Solar radiation over the urban texture: LIDAR data and image processing techniques for environmental analysis at city scale

A complete methodology from the extraction of Light Detection and Ranging (LIDAR) data to the environmental analysis of urban models and the visualization of results is presented. Aim of the work is to establish a process to investigate digital urban models integrating cross-disciplinary competences, like remote sensing, GIS, image processing and urban and environmental studies. Toward this goal, working on several interfaces, tools and datasets was necessary to provide a consequent structure to the introduced methodology. Case study for application was a squared area 300 metres wide in central Geneva where LIDAR data are available. The use of a hybrid ap-proach from raw LIDAR data and vectorial digital maps (GIS data) of buildings footprints for the interpolation of a 2.5-D urban surface model, with a resolution grid of 0.50 by 0.50 metres, allowed to refine vertical surfaces of buildings and to process facades and roofs separately. This step reveals itself as fundamental for processing the environmental analysis of the urban texture. In particular, the implemented tool calculates solar radiation and solar accessibility on urban surfaces, in order to investigate the energy-performance of cities