These Images of Cities Across the World Reveal Things the Human Eye Can’t See
Most of the human population now lives in urban areas. But the growth of these urban landscapes is something that we can only partially appreciate from the ground. Instead, we should also look from the sky. Imagery produced from satellites and infrared technology shows the ingenuity and expansion of cities, the symbiosis of urban and natural landscapes and how a changing climate is also changing the places most humans call home. Our goal as remote-sensing scientists — and the aim of our new book, City Unseen: New Visions of an Urban Planet — is to offer insights from these satellite-enabled perspectives.
Delhi, India 1:675,000 Highly vegetated areas like thriving agricultural crops are shown in light gray, while areas of low vegetation, such as the rivers (on the right) and the city of Delhi itself (on the lower left) are pictured in black
Garden City, Kansas, U.S. 1:202,000 Frank Zyback, a farmer from Colorado, invented “center-pivot” or circular irrigation in the 1940s, to provide efficient irrigation of croplands. This image captures different growth stages, water content, crop types and vegetation health of these circular plots. Less dense, newly planted crops, for example, appear in a brownish green north of the river horizontally bisecting the image.
Centralia, Pennsylvania, U.S. 1:222,000 Centralia was a coal-mining town. Now it is a ghost town. An underground coal fire started in 1962 and is still smoldering. Int he 1980s, the U.S. government paid to relocate residents from carbon monoxide gas–infested properties. This was created by using two images from the month of May—one from 1985 and the other from 2014. While red shows where vegetation decreased and yellow shows where vegetation stayed the same, green regions show where it increased and are often located where the town once was.
Two images in the book, presented here, recorded some two decades apart, show Las Vegas, Nev., expanding west. Though we’ve witnessed this expansion during our own respective visits to the city (including remote searching for an all-you-can-eat buffet after rock climbing nearby), it was harder to appreciate how this growth tapped a vital resource: water. In the satellite images, we also see clearly Lake Mead’s retreat. Las Vegas’s story of expansion is not unique; constructing and operating cities requires massive resources.
El Paso, Texas, U.S. and Ciudad Juárez, Chihuahua, Mexico 1:271,000 The two cities appear in purple along the Mexican and U.S. border. El Paso, Texas, is concentrated between the border and the Franklin Mountains (in dark green). Ciudad Juárez, Chihuahua, is south of the border. The differences in the two city’s street layouts, infrastructure, building densities and urban materials are clearly evident and shown as various shades of purple. Highly vegetated riparian areas appear in red.
Malé, Maldives 1:32,000 The Republic of Maldives, with an average elevation of just under 8 feet, was the first country to sign the Kyoto Protocol committing to reduce greenhouse gas emissions that cause climate change. A recent study found that many atoll islands are threatened not only by sea-level rise, but also flooding, which will negatively impact freshwater availability and may render these low-lying places uninhabitable by the middle of next century.
Arequipa, Peru 1:325,000 Mina Cerro Verde is an open-pit copper and molybdenum mine shown in blue in the bottom left of the image, just south of the city. The mine, which has a symbiotic relationship with the city, has been expanded in recent years and operates the city’s first wastewater treatment plant.
For this reason, we analyze satellite data not only from places like Seoul, but also from small mining towns, rainforests and other remote reaches of the planet. To understand which attributes of cities increase their chances of success or their fragility, we need to see from where they source timber, ore, rare metals and other raw materials.
One feature of satellite data that helps us depict and analyze this resource use is the ability to “see” beyond the frequencies of light humans can perceive. Just as dogs can hear frequencies of sound that humans cannot, remote-sensing provides information beyond what we can see with our naked eyes. Beyond the borders of the visible spectrum of light, encompassing all the colors of the rainbow, there are also the longer wavelengths of near and far infrared.
Seoul, Republic of Korea 1:148,000 Twenty-seven bridges span the Han River in the center of Seoul (pictured in dark blue), stitching together the two halves of the city and acting as networks between communities on opposite sides of the river.
Osh, Kyrgyzstan 1:175,000 Rectangular crops, producing tobacco, grains, cotton and melon occupy the Alay foothills to the north of the city. The varying colors of the fields highlight the variety of crops and growth stages, while fallow fields are pictured in purple.
Paramaribo, Suriname 1:244,000 A former Dutch colonial town, Paramaribo is formed by long agricultural plots — most likely remnants of what’s called “fishbone” deforestation due to paths (shown in light blue) cut into forested areas (red). These fishbone patterns are reminders of the resources needed to create the region’s Dutch-inspired wooden architecture as well as of the timber exported for urban construction materials.
These other wavelengths help us explore the health of vegetation, the water content of soils, the heat emanating from a concrete surface or the pollutants in the atmosphere. Looking with our eyes only, we see red wavelengths of light as red, green wavelengths as green and, you guessed it, blue wavelengths as blue. When “seeing like a satellite,” though, we don’t have to follow this recipe. Looking closely at the Osh, Kyrgyzstan, image, you are seeing longer shortwave infrared wavelengths displayed as red, shorter shortwave infrared wavelengths as green and visible red wavelengths as blue. By changing our perspective, urban areas become purple, and the image accentuates the differences between urban infrastructure and vegetated land.
Vegetation in forests and crops reflect infrared frequencies of light. By translating satellite-recorded infrared readings into red in the images we produce, we can see more clearly the fishbone pattern of deforestation in Paramaribo, Suriname; the disorder in abandoned Ukrainian cropland in the 30 years after the Chernobyl nuclear power plant reactor meltdown; or the spread of building materials over vegetation after a tornado devastated Joplin, Miss., in 2011.
Las Vegas, Nev., U.S. 1:525,000 In one image from April 10, 1976, urban infrastructure is shown in a gridded grey pattern with highly vegetated areas such as golf courses and parks appearing in red; by the date of the second image, October 12, 2015, Las Vegas is one of the fastest-expanding urban areas in the U.S. Not only can we see the expansion of the city in the western portion of the image, but also the shrinking of Lake Mead to the east, emphasizing the resources required for cities and their inhabitants.
These images can also highlight humanity’s impact. As we show in the book and the images here, with the right satellite image and analysis, the angularity of streetscapes in Detroit, Mich., become apparent to us; we are able to detect differences in street structures and building materials between the border cities of Mexicali in Mexico and Calexico in the United States; geological folds called anticlines and synclines in the oil and gas-rich region of Chongqing, China, are revealed; we can even “see” air pollution over Beijing; and we can gain many more insights, seen in the images here and in others in the book.
As NASA astronaut Kathryn Sullivan said of our work, satellite images can make “familiar places on Earth suddenly seem foreign” and reshape our understanding of them. And understanding cities at this level has never been more important. As an area equivalent to 20,000 American football fields is converted irreversibly to urban areas each day, we need many perspectives to make better decisions about our urban futures. — Karen C. Seto and Meredith Reba