Towards building floor-level nighttime light exposure assessment using SDGSAT-1 GLI data

The profound impact of light pollution on both natural and human systems is well-recognized. Particularly, light pollution at the building scale is inextricably intertwined with human living and has garnered increasing attention in recent years. However, the coarse spatial resolution of nighttime light data, coupled with the inadequacy of existing methods, have precluded detailed investigation into the light pollution at building scale. The high-resolution Glimmer Imager (GLI) sensor onboard the SDGSAT-1 satellite provides nighttime light data with a 40-meter resolution, offering new opportunities for precise assessment of light pollution at the building scale. To this end, this study introduces a novel approach for calculating light exposure at the building floor-level using SDGSAT-1 GLI data. Two measures, Floor Light Exposure Index (FLEI) and Building Light Exposure Index (BLEI), are proposed to quantify the cumulative nighttime light radiation received at each floor and building, respectively, thereby facilitating the analysis of variances in light exposure across different buildings and floors. Utilizing this approach, we computed the floor-level light exposure for 57,221 buildings within three core districts—Yuexiu, Haizhu, and Tianhe—of Guangzhou city, China. The results, perhaps for the first time, quantified the level of light exposure at the building scale, revealing substantial differences in light exposure both inter-building and intra-building across various floors. Comparative analysis with field-collected data confirmed the robustness of our method and the reliability of the calculation results. We found that the light exposure is generally lower on lower floors, with a significant increase in light exposure above the 50th floor. Buildings in proximity to light sources and roads are more susceptible to light pollution, with light exposure in residential areas intensifying from the center to the periphery, and light exposure in commercial outskirts decreasing with increasing distance from the commercial center. The average FLEI in commercial zones is approximately 550 nW cm⁻² sr^-1 higher than that in residential areas. The approach and resultant building floor-level light exposure map generated by this study hold substantial promise in aiding the evaluation of various targets and indicators associated with multiple Sustainable Development Goals (SDGs) targets and indicators, including SDG 3 (Good Health and Well-being), SDG 11 (Sustainable Cities and Communities), and SDG 13 (Climate Action).