Global Distribution and Density of Constructed Impervious Surfaces

This data set provides the first global inventory of the spatial distribution and density of constructed impervious surface area (ISA) based on the brightness of satellite observed and calibrated nighttime lights [U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS)] and population count from ORNL LandScan 2004 [which includes input from three satellite data sources: NASA MODIS land cover, the topographic data from the Shuttle Radar Topography Mission (SRTM), and the high resolution Controlled Image Base (CIB) from the U.S. National Geospatial Intelligence Agency (NGA)]. Examples of ISA include roads, parking lots, buildings, driveways, sidewalks, and other manmade surfaces. While high spatial resolution is required to observe these features, this product was made at one km2 resolution. The reference data used in the calibration were derived from 30-meter resolution ISA estimates of the USA from the U.S. Geological Survey. Nominally the product is for the years 2000-2001 since both the nighttime lights and reference data are from those two years. Investigators used the product to estimate the world’s total ISA, to rank the leading countries in total ISA and to calculate the quantity of ISA per person for individual countries. In addition, they aggregated the ISA density for the major watershed units of the world to identify those watersheds impacted by the proliferation of ISA. Investigators found that 1.05% of the United States land area is impervious surface (83,337 km2) and 0.43% of the world's land surface (579,703 km2) is constructed impervious surface. China has more ISA than any other country (87,182 km2), but has only 67 m2 of ISA per person, compared to 297 m2 per person in the USA. Hydrologic and environmental impacts of ISA begin to be exhibited when the density of ISA reaches 10% of the land surface. An examination of the areas with 10% or more ISA in watersheds finds that with the exception of Europe, the majority of watershed areas have less than 0.4% of their area at or above the 10% ISA threshold. The investigators believe the next step for improving the product is to include reference ISA data from many more areas around the world. For additional information, see Elvidge, C.D., B.T. Tuttle, P.C. Sutton, K.E. Baugh, A.T. Howard, C. Milesi, B.L. Bhaduri, and R. Nemani. 2007. Global Distribution and Density of Constructed Impervious Surfaces. Sensors 7: 1962-1979.