Capturing the Urban Divide in Nighttime Light Images From the International Space Station

Abstract

Earlier studies utilizing coarse resolution DMSP-OLS nighttime light (NTL) imagery suggest a negative correlation between the amount of NTL and urban deprivation. The International Space Station (ISS) NTL images offer higher resolution images compared to DMSP-OLS or VIIRS images, allowing an analysis of intraurban NTL variations. The aim of this study is to examine the capacity of ISS images for analyzing the intraurban divide. NTL images of four cities (one African, two Asian, and one South American) have been processed and analyzed. The results show that deprived areas are generally the darker spots of built-up areas within cities, illustrating the urban divide in terms of access to street lighting. However, differences exist between cities: Deprived areas in the African city (Dar es Salaam) generally feature lower NTL emissions compared to the examined cities in South America (Belo Horizonte) and Asia (Mumbai and Ahmedabad). Beyond, variations exist in NTL emissions across deprived areas within cities. Deprived areas at the periphery show less NTL compared to central areas. Edges of deprived areas have higher NTL emissions compared to internal areas. NTL emission differences between types of deprived areas were detected. The correlation between ISS NTL images and population densities is weak; this can be explained by densely built-up deprived areas having less NTL compared to lower density formal areas. Our findings show ISS data complement other data to capture the urban divide between deprived and better-off areas and the need to consider socioeconomic conditions in estimating populations.