## 5 Discussion  
During the installation of the removable floodwall, it is found that the stage of concrete implementation is more prone to quality problems than any other process. First, the concrete process should be carried out in accordance with the processes and standards in the prepared construction plan, paying particular attention to the accuracy of the module positioning and calibration to ensure its elevation, level, and perpendicularity, so as not to affect the quality of the construction of this process. Then, rigorous quality control is required to perform at the level of millimeters. Current quality control is done by manual means such as rulers and latitude and longitude meters, which are time-consuming and inaccurate in measurement. It is difficult to measure accurately in high-rise locations or harsh environments, and it takes a lot of time and effort to do so. This study first uses BIM to construct a model to form a reference point for quality control. A 3D laser scanning of the construction site is used to form an actual model of the structure. By comparing the two models, an evaluation of the quality tolerance of the modular construction is performed. The construction site adjusts the modules according to the comparison results until the final quality control requirements are met. As there will always be changes at the construction site, there will be differences from the initial design BIM. Therefore, the point cloud data can also be used to modify the BIM model and ultimately become the final as-built model of the structure. The embedded components are the connections of a modular structure, an essential part of modular construction. The embedded parts' location determines the quality of the components and the installation quality of the entire structure. The quality control of modular construction is divided into quality control of prefabricated component production and installation quality control. [PERSON] et al. [7] studied the method of evaluating the dimensional and surface quality of prefabricated components based on BIM and 3D laser scanning. The quality of on-site installation, however, is more difficult to control. The non-contact quality control method based on BIM and 3D laser scanning designed in this paper is of general interest. It can be fully extended to modular buildings' whole life cycle, including design, build fabrication, installation and operation, and maintenance. The processing of point cloud data is at the core of using laser scanning for fine-grained quality management. Also, the process of registering point cloud data and removing noisy data to meet the quality control requirement plays a key factor in the success of quality management. A detailed comparison was performed between the standard quality control procedure and the proposed 3D laser scanning and BIM method. The number of workers needed, the measuring time, and the level of accuracy were documented and compared. The results are shown in Table 5.  
Figure 19: The view of the removable floodwall. Compared with the traditional model, the method proposed in this study has two main advantages: (1) it realizes collaborative management of the whole construction process. The problem solving of the construction process is no longer unilateral. Many stakeholders are involved. (2) In terms of construction quality control, a more accurate and efficient laser scanning and BIM inspection method are integrated, reducing the quality inspection time of the entire construction process, avoiding on-site network, and providing more reliable data support for the construction problems. With the increasing level of information technology in the industry and the continuous innovation of project management models, this method will be more valuable throughout the project life cycle by adding control elements and expanding management stages. The economic feasibility of the proposed quality control system was discussed in the context of other laser scanning applications.