Multi-sensor UAV-platform including SAR for high-fidelity measurement of vertically resolved soil moisture distribution and its coupling with distributed sensor network data

When managing ecosystems & water resources and for applications in precision agriculture, there is a need for improved methods to economically measure and monitor soil moisture versus depth below the surface. There is also a need to properly incorporate these measurements with data from other existing sensors to improve the calibration of complex hydro-biogeochemical models. Addressing the Problem – A prototype novel miniature ground penetrating synthetic aperture radar will be built to provide precise and accurate measurements of soil moisture versus depth below the surface. The radar’s miniaturized size allows deployment on small aircraft and unmanned air vehicles as well as drones. The use of these small platforms results in cost effective operation to allow soil moisture to be measured frequently to monitor changes over short time periods. A new data assimilation framework will be developed to merge the soil moisture profiles with other airborne imagery and point sensor data to generate physically-based hydrological models to improve the estimation of soil hydraulic parameters and evapotranspiration. Phase I Work Completed – A small synthetic aperture radar breadboard was developed and bench- tested. Another synthetic aperture radar was used to collect airborne data over an area saturated with water via a controlled water release. The data collected was processed to provide a remote measurement of soil moisture. Preliminary development work was done on a new data assimilation framework. Phase II Work Planned – Build a fully functional prototype of a miniature synthetic aperture radar to measure soil moisture versus depth. Airborne SAR data will be collect airborne data at several field sites outfitted with ground-based soil moisture sensors to establish ground truth. The data will be processed to provide soil moisture profiles. A new data assimilation framework will be developed and used to merge the moisture profiles with ground-based point sensors and optical/IR imagery to generate improved physically-based hydrological models of the subsurface. Benefits & Commercial Applications – The developed capabilities will benefit researchers who study and model ecosystems and hydrological processes. The project will provide soil moisture data with high spatial resolution and allow monitoring at high temporal rates to help improve ecosystem modeling & understanding of hydrological processes. The soil moisture data and monitoring capability will have strong, commercial applications in precision agriculture, which will provide significant benefits to society by reducing growers’ application of water and chemicals to their fields while increasing crop productivity.