## 3 Materials and Methods  
The performance and compatibility of the GEO Grid ASTER EVI products with MODIS EVI were assessed over a subset of the FLUXNET validation sites ([[http://www.fluxnet.ornl.gov/](http://www.fluxnet.ornl.gov/)]([http://www.fluxnet.ornl.gov/](http://www.fluxnet.ornl.gov/))) that covered a wide range of land cover conditions (Table 1, Figure 2). ASTER EVI products were generated for these sites and their surrounding areas for the summer of 2007 or 2008 using the ASTER Grid system described in Section 2. MODIS L1B calibrated TOA reflectance data (MOD02 HKM) acquired over these areas simultaneously with ASTER were retrieved from the GEO Grid system and processed into atmospherically corrected EVI images using the same ASTER Grid algorithm, but adjusted for MODIS spectral bands. \begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Site Name**} & \multicolumn{2}{l}{**Longitude, Latitude**} & \multirow{2}{*}{**Land Cover Type 1**} & \multirow{2}{*}{**Image**} \\  & & **[Decimal Degrees]** & & & **Acquisition Date** \\ \hline
1 & Niwot Ridge, CO, USA & N40.033, W105.546 & Evergreen Needle-leaf forest & 2007.08.08 \\
2 & Sinop-Mato Grosso, Brazil & S11.412, W55.325 & Evergreen Broad-leaf forest & 2008.07.26 \\
3 & Yakutsk, Russia & N62.241, E129.651 & Deciduous Needle-leaf forest & 2008.06.02 \\
4 & Silas Little Experimental & N39.914, W74.596 & Deciduous Broad-leaf forest & 2007.06.09 \\
5 & Rosenount, MN, USA & N44.722, W93.089 & Croplands & 2007.06.20 \\
6 & South Denver, CO, USA & N39.659, W105.013 & Urban and built-up & 2007.09.25 \\
7 & Sonoran Desert, CA, USA & N33.817, W116.373 & Barren or sparsely vegetated & 2007.09.12 \\ \hline \hline \end{tabular}  
* These land cover types were obtained from the 2007 International Geosphere-Biosphere Programme (IGBP) land cover type information from the MODIS standard, 1 km yearly land cover product (MCD12Q1, Collection 5).  
\end{table} 
Table 1: FLUXNET sites used in ASTER and MODIS EVI compatibility analysis. Figure 2: FLUXNET sites used in ASTER and MODIS Enhanced Vegetation Index (EVI) compatibility analysis mapped on MODIS 2007 International Geosphere-Biosphere Programme (IGBP) land cover data (MCD12Q1, Collection 5). The numbers in this figure correspond to those in Table 1.  
All the ASTER and MODIS scenes were reprojected onto the same geographic projection with the nearest neighbor method. Six 3 km-by-3 km extraction widows were manually located on each of these reprojected ASTER-MODIS scene pairs. The 2007 International Geosphere-Biosphere Programme (IGBP) land cover information from the MODIS Land Cover product (MCD12Q1, Collection 5) were used to assure each of the extraction windows was of uniform land cover, whereas the reprojected ASTER images were used to ensure that each extraction window area was cloud- and cloud shadow-free (Figure 3). After the extraction, ASTER pixel reflectances were spatially aggregated into MODIS 500 m resolution with a square point spread function (PSF) (without MODIS PSF) and also with MODIS PSF [32]. For the former, we used the following equation;  
\[\bar{\rho}_{ASTER}=\frac{1}{n}\sum_{x}\sum_{y}\rho_{ASTER,15m}(x,y) \tag{9}\]  
whereas the following was used for the latter:  
\[\bar{\rho}_{ASTER}=\frac{\sum_{x}\sum_{y}PSF_{MODIS}(x,y)\rho_{ASTER,15m}(x,y)} {\sum_{x}\sum_{y}PSF_{MODIS}(x,y)} \tag{10}\]  
where \(x\) and \(y\) are the pixel and line numbers, respectively, within the extraction window, \(n\) is the number of extracted pixels (\(n=x\times y\)), \(\rho_{ASTER,15m}(x,y)\) is the 15 m ASTER reflectance pixel located at (\(x\), \(y\)), and \(PSF_{MODIS}(x,y)\) is the MODIS PSF weight at (\(x\), \(y\)). These aggregated, 500 m ASTER pixels and also the extracted MODIS 500 m pixels were averaged over a 2-by-2 moving window in order to reduce mis-registration errors between these two sensor data. This resulted in 9 ASTER-MODIS 1 km pixel pairs produced from each 3 km-by-3 km extraction window.