Capacity of nighttime light data in measuring urban human activity: evidence from SDGSAT−1 glimmer imagery and mobile phone data

Accurate and high-resolution urban activity information is essential for quantitatively estimating Sustainable Development Goal 11, but is unavailable. We examined the capacity and limitation of the Sustainable Development Science Satellite−1 nighttime light (SDGSAT−1 GLI NTL) data in capturing the spatial extent and intensity of human activity in two Chinese megacities using mobile phone data. Key findings: (1) Lit areas highly overlap with human activity areas but are smaller. Over 92.62% of lit areas are occupied by humans. Only a minor population (<2.15%) lived in unlit areas, despite these areas accounting for over 20.01% of human activity areas, as revealed by the panchromatic band. Additionally, the NTL better identifies activity areas related to young and middle-aged adults and working and residential populations than those related to older adults and tourists. (2) The intensity relationships between NTL data and population are highly spatially heterogeneous, with weak global but strong local correlations. When accounting for land use, correlation remarkably improved, with an R2 value of even 0.85. (3) Notably, the correlation increased from fine to coarse resolution. In summary, NTL data effectively capture the spatial extent and intensity of urban human activity, especially when considering land use, but its limitations should be noted.