[1] A map of human influence became possible with the advent of high-resolution satellite imagery in the 1990s.
[2] The map is made to a resolution of 1 km2 (0.39 sq mi) and is an aggregate of eight factors: major roadways, navigable waterways, railways, crop lands, pasture lands, the built environment, light pollution, and human population density.
[1] The first Human Footprint map was published in 2002 with data that had been collected in the early 1990s, approximately 1993.
[4] Due to incomplete satellite imagery, the original Human Footprint map did not include Antarctica nor some of the Small Island Developing States of the Pacific Ocean.
Marine and freshwater systems are excluded, as different factors would be necessary to map human influence.