Analysis and Correction of Trunk Effect for Fractional Vegetation Cover Measurement Using Digital Photography in Woodland

Fractional vegetation cover (FVC) is of great significance to vegetation-related research, and FVC ground measurement is of irreplaceable importance. Among them, the digital photography method is more commonly used. The photograph is a perspective (central) projection that causes the trunk appear in the photograph, resulting in an error in the measurement of FVC. Based on the three-dimensional reconstruction, this study proposed a method to correct the influence of tree trunks in FVC ground-based measurement. The experimental results show that the absolute error due to the trunk effect ranged from 0.31% to 5.87% under the experimental conditions of this study, and the error can be significantly reduced to within 0.5% after correction. How to promote the quality and efficiency of 3D reconstruction and extraction of trunk points in this method is a research direction that needs to be further explored.