Global and Regional Coverage of Built-Up Land

Before this data set was published, urban areas were represented world-wide by only one single category, which essentially said that all the urban lands around the world looked the same. Overall the planet's urban lands were also under-classified, since in most classification schemes, built up land was usually the area left-over after all other categories had been classified.

Two sources were used to create this data set: the DMSP/OLS Nighttime Lights and the IGBP land cover characterization data set.

Initially the two source data sets were re-gridded to 5 minute resolution. In the newly produced nighttime lights data, each cell represented the average nighttime light value of 4 cells, while each cell in the new land cover data represented the number of cells out of 100 which were categorized in the original IGBP data as “Urban or Built-up land”.

A linear regression was developed for all non-zero values to establish the relation between the built-up area density, as the dependent variable, and nighttime lights, as the independent variable. The statistics were then applied to the nighttime data set to develop modeled built-up area density. To this data set, the investigator added the positive difference to the fractional re-gridded IGBP data set. Thus, the resultant data contains a combination of modeled built-up areas (base on nighttime lights) and observed built-up areas (based on IGBP land cover data).

Map coverages are global and regional in spatial extent. Users can download map images (jpg) and data (a GIS grid of the data in ESRI ArcView Format).