# Estimating the Fractional Vegetation Cover from GLASS Leaf Area Index Product
## 4 Result Analysis
### Comparison with GEOV1 FCover Product
#### 4.1.1 Spatial Consistency
For the evergreen broadleaf forests, TRAGL and GEOV1 FCover values have distributions with a narrow peak, but the TRAGL frequency distribution peak (approximately 0.8) is slightly lower than that of GEOV1. Figure 2: Global mean FCover for TRAGL (**a**,**b**) and GEOV1 (**c**,**d**) products from 2001\(-\)2005. **Left panels**: January. **Right panels**: July. Areas masked in dark gray correspond to pixels where the FCover values are zero and areas masked in light gray correspond to pixels where the FCover values are missing. Figure 3: Histograms of the TRAGL and GEOVI FCover products for 2001–2005 for different biome types. Figure 4 shows mean values of the FCover differences for different 10\({}^{\circ}\)-latitude bands in each month for 2001-2005. In most latitude bands for each month, the mean FCover differences between TRAGL and GEOV1 FCover products are within \(\pm\)0.05, indicating that the TRAGL FCover values for these regions are in good agreement with the corresponding GEOV1 FCover values. However, there are slight discrepancies between them for low and high latitudes. The TRAGL FCover values were smaller than those of GEOV1 over the 5\({}^{\circ}\)N-15\({}^{\circ}\)N latitude band from July to October, and the 5\({}^{\circ}\)S-15\({}^{\circ}\)S latitude band from January to April. The mean values of the FCover differences over these regions reach 0.14. The TRAGL FCover values were also smaller than those of GEOV1 over the 65\({}^{\circ}\)N-75\({}^{\circ}\)N latitude band, especially in October. However, the TRAGL FCover values were larger than those of GEOV1 over the 55\({}^{\circ}\)N-65\({}^{\circ}\)N latitude band in February and April and the 65\({}^{\circ}\)S-75\({}^{\circ}\)S latitude band, especially in May and August. Figure 5 shows mean values of TRAGL and GEOV1 FCover products for different biome types in each month for 2001-2005. The standard deviations and the relative differences [100\(\times\) 1 FCoverTRAGL-FCoverGEOV1 / FCoverTRAGL] for the mean values are also shown in Figure 5. The numbers of pixels to calculate the mean values and standard deviations across different biomes for each month are shown in Table 3. The largest relative differences between TRAGL and GEOV1 FCover products occur for grasses/cereal crops and savannah, where the TRAGL FCover values were always lower than the GEOV1 FCover values in all months. For the grasses/cereal crops, the TRAGL FCover values were between 15% and 35% lower than the GEOV1 FCover values, whereas for the savannah, the TRAGL FCover values were between 20% and 30% lower than the GEOV1 FCover values. For shrubs, there are large differences between the TRAGL and GEOV1 FCover products from April to November, when the relative differences were more than 15% and the TRAGL and GEOV1 FCover values also show the largest standard deviation. There is an excellent agreement between TRAGL and GEOV1 FCover products for evergreen broadleaf forests in all months, with maximum relative differences of only 3.75% in July. The TRAGL and GEOV1 FCover products also show an excellent agreement for evergreen needleleaf forests, where the relative differences are less than 5% for all months except March, November, and December. The largest differences for the  
Figure 4: Hovmoller diagram of mean values of the FCover differences between TRAGL and GEOV1 FCover products for different 10\({}^{\circ}\)-latitude bands in each month for 2001–2005. evergreen needleaf forests are observed in December, when the TRAGL FCover values were 27% lower than the GEOV1 FCover values. For deciduous broadleaf forest, small differences between the TRAGL and GEOV1 FCover products are observed from January to August, while the TRAGL FCover product achieves good agreement with the GEOV1 FCover product from September to December. The TRAGL FCover values are between 0.05 and 0.1 lower than those of GEOV1 from June to August, but the TRAGL FCover values are slightly higher than those of GEOV1 for the other months.