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A Landsat photo of the coastline of the West African nation Guinea-Bissau. Photo credit: U.S. Geological Survey A Landsat photo of the coastline of the West African nation Guinea-Bissau. Photo credit: U.S. Geological Survey

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The field of remote sensing is tracking disasters and saving endangered species.
By Michael Price

This story appears in the spring 2016 issue of 360: The Magazine of San Diego State University. 

Today, Doug Stow is a whiz with a grid. But before the San Diego State University geography professor became one of the foremost researchers in a field known as remote sensing, he was more interested in the gridiron. Stow attended De Anza College in Cupertino, California primarily to play football, but shortly thereafter he decided to explore his academic options.

It was a physical geography class that most captured his interest. When he transferred to the University of California, Santa Barbara, to finish his degree, he sought out an education in geography. As part of his curriculum, he took classes from geographer John Estes, considered one of the pioneers in the remote sensing discipline. After earning his bachelor’s degree in geography, Stow became one of UC Santa Barbara’s first master’s degree students in the newly-formed geography program.

These were pioneering days for remote sensing, a field that concerns itself with using satellite and aerial imagery to extract useful information about conditions on the ground. It can be used to track the expansion of housing developments in growing cities, or to measure the impact of natural disasters, or to keep tabs on deforestation. And it’s intensely interdisciplinary, calling upon expertise in traditional geography, geology, optics, mathematics, physics, and human behavior to decipher what exactly remotely sensed imagery reveals.

Budding lab

As he was finishing his doctorate at UC Santa Barbara, Stow applied for and was given a job as an assistant professor of geography at SDSU in 1983.

“At the time, SDSU was just beginning to emerge as a research university,” Stow recalled. “The geography department had just one computer that everyone had to share."

He continued to do research in remote sensing, but the pace was slow, hampered by costly technology and a relatively small budget. But in 1990, “the department really started moving,” as Stow put it. The Center for Earth Systems Analysis was established with a bevy of new, state-of-the-art computers, enabling faculty to seriously compete for and win research funding and support student assistants. Due partly to Stow’s background with the university, SDSU formed a joint doctoral geography program with UC Santa Barbara.

Ever since, Stow and his colleagues have worked to turn SDSU into a powerhouse for remote sensing research. He was selected by a faculty committee as this year’s Albert W. Johnson Research Lecturer.

This year, Stow is wrapping up a NASA-funded project looking at rural-to-urban migration of people living in western Africa, primarily in Ghana. Over the past three years, Stow and his team have used satellite imagery to map urbanization and land cover change in relation to population growth and health outcomes in urban and peri-urban areas.

“With the resolution of these land satellites, you’re not going to pick up individual houses, but you can see developments and compare before-and-after patterns of land cover change,” Stow said.

The researchers discovered that peri-urban areas in Ghana were experiencing sprawl as people migrated from rural villages. Within this sprawl, Stow and colleagues picked up on the fact that the satellite imagery could discriminate between higher and lower socioeconomic sectors. Less wealthy areas tended to have less vegetation than the more well-to-do neighborhoods.

Knowing this will allow western African nations to better track their populations’ migration trends, as well as help conservationists understand the environmental effects of nascent sprawl.

Monkey business

Another project with fellow geography professor Li An found Stow using satellite imagery to track the loss of forest canopy in the Fanjingshan National Nature Reserve in south-central China. The forest canopies are the exclusive habitat of the endangered gray snub-nosed monkey.

With funding from the National Science Foundation (NSF), Stow and An are exploring whether reimbursing people who live in the nature reserve for not cutting down trees for agriculture—and indeed, for planting new trees instead—will help preserve the canopy and protect the dwindling snub-nosed monkey population.

For both of these projects, Stow has also traveled extensively to see how ground conditions match up with what he’s observed with satellite data. That’s been particularly tricky for the China project. In Guizhou province, after the snow cover melts in March, there’s only a month’s respite before the venomous snakes come out, he said.

Disaster response

Two of Stow’s most recent projects are studies funded by the Department of Transportation and NSF to assess damage to critical infrastructure after natural or man-made disasters. It’s important for emergency responders and government officials to know, for example, whether bridges are safe, roads are clear and hospitals are accessible.

Rather than relying upon satellite images, Stow and colleagues are making use of manned and unmanned aircraft to take aerial photographs of critical sites, then precisely mark the height and GPS coordinates the photos were taken at. After a disaster, aircraft could return to the same spot to take new photos.

The researchers are working on new image comparison software that can point out differences between the images that might indicate damage.

“We’re teaching the programs to differentiate between a new rubble pile or a crack, or simply a shift in the shadows,”
Stow said.

While these programs grow more sophisticated by the day, there will always be a need for experts to add the human touch to verify post-disaster conditions, he added.

“Automatic recognition is the holy grail,” Stow said, “but there’s always going to need to be an analyst in the loop.”