*2.3. Quality Assessment and Control*

Traditionally, structural dimension checks are performed manually. Two main inspection methods are widely used: (1) directly check based on visual observations or using a measuring tape; (2) obtain coordinates of serval feature points by using total station. However, these methods are laborious, time-consuming, and insufficiently accurate. Recently, TLS has been widely used in quality assessment and control, such as surface-defect detection [45,46] or structure dimensional check in the Architecture, Engineering & Construction (AEC) industry [47–49]. Moreover, some studies have proposed using TLS to check the dimensions of structures. For example, Wang et al. [50] developed an automatic method to estimate the dimensions of a precast concrete panel using point clouds data. Bosch'e [51] proposed an approach to automatically detect and calculate the as-built dimensions of a steel structure based on laser scan data. Lee & Park [52] proposed a method using both TLS and an AI model to perform a dimensional check. And Nuttens et al. [53] provided a clear work flow to illustrate how to use TLS to measure the dimensional changes in two tunnels in Belgium and to generate results with submillimeter accuracy.

Although these studies provided good examples about the adoption of TLS technology in the AEC industry, they also admitted some issues about TLS measurement. First, TLS can quickly provide as-built data, but the scan strategy should be properly designed in order to provide good-quality data. Moreover, some techniques should be used to rapidly extract important data from dense scan data. In addition, the accuracy level of the TLS measurement should be improved to satisfy the requirements.

The contribution of the study lies in three aspects. First, the study proposes using TLS technology in the inspection of high formwork installation quality. Due to the unique complex structure of the high formwork and the labor and cost concerns of the inspection process, this study provides a reasonable and cost-effective way to conduct the inspection process. Secondly, the study provides an effective to quickly extract the data related to the important components of the high formwork such as vertical poles and horizontal tubes. Thirdly, the study used genetic algorithm optimized ANN model to improve the accuracy of the TLS measurements, which can provide coordinates of the cross points of the poles and tubes at millimeter level.
