## 4 Results and Discussion  
### Horizontal Displacement and Amplitude Extraction Analysis  
The power profiles obtained from working base points S1 and S2 are shown in Figures 6 and 7, respectively. Many peaks are visible in Figures 6 and 7. These peaks correspond to the positions of the monitored points characterized with good electromagnetic reflectivity. To analyze the displacement of the WGC, we selected the monitored points with good electromagnetic reflectivity located on the roof of building (i.e., the location of point A) and the middle position of the main structure of the building (i.e., the location of point B) to analyze its horizontal displacement during the monitoring period. Point A in the two figures is located on the roof of the WGC. The height of the roof relative to working base point S2 was 447 m, whereas Point B was 300 m high from the building relative to working base point S2 when we used GB-RAR to monitor the building. The heights of points A and B in the analysis are relative to working base point S2. As shown in Figures 6 and 7, the thermal signal-to-noise ratio (SNR) of the radar signal is basically greater than 30 dB within the range of 100 m to 447 m relative to the height of the building. The thermal SNRs of points A and B in the north-south monitoring direction are 37.4 and 60.8 dB, respectively, and the thermal SNRs of points A and B in the east-west monitoring direction are 39.0 and 62.2 dB, respectively. The above analysis demonstrates that the data collected by the radars at S1 and S2 are of good quality. \begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter** & **Value** \\ \hline Vertical tilt & 50\({}^{\circ}\) \\ Antenna type & Type3 (Azimuth 17\({}^{\circ}\), Vertical 15\({}^{\circ}\)) \\ Maximum range & 800 m \\ Resolution in range & 0.75 m \\ Sampling & 20 Hz \\ Start time & 12:21 5 July 2017 \\ End time & 12:14 7 July 2017 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Configuration of IBIS-S systems for the measurement campaign. Figure 5: Location of the IBIS-S-2 system in the east–west direction. **(a)** View of the IBIS-S-2 interferometric radar on S2 (located in the Wuchang River Beach Park). **(b)** Ground view of the WGC from the location of the IBIS-S-2 interferometric radar. We selected and analyzed some feature points of the WGC to analyze its horizontal displacement during monitoring. The feature points were distributed at points A and B of the building. The LOS displacement time series of feature points was extracted using the method described in Section 2, and the horizontal displacement time series of feature points was calculated through geometric projection based on the geometric relationship between the feature points and the radar position. Figure 8 shows the horizontal displacement time series in the north-south and east-west directions at the top of the WGC during the monitoring period, and the red and black curves represent the original and denoised horizontal displacement time series, respectively. The negative values in Figure 8a indicate that the building is moving westward, whereas the positive values indicate that the building is moving eastward. As shown in Figure 8b, the negative values indicate that the building is moving northward, whereas the positive value denotes that the building is moving southward. As shown in Figure 8b, the maximum negative horizontal displacement of the roof in the north-south direction is 7.99 mm, and the maximum positive horizontal displacement is 10.85 mm. Therefore, the maximum  
Figure 6: **(a)** Power profile of the WGC obtained from working base point S1 and selection of monitoring points. The red triangle denotes the monitoring point. The relative height of the building in the left figure is relative to working base point S1. Point A in the right figure is at the top of the building, with a height of 447 m relative to working base point S2. Point B is 300 m high relative to working base point S2. **(b)** Ground view of the WGC from the location of the IBIS-S-1 system.