GB/T 20148-2006 in English

《GB/T 20148-2006日光的空间分布 CIE一般标准天空》由TC224（全国照明电器标准化技术委员会）归口，TC224SC4（全国照明电器标准化技术委员会照明基础分会）执行，主管部门为中国轻工业联合会。
本标准规定了一组从理论和实际应用上均与太阳光和天棚照明有联系的室外日光条件。 所给定的亮度分布具有下述特性： i)它们都对称于太阳子午线，并且均为太阳和天顶之间的角距离ZS的函数。 ii)它们被定义为平滑连续的函数。 iii)天空中任一点的相对亮度取决于该天空的面与太阳之间的角度x以及该天空面与天顶之间的角度Z。

Scope

This standard specifies a set of outdoor daylight conditions that are theoretically and practically related to sunlight and ceiling lighting. The given luminance distributions have the following characteristics: 1) They are all symmetrical about the solar meridian and are a function of the angular distance Z_S between the sun and the zenith. 2) They are defined as smooth continuous functions. This distribution of brightness is typical of a clear sky, characterized by clouds that are monochromatic. They provide an approximation of a patchy cloudy sky that is accurate enough for many practical daylight calculations. 3) The relative brightness of any point in the sky depends on the angle x between the bin of the sky and the sun and the angle Z between the bin of the sky and the zenith. This relative brightness is given by two functions: the relative scattering characteristic curve f(x) and the brightness hue Φ(Z) between the viewing distance and the zenith.