A research team from the Aerospace Information Research Institute of the Chinese Academy of Sciences has developed a new method for evaluating urban sustainability, leveraging high-resolution data from the SDGSAT-1 satellite, according to a recent study published in Remote Sensing of Environment.

The study focuses on three of China's most prominent urban agglomerations—the Beijing–Tianjin–Hebei (BTH) region, the Yangtze River Delta (YRD), and the Guangdong–Hong Kong–Macao Greater Bay Area (GBA)—demonstrating that 10-meter resolution observations from SDGSAT-1's Glimmer Imager can unlock fine-grained details about human activity patterns, population aggregation, and intercity connectivity across these megaregions.

To quantify key urban metrics, the researchers introduced two novel indicators: the City Activity Index (CAI), designed to measure urban development levels, and the Population Activity Index (PAI), which assesses the efficiency of population aggregation. Beyond these indices, the team also developed a proprietary technique to extract intercity connection intensity from Glimmer Imager data, enabling the construction of an urban nighttime "light flow" network. This visualization tool maps the spatial distribution of resource flows and intercity connectivity in a clear, intuitive format.

Analysis of the three agglomerations revealed distinct structural differences:

The BTH and YRD regions showed strong connectivity patterns shaped by functional zoning and provincial administrative boundaries. In the BTH region, for instance, the light flow network is closely aligned with the functional layout outlined in the Beijing Urban Master Plan (2016–2035). In the YRD, intercity connections were primarily clustered along provincial lines.

By contrast, the GBA exhibited a highly integrated and balanced network structure, with the strongest intercity connectivity among the three. This pattern reflects the GBA's more collaborative and spatially balanced urban development model, the study noted.

"Our findings underscore the unique value of SDGSAT-1's high-precision nighttime imagery: it can capture subtle yet critical dynamics of urban systems that are often hard to detect with conventional methods," said Prof. ZHANG Lu, the first author of the study. 

This study not only offers new insights into the spatial structure and resource flow dynamics of China's mega-city regions but also delivers a practical tool for policymakers and urban planners, the researchers noted.