An Intensity Gradient/Vegetation Fractional Coverage Approach to Mapping Urban Areas From DMSP/OLS Nighttime Light Data

Many studies have demonstrated the efficient extraction of the spatial extent of urban areas from Defense Meteorological Satellite Program/Operational Linescan System imagery using a fixed thresholding technique. These studies may underestimate and overestimate the extents of small and large cities, respectively. To overcome this problem, a new intensity gradient (IG) and vegetation fractional coverage (VFC) method is developed for identifying cities or towns, principally based on the assumption that there is a border around a city at which the nighttime light intensity decreases sharply. Using this method, the spatial extents of urban areas for two of the biggest countries in the world, namely China and the United States, were extracted in 2010. The urban areas thus identified are compared with the urban areas interpreted from Landsat Thematic Mapper imagery, and the results showthat there is a significant linear relationship between the former and latter areas. This demonstrates that the IG/VFC model is effective for efficiently extracting the extent of urban areas fromnighttime light imagery.