The method of aperture meridians: a simple calculation tool for applying the ISO/CIE Standard General Sky

Abstract

Following the recent publication of the CIE Standard General Sky, 1 adopted as an ISO Standard, 2 an Application Guide is expected to be prepared by CIE Technical Committee 3-37 with the aim of explaining and simplifying its practical use. The advantage of the 15 Standard Sky Luminance Distributions (SSLD) adopted by CIE and ISO in relative terms normalized to zenith luminance is not only in the more versatile definition of skylight in various locales and daylight climate regions, but also in the possibility of simulating annual daylight profiles in absolute units based on typical luminance sky patterns. As well as complex computer programs for producing isoluminance contours in plan projections of the sky vault, a simpler tool is needed to calculate absolute sky luminance within the solid angle of arbitrarily dimensioned apertures, especially vertical windows. With this objective in mind, the Method of Aperture Meridians or MAM for any SSLD is introduced in this paper.