sky factor

sky factor

The ratio of the illumination on a horizontal plane at a given point inside a building due to the light received directly from the sky, to the illumination due to an unobstructed hemisphere of sky of uniform luminance equal to that of the visible sky.
References in periodicals archive ?
The observation points were also selected with regard to the sky factor and the presence of buildings, trees, and so forth and the proportion of the solid angle of components of greenery, water, and so forth comprising the solid angle of the total celestial sphere (hereafter, green cover ratio).
The sky factor was measured by a photograph of the sky taken 1.2 m above the ground at the observation point with a fisheye lens with an orthographical projection format (Nikon: OP Fisheye Nikkor 10 mm f/5.6) and a 35 mm digital SLR camera.