This document was prepared by International Commission on Illumination (CIE) Technical Committee 3-15, Spatial Distribution of Daylight, in cooperation with Technical Committee ISO/TC 274, Light and lighting.
This third edition cancels and replaces the second edition (ISO 15469:2004/CIE S 011:2003), which has been technically revised.
The luminance distribution of the sky depends on weather and climate, and it changes during the course of a day with the position of the sun. This standard lists a set of luminance distributions, which model the sky under a wide range of conditions, from the heavily overcast sky to cloudless weather. It is intended for two purposes:
- to be a universal basis for the classification of measured sky luminance distributions;
- to give a method for calculating sky luminance in daylighting design procedures.
The Standard defines relative luminance distributions: the luminance of the sky at any point is given as a function of the zenith luminance. For daylighting calculation purposes, it may be used with values of zenith luminance or of horizontal illuminance to obtain absolute luminance distributions.
The Standard incorporates both the CIE Standard Clear Sky and the CIE Standard Overcast Sky, which are treated as particular cases of the General Sky. The Overcast Sky is retained as a separate formula because there are many calculation procedures that embody the mathematical formulation of this particular distribution.
This DIS is not available for purchase. It is only available from National Committees (NCs) and Associate National Committees (ANCs) of the CIE for the purpose of commenting. Please approach your NC or ANC to request a copy of the DIS for the purpose of commenting. It is left to the discretion of the NCs and ANCs to follow-up on such a request.