# Error Source Analysis and Correction of GF-3 Polarimetric Data
## 1 Introduction
A more efficient and affordable method is needed for GF-3 polarimetric calibration mission. In this study, several assisted data with external reference calibrators, polarimetric calibration and correction of GF-3 data is efficiently performed during the in-orbit-test phase. The key point of \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Work Modes**} & \multirow{2}{*}{**Incidence Angle (\(\lx@overaccentset{{\circ}}{\text{\text{\text{\text{\text{ \text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\texttext{      }}}}}}}}}}}}} \text{}}\text{}\text{}}\text{)}\) & \multirow{2}{*}{**Resolution (m)**} & \multicolumn{2}{c}{**Imaging Bandwidth (km)**} & \multirow{2}{*}{**Polarization Mode**} \\ \cline{5-6}  & & & **Nominal** & & & & & & **Nominal** & **Size** \\ \hline
1 & Spotlight (SL) & 20–50 & \(1\times 1\) & 1 & 1.0–1.5 & 0.9–2.5 & 10\(\times\)10 & \
\begin{tabular}{c} 10 \(\times\) \\ 10 \\ \end{tabular} &
\begin{tabular}{c} Optional single \\ polarization \\ \end{tabular} \\ \hline
2 & Ultra-fine strip (UFS) & 20–50 & \(1\times 1\) & 3 & 3 & 2.5–5 & 30 & 30 &
\begin{tabular}{c} Optional single \\ polarization \\ \end{tabular} \\ \hline
3 & Fine strip I (FSI) & 19–50 & \(1\times 1\) & 5 & 5 & 4–6 & 50 & 50 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
4 & Fine strip II (PSII) & 19–50 & \(1\times 2\) & 10 & 10 & 8–12 & 100 & 95–110 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
5 & Standard strip (SS) & 17–50 & \(3\times 2\) & 25 & 25 & 15–30 & 130 & 95–150 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
6 & Narrow scan (NSC) & 17–50 & \(1\times 6\) & 50 & 50–60 & 30–60 & 300 & 300 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
7 & Wide scan (WSC) & 17–50 & \(1\times 8\) & 100 & 100 & 50–110 & 500 & 500 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
8 & Global (GLO) & 17–53 & 2 \(\times\) (2–4) & 500 & 500 & 350–700 & 650 & 650 &
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline
9 &
\begin{tabular}{c} Full Polarized Strip \\ 1 (QPSI) \\ \end{tabular} & 20–41 & \(1\times 1\) & 8 & 8 & 6–9 & 30 & 20–35 & full polarization \\ \hline
10 &
\begin{tabular}{c} Full Polarized Strip \\ II (QPSII) \\ \end{tabular} & 20–38 & \(3\times 2\) & 25 & 25 & 15–30 & 40 & 35–50 & full polarization \\ \hline
\begin{tabular}{c} Optional dual \\ polarization \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 1: Observation patterns of the GaoFen-3 (GF-3) satellite. this correction process is that error parameters that must be calibrated by the external calibration are reduced by the establishment of error model and influence analysis of error sources for GF-3 polarimetric system, especially including the analysis of the error component of the antenna part. The organization of this study is as follows. In Section 2, the full-link error model of polarization observation is given. Then, Section 3 introduces every error source in the error model and comprehensively analyzes their influence on the GF-3 polarization observation. Based on this, the correction method of GF-3 polarimetric data is proposed in Section 4, and the point-target method and the distributed-target method are used to assess the quality of the corrected data. The evaluation results show that the polarimetric correction method is effective and that the quality of corrected PolSAR data satisfies requirements of GF-3 polarimetric performance. Discussion and conclusions are drawn in Sections 5 and 6, respectively.