Global Urban Estimates: A Comparison

David Potere, Princeton University

The United Nations Population Division predicts that by 2007, an unprecedented one half of the world’s 6.1 billion people will dwell in urban centers. Urban growth in less developed regions is expected to account for nearly all of the global population increase from 2000-2030. Rapid land conversion implied by these projections will have severe consequences for local and regional ecosystems, food production, and climate. Understanding the extent and spatial distribution of this urbanization is critical. Satellite remote sensing, with its synoptic global coverage, offers the only realistic means of staying abreast of the largest urban expansion in world history.

Today, there are at least six independently-created global maps of urban land cover. Although most of these maps share common imagery sources, they differ by as much as a factor of five in their estimate of the total extent of urban areas globally. We compare these six products at both global and regional scales, identifying areas of agreement and disagreement. We relate variance in the extent and spatial distribution of urban land cover to methodological differences among the six mapping efforts. In the absence of a global validation effort focused on urban land cover maps, this comparison study offers those who would use such maps a first glimpse at their relative merits.

Abstract Author(s): David Potere, Annemarie Schneider