## 5 Conclusions  
In this paper, a dense feature extraction, matching, and dual-step mismatch-removal-based full-field structural dynamic deflection measurement method was proposed, and the method was validated through indoor cantilever beam experiments by commercial GOM correlation software. The main conclusions are summarized as follows:  
(1) This proposed method achieves full-field dynamic displacement measurement of a vertical cantilever beam by dense feature extraction from the grayscale differences of structural surface textures, using a dual-step mismatch removal method to eliminate mismatched feature pairs, and the method shows good measurement accuracy and computational stability.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Times**} & **Maximum Error** & **Average Error** & \multicolumn{2}{c}{**Correlation Coefficient \(\rho\)**} \\  & **/mm** & **/mm** & **DFEM-DSMR** & **References** \\ \hline \(t=0.4\) s & 0.037 & 0.008 & 0.9994 & \\ \(t=0.8\) s & 0.047 & 0.011 & 0.9991 & 0.9689–0.9887 \\ \(t=1.2\) s & 0.038 & 0.010 & 0.9969 & [29] \\ \(t=1.6\) s & 0.046 & 0.012 & 0.9984 & 0.9805 [30] \\ \(t=2.0\) s & 0.047 & 0.012 & 0.9964 & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Spatial deflection measurement error of DIC and DFEM-DSMR.  
Figure 17: Comparison of the deflection at \(t=1.2\) s between the two methods.  
(2) In the structure motion tracking using SIFT feature extraction and FLANN matching, a large number of mismatches were found in the dense feature matching results, and the mismatch proportion accounts for as much as 60.62%, varies over time, and cannot be removed manually. The proposed DSMR method, combining the RANSAC and the SDCCs, can efficiently and accurately remove approximately 37% and 18% of mismatched feature pairs, respectively.  
(3) Compared with GOM software, the DFEM-DSMR method shows good measurement accuracy temporally and spatially. Temporally, the maximum error in the dynamic deflection-time curves of measurement points at different positions ranged from 0.025 to 0.053 mm, the maximum average error was 0.013 mm, and the _RMSE_ was 0.01 mm. Spatially, the maximum errors in the deflection curves of the global structure at five different times ranged from 0.037 to 0.047 mm, the maximum average error was 0.012 mm, and the minimum correlation coefficient \(\rho\) was 0.9964.  
The conclusions above were derived in stable indoor illumination conditions. While the application of the proposed method in engineering should consider the influence of complex weather conditions such as cloudy, foggy, or rainy weather, the contrast differences of the structural surface texture and the influence of environmental background still necessitate further research.  
Conceptualization, J.Z.; methodology, software, validation; formal analysis, writing--original draft preparation Y.T.; writing--review and editing, supervision, H.L.; visualization, J.H.; funding acquisition, Z.Z. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (Grant. No. 51778094), the National Natural Science Foundation of China (Grant. No. 51708068), the Joint Training Base for Postgraduate Construction Project of Chongqing (Grant. No. JDLHYPJD2020019), and the Postgraduate Tutor Team Construction Project of Chongqing (Grant. No. JDDSTD2022003). We also acknowledge the State Key Laboratory of Mountain Bridge and Tunnel Engineering for providing experimental equipment.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy.  
Author [PERSON] was employed by the company China Merchant Chongqing Communication Research & Design Institute Co., Ltd., Chongqing 400067, China. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as potential conflicts of interest.