Precise Urban Green Volume-Enabled Building and Environment Simulation: Sub-meter Voxel Modeling of Airborne and Hand-Held 3D Scans of Urban Trees

High-rise high-density cities around the world suffer from severe urban heat island effects. Greenery has the potential to heal urban microclimates, such as shading, lowered air temperatures, and increased humidity, apart from other benefits to urban health. Existing numerical simulation studies employing simplified, proxy greenery models have validated the potential at a macro level; However, the human-centric three-dimensional nature of greenery (e.g., tree crown volume, canopy density, and leaf area index) was ignored, leading to inaccurate results for buildings and blocks, especially in the high-rise high-density settings. This research proposes a precise voxel modeling of urban green volume for building and environment simulations. First, two scans, i.e., the airborne scan of tree canopies and hand-held LiDAR scan of lower parts, are registered and merged into a voxel model at 0.5-m resolution. Then, simulations and analysis of the voxelized green volume are conducted using Rhinoceros and Grasshopper. A preliminary experiment of shading on a university campus in Hong Kong proved the concept of this study. Future work will be directed to analysis of the voxel resolution and more types of simulations such as winds and urban thermal exposure.