Modeling the Distribution of Human Population with Night-time Satellite Imagery and Gridded Population of the World

The spatial distribution of human population is a fundamental determinant of both the societal impacts and anthropogenic drivers of global change. Version 2 of the Gridded Population of the World (GPW2) is the most recent, detailed global population dataset based solely on administrative unit data. The gridding approach is based on the assumption of uniform spatial distribution of population within each of the 127,105 administrative units, thus the spatial detail of the gridded data is directly related to the spatial resolution of the administrative data on which they are based. Night-time light imagery resolves lighted settlements as small as 2.7 km in diameter thereby providing more spatially explicit information on spatial distribution of population in areas lacking detailed census data. In this study we look at the World Stable Lights dataset as a potential means to refine the spatial detail of the population dataset. We compared the Log10 of population density to the nighttime light frequency for sample of regions of the world with spatially detailed administrative data and found a consistent relationship between population density and light frequency. Based on this relationship, we developed a transfer function to relate light frequency to population density and a mass-conserving algorithm that relocates fractions of populations within large administrative units to locations of lighted settlements. This partial reallocation of population into urban centers provides a more spatially explicit representation of population distribution than the original GPW2 while making minimal assumptions about factors influencing population distribution.