Applications of Fisheye Imagery in Urban Environment: A Case Based Study in Nanjing

Abstract

Urban greening helps cooling and humidifying the air; shading provided by buildings also affects outdoor thermal environment. Therefore, they both influence the thermal perceptions of people in outdoor spaces. The sky view factor (SVF) is a commonly used parameter in the research on urban climate, indicates the relationship between the visible area of the sky and the area covered by urban structures. The current paper first gives a brief introduction of the SVF and fisheye imagery. It then describes a method conducted to estimate SVF for urban environment analysis by using fisheye lenses and applying the ENVI platform as well. Finally, micro-climate characteristics over three typical urban underlying surfaces, including sunlit asphalt roads, shaded roads by building and by chinars were analyzed based on on-site observations. For a high-density city such as Nanjing, the present study reveals that the higher building shaded, chinar canopy density, and the lower sky transmittance, humidification and cooling of the air is more significant under the same climate condition and the same road. For benefiting urban environmental planning and assessment in high-density cities, more cases simulation with different combinations of factors are needed, which can provide a set of better greening guides and the optimal shading level.