## 2 Study Area and Data Sources
### Data and Processing  
This study used ALOS-2 high-precision, full-polarization pattern (HH + VH + VV + HV) data. The imaging period was 27 May 2015; the product level was 1.1, range and single look azimuth compressed data is represented by complex I and Q channels to reserve the magnitude and phase information. In the case of ScanSAR mode, an image file is generated per each scan. The observation direction was right view, the track direction was ascending, the data format was Committee on Earth Observation Satellites (CEOS), the pixel spacing of range) was 2.861 m, and the pixel spacing of azimuth was 3.112 m. Furthermore, we used two-phase OLI data of different cloud coverage in order to perform the LCC test (LC81280392015173 LGN00 and LC8128039 2015189 LGN00); the imaging period was from 22 June 2015 to 8 July 2015, the cloudiness was 8.43% and 26.28%, respectively. The parameters of both ALOS 2 and Landsat 8 OLI images are listed in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Advanced Land Observing Satellite 2 (ALOS-2) SAR Data**} \\ \hline
**Acquisition Date** & **Mode** & **Orbit** & **Incidence angle** & **Fixel Spacing (m)** & **Polarization** \\ \hline
2015-03-27 & Ultra-Fine Descending & 8\({}^{\circ}\)–70\({}^{\circ}\) & 2.861 \(\times\) 3.112 & HH/VH/VV/HV \\ \hline \multicolumn{5}{c}{**Landsat 8 Operational Land Imager (OLI) Data**} \\ \hline
**Acquisition Date** & **Path** & **Row** & **Resolution (m)** & **Bands** & **Cloud Cover (\%)** \\ \hline
2015-06-22 & 126 & 40 & 30 \(\times\) 30 & 1–5, 7 & 8.43\% \\
2015-07-08 & 126 & 40 & 30 \(\times\) 30 & 1–5, 7 & 26.28\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of Advanced Land Observing Satellite (ALOS) 2 and Landsat 8 operational land imager (OLI) images. Figure 1: Map of the cloudy mountainous study area and its location. Landsat 8 OLI images were provided by the United States Geological Survey (USGS), and the data were L1T level. The pre-processing included system radiation error correction, geometric rough correction, ground-control point geometry correction, and terrain correction using digital elevation model. After preprocessing, the radiation calibration was performed using the annual absolute radiation calibration coefficient of Landsat 8 OLI with ENVI (Exelis Visual Information Solutions) 5.3, following which the atmospheric correction was implemented using the fast line-of-sight atmospheric analysis of spectral hypercubes (FLAASH) module [22] with ENVI 5.3. The processing results are shown in Figure 2. The spatial resolution of the OLI images was 30 m \(\times\) 30 m and the projection was WGS_1984_UTM_Zone_33N. The pre-processing of ALOS-2 SAR data [23] included polarization filtering, polarization decomposition, and terrain correction. According to the characteristics of SAR data, [PERSON] [17] analyzed the effects of [PERSON] filtering, Kuan filtering, Frost filtering, local sigma filtering and gamma filtering processing. Based on the polarized SAR coherent filtering criteria, this study used the directional non-square window and minimum mean square error filtering algorithm proposed by [PERSON] et al., 2009. The filtering method avoids crosstalk between channels, and also maintains polarization information in a uniform region to the greatest extent. The boundary alignment windows maintain the sharpness of the image. Filtering can be performed in a sliding-window that the sizes were \(5\times 5\), \(7\times 7\), or \(9\times 9\). Figure 3 shows the comparison diagram of filtering effect, the filtering effect of \(5\times 5\) and \(7\times 7\) windows is equivalent, while large windows (i.e., \(7\times 7\), \(9\times 9\)) can better smooth the coherent spots, and small windows can better retain the texture information. This study chooses the refined Lee filter, the filter window uses \(5\times 5\), which can appropriately maintain the texture information.