878-MP nightscape image reveals light pollution

Caren B. Les, caren.les@photonics.com

Bright city lights help us get around more easily at night, but they also can affect nocturnal wildlife, the environment, sleep patterns and more.

“I became interested in light pollution because we know so little about it,” said Helga Küchly of the Leibniz Institute of Freshwater Ecology and Inland Fisheries. “Many negative effects of artificial light at night on the environment are still unknown, and basic information about light emission sources [is] missing.”

To illuminate the impact of Berlin’s artificial lighting on the environment, Küchly and colleagues have produced a very high resolution aerial nighttime photo of the metropolis for the Verlust der Nacht (Loss of the Night) project in Berlin, which includes Free University Berlin.

The 878-megapixel mosaic image – at one pixel per square meter – is the highest-resolution image ever published of a city at night, according to Free University Berlin, where the map was produced. It is a composite of 2647 photographs taken in a series of 14 tracks at 3 km (about 9800 ft) above the city in September 2010.

This very high resolution mosaic image of Berlin at night is made up of thousands of individual aerial photographs. It was produced as a tool for light pollution. The Tiergarten park is the dark spot in the middle, and the bright Berlin Tegel Airport is in the upper left corner.

The researchers are working to understand what the sources of upward-directed light are and to identify patterns in the distribution of the lights. Aerial observation of light pollution can fill a gap between ground-based surveys and nighttime satellite data, they noted. Ground surveys are labor-intensive and usually limited to a smaller area, and satellite data has lower resolution, they said.

Using the photo, they measured how much light comes from different types of land-use areas, including streets and parks, comparing the light emitted from each point to Berlin land-use information.

More than one-third of the upward-directed light came from streetlights, auto headlights and advertisements; half of the city’s total light came from only one-quarter of its area, the map revealed.

City parks are part of the reason that Berlin still contains large unlit areas, and they are important dark resources for nocturnal animals. The researchers found that natural areas accounted for almost one-third of the study area but emitted only 6 percent of the total light.

The findings were published in the journal Remote Sensing of Environment (dx.doi.org/10.1594/PANGAEA.785492).