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    Urban Radiance - a new visualization of urban data


    Data sets that measure population density, economic productivity, and even rural poverty are pivotal pieces of information that help us to learn more about our environment and give us insight into how we can improve the world around us. This type of data is compiled in numerous ways, but did you know it can also be collected from examining images of city lights? 

    In the United States, these images are captured by Operational Line Scanner (OLS) sensors on satellites that belong to the US Defense Meteorological Satellite Program (DMSP). These sensors were originally used by the US Air Force in the 1950s to predict weather, but engineers soon realized that the sensors were sensitive enough to capture the radiance of cities during moonless nights. Radiance, within this context, is the artificial light emitted from the surface of the Earth, not necessarily the reflections of sun or moonlight.
    urban radiance of US

    These DMSP images are typically utilized to show regional differences. One example is an image of Jordan in 2005 and Syria in 2011 after their respective wars. The images show those two countries going significantly darker (due to disrupted power supply) compared to neighboring countries.


    Dietmar Offenhuber, an Assistant Professor at Northeastern University in the departments of Art + Design and Public Policy, is using these images for a different purpose. He has completed a project that visualizes temporal changes in urban radiance from 1992 until 2015, making it the first interactive visualization of radiance time series data, allowing users to change the time difference by moving their mouse over the map. The images of the maps are a combination of two different points in time. The blue areas indicate an earlier moment, which darkened over time, meaning there was a decrease in public illumination. The orange areas are from a later time, and signify areas that have increased in public illumination. Black and white areas in the map are ones that  showed no change.

    urban radiance of Middle East

    According to Offenhuber, “the DPMS story illustrates an important characteristic of large data sources - they can be read "against the grain" and become useful in ways unanticipated by their original creators. A military satellite program for mapping clouds has become a main tool for urban researchers and economists for tracking global urbanization across time.”


    Offenhuber had the chance to exhibit his project at Habitat III, a UN Conference in Quito, Ecuador and at the IEEE VIS Arts Program, “Metamorphoses,” in Baltimore, Maryland.


    To learn more about the Urban Radiance project and other work by Dietmar Offenhuber, visit his website here.