Monika Kuffer sees on satellite images what people see at night

Monika Kuffer sees on satellite images what people see at night

Houses, a university building, roads, an airport. In satellite images taken during the day, social geographer Monika Kuffer was still able to clearly distinguish the megacity of Nyala – the capital of the state of South Darfur in southwestern Sudan – from the flat desert that stretches around the city. But on night-time satellite images, that same city – where more than a million people once lived, partied, ate, worked – was just a pitch-black spot. All lights were off. The people have left their homes behind because of the war that has been raging in Sudan for more than a year.

How can satellites from space reveal something about the behavior of people on the ground, such as migration? It is a question that Kuffer, professor at the University of Twente, has been working on for decades. She talks about her research in a small room on campus.

When Kuffer, as a young student of human geography in Munich at the end of the last century, took a minor in satellites, remote sensing, she felt uncomfortable. “My fellow students in this course were physical geographers. They used satellites to explore forests, the sky, mountains and volcanoes. It was crazy at the time to use satellites to study human behavior.”

Still: her interest in space travel remained, as a child she wanted to become an astronaut. For her internship, Kuffer looked for other social geographers who used satellites and ended up at the International Institute for Aerial Mapping and Earth Science (ITC) in Enschede. Here satellites were used to investigate the development of African cities. Laughing: “The resolution of the images was bizarrely low at the time.” They worked with images from the American Landsat TM, which could distinguish areas of thirty by thirty meters. Commercial satellites today have a resolution of several tens of centimeters. For the latest Landsat satellites, this is still fifteen to thirty meters. “And we analyzed images that students had taken themselves from airplanes.” After her internship, she completed a master’s degree in satellite research at London’s Birkbeck College. She then came to Twente for her research into urbanization, and recently into migration in Sudan.

In April 2023, fighting broke out in the Sudanese capital Khartoum, the capital of Sudan. The light also went out.

Satellites in orbit are sometimes the only source of information for areas where it is dangerous to report on the ground. The sudden absence of relief in Sudan reveals the disappearance of human activities in Nyala. Other satellite images, which showed a sharp reduction in air pollution in Nyala, confirmed this. “I couldn’t really figure out where the people fled to. From local sources I knew that they were traveling to the town of Al Fasher [circa 170 kilometer naar het noorden]. On night-time satellite images I indeed saw an deviation in the amount of light. But was that due to the setting up of refugee camps? Or were they fires? There is a lot of violence in Al Fasher.”

Kuffer forwards the satellite images in Twente to NGOs worldwide that are committed to peace. “But I think that the images mainly contribute to awareness. The fact that the megacity of Nyala was completely wiped out was relatively little in the news, because there are hardly any journalists on the ground.”

The amount of light in nighttime satellite images can also show the opposite: an increase in human activity in a given area. The thirtieth anniversary of the Olympic Games in the South Korean capital Seoul in 2018 was clearly visible through a spike in lighting around the Olympic stadium. In Sanaa, the capital of Yemen, the lights went out in 2015 after an airstrike that destroyed the local electricity grid. But every year a sharp peak in lighting can be seen shortly after Eid-ul-Fitr, with people probably making their own lights with generators.

Satellites saw the consequences of the population fleeing Nyala

The downside of urbanization

A permanent, gradual, increase in lighting can be seen in many areas of the world due to urbanization. More than half of the world’s population lives in urban areas, the United Nations writes. Africa and Asia in particular are urbanizing rapidly. Cities are a source of opportunity, employment and schools.

But satellite images also show the downside of urbanization.

“Look,” says Kuffer, pointing to her screen. Her screen shows a satellite image of the Nigerian city of Lagos. You see big differences in morphology in this city: straight, arranged buildings in the middle and on some edges chaotic, small buildings close together. “Slums – densely populated areas with houses that were not built by the municipality – can be easily recognized by the irregular structures of the houses,” she says. According to United Nations estimates, more than a billion people live in slums. For example, in Asia’s largest slum, Dharavi in ​​the Indian city of Mumbai, a million people live on two square kilometers. Urbanization is increasing the number of people living in slums, an estimated 2 billion over thirty years.”

Together with colleagues, Kuffer is working on a system to use artificial intelligence to recognize slums on satellite images. “Governments’ estimates of the number of slums are still very rough, meaning people are ignored when making decisions. Sometimes houses in slums are destroyed because governments have other plans for them. Without warning, bulldozers come and crush what little people have. But people live here, these are their homes, their schools.”

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Greenery and roads are lacking

If you zoom in further on satellite images of slums, you will see the lack of roads and the lack of greenery. Many houses are close together, there are piles of rubbish and there is little lighting. Using satellite images, Kuffer has mapped the amount of waste based on morphology in the Kenyan capital Nairobi, helping to convince local governments to collect the waste.

Since her minor at the end of the last century, a lot has changed in her field of research. “The resolution of satellite images is improving and we are increasingly understanding which features we can use from space to monitor human activities, in addition to forests, the atmosphere and mountains.”

But the quality of the nighttime images is still poor, she says. Lighting is an important source of information for a social geographer, “but if, for example, the satellites only distinguish areas of 750 by 750 meters, this means that if there is one lamp in the 750 meter area, the satellite sees the entire area as illuminated. Kuffer has submitted a proposal to the European Space Agency ESA for a new night satellite that can observe in more detail. “But limitations will always remain. It remains difficult to attribute changes in patterns on satellite images to human choices. Collaboration between satellites and ground sources will continue to be necessary to know what is happening on the ground.”




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