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Continuous sky view factor from high resolution urban digital elevation models

Journal article
Authors Fredrik Lindberg
C.S.B. Grimmond
Published in Climate Research
Volume 42
Issue 3
Pages 177-183
ISSN 1616-1572
Publication year 2010
Published at
Pages 177-183
Language en
Keywords Urban climate, Urban geometry, Urban surface parameters, Geographical Information Systems, Sky view factor, London
Subject categories Climate Research

Abstract

This paper presents a new method to calculate sky view factors (SVFs) from high resolution urban digital elevation models using a shadow casting algorithm. By utilizing weighted annuli to derive SVF from hemispherical images, the distance light source positions can be predefined and uniformly spread over the whole hemisphere, whereas another method applies a random set of light source positions with a cosine-weighted distribution of sun altitude angles. The 2 methods have similar results based on a large number of SVF images. However, when comparing variations at pixel level between an image generated using the new method presented in this paper with the image from the random method, anisotropic patterns occur. The absolute mean difference between the 2 methods is 0.002 ranging up to 0.040. The maximum difference can be as much as 0.122. Since SVF is a geometrically derived parameter, the anisotropic errors created by the random method must be considered as significant.

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