Enhancing 3Dskyview extension performance: a multi-observer determination of Sky View Factors

Abstract

This paper presents a second version of the 3DSkyView extension. The purpose of that extension was to develop a calculation algorithm for assessment and visualization of sky view factors (SVF), by means of tools available in a Geographical Information System (GIS). The sky view factor is a thermal and geometric parameter pointed out in the specialized literature as one of the main causes of urban heat islands. A 3D-GIS is a powerful tool for reaching the goal of this research because it allows the storage, treatment and analysis of tri-dimensional urban data, in addition to a high level of flexibility for incorporating calculation algorithms. The objective in the 3DSkyView extension is to optimize the determination of that factor, not only reducing its demanding calculation and graphical representation time, but also generating a simplified tool for replacing expensive photographic equipment usually applied on this matter. Enhancing functions of ArcView GIS 3.2, the first version of that extension showed a very good performance allowing the automatic delineation and determination of SVF. That performance was although limited for a single observer point. The simulation of SVF for several view points in urban canyons was only possible by applying the extension as many times as the number of observers needed. Therefore, this second version was here developed in order to allow simultaneous determination of SVF for many view points. In addition, the 3DSkyView new interface is more flexible, in a way that the user may choose the kind of output he wants (graphical or tabular). With this new feature it is then easier to create a continuous SVF map for an entire area.