## 4 Results and Discussion
Figure 6 are ASTER NDVI and EVIs aggregated without MODIS PSF (Equation (9)) _vs._ those aggregated with MODIS PSF (Equation10), and the differences (\(D^{\prime}_{NDVI}\) and \(D^{\prime}_{EVI}\)) and relative errors (\(RD^{\prime}_{NDVI}\) and \(RD^{\prime}_{EVI}\)) plotted against ASTER NDVI and EVIs without MODIS PSF (Equations (16a-17b)). The slopes and intercepts of these relationships were nearly one and zero, respectively. NDVI values over croplands, deciduous needle-leaf forest, evergreen broad-leaf forest, and evergreen needle-leaf forest, were higher than EVI values, but NDVI differences and relative errors were almost same as those of EVIs. These results indicated that the aggregation method did not have any impacts on ASTER VI values for the extracted pixels in these selected land cover types. Table 2 compares RMSE values amongst ASTER NDVI and EVIs. In case of those aggregated without MODIS PSF, RMSE for \(EVI_{B}\), \(EVI_{P}\), and \(EVI_{C}\) were all the same (0.018). Aggregated ASTER EVIs with MODIS PSF also had the same RMSE values of 0.019. These RMSE values were slightly higher than those for EVIs aggregated with MODIS PSF, but the magnitudes of the differences can be considered negligible. RMSE for NDVI without MODIS PSF (0.046) and with MODIS PSF (0.046) were larger than those for ASTER EVIs with or without MODIS PSF. This was mainly caused by  
Figure 5: Same as Figure 4, but with ASTER reflectances aggregated with MODIS PSF. (**a**) ASTER NDVI _vs._ MODIS NDVI, (**b**) ASTER _EVI\({}_{B}\) vs._ MODIS EVI, (**c**) ASTER _EVI\({}_{P}\) vs._ MODIS EVI, (**d**) ASTER _EVI\({}_{C}\) vs._ MODIS EVI, (**e**) \(D_{NDVI}\) vs._ MODIS NDVI, (**f**) \(D_{EVI_{B}}\) vs._ MODIS EVI, (**g**) \(D_{EVI_{P}}\) _vs._ MODIS EVI, (**h**) \(D_{EVI_{C}}\) _vs._ MODIS EVI, (**i**) \(RD_{NDVI}\) _vs._ MODIS NDVI, (**j**) \(RD_{EVI_{B}}\) _vs._ MODIS EVI, (**k**) \(RD_{EVI_{P}}\) _vs._ MODIS EVI, (**l**) \(RD_{EVI_{C}}\) _vs._ MODIS EVI. NDVI values over evergreen needle-leaf forest. It could be said that it was difficult to have enough accuracy because reflectances over evergreen needle-leaf forest were lower than reflectances over other land cover types in ASTER NIR, MODIS red and NIR bands (Table 3). \begin{table}
\begin{tabular}{c c c c c} \hline  & _NDVI_ & _EVI\({}_{B}\)_ & _EVI\({}_{P}\)_ & _EVI\({}_{C}\)_ \\ \hline Aggregated without MODIS PSF & 0.046 & 0.018 & 0.018 & 0.018 \\ Aggregated with MODIS PSF & 0.046 & 0.019 & 0.019 & 0.019 \\ \hline \end{tabular}
\end{table} 
Table 2: RMSE of ASTER NDVI/EVIs against MODIS NDVI/EVI. Figure 6: Scatterplots of ASTER NDVI and EVI aggregated with _vs_. without MODIS square point spread function (PSF). (**a**) ASTER NDVI by aggregation method **without MODIS PSF _vs_. aggregation **with** MODIS PSF, (**b**) _EVI\({}_{B}\)_**without** MODIS PSF _vs_. aggregation **with** MODIS PSF, (**c**) _EVI\({}_{P}\)_**without** MODIS PSF _vs_. aggregation **with** MODIS PSF, (**d**) _EVI\({}_{C}\)_**without** MODIS PSF _vs_. aggregation **with** MODIS PSF, (**e**) ASTER NDVI **without** MODIS PSF _vs_. \(D^{\prime}_{NDIV}\), (**f**) ASTER _EVI\({}_{B}\)_**without** MODIS PSF _vs_. \(D^{\prime}_{EVI_{B}}\), (**g**) ASTER _EVI\({}_{P}\)_**without** MODIS PSF _vs_. \(D^{\prime}_{EVI_{P}}\), (**h**) ASTER _EVI\({}_{C}\)_**without** MODIS PSF _vs_. \(D^{\prime}_{EVI_{C}}\), (**i**) ASTER _NDVI without** MODIS PSF _vs_. \(RD^{\prime}_{NDIV}\), (**j**) ASTER _EVI\({}_{B}\)_**without** MODIS PSF _vs_. \(RD^{\prime}_{EVI_{B}}\), (**k**) ASTER _EVI\({}_{P}\)_**without** MODIS PSF _vs_. \(RD^{\prime}_{EVI_{P}}\), (**l**) ASTER _EVI\({}_{C}\)_**without** MODIS PSF _vs_. \(RD^{\prime}_{EVI_{C}}\).