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A Comparison of Nighttime Satellite Imagery and Population Density for the Continental United States

The striking apparent correlation between nighttime satellite imagery and human population density was explored for the continental United States. The nighttime stable-lights imagery was derived from the visible near-ZR band of 231 orbits of the Defense Meteorological Satellite Program Operational Linescan System (DMSP-OLS). The population density data were generated from a gridded vector dataset of the 1992 United States census block group polygons. Both datasets are at a one-square-kilometre resolution. The two images were co-registered and correlation between them was measured at a range of spatial scales, including aggregation to state and county levels. DMSP imagery showed strong correlations at aggregate scales, and analysis of the saturated areas of the images showed strong correlations between the areas of saturated clusters and the populations those areas cover. The non-zero pixels of the DMSP imagery correspond to only 10 percent of the land cover yet account for over 80 percent of the continental United States population. Spatial analysis of the clusters of the saturated pixels predicts population with an R2 of 0.63. Consequently, the DMSP imagery may prove to be useful to inform a "smart interpolation" program to improve maps and datasets of human population distributions in areas of the world where good census data may not be available or do not exist.