3D Skyview: a 3D GIS tool for urban canyon geometry and solar access

Abstract

This paper uses a 3D - GIS environment for simulating a spatial representation of urban canyons in place of many other high cost -equipment methods for determining Sky View Factors (SVF), allowing also the visualization of urban solar access by sunpaths simulation. The sky view factor is an estimation of the visible area of the sky from an earth viewpoint, being defined as the total amount of radiation received from a plane surface and that received from the whole radiant environment. In this way the sky area results fro m the limits of the urban canyon generated by urban elements, which is basically a result of a tri-dimensional environment. The tool here developed which is called 3D SkyView, aimed the substitution of a camera equipped with a 180º fisheye-lens by an algor ithm of calculation and visualization to be applied on a three-dimensional GIS. The 3D SkyView extension was generated in Avenuecomputational language, developed in ArcView 3.2 software, and used its 3D Analystextension. This first version of 3D SkyView calculates a new coordinate system for stereographic and equidistant projections of urban areas on a horizontal plan, and calculates SVF values for any observation point inside urban areas. In addition, the results create an environment suitable for sunpaths analysis and visualization of the whole scene desired in a fish-eye-lens 3D scene representation, as discussed in this paper.