Nighttime Satellite Data Illuminates Urban Development of China's Mega-Cities

Researchers at the Aerospace Information Research Institute (AIR), Chinese Academy of Sciences, have developed a novel approach for assessing urban sustainability using data from the SDGSAT-1 satellite. Their study, published in Remote Sensing of Environment, demonstrates that high-resolution (10 m) Glimmer Imager observations can reveal detailed patterns of human activity, population aggregation, and intercity connectivity across China’s three major urban agglomerations: the Beijing–Tianjin–Hebei region, the Yangtze River Delta, and the Guangdong–Hong Kong–Macao Greater Bay Area.

"Our work shows that satellites like SDGSAT-1 can provide a powerful lens to understand the dynamics of urban growth and resource flow at an unprecedented spatial resolution," said Prof. ZHANG Lu, lead author of the study.

The research introduces two innovative indicators—the City Activity Index (CAI) and the Population Activity Index (PAI)—to quantify urban development levels and population aggregation efficiency. In addition, the team developed a new method to extract intercity connection intensity from Glimmer Imager data, constructing an urban nighttime "light flow" network that visually maps the spatial patterns of resource flows and connectivity among cities.

Results reveal striking differences among the three urban agglomerations. The Beijing–Tianjin–Hebei and Yangtze River Delta regions exhibit strong patterns shaped by functional zoning and provincial boundaries. For example, the light flow network in the Beijing–Tianjin–Hebei region mirrors the functional zoning layout outlined in the Beijing Urban Master Plan (2016–2035), while connections in the Yangtze River Delta cluster predominantly align along provincial lines. In contrast, the Guangdong–Hong Kong–Macao Greater Bay Area presents a highly integrated and balanced network structure, with the strongest intercity connection, reflecting a more collaborative and balanced urban development model.

"Our findings highlight the unique capability of high-precision nighttime imagery of SDGSAT-1 to capture subtle but crucial urban dynamics," Prof. Zhang noted. "This information can support smarter urban planning, infrastructure development, and governance, helping cities move towards sustainable and resilient growth in line with the United Nations Sustainable Development Goal 11."

By leveraging SDGSAT-1's fine-scale observations, this study provides new insights into the spatial structure and resource flows of China's mega-city regions, offering a valuable tool for policymakers and urban planners seeking to optimize development and connectivity.