Thermal Radiation Dynamics of Soil Surfaces with Unmanned Aerial Systems

Thermographies are a source of abundant and rapid information, valuable in precision agriculture tasks such as crop stress assessment, plant disease analysis, and soil moisture evaluation. Traditionally, practitioners obtain soil temperature directly from the ground or using satellites and other airborne methods, which are costly and have a low spatial and temporal resolution. In this paper, we introduce a method for short term tracking of thermal radiance inertia with the use of an unmanned aerial system (UAS). In our approach, we retro-project the spatial reconstruction obtained with structure from motion (SfM) to estimate the thermal radiation corresponding to three-dimensional structures. Then, we register the resulting orthomosaics using a pyramidal scheme. We use the first cloud of points as the fixed reference as new orthomosaics become available. Finally, we estimate the dynamics of the thermal radiation using the difference of the registered orthomosaic radiation intensity measurements.