International Organization for Standardization (ISO)
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ISO 15469:2004
Scope
This Standard defines a set of outdoor daylight conditions linking sunlight and skylight for
theoretical and practical purposes.
The luminance distributions given have the following characteristics:
i. They are symmetrical about the solar meridian and are functions of the angular
distance, Zs, between the sun and the zenith.
ii. They are defined by smooth continuous functions. Such distributions are typical of
cloudless skies and of those where the cloud cover is homogeneous. They provide an
approximation to skies of broken cloud that is sufficiently accurate for many practical
daylight calculation purposes.
iii. The relative luminance at any point in the sky depends on the angle, , between that
sky element and the sun, and on the angle, Z, between the sky element and the
zenith. It is given in terms of two functions: the relative scattering indicatrix, f(), and
the luminance gradation between horizon and zenith, (Z).
ISO 15469:2004 history
2004ISO 15469:2004 Spatial distribution of daylight - CIE standard general sky
1997ISO 15469:1997 Spatial distribution of daylight - CIE standard overcast sky and clear sky