## 2 Materials and Methods
### Satellite Image Preprocessing
#### 2.3.2 RADARSAT-2  
Four polarization RADARSAT-2 fine quad-pol single-look complex (SLC) images were obtained from March-May 2014. The specific information of RADARSAT-2 is also shown in Table 3. The detailed scene ID, acquisition time, illumination conditions, and absolute orbit for each scene are given \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Huanjing-1A/B** & & & & & \\ \hline \multirow{2}{*}{**Date**} & \multirow{2}{*}{**Scene ID**} & \multirow{2}{*}{**Acquisition Time (GMT)**} & \multicolumn{3}{c}{**Illumination (\({}^{\circ}\))**} & \multirow{2}{*}{**Path**} & \multirow{2}{*}{**Row**} \\ \cline{5-6}  & & & **Sun Zenith** & & & \\ \hline
4 March 2014(tillering) & 1182664 & 02:45:12.03 & 38.679 & 317.856 & 15 & 72 \\
7 April 2014(jointing) & 1190156 & 02:22:15.49 & 47.867 & 300.079 & 7 & 76 \\
29 April 2014(anthesis) & 1200272 & 02:39:02.22 & 54.754 & 297.400 & 12 & 72 \\
20 May 2014(filling) & 1208502 & 02:30:07.89 & 56.114 & 283.492 & 8 & 76 \\ \hline
**RADARSAT-2** & & & & & \\ \hline \multirow{2}{*}{**Date**} & \multirow{2}{*}{**Scene ID**} & \multirow{2}{*}{**Acquisition Time (GMT)**} & \multicolumn{3}{c}{**Illumination (\({}^{\circ}\))**} & \multirow{2}{*}{**Absolute Orbit**} \\ \cline{5-6}  & & & **Incidence Angle** & & & \\ \hline
5 March 2014 (tillering) & 313491 & 10:41:46.789 & 27.778 & 349.708 & 32483.0936 \\
29 March 2014 (jointing) & 317448 & 10:41:47.153 & 27.777 & 349.710 & 32826.0936 \\
22 April 2014 (anthesis) & 321564 & 10:41:47.289 & 27.773 & 349.709 & 33169.0936 \\
16 May 2014 (filling) & 325928 & 10:41:47.413 & 27.781 & 349.712 & 33512.0936 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Detailed information of the acquired Huanjing-1 A/B and RADARSAT-2 satellite images. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**HJ-1 A/B** & & & \\ \hline
**Spectral Region (\(\mu\)m)** & **Spatial Resolution (m)** & **Orbit Altitude (km)** & **Swath (km)** \\ \hline B1: 0.43–0.52 & & & \\ B2: 0.52–0.60 & & & \\ B3: 0.63–0.69 & & & \\ B4: 0.76–0.90 & & & \\ \hline
**RADARSAT-2** & & & \\ \hline
**Imaging Mode** & **Center Frequency** & **Spatial Resolution (m)** & **Mean incidence Angle (\({}^{\circ}\))** & **Orbit Direction** & **Beam Mode** \(\times\)**Azimuth (m)** \\ \hline Fine quad-polarization & 5.405 GHz & & & \\ (HH, HV, VH, VV) & (C-band) & 8 & 37 & Ascend & FQ18 & \(5.2\times 7.2\) \\ \hline
**Note:** HH, the normalized radar cross-section (NRCS) measured from the horizontally transmitted and horizontally received signal; VV, the NRCS measured from the vertically transmitted and vertically received signal; HV and VH, the vertically transmitted and horizontally received signal. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Detailed information regarding the HJ-1 A/B and RADARSAT-2 satellite images used in the study. in Table 4. The Radarsat-2 images were processed using PolSARPro version 5.0 (from the European Space Agency) and Alaska Satellite Facility (ASF) Mapready version 3.1. The following specific processing steps were conducted. (1) The Radarsat-2 SLC images were radiometrically calibrated to obtain the linear radar backscattering coefficients (\(\mathrm{\SIUnitSymbolDegree}\)) transformed from the digital number (DN) [38,39] using a look-up table in the product file. (2) A 5 \(\times\) 5 boxcar filter was used to multi-look and filter for suppressing speckle. (3) The filtered Radarsat-2 images were formed into a scattering matrix (S2), which was then converted to a symmetrized 3 \(\times\) 3 covariance matrix (C3), which averages the cross-pol backscatter to a single cross-pol value [40,41]. (4) The dataset was ortho-rectified using digital elevation model (DEM)-simulation and registration.