Comparing multispectral and hyperspectral UAV data for detecting peatland vegetation patterns
Yuwen Pang, Aleksi Räsänen, Franziska Wolff, Teemu Tahvanainen, Milja Männikkö, Mika Aurela, Pasi Korpelainen, Timo Kumpula, Tarmo Virtanen
Abstract
• We detected spatial patterns of plant community clusters, plant functional types, and plant species in two northern peatlands. • We utilized uncrewed aerial vehicle (UAV) hyperspectral and multispectral imagery and topography data. • The combination of multispectral and topography data yielded the best performance in most cases. • The UAV hyperspectral data aided in the identification of some vegetation characteristics. Northern peatland vegetation exhibits fine-scale spatial and spectral heterogeneity that can potentially be captured with uncrewed aerial vehicle (UAV) data due to their ultra-high spatial resolution (<10 cm). From this perspective, the contribution of different spectral sensors in mapping various vegetation characteristics has not been thoroughly investigated. We delineated spatial patterns of plant community clusters, plant functional types (PFTs), and selected plant species with UAV hyperspectral (HS), UAV multispectral (MS), and airborne LiDAR (light detection and ranging) topography (TP) data in two northern peatlands. We conducted random forest (RF) regressions in a geographic object-based image analysis (GEOBIA) framework and compared the relative contributions of the different datasets. In the best regression models, the percentage of explained variance was 24–74 % (RMSE:0.24–0.31), 40–90 % (RMSE:0.12–0.41), and 18–90 % (RMSE:0.03–0.40) for plant community clusters, PFTs, and plant species, respectively. The MS-TP combination had, in many cases, the highest performance, while HS-based models had better performance for some plant community clusters, PFTs, and plant species. TP features were useful only in certain situations. Overall, our results suggest that UAV MS imagery combined with TP data outperformed or performed at least almost as well as the models using UAV HS data and while all data combinations are capable for fine-scale detection of vegetation in northern peatlands. A more comprehensive investigations of data processing and methodology selection is needed to conclude if there is an added value of UAV HS data for peatland vegetation monitoring.