Use of fixed-wing and multi-rotor unmanned aerial vehicles to map dynamic changes in a freshwater marsh1

Abstract

We used a multi-rotor (Phantom 2 Vision+, DJI) and a fixed-wing (eBee, senseFly) unmanned aerial vehicle (UAV) to acquire high-spatial-resolution composite photos of an impounded freshwater marsh during late summer in 2014 and 2015. Dominant type and percent cover of three vegetation classes (submerged aquatic, floating or emergent vegetation) were identified and compared against field data collected in 176 (2 m × 2 m) quadrats during summer 2014. We also compared these data against the most recently available digital aerial true colour, high-resolution photographs provided by the government of Ontario (South-western Ontario Orthophotography Project (SWOOP), May 2010), which are free to researchers but taken every 5 years in leaf-off spring conditions. The eBee system produced the most effective data for determining percent cover of floating and emergent vegetation (58% and 64% overall accuracy, respectively). Both the eBee and the Phantom were comparable in their ability to determine dominant habitat types (moderate kappa agreement) and were superior to SWOOP in this respect (poor kappa agreement). UAVs can provide a time-sensitive, flexible, and affordable option to capture dynamic seasonal changes in wetlands, information that ecologists often require to study how species at risk use their habitat.