## 4 Results and Discussion
### CR-InSAR Deformation Monitoring Results  
Nine artificial triangular CRs measuring 1 m in side length were deployed in the Jinchuan mining area to ensure operational safety, with heading and elevation angle adjustments performed on 3 March 2025 to enable the CR-InSAR technology to perform localized deformation monitoring and the validation of TS-InSAR results. Four Sentinel-1A scenes acquired from February to March 2025 and downloaded from the ESA website were utilized for corner reflector identification and deformation analysis, taking both ascending and descending orbit characteristics into account to facilitate reflector detection and intensity variation assessment. The RD model was employed to transform nine geographic CRs coordinates obtained through field measurements into SAR coordinates, with the initial visual identification of CRs performed using the Sentinel-1A intensity mean image, revealing an average offset of approximately 2 pixels following coordinate transformation. The pixels exhibited regular patterns, prompting the systematic adjustment of the CR SAR coordinates using this offset, with final precise positioning achieved through the application of the maximum-intensity principle within a \(7\times 7\) pixel window, as illustrated by the CR intensity images and deployment locations presented in Figure 17. The weak background scattering energy enabled the clear visual identification of all nine triangular CRs, with Figure 17 displaying zoomed-in mean intensity images of the CR targets annotated with their corresponding intensity values, while quantitative analysis of the CR echo-signal strength using dB values revealed that the central reflector points exhibited intensities exceeding 60 dB and occupied between 4 and 6 pixels in the imagery. Figure 18 demonstrates the intensity time series for all nine CRs, showing that after heading and elevation angle adjustments were made to seven CRs (excluding CR01 and CR09, which required no adjustment), their dB values increased substantially from the initial 50-60 dB levels to 68-75 dB, representing a nearly 15 dB enhancement, with the mean intensity images revealing that all nine triangular CRs achieved approximately 70 dB intensity. Figure 17: Intensity images of CRs and their deployment locations. The accuracy estimation of phase deformation monitoring using corner reflectors is typically based on their signal-to-clutter ratio (SCR) [37; 38]. For targets such as corner reflectors, the complex echo signal from a resolution cell can be considered as the vector sum of the corner reflector's echo signal and other clutter signals. The greater the signal energy of the corner reflector, or the higher its energy ratio to clutter, the smaller the resulting phase error. The relationship between SCR and phase error can be expressed using Formula (4) [37]:  
\[\sigma_{\phi p\approx}\frac{1}{\sqrt{SCR}} \tag{4}\]  
This relationship can be converted to deformation error based on wavelength:  
\[d_{\phi p}=\frac{\lambda}{4\pi}*\sigma_{\phi p} \tag{5}\]  
It can be observed that with the same accuracy requirements, sensors with longer wavelengths demand a higher SCR. For instance, to achieve 1 mm monitoring accuracy, a C-band sensor requires an SCR of 10 dB. As shown in Figure 18, the CRs deployed in this study all exhibit SCR values around 20 dB, which can meet the requirements for high-precision monitoring. Following topography residual compensation in differential interferometric phases using GPS-measured corner reflector heights, significant atmospheric delays persist in certain differential interferograms, potentially distorting deformation measurements. This study adopts the same strategy as PS-InSAR, performing large-scale spatial filtering on unwrapped phases to remove these spatially correlated low-frequency atmospheric phase components. Figure 19 provides a comparative visualization of differential interferograms (master, 20250319; slave, 20250331) before and after atmospheric phase correction.