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ERDC scientist creates algorithm to distinguish the forest from the trees

Dr. Sarah J. Becker, a physical scientist at the U.S. Army Engineer Research and Development Center’s Geospatial Research Laboratory (ERDC-GRL), posed in Colombia where she and other ERDC-GRL personnel collected ground-based hyperspectral data on native plants to determine if spectrally separable signatures between the different plants could be determined.

Dr. Sarah J. Becker, a physical scientist at the U.S. Army Engineer Research and Development Center’s Geospatial Research Laboratory (ERDC-GRL), posed in Colombia where she and other ERDC-GRL personnel collected ground-based hyperspectral data on native plants to determine if spectrally separable signatures between the different plants could be determined.

VICKSBURG, Miss. — When people think about the U.S. Army Engineer Research and Development Center (ERDC), there are many innovative solutions that come to mind — from blast-proof wallpaper used to protect employees at the Pentagon to the rover wheels created for landing on the moon.

However, two other innovative solutions deserve to be noticed: land cover mapping and statistical modeling, which both support our nation’s Warfighters. 

Forest cover maps derived from satellite and aerial imagery directly support military operations, but distinguishing tree cover from other vegetative land covers is an analytical challenge. Tree cover impacts military operations by hindering vehicle and troop movement, preventing helicopter access and providing concealment to the enemy, and it’s upon these challenges that ERDC’s Geospatial Research Laboratory’s (GRL) Physical Scientist Dr. Sarah J. Becker and her team recently focused their efforts.

Exploring nature is a passion for Becker, a Corte Madera, California, native, and working at GRL allows her to marry her passion and job. “I love exploring local parks and hiking trails, like Great Falls Park and the Washington & Old Dominion Trail in Virginia,” she said.

“While the commonly used Normalized Difference Vegetation Index can identify vegetative cover, it does not distinguish between tree and low-stature vegetation consistently,” Becker said. “We developed the Forest Cover Index (FCI) algorithm take the multiplicative product of the red and near infrared bands to separate tree cover from other land covers in multispectral imagery.”

Becker, along with GRL’s Megan C. Maloney and Andrew W.H. Griffin, first conducted a multi-biome study of tree cover detection. This study expanded testing on an algorithm that was developed in 2014 and has been tested in multiple studies since then.   

While tree maps already exist, they are static and may be outdated. This study provided a user-interactive way to generate updated tree maps. 

“We developed the FCI algorithm to identify tree cover in satellite imagery,” Becker said.  “Our first two papers focused on testing the algorithm in one location.  A recently submitted journal article expanded testing to other locations to determine if the algorithm was more widely applicable.”

Charting agriculture is work Becker is very familiar with.

“I spent many years mapping agriculture, which was how I came up with the idea to develop an algorithm to mask out tree cover, since trees are often confused with agriculture and other vegetation using traditional remote sensing techniques,” Becker said.  “My prior agricultural projects included hyperspectral ground-based data collection of agriculture and other objects.  I also completed projects to identify the optimal pixel size when working with data of different spatial resolutions and to study the relationship between environmental variables and conflict in Bangladesh.”

Becker earned her doctorate in environmental health, science, and policy from the University of California, Irvine, and her bachelor's degree in earth and planetary sciences from Johns Hopkins University. In her free time, she enjoys visiting her hometown and hiking the forested hillsides in and around Corte Madera, California, and in Virginia.

“Now that I study trees for a living, I pay more attention to trees in my recreational life too,” she said.