A small fleet of drones recently buzzed through the sky over the USGS Earth Resources Observation and Science (EROS) Center.
The EROS Cal/Val Center of Excellence (ECCOE) invited the USGS National Uncrewed Systems Office (NUSO) to Sioux Falls, South Dakota, to evaluate how data captured by NUSO’s aircraft match up with data captured by satellites during direct flyovers.
The uncrewed aerial systems (UAS), more commonly known as drones, were flown at USGS EROS the same time a Landsat 9 satellite passed overhead in its orbit. On the heels of Landsat 9, just 8 minutes later, Europe's Sentinel 2-B passed over with the UASs performing their same maneuvers. Two overpasses of the German Environmental Mapping and Analysis Program (EnMAP) satellites offered more opportunities to test the concept during the July 15-18, 2023, trial period.
The dream is for scientists to someday do field validation via UASs—but the concept is still in the early experimental stage, said Jeff Irwin, survey and field campaign lead at EROS for ECCOE and Terrain Monitoring and Modeling.
For this drone overflight, the uncrewed aircraft carried multispectral and hyperspectral instruments, explained Lance Brady, who leads NUSO, which is based at the USGS Geosciences and Environmental Change Science Center in Denver. “Working with the calibration and validation team is looking at how we can utilize these instruments to do satellite validation, if it’s even possible,” he said.
To collect the best data, Brady and fellow team members Matt Burgess, Joe Adams and Victoria Scholl ran test flights at 10 a.m., noon and 2 p.m. during the experiment. The drones flew in preprogrammed “lawn mower” patterns, making a grid both horizontally and vertically.
Irwin as well as ECCOE’s Mahesh Shrestha, along with Travis Kropuenske, contractor with KBR in the satellite ground system division, took part in and oversaw the experiment. They performed regular field validation in coordination with the drones.
During normal operations, for every satellite overfly, EROS personnel walk with a backpack of equipment on a field on the far side of the warehouse for validation purposes. When good weather conditions permit, that happens every eight days for Landsat and every five days for Sentinel-2 (although not on weekends for Sentinel-2).
The idea for the drone exercise was to carry out ground monitoring on this well-studied field, overflown by the drones and Landsat 9. That gives multiple layers of data for the scientists to evaluate.
A major focus of the work was to further ECCOE’s work on developing guidelines for calibrating UAS imagery for DOI agencies. This included testing several “homemade” calibration panels. In fact, the first set of guidelines for the idea already have been published. EROS’ Shrestha and NUSO’s Scholl were two of the four authors.
An EROS team traveled to NUSO’s home base in Denver in November 2022 for a similar experiment, but the weather failed to cooperate. July in South Dakota provided more suitable conditions, although high wind speeds hampered a flight one afternoon.
The NUSO team travels throughout the United States to assist various USGS science and mapping efforts as well as other agencies within the Department of Interior and other government entities, including training personnel to fly uncrewed aircraft. Learn more about their work here.
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