## 3 Results and Discussion
### Discussion  
In the Denpasar area of Bali, the GPP measured by the ALOS/AVNIR-2 and Aster satellites is smaller than that from the MODIS MOD17 product. This difference is primarily an artifact of the larger spectral range of MODIS. For MODIS, the spectral range is 0.05 micrometers for the red band \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \multirow{3}{*}{Land use} & \multirow{3}{*}{
\begin{tabular}{c} Area \\ (Ha) \\ \end{tabular} } & \multicolumn{6}{c}{GPP (gC m\({}^{-2}\) yr\({}^{-1}\))} & \multicolumn{6}{c}{Total GPP (tC yr\({}^{-1}\))} \\ \cline{3-10}  & & \multicolumn{3}{c}{ALOS/AVNIR-2} & \multicolumn{3}{c}{Aster} & \multicolumn{3}{c}{ALOS/} & \multirow{3}{*}{Aster} \\ \cline{3-10}  & & \multicolumn{1}{c}{Max} & \multicolumn{1}{c}{Mean} & \multicolumn{1}{c}{Min} & \multicolumn{1}{c}{Max} & \multicolumn{1}{c}{Mean} & \multicolumn{1}{c}{Min} & \multicolumn{1}{c}{AVNIR-2} & \multicolumn{1}{c}{Aster} \\ \hline Settlement & 7,179.17 & 2,511.43 & 540.49 & 0.13 & 2,353.91 & 492.44 & 0.14 & 12,675.23 & 15,992.84 \\ Rice field & 2,616.34 & 2,586.18 & 1,030.08 & 0.13 & 2,371.86 & 1,020.65 & 0.14 & 20,254.15 & 22,571.65 \\ Forest (Mangrove) & 700.69 & 2,501.92 & 1,123.58 & 0.13 & 2,595.26 & 1,177.40 & 0.14 & 6,255.51 & 7,081.16 \\ Shrub & 81.10 & 2,427.54 & 882.11 & 0.13 & 2,305.14 & 794.37 & 0.14 & 469.55 & 460.96 \\ Perennial plant & 961.75 & 2,456.39 & 1,034.77 & 0.13 & 2,257.76 & 989.24 & 0.14 & 8,300.74 & 8,567.52 \\ Dry land & 263.26 & 2,414.05 & 893.46 & 0.13 & 2,261.80 & 830.61 & 0.14 & 1,888.87 & 1,930.72 \\ Bare land & 827.39 & 2,489.12 & 771.56 & 0.13 & 2,244.33 & 648.17 & 0.14 & 2,577.41 & 2,750.65 \\ \hline \end{tabular}
\end{table} 
Table 4: Total annual GPP for different types of land use in the ALOS/AVNIR-2 and Aster data. Figure 3: Annual GPP for different types of land use from ALOS/AVNIR-2 and Aster. Figure 2: Annual GPP distribution from two satellites: **(a)** ALOS/AVNIR-2 and **(b)** Aster. and 0.035 micrometers for the NIR band. Meanwhile, ALOS/AVNIR-2 has a spectral range of 0.08 micrometers in the red band and 0.13 micrometers in the NIR band, and Aster has a spectral range of 0.06 micrometers in the red band and 0.08 micrometers in the NIR band. The smaller spectral ranges of the ALOS/AVNIR-2 and Aster instruments increase the capability of these sensors to detect object on the surface. As spectral range decreases, the sensors lose the ability to map fine spectral features and to distinguish details [32]. The spectral range is directly related to both the material that is being identified by the sensor and the contrast between that material and the background materials [33]. The top-of-atmosphere (TOA) reflectance in band 4 of AVNIR-2 appears to be lower than the TOA reflectance from exogenous sensor bands centered at 860 nm. This trait can be explained by the significant water vapor and dioxygen absorption that occurs in this band [27]. This difference in TOA reflectance may be responsible for the different estimate of annual GPP from ALOS/AVNIR-2. Different values of GPP may also reflect differences in land use, which include differences in vegetation type, percent vegetation cover and dissemination. The measured vegetation index is related to the percent cover of vegetation in a given region [10,29]. Forests (magnroves) and rice fields are two types of land use that typically result in a higher mean GPP due to extensive and homogeneous vegetation cover. In contrast, areas dominated by settlements tend to have a higher maximum GPP but a lower mean GPP because the vegetation indices and GPP estimates of a given pixel are based on the average spectral value of that pixel. Denpasar is a unique city because it contains a \"holy area\" in the center of town that is characterized by extensive vegetation cover. The result is a high maximum GPP associated with settlement land use in Denpasar. Additional complication in the city comes from the fact that factories emitting CO\({}_{2}\) may be hidden beneath the same type of roof as found in residential areas.