UAS could improve management of complex forest environments

Unmanned aircraft systems (UAS) offer the potential to provide timely and accurate reference data in forests and other complex environments for research and management applications, according to researchers at the University of New Hampshire.

Benjamin Fraser and Russell Congalton with the UNH Department of Natural Resources authored a paper published this month in a special issue of the peer-reviewed “Forests" journal, which is devoted to using unmanned aerial vehicles (UAV) for forestry applications.

The researchers conducted a study on about 1,300 acres of New England forest to evaluate the effectiveness of UAS to collect accurate map reference data. They noted that while advancements in remote sensing and computer science technologies have provided the ability to map increasingly complex environments, the accuracy of thematic maps based on this data must be assessed against reliable reference data, which can be difficult to obtain because of time and cost restraints.

“As UAS hardware, software, and implementation policies continue to evolve, the potential to meet the challenges of accurate and timely reference data collection will only increase,” the researchers wrote in their study. This is important, they said, because disagreements over the causes and impacts of environmental change “has forced an ever-increasing need for data accuracy and certainty.”

Thematic mapping relies on imagery from remote sensing to label objects and features in defined groups. It also provides information on land use and cover, which helps identify “both natural and artificial patterns and increase our ability to make informed decisions,” according to the paper.

Aerial imagery was collected during June and July 2017 using a senseFly eBee Plus fixed-wing UAS equipped with a sensor optimized for drone applications. The autonomous flight missions were performed using senseFly’s eMotion3 software. Agisoft PhotoScan was used for high-accuracy photo alignment and image tie-point calibration.

Validating data quality is a necessary step in the decision-making process when using conclusions drawn from remote sensing, the researchers said, adding that in the past, this has been difficult and costly to accomplish. However, the availability of UAS as low-cost, flexible platforms capable of generating on-demand, high-resolution images changes this. “UAS now assimilate microcomputer technologies that allow them to operate for forestry sampling, physical geography surveys, rangeland mapping, humanitarian aid, precision agriculture and many other applications,” the paper says.

The UNH researchers noted that all reference data has an intrinsic error and that UAS are not a replacement for on-site data collection. “The continual advancement of the platform, however, should be the basis for investigating their use in a greater number of environments, for the comparison to more varied ground-based reference data frameworks, and with the inclusion of more technologically advanced classification procedures,” their study concluded.