Shot from space, sorted on Earth: An epic night-time map
It was visible in the Delhi sky from January 15 to 30, moving across the heavens, astounding star-gazers. It wasn’t a shooting star or a meteorite, but the International Space Station (ISS), which orbits Earth at the speed of 5 miles per second. ISS has been circling the planet, hosting astronauts from around the world, for 20 years. In that time, it’s taken millions of photographs. The US’S National Aeronautics and Space Administration (NASA) alone has almost half a million pictures taken by astronauts using cameras aboard ISS. Several of these are scheduled shots of the land, storms, wildfires, oceans, the atmosphere and the Moon. But the vast bulk, often captured automatically by the on-board cameras, remains unidentified.
A global citizen-science project is hoping to use the night-time shots from the NASA archive in an unprecedented way. Cities At Night, started by UK astrophysicist Alejandro Sánchez in 2014, invites the public to collaborate on an epic sort-tag-and-arrange mission to create a map of Earth at night.
The human eye can identify places and sort out images faster and more efficiently than any existing bot or algorithm, says Sánchez. The project was opened up to the public, he adds, because “it was impossible for just a couple of us to process the NASA archive ourselves. Also, the images are very beautiful, and everybody should be able to access them.”
Many eyes, it turns out, make light work. So far, about 3 lakh people and 24 institutions such as the Madrid-based cultural organisation Medialab-prado; the science-volunteer site Crowdcrafting; and international space agencies have contributed their energies. Sánchez says their most active users are from the US, Spain, the UK and India.
Inbuilt apps on the project’s website (lostatnight.org) help volunteers identify places in the ISS images. New volunteers can sign up on the site too. So far, the project has catalogued thousands of photographs taken between 2003 and 2014.
A night map of the world will do more than look pretty. It can point out cultural differences in how areas and governments illuminate neighbourhoods, it can help estimate GDP, chart the spread of poverty, and monitor disasters, armed conflicts and political uprisings.
“Tracking night lights helps estimate threats to ecosystems, the impact of ecological light pollution, greenhouse gas emissions,” Sánchez says.
Currently, the best available nocturnal look at Earth is the Black Marble Map. It was created in 2012 with data from an American weather satellite using an infrared camera. But its black-and-white images were artificially coloured so the map could be read easily by non-academics wanting a comprehensive peek of the planet at night.
Cities At Night is building a map of the earth at night, in real colour, for the first time. They use pictures with up to 150 times more resolution than the images used to build the Black Marble Map. The map will also be available for use by researchers and professionals in areas such as ecology, health, economics.
“This is an interdisciplinary project,” Sánchez says. “Without technology, we would not have maps. Without citizens, we would not be able to catalogue such a vast amount of data. And without our colleagues, these images might have been restricted for use only in academic studies. Hence, we are grateful to everybody and everyone’s efforts are important and necessary.”
CITIES AT NIGHT IS BUILDING A MAP OF THE EARTH AT NIGHT, IN COLOUR, FOR THE FIRST TIME, USING SATELLITE PHOTOS SORTED BY VOLUNTEERS FROM AROUND THE WORLD