Visualizing global light pollution with GIS

October 15, 2015

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In Central Idaho, a hiker lays with his head outside of his tent, despite the chilly temperatures, and looks up at the night sky. The stars are breathtaking in number, clarity and brightness.

Thousands of people will never see a night sky like that, due in large part to light pollution, a growing problem that may be more serious than we know — some studies suggest it may be contributing to the rise of obesity and possibly even cancer. To learn more about the possible long-term effects of light pollution, several projects are currently underway to map and analyze the areas that are most affected, and amateur GIS enthusiasts are welcome to help.

What is light pollution?

According to Dark Skies Awareness, light pollution consists of four things that often overlap or are combined:

●        Urban Sky Glow — the brightening of the night sky over inhabited areas.

●        Light Trespass — light falling where it is not intended, wanted or needed.

●        Glare — excessive brightness which causes visual discomfort.

●        Clutter — bright, confusing and excessive groupings of light sources, commonly found in over-lit urban areas.

Many techniques are being used to map different types of light pollution, including Bluesky’s night time aerial photo trials, conducted in 2014. Excess light at night is a growing concern, not only because of its effect on astronomers, but because studies increasingly show it affects migratory birds and the ecosystem of nocturnal animals. This is at least in part related to “the attraction due to lighting at commercial towers and tall buildings,” as Dr. Travis Longcore, GIS professor at USCand an Urban Conservation Scientist explained in his discussion with Dark Skies advocate Dr. Andreas Haenel on Light Pollution’s Effect on Wildlife.

Bluesky uses specially developed survey equipment which includes a low light camera that copes well with lumen levels and temperatures at night. The system also includes Light Imaging Detection and Ranging to accurately determine the distance between the sensor and the ground, buildings and vegetation. The accuracy of the data and the images from these surveys are amazing.

Bluesky's nighttime aerial photography takes advantage of special cameras, LiDAR and thermal imaging technology. (BlueskyPhoto)

Another project, Cities at Night, is using photos taken from the International Space Station to map light pollution in cities all around the world. The photos have ten times the resolution of any photos previously available to the public, and the project requires the georeferencing of more than 130,000 photos. 

These photos taken from the International Space Station have ten times the resolution of any previously available to the public. (Cities at Night Images)

How does light pollution affect me?

Setting aside the effect on wildlife, light pollution is a huge waste of energy. Experts say that over 30 percent of all outdoor lighting in the United States is wasted, mostly by lights that are not shielded. While LED’s and other lights can be more efficient, their impact on the environment has not been fully studied.

Finally, light pollution affects human health, although we don’t yet know how much. The obvious effects are on the eyes, due to excessive glare and exaggerated darkness. Studies suggest it may go further, interrupting our Circadian rhythms and sleep patterns, perhaps even causing cancer and leading to obesity. 

This map shows areas of light pollution across the U.S., with data provided by Earth Observation Group, and NOAA National Geophysical Data Center.  (Light Pollution Map Image)

How Can I help?

Light pollution affects all of us in one way or another - from the environment and energy expenditure to our health. Want to make a difference? There are a number of ways to pitch in:

●        Watch your own nighttime light use and only use what is necessary.

●        Get involved in your community to discuss lighting plans and options, and participate in programs at work and at home. Chicago and NYC already have such programs.

●        Help georeference and identify cities in the Cities at Night project. 


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