Remote Sensing of Soil Moisture Using the Propagation of Loran-C Navigation Signals

The fractional water content of soil plays a central role in the complex interactions between the Earth and its hydrological cycle. However, obtaining continuous measurements of wide-area soil moisture is difficult. In our study, a novel method for the remote sensing of soil moisture is explored that makes use of the variations in time delay on Loran-C surface waves. An analysis was carried out using such signals recorded over a three-week period at the University of Bath, Bath, U.K., from a Loran-C transmitting station in Northern France. Model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) were used for calculation, calibration, and intercomparison. Reasonable correspondence between the soil moisture estimated using the Loran-C method and the ECMWF product was found for a soil depth of 0-28 cm.