## 3 Methodology  
This section presents a methodology of using 3D laser scanning and BIM technology for quality tolerance control on a modular construction project. A research framework was developed, as shown in Figure 1.  
Figure 1: Research framework. Step 1: Literature review. This study first conducted a thorough literature review and background study to evaluate the feasibility of using 3D laser scanning and BIM for modular construction quality control and tolerance analysis. Step 2: Identify the critical quality control procedures. This study categorized the modular construction installation into three main construction phases: preconstruction, construction, and post-construction, as shown in Figure 2.  
In the preconstruction phase, first of all, quality control was carried out from the aspect of raw materials, and quality inspection was carried out on the incoming modules to ensure that the incoming modules met the corresponding quality standards and met the installation requirements, such as the size problem in the manufacture of large steel structures [5]. The prefabricated components, including embedded parts and fabricated modules, were inspected and calibrated according to the specifications and manuals. A detailed on-site quality control plan was prepared based on the manufacturer's recommendation. Construction equipment and construction staging area were well-planned before installation. Proper use of professional equipment can improve construction quality and significantly improve construction efficiency. Then, the coordinates of the embedded parts were measured by the licensed surveyor on-site. The surveyor defined the position of the embedded parts' axes via a local coordinate system. This study chose to utilize laser scanning technology for defining the location and the alignment of embedded parts. In addition, a licensed quality control manager was assigned on-site, and quality control training was provided for all construction personnel. From the perspective of improving the quality of construction personnel for quality control, installation personnel were required to have the corresponding qualification and professional training to understand the specific construction sequence of module installation and possible problems and treatment measures. In the construction phase, the installation process and the detailed quality control procedure of installing embedded parts and fixed fabricated modules were identified. Special attention was given to the accuracy of module positioning and calibration to ensure its levelness and alignment do not affect  
Figure 2: Modular installation and quality control process. the construction quality of the process and its immediate aftermath. A pre-final quality evaluation was performed after the concrete foundation was cured to check the position and fabricated modules' alignment. Supervision personnel were present for the key processes to ensure that the installation meets the standards. In the post-construction phase, final quality assurance was conducted before the project is turned over to the owner, ensuring the quality standards are met. Step 3: Develop BIM model. This study decided to utilize BIM and laser scanning technology to conduct a quality control process. BIM models, including embedded parts, fabricated modules, reinforcement, and concrete foundations, were created based on the design and the assembly instructions of the construction structure. Establishing a quality BIM model in this modular construction project helps the construction professionals check and solve design errors. It also ensured the project was delivered on time, and the cost is maintained. Step 4: Capture of point cloud data. This work included selecting a suitable laser scanner, locating the scanning position, optimizing scanning methods, parameters, and removing the noise data. The scanner set-up plays a vital role in the quality of the resulting point cloud [44]. Time-of-flight scanners are commonly used for construction engineering projects.