## 3 Data and Methods
### Methods
#### 3.2.2 Errors Analysis  
In space, satellite imaging faces challenges such as space debris, solar wind, and various types of radiation, which can change satellite flight orbits and imaging attitudes, eventually leading to errors in the offset field obtained by SPC. These errors are usually not  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Pair No.** & **Acquisition Dates of Image Pairs** & **Track Num.** \\  & **Master Scene–Slave Scene** & **Track Num.** \\ \hline
1 & & 1155 512 \\
2 & 21/04/2019–29/06/2019 & 1155 513 \\
3 & 21/04/2019–29/06/2019 & 1155 612 \\
4 & & 1155 613 \\ \hline
5 & & 1155 512 \\
6 & 07/09/2019–21/09/2019 & 1155 513 \\
7 & 1155 612 \\
8 & & 1155 613 \\ \hline \hline \end{tabular}
\end{table}
Table 2: RapidEye data information.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Acquisition Dates of** & **Track** & \multicolumn{4}{c}{**RMSE in E-W Direction (m)**} & \multicolumn{4}{c}{**RMSE in N-S Direction (m)**} \\
**Image Pairs** & **Nam.** & **Band 1** & **Band 2** & **Band 3** & **Band 4** & **Band 5** & **Band 1** & **Band 2** & **Band 3** & **Band 4** & **Band 5** \\ \hline  & 1155 512 & 0.812 & 0.693 & 0.799 & 0.890 & 0.712 & 0.836 & 0.699 & 0.803 & 0.867 & 0.769 \\
21/04/2019–29/06/2019 & 1155 513 & 0.949 & 0.746 & 0.899 & 0.892 & 0.813 & 0.898 & 0.664 & 0.756 & 0.823 & 0.691 \\
29/06/2019 & 1155 612 & 0.935 & 0.779 & 0.871 & 0.989 & 0.733 & 0.922 & 0.700 & 0.806 & 0.881 & 0.641 \\
155 613 & 0.960 & 0.940 & 0.832 & 0.940 & 0.856 & 0.774 & 0.711 & 0.772 & 0.834 & 0.640 \\  & RMSE & 0.914 & 0.789 & 0.850 & 0.950 & **0.779** & _0.858_ & _0.694_ & _0.784_ & _0.851_ & _0.665_ \\  & 1155 512 & 0.686 & 0.598 & 0.634 & 0.746 & 0.597 & 0.821 & 0.638 & 0.625 & 0.710 & 0.531 \\
07/09/2019–1155 513 & 0.813 & 0.631 & 0.730 & 0.812 & 0.610 & 0.824 & 0.615 & 0.630 & 0.697 & 0.508 \\
21/09/2019 & 1155 612 & 0.893 & 0.667 & 0.666 & 0.731 & 0.676 & 1.001 & 0.714 & 0.656 & 0.698 & 0.600 \\  & 1155 613 & 0.976 & 0.726 & 0.781 & 0.802 & 0.714 & 0.950 & 0.660 & 0.632 & 0.651 & 0.543 \\  & RMSE & 0.842 & 0.656 & 0.703 & 0.773 & **0.649** & _0.899_ & _0.657_ & _0.636_ & _0.689_ & **0.546** \\ \hline \hline \end{tabular}
\end{table}
Table 3: RMSE of different bands for offset fields.  
fully presented in a single offset field, so this study examined four RapidEye image pairs acquired before and one pair after the earthquake to analyze the error of the initial offset fields in the E-W direction, the N-S direction, and the signal-to-noise ratio (SNR) obtained by COSI-Corr.  
RapidEye images containing fewer clouds before the event were selected for imaging groups (Table 4). COSI-Corr was utilized to acquire the offset field of these image pairs. The parameters of COSI-Corr software for all experiments and for the cross-correlation calculation are as follows: in the frequency domain, the initial sliding window is 64 \(\times\) 64 pixels, the final sliding window is 32 \(\times\) 32 pixels, and the sliding step size is 2 pixels (10 m). The iteration repeats two times, and the mask threshold is 0.9. See Figure 2.  
The offset fields obtained by SPC mainly contain decorrelated noise, orbital error, attitude jitter distortions, inter-satellite bias, and terrain shadow disturbances.