## 5 Conclusions  
In this study, a VLBI antenna monitoring program was developed to maintain the accuracy of the antenna's performance by monitoring its structural stability. The monitoring program was designed to measure the static displacement of the main reflector of a VLBI antenna, which can directly influence the antenna's performance. The conclusions derived from the study are as follows.  
A static displacement monitoring program capable of measuring the position of an object with mm-level accuracy through close-range photogrammetry was developed using high-resolution CCD cameras. To analyze the accuracy of the 3D position coordinate results for the conjugate point of the stereo image calculated from the developed program, the experimental results were compared with total station measurement values for the same target. Both measurements resulted in mm-level accuracy: X = 1.13 \(\pm\) 3.02 mm, Y = \(-\)0.92 \(\pm\) 3.35 mm, Z = \(-\)1.05 \(\pm\) 3.67 mm.  
The VLBI antenna static displacement monitoring program developed in this study will be used to evaluate the structural soundness of the VLBI antenna based on the continuous displacement measurements. Furthermore, the results from this study can be used as basic data for repair and reinforcement work in the future.  
Because the objective of this study was to use the time series analysis of static displacements of the VLBI antenna surface as supplementary material for detecting excessive deformation of the VLBI antenna surface, the precision of the calculated 3D coordinates was regarded as sufficient for  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Statistical Indicator**} & x-Axis & y-Axis & z-Axis & Average \\  & Coordinates (mm) & Coordinates (mm) & Coordinates (mm) & Coordinates (mm) \\ \hline Maximum Deviation & 8.56 & 7.37 & 5.69 & - \\ Minimum Deviation & \(-\)6.82 & \(-\)8.85 & \(-\)7.75 & - \\ Average Deviation & 1.13 & \(-\)0.92 & \(-\)1.05 & \(-\)0.28 \\ Root Mean Square Error (RMSE) & \(\pm\)3.02 & \(\pm\)3.35 & \(\pm\)3.67 & \(\pm\)3.35 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Statistical indicators of accuracy for the 3D position coordinates of the conjugate point compared with total station measurements.  
Figure 12: Measurement and accuracy analysis results for the 3D position coordinates from the developed software.  
monitoring. Furthermore, the developed program has economic advantages, due to lower material and manpower costs, compared to monitoring methods used for other devices.  
To present a more general and stricter standard of accuracy for measuring permanent deformation of the VLBI antenna in the future, additional research and experiments are required to automate the measurements; two potential avenues of research include developing an image recognition algorithm or introducing a new data processing algorithm.  
This research was supported by a grant (16 CTAP-C116607-01) from the Infrastructure and Transportation Technology Promotion Research Program funded by the Ministry of Land, Infrastructure and Transport (MOLIT) of the Korea government and the Korea Agency for Infrastructure Technology Advancement (KAIA). In addition, this research was funded by the Basic Science Research Program through the National Research Foundation of Korea (NRF), and funded by the Ministry of Education (2016R1A6A3A11931804).  
[PERSON] designed, developed and analyzed the system. He also prepared the manuscript. [PERSON] supervised the whole process and revised the manuscript. [PERSON] and [PERSON] participated in the conception, design and experiment.  
The authors declare no conflict of interest.