Citrus canopy volume estimation using UAV oblique photography

Abstract: The canopy volume estimation method based on UAV oblique photography combined with pointed cloud processing technology was proposed in this study.  Navel orange trees with irregular crown and landscape trees with regular crown were used as research objects in the experiment.  Based on the multi-angle aerial images acquired by oblique photography with a low-cost four-rotor UAV, the three-dimensional point cloud and True Digital Ortho Map (TDOM) of the target area were generated after 3D reconstruction.  Then, processing and classification were taken successively to obtain the Canopy Height Model (CHM) of individual tree.  The cone sum algorithm, the convex-hull algorithm and the trapezoid segmentation algorithm were employed to estimate crown volume of individual tree.  For orange trees, the R 2  between the cone volume sum algorithm and manual volume measurement was 0.63 of orange trees, and it is higher than that by the other two algorithms.  For the landscape tree, the convex-hull algorithm did best, and the R 2 was 0.89.  The results show that UAV oblique photography technology could be used to extract the individual canopy parameters of citrus orchard and to meet the requirements of large-scale and low-cost orchard management. Keywords: canopy volume estimation, oblique photography, Unmanned Aerial Vehicles (UAV), Canopy Height Model (CHM), point cloud DOI:  10.33440/j.ijpaa.20210401.157 Citation: Wang T, Li J C, Lin H, Deng L, Zheng Y Q, Yi S L, Xie R J, Lyu Q.  Citrus canopy volume estimation using UAV oblique photography.  Int J Precis Agric Aviat, 2021; 4(1): 22–28.