Lighting characteristics of public space in urban functional areas based on SDGSAT-1 glimmer imagery:A case study in Beijing, China

The artificial light sources in urban areas constitute the primary source of stable nighttime illumination, which can be utilized to reflect the nighttime human activity and the conditions of public space lighting. The previous studies have focused on the evaluation of lighting environments in specific scenarios and the public's perception of these lighting environments. There has been limited analysis of the characteristics of public space lighting and its influencing factors in detail across different urban functional areas. This study primarily utilizes high-resolution SDGSAT-1 glimmer imagery and data from field measurements of lighting attributes to analyze the characteristics of public space lighting and its influencing factors in various urban functional areas. Furthermore, it establishes a quantitative relationship between measured illuminance and glimmer imagery to assess public space lighting levels. The results show that: (1) Various urban functional areas exhibit different illuminance levels, but they all maintain good illuminance uniformity. Additionally, to reduce the impact of the blue light spectrum on public visual perception, urban public space lighting primarily utilizes warm color temperatures with low color rendering properties. However, nighttime public space lighting cannot always achieve a balance between public comfort and high color rendering; (2) In the main urban area of Beijing, 98.5% of illuminance values fall within the range of 0 to 35 lx, indicating that most areas have good public lighting conditions. However, cases of over-illumination are also observed; (3) The building height has a positive correlation with public space lighting, while vegetation density exhibits a negative correlation. This study explored the characteristics of public space lighting in different urban functional areas and conducted a large-scale analysis of urban public lighting conditions using high-resolution nighttime images, providing evidence for the design and optimization of public space lighting in cities and better serving urban sustainable development, and contributing to the achievement of UN Sustainable Development Goal 11.7: By 2030, provide universal access to safe, inclusive, accessible, green and sustainable public spaces, particularly for women, children, older persons and persons with disabilities.