Analysing sky luminance scans and predicting frequent sky patterns in Singapore

A thorough analysis of sky distributions can help in the prediction of daylight patterns and thus provides a good understanding of architectural window and building envelope design. This paper introduces three methods of analysis for sky distributions, namely the relative indicatrix and gradation classification, and two other independent methods established by Kittler and Tregenza. All these three methods were verified for their feasibility for analysing the extreme daylight conditions in Singapore, which is located at the equator. The most suitable approach, from Tregenza, was eventually adopted in analysing the measured data from Singapore IDMP station. The prediction of frequent sky patterns in Singapore was based on the CIE Standard General Skies, as well as a complete version considering all 36 theoretical sky types.