New Delhi, April 13: NASA has released its latest global maps of Earth at night, providing the "clearest yet composite" view of the patterns of human settlement across planet.
Satellite images of Earth at night - often referred to as night lights - have been a source of curiosity for public and a tool for fundamental research for nearly 25 years.
And now, NASA has released broad, beautiful pictures of night lights as observed in 2016, as well as a revised version of the 2012 map of different countries including India showing how humans have shaped the planet and lit up the darkness.
A research team led by Earth scientist Miguel Roman of NASA's Goddard Space Flight Center in Greenbelt, Maryland, plans to find out what they would observe if night lights imagery could be updated yearly, monthly or daily.
In the years since the 2011 launch of the NASA-National Oceanic and Atmospheric Administration Suomi National Polar-orbiting Partnership (NPP) satellite, Roman and his colleagues have been analysing night lights data and developing new software and algorithms to make night lights imagery more accurate and readily available.
The principal challenge in nighttime satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways.
Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.
The new maps were produced with data from all months of each year. The team wrote code that picked the clearest night views each month, ultimately combining moonlight-free and moonlight-corrected data.