## 3 Results and Analysis
### Phenological Consistency between Remote Sensing and Ground Data
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Different Regions** & **Different Methods** & **R** & \(p\) & **RMSE** \\ \hline \multirow{6}{*}{Above 30\({}^{\circ}\)N} & Method 1 & 0.82 & 0.037 \({}^{\ast}\) & 7.61 \\  & Method 2 & 0.63 & 0.046 \({}^{\ast}\) & 10.97 \\  & Method 3 & 0.94 & 0.025 \({}^{\ast}\) & 4.35 \\  & Method 4 & 0.83 & 0.038 \({}^{\ast}\) & 6.56 \\  & Method 5 & 0.96 & 0.019 \({}^{\ast}\) & 7.11 \\ \hline \multirow{6}{*}{30\({}^{\circ}\)–45\({}^{\circ}\)N} & Method 1 & 0.58 & 0.053 & 9.28 \\  & Method 2 & 0.87 & 0.009 \({}^{\ast}\) & 3.75 \\  & Method 3 & 0.49 & 0.039 \({}^{\ast}\) & 8.52 \\  & Method 4 & 0.83 & 0.037 \({}^{\ast}\) & 4.43 \\  & Method 5 & 0.67 & 0.065 & 10.37 \\ \hline \multirow{6}{*}{45\({}^{\circ}\)–60\({}^{\circ}\)N} & Method 1 & 0.72 & 0.035 \({}^{\ast}\) & 9.16 \\  & Method 2 & 0.36 & 0.048 \({}^{\ast}\) & 10.72 \\ \cline{1-1}  & Method 3 & 0.81 & 0.023 \({}^{\ast}\) & 4.27 \\ \cline{1-1}  & Method 4 & 0.46 & 0.072 & 11.39 \\ \cline{1-1}  & Method 5 & 0.77 & 0.016 \({}^{\ast}\) & 6.14 \\ \hline \multirow{6}{*}{60\({}^{\circ}\)–75\({}^{\circ}\)N} & Method 1 & 0.51 & 0.031 \({}^{\ast}\) & 9.77 \\  & Method 2 & 0.64 & 0.044 \({}^{\ast}\) & 10.33 \\ \cline{1-1}  & Method 3 & 0.91 & 0.027 \({}^{\ast}\) & 6.54 \\ \cline{1-1}  & Method 4 & 0.72 & 0.062 & 8.66 \\ \cline{1-1}  & Method 5 & 0.86 & 0.036 \({}^{\ast}\) & 7.37 \\ \hline \hline \end{tabular} R represents the correlation coefficient of the SOS between remote sensing data and ground data. \(p\) represents the significant correlation of the two, and \({}^{\ast}\) indicates the significant level is 0.05 (\(p\)! 0.05), \({}^{\ast\ast}\) indicates the significant level is 0.01 (\(p\)! 0.01). RMSE represents the root mean square error, the higher the value, the worse the fitting degree between remote sensing data and ground data; on the contrary, the lower the value, the better the fitting degree between them.  
\end{table} 
Table 4: The consistency of the SOS between image data and ground data above 30\({}^{\circ}\)N. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Different Regions** & **Different Methods** & **R** & \(p\) & **RMSE** \\ \hline \multirow{6}{*}{Above 30\({}^{\circ}\)N} & Method 1 & 0.56 & 0.049 \({}^{\ast}\) & 11.30 \\  & Method 2 & 0.66 & 0.034 \({}^{\ast}\) & 10.95 \\ \cline{1-1}  & Method 3 & 0.80 & 0.045 \({}^{\ast}\) & 7.67 \\ \cline{1-1}  & Method 4 & 0.83 & 0.023 \({}^{\ast}\) & 7.49 \\ \cline{1-1}  & Method 5 & 0.74 & 0.032 \({}^{\ast}\) & 10.11 \\ \hline \multirow{6}{*}{30\({}^{\circ}\)–45\({}^{\circ}\)N} & Method 1 & 0.44 & 0.043 \({}^{\ast}\) & 9.66 \\ \cline{1-1}  & Method 2 & 0.39 & 0.051 & 9.35 \\ \cline{1-1}  & Method 3 & 0.69 & 0.041 \({}^{\ast}\) & 8.33 \\ \cline{1-1}  & Method 4 & 0.73 & 0.033 \({}^{\ast}\) & 8.02 \\ \cline{1-1}  & Method 5 & 0.57 & 0.072 & 10.11 \\ \hline \multirow{6}{*}{45\({}^{\circ}\)–60\({}^{\circ}\)N} & Method 1 & 0.27 & 0.073 & 11.65 \\ \cline{1-1}  & Method 2 & 0.54 & 0.068 & 9.54 \\ \cline{1-1}  & Method 3 & 0.41 & 0.046 \({}^{\ast}\) & 10.37 \\ \cline{1-1}  & Method 4 & 0.73 & 0.023 \({}^{\ast}\) & 5.36 \\ \cline{1-1}  & Method 5 & 0.56 & 0.066 & 9.29 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The consistency of the EOS between image data and ground data above 30\({}^{\circ}\)N.