Voxel-based Volume Modelling of Individual Trees Using Terrestrial Laser Scanners

Accurate modelling of individual trees is essential for forestry applications e.g. forestry inventory and biomass estimation. This paper aims to utilise Terrestrial Laser Scanners (TLS) in order to derive a three dimensional (3D) tree structure and compute its volume. A new approach is proposed and tested to estimate the tree structure and leaf area using precise voxel-based tree models. In this study, four different types of trees were chosen from Centennial Park, Sydney, and the corresponding TLS data was obtained and co-registered. The 3D information from the TLS data was reproduced in terms of voxel attributes in the 3D voxel arrays and the K-Dimensional tree (KD-tree) algorithms were applied to the voxelisation of the point cloud data and the 3D visualization of trees. This voxel method has advantages for 3D modelling of trees over a pixel-based method as it can be used to render discontinuous surfaces and allows for the simultaneous representation of the trunk and branches as well as the foliage. The 3D visualisation of individual tree surfaces derived from the TLS testing was compared with 3D point cloud data obtained by Airborne Laser Scanning (ALS). These TLS results were processed with the KD-tree algorithms (raw data, 10 cm, 50 cm and 100 cm) acquired by the voxelisation of the tree trunk, branches and the total leaf volume which were then further compared with the ALS data. Key word: KD-tree algorithms, Voxelisation, 3D Modelling, forestry inventory, Terrestrial Laser Scanner (TLS), Airborne Laser Scanner (ALS)