform's effectiveness and scalability. BIM is utilized to generate detailed digital representations of RMB modules and associated projects. BIM captures geometric and spatial attributes while embedding extensive metadata properties, including material specifications, module conditions, and lifecycle data [47; 48]. This results in a comprehensive virtual asset repository that supports visualization and informed decision making. BIM is particularly valuable for managing individual components of RMB projects and fostering collaboration among stakeholders. By enabling seamless communication, it mitigates the \"information silos\" that often hinder construction projects [49; 50]. However, BIM alone is insufficient for managing RMBs, which require extensive spatial and logistical analyses due to their dynamic relocation and reconfiguration processes across multiple sites and project phases [51; 52]. To address these limitations, GISs are integrated into the platform, providing capabilities for spatial data analysis and geographical visualization. GISs enable the acquisition, storage, and management of geospatial data critical for RMB projects, including topological information, transportation routes, and regulatory constraints between project sites [53; 54]. This integration ensures that modular units are not only visualized in 3D but are also spatially and temporally accurate, facilitating the analysis of factors such as proximity to new project sites, optimal transportation routes, and site-specific conditions. By enhancing the spatial  
Figure 3: DT framework for reused module allocation plan. awareness of RMB management, GISs complement BIM, bridging the gap between virtual design and real-world logistics. IoT technology serves as the dynamic link between the physical and digital layers, providing real-time data streams essential for maintaining synchronization between the physical assets and their virtual counterparts [44; 55]. The integration of IoT data in real time has become a cornerstone for developing DT applications, significantly enhancing construction productivity. These applications have been extensively utilized across various domains, including construction operation monitoring [56], health and safety management [57], construction logistics and supply chain optimization [58], and facility management [59]. In this study, IoT-enabled devices such as RFID tags and GPS sensors continuously collect and transmit data on the location, status, and condition of RMB modules. This ensures that the virtual models reflect real-time changes occurring in construction sites or during module transportation. For instance, GPS data track the movement of modules, enabling managers to monitor their progress from factories to installation sites. Similarly, RFID tags provide granular information about module conditions, such as whether it is reusable or in maintenance, ensuring that decision makers have accurate and current data for planning reuse or reallocation. The integration of BIM, GIS, and IoT within the digital layer occurs in three distinct stages: data input and integration, data management and visualization, and platform deployment (Figure 4). In the first stage, BIM models and IoT sensor data are imported and georeferenced to create a spatially accurate representation of the project. This ensures that all digital assets are aligned with real-world coordinates, enhancing the precision of virtual simulations.