The Square Density visualization was created by Garrett Dash Nelson, 2019.

Cells are 30 arc-second grid cells, which are approximately, but not exactly, one square kilometer. Due to the curvature of the earth, cells are also larger closer to the equator; a 30 arc-second cell at the southern tip of Florida is approximately 1.4 times larger than one along the Canadian border. I have not normalized for this size variance, which is negligible within a single metropolitan area. I have also not normalized for water/land areas within grid cells.

Cities are treated as Census Bureau Combined Statistical Areas, buffered by 1 minute to capture edge pixels.

Population data is attributable to: Center for International Earth Science Information Network - CIESIN - Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Count, Revision 11. Palisades, NY: NASA Socioeconomic Data and Applications Center (SEDAC). https://doi.org/10.7927/H4JW8BX5.

Inspired in part by Alasdair Rae’s work on global gridded population.