ABSTRACT: A boosting nighttime economy in modern metropolis leads to a large scale application of colorful facade display lighting, therefore forming complicated and excessive artificial light at night (ALAN) and causing light pollution. However, there is a lack of quantification metrics regarding to the spectral impacts on eco-environment, especially for scales near the ground. This study conducts a first ground-level hyperspectral imaging (HSI) measurement and quantitative evaluation on luminous building facades from an observer’s perspective. Based on the HSI data, the spectral compositions across regions using different lighting types were summarized, in which LEDs covered most of facade lighting types. We further derived the luminance and chromatic distribution maps of the regional facades, and performed a characteristic comparison. We further analyzed the potential biological effects and the features of spectral compositions corresponding to high- or low- impact. Results show that, first, using LEDs has drastically increased both the color gamut and intensity; second, spectra with narrow-band shapes, i.e. RGB LEDs, may well have higher photobiological effects than the others when matching species’ sensitive bands; third, chromatic information of lighting is highly correlated with spectral impacts and therefore has potential for characterization. In this study, we clarify the general spectral features in night-time metropolis, and build up an ecological impact-oriented spectral assessment framework in urban lighting. This work provides fresh insights and feasible measures for the administrations in ground-level urban lighting masterplan, and proposes a possible way of real-time ALAN evaluation from redundant spectra. This work may provide references for lighting policy-makers, help relieve energy consumptions and carbon emissions, and decrease light pollutions for metropolis.
 

Artificial light at night; Spectral quantification; Photobiological effect; Ecological environment