The Potential of Optical UAS Data for Predicting Surface Soil Moisture in a Peatland across Time and Sites

• Published in: Remote sensing (Basel, Switzerland) Vol. 14; no. 10; p. 2334
• Main Authors: de Lima, Raul Sampaio, Li, Kai-Yun, Vain, Ants, Lang, Mait, Bergamo, Thaisa Fernandes, Kokamägi, Kaupo, Burnside, Niall G., Ward, Raymond D., Sepp, Kalev
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.05.2022
• Subjects: Accuracy; Carbon; Datasets; Drought; Environmental conditions; Image acquisition; Least squares method; Machine learning; microtopography; Moisture effects; multi-spectral; Peatlands; Photogrammetry; Physiology; Regression analysis; Remote sensing; Root-mean-square errors; Sensors; Soil moisture; Soil surfaces; Statistical analysis; unmanned aerial vehicle (UAV); Unmanned aerial vehicles; Variables; Vegetation; vegetation indices; volumetric water content; Water stress
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs14102334

Advances in unmanned aerial systems (UASs) have increased the potential of remote sensing to overcome scale issues for soil moisture (SM) quantification. Regardless, optical imagery is acquired using various sensors and platforms, resulting in simpler operations for management purposes. In this respect, we predicted SM at 10 cm depth using partial least squares regression (PLSR) models based on optical UAS data and assessed the potential of this framework to provide accurate predictions across dates and sites. For this, we evaluated models’ performance using several datasets and the contribution of spectral and photogrammetric predictors on the explanation of SM. The results indicated that our models predicted SM at comparable accuracies as other methods relying on more expensive and complex sensors; the best R2 was 0.73, and the root-mean-squared error (RMSE) was 13.1%. Environmental conditions affected the predictive importance of different metrics; photogrammetric-based metrics were relevant over exposed surfaces, while spectral predictors were proxies of water stress status over homogeneous vegetation. However, the models demonstrated limited applicability across times and locations, particularly in highly heterogeneous conditions. Overall, our findings indicated that integrating UAS imagery and PLSR modelling is suitable for retrieving SM measures, offering an improved method for short-term monitoring tasks.