## 4 The Deformation Detection Experiment and Results
### The Deformation Detection Experiment Results  
In this paper, six experimental scenarios were constructed, each corresponding to different displacements of the corner reflector, from which multiple echoes were obtained for  
Figure 10: The illustration of the deformation target (**a**) The Deformation target scene. (**b**) The Deformation target. (**c**) The high-precision shift spiral micrometer. (**d**) The Line of Sight direction of the deformation target towards the Communication Base Station. (**e**) The Communication Base Station. (The red box and arrow represent a partial enlargement of the content inside the box). data processing. The first scenario, designated as A, serves as the reference for deformation detection. Each subsequent scenario sequentially displaces the corner reflector by 2 mm relative to the previous one, simulating ground deformation, and they are labeled from B to F. (The principle analysis for selecting the 2 mm increment in displacement can be found in Appendix A). The relationship between the displacement of each observation scenario marker and the corner reflector target is shown in Table 2.  
Similarly, 256 consecutive observations were conducted for each scenario at intervals of 2.5 milliseconds. The echo data were processed using the BPA imaging technique, resulting in 256 SAR images for each scenario. Subsequently, the 256 SAR images from each scenario underwent temporal multi-look processing to yield a single SAR image, as illustrated in Figure 11. Among these images, (a)-(f) correspond to scenarios A-F, with the corner reflectors highlighted by red circles, and the color bar represents SAR image amplitude. Prior to performing interferometric processing, it is essential to verify the coherence between the SAR images to ensure the reliability of deformation measurements obtained through D-InSAR technology. Here, we performed multi-look processing on the 256 SAR images acquired for scenario A to obtain a multi-look SAR image of scenario A as the common reference image. Then, we calculated the coherence coefficients between all the single-look SAR images obtained from the remaining five scenarios and the common reference image, and statistically analyzed the coherence coefficients at the corner reflector targets. Its distribution is shown in Figure 12. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Scenarios** & **A** & **B** & **C** & **D** & **E** & **F** \\ \hline
**Displacement** & 0 mm & 2 mm & 4 mm & 6 mm & 8 mm & 10 mm \\ \hline \end{tabular}
\end{table} 
Table 2: The correspondence between the observation scenario markers and the displacement of the corner reflector. Figure 11: Imaging results for each scenario. (**a**) 0 mm displacement. (**b**) 2 mm displacement. (**c**) 4 mm displacement. (**d**) 6 mm displacement. (**e**) 8 mm displacement. (**f**) 10 mm displacement. It is evident that the coherence coefficient of the corner reflector targets in the SAR images obtained from CBS observations is distributed above 0.7, with a minimum value of 0.72. A value of 0.7 is a typical threshold used when InSAR technology (especially PSI) is used for deformation detection applications. This indicates that the corner reflectors maintain good coherence during multiple observations in the experimental scenario, enabling reliable deformation monitoring. Two primary reasons account for the high coherence observed between SAR images. Firstly, the corner reflectors exhibit stable backscattering characteristics, ensuring consistent phase features during the observation period. Secondly, all imaging scenarios (A-F) in the experiment were completed within one hour, resulting in a short observation time that minimized the influence of atmospheric and other noise, thereby preserving good coherence throughout the observation. Based on the analysis in Section 3.3, the SAR images obtained through multi-look processing in scenario A are utilized as a common reference image, which allows for a higher SNR.