Assessment of urban tree shade using fused LIDAR and high spatial resolution imagery

Advancements in high spatial resolution remote sensing technologies including multispectral satellite (Quickbird, IKONOS) and active airborne sensors (LIDAR - Light Detection and Ranging) are enabling detailed analysis of physical features across the urban environment. Often these datasets have been applied in isolation, however by fusing these technologies significant added benefit can be gained. Specifically, LIDAR data enables highly accurate extraction of three dimensional urban structures such as buildings, trees, and the underlying terrain; while multispectral data can provide accurate estimates of surface cover type. In this paper we present a technique to model and map seasonal solar radiation effects related to urban trees by integrating structural and spectral data. Results indicate that across the study area (The District of North Vancouver) trees reduce incoming potential solar radiation in summer by 4.38 MJm^-2day^-1 (24%) and in winter by 0.28 MJm^-2day^-1 (13%). In addition, solar radiation is decreased by 0.2 MJm^-2day^-1 (11%) in winter when deciduous tree species are removed. Finally, solar radiation is summarized by urban land use and results suggest that radiation in developed regions is most affected by tree shading in single-family residential areas (3.5 MJm^-2day^-1) and least affected in commercial areas (1.22 MJm^-2day^-1).