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The Global Urban Footprint: A map of nearly every human settlement on Earth

Thomas Esch's picture


Urbanization is increasingly central to the global development process, but until recently, basic spatial information on the world’s urban areas has been unavailable, inconsistent, or unreliable. The lack of consistent data on the world’s cities makes it hard to understand the overall impact of urbanization. However, innovations in geospatial mapping are now helping to provide one major piece of the puzzle:maps of practically all built-up areas around the world are available thanks to new uses of satellite data.
 
Scientists at the German Aerospace Center (DLR) have succeeded in using a newly developed method to map the world’s built spaces at an unprecedented spatial resolution, resulting in the ‘Global Urban Footprint’ (GUF), a global map of human settlements at a spatial resolution of 12 meters per grid cell (aggregated to 75m for public use).
 
The German radar satellites TerraSAR X and TanDEM X acquired over 180,000 images between 2010 and 2013, which were processed, together with additional data such as digital terrain models, to produce the Global Urban Footprint. In total, the researchers processed over 20 million datasets with a combined volume of more than 320 terabytes.

Bright Lights, Big Cities

Mark Roberts's picture

Delhi night-time lights data imageIf you visit the National Museum of Natural History in Washington, D.C., one of the exhibits you’ll come across is a map of the Earth, which shows lights detected by satellites at night. With even a cursory look, it’s clear the lights pick out spatial patterns of urban and economic development.  Look at the USA, and you see the coasts are brightly lit, whereas the country’s interior is much less so.  Look at the Korea peninsula and you see that whilst South Korea is almost ablaze with light, the North is noteworthy for its almost complete absence of light.

The potential ability of night-time lights imagery to detect spatial patterns of urban and economic development has been known in the remote sensing community since the late 1970s.  However, it has only recently been brought to the attention of economists following a paper by Vernon Henderson, Adam Storeygard and David Weil entitled “Measuring Economic Growth from Outer Space.”  This paper alerted economists to the strong correlation between a country’s rate of GDP growth and the growth in intensity of its night-time lights, and the fact that the lights represent (for economists) a relatively untapped dataset with global coverage and a time-series dating back more than twenty years.