From space, one of the most visible signs of human activity is the presence of large cities and urban regions. Urban regions have grown very rapidly in the last two centuries, as economies have shift first to industrialism to then service-based focus. Even in less developed countries, cities is where people see opportunities, driving global growth. Mapping this change has been a major goal for scientists in order to plan for a world where a high percentage of people live in high density spaces.
The world settlement footprint, created in a online application called Urban Thematic Exploration Platform (TEP) sponsored by the European Space Agency (ESA), is the first map that combines optical and radar satellites to create a human urban footprint map of the world. This allows researchers and planners access to maps that can be used to document urban growth and change around different countries, where planning and infrastructure remain great challenges as the world becomes more urban, with estimates now around 70% of the world’s population living in cities. The initial map was created using 2014-2015 data from the Copernicus Sentinel-1 radar-based satellite and Landsat-8 multi-spectral satellite images.
What is most useful about this tool is that it provides web-based information using aggregate satellite data, where countries with the greatest urban growth rates often have the least resources for planning and development and limit capacity for accessing satellite data. The data helps those with limited resources to better monitor and plan how best to serve their growing cities. Data are also updated and projected into the future, where population estimates and urban growth patterns allow researchers to determine where likely growth in urban population is more likely to occur. This is particularly useful for regions in Africa, Asia, and South America, which are the continents experiencing the most rapid urban growth. Overall spatial resolution covering every grid point of the mapped areas is 12 meters, making it the best resolution global-scale map of urban systems there is. The German Aerospace Centre (DLR) has led much of the development of the new system and processing of data.
The challenge that projects such as Urban TEP create is aggregating larger sets of data, with continual updates planned, at increasingly more fine-scale resolution. Such maps need greater processing capabilities and need to provide data rapidly to end users and analysts. Projects have been created to enable streamline processing of such data, one of which is TimeScan, The tool allows integration and analysis of multi-scene data, where the software was tested and applied on 452,799 multi-spectral Landsat–8 covering two years of global-scale data coverage.
With growth in using high performance computing and big data analysis, Google and Urban TEP are planning to partner for the next phase of development, which includes integrating most of the Landsat archive to document urban growth from 1985-2015. Furthermore, cloud-based services are provided by Urban TEP so that users can now better process data as they download and apply analysis on their research interests.
While there are advancements now in mapping, at a global-scale, urban growth and transformation, the question for scientists is what to do with the data. Sustainable cities have been an important theme for planners and scientists, thus a challenge will be for researchers is to integrate data from Urban TEP and similar tools to better create policy and forecasts that document likely urban change, where results can be directly applied by urban planners and governments. This might mean combining indices with global-scale mapping such as Urban TEP to best plan for development and allow assessment of how well urban regions are balancing population growth with development goals such as attaining education, health care, and basic needs sufficiently. The World Bank has also created global-scale data on the Atlas of Sustainable Development Goals. These data provide a wide range of information on trend and analysis showing how well countries are meeting sustainability goals. Such data have the potential to be integrated with Urban TEP.
Mapping urban change at a global scale has potential uses in urban planning and government policy. Urban sustainability has also been a challenge for social scientists and policy makers for decades as cities grow far faster than infrastructure and development can keep pace. While our analytical and data capture abilities improve, relatively few cases exist where countries were able to have recently better addressed sustainability goals. This will be one challenge in the application of recent data in the years to come.
 For more on Urban TEP, see: https://urban-tep.eu/puma/tool/?id=574795484&lang=en.
 For more on the development of the urban footprint project, see: Esch, Thomas, Felix Bachofer, Wieke Heldens, Andreas Hirner, Mattia Marconcini, Daniela Palacios-Lopez, Achim Roth, et al. “Where We Live—A Summary of the Achievements and Planned Evolution of the Global Urban Footprint.” Remote Sensing10, no. 6 (June 7, 2018): 895. https://doi.org/10.3390/rs10060895.
 For more on TimeScan, see: Esch, T., S. Üreyen, J. Zeidler, A. Metz–Marconcini, A. Hirner, H. Asamer, M. Tum, et al. “Exploiting Big Earth Data from Space – First Experiences with the Timescan Processing Chain.” Big Earth Data2, no. 1 (January 2, 2018): 36–55. https://doi.org/10.1080/20964471.2018.1433790.
 For more on Urban TEP and its platform, see: http://www.esa.int/Our_Activities/Observing_the_Earth/Mapping_our_global_human_footprint
 For more on the Atlas of Sustainable Development Goals, see: http://datatopics.worldbank.org/sdgatlas/
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