Quickly determining grassland cover using the digital image

The improving efficiency and accuracy of vegetation cover is very important because the cover is a necessary parameter to estimate the health of grassland ecosystem. This study proposed a quickly calculating vegetation cover method by Excess Green Index and semiautomatic threshold (ST). Efficiency of the algorithm was evaluated by comparing with Maximumlikelihood supervised classification (MC) and HueSaturation method (HS). 32 digital images were used to test the efficiency of three methods. Vegetation cover estimated by each method was regressed with accurate cover obtained by visual interpretation via slope, intercept, and regression coefficient. The three methods did not consider nongreen component of vegetation, resulting in slightly underrating problem. In conclusion, ST not only achieved similar accuracy with MC but also avoided overrating problem of MC when cover was low. ST showed little human intervention, and achieved accurate cover; however, it failed to extract greygreen vegetation.