## 5 Discussion  
### Comparison with Existing Method and Identified Limitations  
Constellation satellites, leveraging their multi-satellite imaging capabilities, offer high-frequency coverage of the earth's surface, providing redundancy and reliability compared to single-satellite systems. Even if one satellite malfunctions, others can continue working, ensuring the continuity and stability of data acquisition. Table 8 presents some common satellite constellations and their parameters. With similar spatial resolutions, RapidEye has a larger swath width compared to PlanetScope. SkySat and WorldView have sub-meter spatial resolution, but they have smaller imaging swath widths. Therefore, for large-scale disaster identification, it is necessary to consider the stitching of multi-scene images acquired at different times and under different conditions. Sentinel-2 holds an absolute advantage in imaging swath width, but its temporal resolution is relatively lower. In terms of swath width and spatial-temporal resolution, RapidEye imagery is a practical choice. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multirow{2}{*}{**GNSS Station**} & \multirow{2}{*}{\begin{tabular}{c} **GNSS** \\ **Observations (m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **RapidEye** \\ **before Error** \\ **Correction (m)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **RapidEye** \\ **after Error** \\ **Correction (m)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **\(|\Delta|\)** \\ **after Error** \\ **Correction (m)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **\(|\Delta|\)** \\ **after Error** \\ **Correction (m)** \\ \end{tabular} } \\ \hline \multirow{10}{*}{E-W} & P594\_G49 & 0.07 & \(-\)0.75 & 0.09 & 0.82 & 0.02 \\  & P595\_G49 & 0.52 & \(-\)0.36 & 0.30 & 0.87 & 0.22 \\  & TOWG\_G49 & \(-\)0.58 & 1.13 & \(-\)0.38 & 1.71 & 0.19 \\  & LGWD\_G49 & \(-\)0.16 & 0.81 & \(-\)0.11 & 0.97 & 0.05 \\  & Q0072 & \(-\)0.11 & 0.75 & \(-\)0.15 & 0.86 & 0.04 \\  & SRT & \(-\)0.25 & 1.58 & \(-\)0.16 & 1.83 & 0.09 \\  & CLC & 0.41 & 0.93 & 0.43 & 0.53 & 0.02 \\ \hline \multirow{10}{*}{N-S} & P594\_G49 & \(-\)0.12 & 1.72 & \(-\)0.10 & 1.85 & 0.02 \\  & P595\_G49 & \(-\)0.25 & \(-\)0.01 & \(-\)0.23 & 0.25 & 0.03 \\ \cline{1-1}  & TOWG\_G49 & 0.04 & \(-\)0.51 & 0.12 & 0.56 & 0.08 \\ \cline{1-1}  & LGWD\_G49 & 0.29 & \(-\)0.54 & 0.12 & 0.83 & 0.17 \\ \cline{1-1}  & Q0072 & 0.26 & \(-\)0.33 & 0.18 & 0.58 & 0.08 \\ \cline{1-1}  & SRT & 0.10 & \(-\)0.92 & 0.14 & 1.03 & 0.04 \\ \cline{1-1}  & CLC & \(-\)1.11 & \(-\)0.43 & \(-\)0.90 & 0.68 & 0.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison of the deformation obtained by SPC and GNSS. Figure 7: Comparison of the deformation value of Mw 7.1 obtained by SPC and GNSS. (Red dots represent GNSS station locations, purple pentagrams represent the foreshock epicenter, the red star represent the main shock epicenter, black arrows represents the GNSS observations, and red arrows represent the observations calculated from RapidEye imagery). The attitude jitter distortion in the offset fields obtained from RapidEye images exhibits a banded distribution. The traditional mean elimination method can effectively correct this error, but it has limitations when the attitude jitter distortion demonstrates a linear trend. The polynomial fitting method proposed in this study can accommodate errors exhibiting either constant characteristics or linear trends. As shown in Figure 3, when n = 1000, the error displays a significant linear trend in the E-W offset field. The region (n = 500-1500) was selected to validate the effectiveness of the proposed method. After removing the satellite attitude angle error using the traditional mean elimination method, the standard deviation was 1.153 m. By applying the proposed method, the standard deviation was reduced to 1.130 m.  
Furthermore, this study recognizes several limitations: (1) The SNR represents the noise level of each pixel.