Influência da divisão do céu em cálculos de disponibilidade de luz a partir de imagens de grande alcance dinâmico

Abstract

Digital systems play an important role in sky measurements due to the evaluation possibilities they possess. Current equipments used for sky vault luminance measurements are programmed according to the International Commission on Illumination (in french, Commission Internationale de L’éclairage ”“ CIE) recommended sky division, useful for overcast skies, but when the sun is present the luminance values maybe incorrectly interpreted. High Dynamic Range (HDR) images do not show this kind of limitation and can be divided into any number of segments and zones. This paper investigates the influence of sky subdivision in luminance and illuminance calculations. The HDR values were divided using several segmentation methods, and calculations were compared to measurements made with illuminance meters. The results suggest that larger subdivisions deal better with the solar corona and may be useful to properly register the partly cloudy and clear sky conditions.