Voxel-based leaf area estimation from three-dimensional plant images

Leaf area is one of the most important elements of information in plant management. Leaf area is associated with many agronomic and physiological processes including growth, photosynthesis, transpiration, photon interception, and energy balance. Three-dimensional ( 3D ) plant architecture is required for monitoring, since plants have three-dimensionally complex structures. A photogrammetric approach called structure from motion ( SfM ) was used for the 3D measurement. A method using the total area of a horizontal face of voxels could possibly be employed to estimate leaf area in 3D plant images. However, the leaf inclination angle of each small part, the voxel size, and misconfigured voxels in a vertical direction near leaf surfaces should be considered in the calculation. We propose a method for leaf area estimation in voxel-based models that overcomes these problems of estimation error. Using our method, the leaf area was estimated with an absolute error of 8.87 % . This result was obtained by fully utilising 3D information such as voxel size and leaf inclination angle at each voxel. Moreover, our method does not involve manual operations for its construction, unlike a previous method. From the perspectives of high degrees of accuracy and automatic procedures, this voxel-based leaf area calculation method is advantageous.