MODIS 500-m map of global urban extent (URB_MAP)

 The global map of urban extent has a spatial resolution of 15 arc-seconds (about 500 m) and was obtained from MODIS imagery through a supervised decision tree classification algorithm using region-specific parameters. It provides a consistent and seamless map of urban, built-up and settled areas for the Earth’s land surface for the period 2001-2002. The map is in raster structure, generic binary format which can be imported in most GIS packages.

Urban areas are defined as places that are dominated by the built environment. The ‘built environment’ includes all non-vegetative, human-constructed elements, such as buildings, roads, runways, etc. (i.e. a mix of human-made surfaces and materials), and ‘dominated’ implies coverage greater than or equal to 50 percent of a given landscape unit (here, the pixel). Pixels that are predominantly vegetated (e.g. a park) are not considered urban, even though in terms of land use, they may function as urban space. surrounding the impervious surface concept. Finally, a minimum mapping unit is defined: urban areas are contiguous patches of built-up land greater than 1 km2.

An accuracy assessment based on sites from a stratified random sample of 140 cities shows that the new map has an overall accuracy of 93% at the pixel level and a high level of agreement at the city scale (R2 = 0.90). The map is useful for combining with other land cover datasets at global or regional scale.