# Uncertainty Analysis of Multisource Land Cover Products in China
## 3 Results
### Spatial Uncertainty
between VCF products and these two products in the North China Plain was 10-20%. The percentage of various pixels varied with the resolution, as shown in Figure 3b. In general, the uncertainty between products decreased as the resolution decreased. As the resolution decreased from 0.1 to 0.3\({}^{\circ}\), pixels with high uncertainty were reduced by 2.6% on average, and pixels with low uncertainty increased by 10%. Pixels with a difference greater than 0.2 decreased by 7.8% as the resolution decreased. According to the histogram of the pixel difference, the two products of CCI-MODIS had the fewest high-uncertainty pixels (13%), and the consistency was strong, while the two products of VCF-MODIS had the highest uncertainty pixels (18%), and the consistency was the worst. In general, the consistency of nontree vegetation cover was worse than that of forest cover since the classification system of nontree vegetation was quite different. The spatial consistency of the three products in the study area was strong, but there were significant differences in local areas. The consistency of plains and basins was better than that of mountains and hills; the consistency of northern China was bett  
Figure 3: The spatial difference in nontree vegetation coverage among the three products. Panel (**a**) shows the resolution and spatial difference between products, “CCI\(-\)MODIS” represents the difference between the forest percentage of ESA CCI and MODIS products, the horizontal is the product consistency comparison, and the vertical is the consistency comparison of different resolutions. The darker the color, the greater the product difference. Panel (**b**) shows the PFT statistics and the percentage of various pixels with the change in resolution. regions; and the consistency of the inland areas was better than that of the coastal areas. In general, the uncertainty between products decreased as the resolution decreased. When the forest cover was studied, the semiquantitative ESA CCI product and qualitative VCF product had the least uncertainty. When the nontree vegetation cover was studied, the qualitative MODIS product and semiquantitative ESA CCI product had less uncertainty. This conclusion was the same as that obtained when discussing the area uncertainty. Since the new unified classification system had only three classes, more classes were worthy of investigating. We investigated the spatial uncertainty of the grass cover and crop cover. The products were divided into three groups with three resolutions, as shown in Figure 4. The spatial distribution of the grass and crop cover of the three products was relatively consistent but differed significantly in different regions. The North China Plain and Xinjiang Basin in China have good consistency, with a difference in the area of less than 10%. The Greater Khingan Mountains, Hengduan Mountains, and Yunnan-Guizhou Plateau had poor consistency and greater spatial uncertainty, with a difference in the area of more than 20%. The reason for this difference was the influence of mixed pixels in hilly areas. In general, the uncertainty between products decreased as the resolution decreased. Figure 4: Spatial difference in crop and grass coverage of the ESA CCI and MODIS products. The darker the color, the greater the product difference.