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A raw nighttime stable lights image (2012) from the US DMSP/OLS (in Behrmann equal-area projection at a resolution of 810 × 810 m). Digital number indicates light intensity with 0 representing darkness and 63 indicating the brightest pixels. Histograms show data from this image a without and b with 0 digital number values. c Grey graphs show the mean digital number for particular columns/rows (latitudes/longitudes)
