Soil water content determination using a digital ground-penetrating radar

We evaluated the potential of a digital ground-penetrating radar (GPR) for soil moisture determination. Ground-penetrating radar offers a fast and nondestructive way for estimating the soil dielectric constant and may be an interesting tool for low-cost mapping of soil moisture. Two modes of operation were considered: (i) the ground mode where signal propagation between the antennas placed on the surface was studied; (ii) the airborne mode where the antennas are raised 5-15 m above the soil surface. Variables describing the GPR response were defined and related to the soil moisture. It is shown from field experiments that the GPR measurements performed at 200 MHz in both modes are mainly affected by the moisture in the 10- to 20-cm topsoil layer. In the ground mode, the obtained soil moisture error after calibration was lower than 0.03 m(3)/m(3). In the airborne mode, soil moisture estimations were less accurate (0.046 m(3)/m(3)). The wave spreading loss characterization has to be improved to get an altitude-independent GPR measurement.