Mapping of surface soil water content using a droneborne GPR and Sentinel-1 SAR

Soil water content is a key parameter in many hydrological, climatological and environmental processes. It can be measured at different scale with different techniques. In this thesis, two methods for mapping the soil water content are explored. First, the ground-penetrating radar (GPR), which is based on soil electromagnetic properties, allows to measure the soil water content through soil relative dielectric permittivity characterisation. In this study, this method is taken one step further as the GPR is fixed to a drone. This allows for a low time-consuming method for soil water content characterisation at field scale. The second method uses SAR from Sentinel-1. Sentinels are satellites developed by the European Space Agency and launched as a part of the Copernicus programme. All the Sentinel products are open access and totally free. Maps from both methods present convincing results as they are in line with the pluviometry and the topography. However, the correlation between the results of both the droneborne GPR and the Sentinel-1 data is not satisfactory. The effect of the drone tilting while flying is also explored. Low tilt angles (<10°) have little impact on the measurements but higher tilt angles, especially for lateral tilting, have a significant impact. Sentinel-1 soil water content monitoring presents more interest at a bigger scale but the droneborne GPR stands out as a promising tool for soil water content monitoring at field scale, with a lot of potential applications in the near future.