How are small unmanned aircraft systems (sUAS) such as drones being used at Princeton? How do they help students accomplish their classroom and research goals?
An example of sUAS in action comes from a course jointly offered by the Department of Geosciences and the Princeton Writing Program, “Measuring Climate Change: Methods in Data Analysis and Scientific Writing” (GEO/WRI 201).
This course, which took students to Utah over Fall Break to test hypotheses on the effects of climate change on a diversity of landscapes, made extensive use of drones in the field.
“The entire class is devoted to teaching students how to conduct a combination of image analysis and ground truthing to detect change in landscapes, and to communicate their findings in a scientific paper,” said Adam C. Maloof, associate professor of geosciences.
Students began with Landsat satellite data, mapping out and analyzing changes in vegetation density, type, and health. By comparing this information with weather station data, students formulated theories as to how changing weather patterns affect ecosystems.
On the trip, students used fixed-wing eBee Sensefly drones—about two pounds of Styrofoam with a camera—to gather 4-band (blue, green, red, and near infrared) photomosaics and digital elevation models. The drone imagery achieves 650x the spatial resolution of satellite data.
"These highly resolved drone datasets allow students to make tree-by-tree analysis and to test for links between metrics such as tree health and abundance with variables such as elevation, slope, and slope aspect (north-facing, south-facing, etc.)," Maloof explained.
Students studied the effect of climate warming on snowpack volume, forest fire recovery, the spread of invasive vegetation, drainage patterns, beetle infestations and tree mortality, and sand dune migration.
Drones in Action: Fieldwork Examples
Post-Fire Forest Recovery
Emily Geyman ’19 studied post-fire conditions in Utah’s Fishlake National Forest, examining the role of topography and vegetation in the rate of post-fire forest recovery. Using satellite, weather, and drone data, calibrated by in situ field surveys of tree species, tree height, soil depth, etc., Geyman concluded, among other things, that deciduous trees recover faster than juniper, and that, while the degree of mountain slope did not influence recovery, the aspect (facing) of a slope did. It turns out that north-facing slopes recovered more quickly, perhaps due to increased moisture retention on the cooler north faces.
Invasive Tamarisk Narrows the River
When conducting on-site surveys of tamarisk in the Colorado River floodplain, the Princeton group found collecting samples difficult due to thick groves of the invasive tree. This was no obstacle for the drones, which gathered important elevation and color data from above.
"Many of the thickets of willow and tamarisk trees in the floodplain were impassible," said Artemis Eyster ’19. "Because we couldn't collect ground-based elevation measurements of the floodplain I used the digital surface model obtained from flying a [drone] to determine the the topography of the floodplain."
Floodplain topography was key to understanding the difference in elevation between tamarisk and willow-dominated regions. Used alongside satellite images, hydraulic measurements and tree cores, the information allowed Eyster to determine how tamarisk's colonization of the floodplain impacts river flow.
The conclusion? Eyster found that tamarisk trees stabilized and preserved once-shifting sand bars, which narrows the river over time, making the region more prone to flooding.
Section 336 Exemption for sUAS
In May 2016, the Federal Aviation Administration clarified the educational use of unmanned aircraft systems as applicable under section 336 of the FAA Modernization and Reform Act of 2012, an important step which now enables students to learn first-hand about small unmanned aircraft systems (sUAS) as useful tools in various academic curricula such as this one.
The exemption allows students to operate sUAS (including drones and model aircraft) under the provisions set out for hobby and recreational use, rather than those required for commercial operators. Learn More »