## 2 Literature Review
### Development of Equipment for Identifying Surface Damage
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Traditional Building Materials** & **Year** & **Case and Location** & **Analytical Techniques** & **Surface Damage Types or Characteristics** \\ \hline \multirow{8}{*}{Chinese Gray-Brick} & \multirow{2}{*}{2024} & White Temple Tower in & Experiment on visual & Brick carvings and bricks in four different solutions \\  & & Lanzhou City & degradation characteristics & were analyzed for compressive strength, surface \\  & & & during aging & hardness, mass, elastic wave velocity, and color \\  & & & & differences [17]. \\ \cline{2-5}  & \multirow{2}{*}{2024} & Badaling section of & Improved-YOLOv5n object & Four types are identified: bricks missing, weathering, plant growth, and cracks [18]. \\  & & the Great Wall & & plant growth, and cracks [18]. \\ \cline{2-5}  & \multirow{2}{*}{2024} & Fuzhou’s Ancient Houses (Gu-Cuo) & YOLOv8 in computer vision & Identify two types of damage: efflorescence and plant growth [19]. \\ \cline{2-5}  & \multirow{2}{*}{2023} & Macau World Heritage & & Identifies five types of damage: missing, cracking, plant or microbial erosion, yellowing, and pollution on the exterior walls of ancient gray brick buildings [5]. \\ \cline{2-5}  & & & & It automatically detects four types of damage (chalking, plants, ubiquinol, and cracking) on the surface [20]. \\ \cline{2-5}  & \multirow{2}{*}{2023} & Plain Great Wall & & Detects two types of damage (efflorescence and spalling) [21]. \\  & & of Shankhugian & & plants, ubiquinol, and cracking on the surface [20]. \\ \cline{2-5}  & \multirow{2}{*}{2019} & Palace Museum Wall in & Faster R-CNN based on & Detects two types of damage (efflorescence and spalling) [21]. \\  & & Beijing City & ResNet101 & Identifies and locates four categories of damage (intact, crack, efflorescence, and spall) with an accuracy of \\ \cline{2-5}  & \multirow{2}{*}{2018} & Forbidden City Wall in & A sliding window-based & Identifies and locates four categories of damage (intact, crack, efflorescence, and spall) with an accuracy of \\  & & Beijing City & CNN method & 94.3% [22]. \\ \hline \multirow{2}{*}{Shed-thin tile} & \multirow{2}{*}{2024} & The Classical Gardens & \multirow{2}{*}{YOLOv4 in computer vision} & Identifies four types of damage: water staining, surface \\  & & of Suzhou & & scaling, color aberration, and excessive gaps [23]. \\ \hline \multirow{4}{*}{Brick and stone surface} & \multirow{2}{*}{2025} & White Pagoda in Lanzhou & The improved YOLOv8 & Identifies four types of damage: alkalinity, erode, spalling and cracking [24]. \\  & & & & \\ \cline{1-1} \cline{2-5}  & \multirow{2}{*}{2024} & Gulang Island in & Based on Swin Transformer & Identification of six types: plant penetration, moss, cracking, alkalization, staining, and deterioration [25]. \\ \cline{1-1} \cline{2-5}  & & Xiamen City & & \\ \cline{1-1} \cline{2-5}  & \multirow{2}{*}{2019} & Anyuan Railway and & Visual inspection and & The physical and mechanical condition of the \\ \cline{1-1} \cline{2-5}  & & Miners’ Club in Anyuan & NDT methods & structural components is evaluated [26]. \\ \cline{1-1} \cline{2-5}  & & Town, Pingxiang City & & \\ \hline \end{tabular}
\end{table} 
Table 1: Technology and progress in research on surface damage of traditional building materials in China.