Identifying surface water content from full wave inversion of off-ground monostatic ground penetrating radar signal
(2005) Internat. workshop “Measuring soil water contents at different scales” — Location: Forschungzentrum Jülich (Germany)
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- Abstract
- Knowledge of the spatial distribution and dynamics of the shallow subsurface water content at a scale being relevant for the understanding and management of the soil-plant-atmosphere system is essential in many agricultural and environmental engineering applications. Existing techniques to characterize the inherently variable soil water content are either suited to small scales, such as the gravimetric method or time domain reflectometry, or to large scales, such as airborne and spaceborne passive microwave radiometry and active radar techniques. As yet, no practical method is available to measure the variability of soil water content at field or watershed scales, which is crucial in applications that include agricultural water management and soil and water conservation. In that respect, ground-penetrating radar (GPR) constitutes a tool with great potential for mapping the soil water content at an intermediate scale. Recently, Lambot et al. proposed a new promising approach for identifying the soil hydrogeophysical properties using GPR. Relying on a conceptual GPR model, the method is based on full-wave inversion of the GPR signal in the frequency domain for an off-ground monostatic antenna configuration. The approach has been successfully validated in laboratory conditions for identifying both the dielectric permittivity and electric conductivity of a two-layered sandy soil subject to a range of water contents, to identify a continuous water content profile in controlled outdoor conditions using hydrostatic concepts, to monitor the dynamics of water in a sand column and subsequently derive the soil hydraulic properties using hydrodynamic inverse modeling, and to investigate the frequency dependence of the soil dielectric permittivity and electric conductivity of a sandy soil for different water contents. In the continuation of these advances, the objective of the ongoing research is to particularly investigate the theoretical and practical feasibility of identifying the surface dielectric permittivity and water content from full-wave radar inversion, by focusing in the time domain on the surface wave reflection. Numerical experiments were performed to elucidate the physical limitations of the current surface reflection method and to investigate the well-posedness of the inverse scattering problem. Then, laboratory and field scale experiments were conducted to give insights into the sensitivity of signal inversion with respect to actual modeling and measurement errors. Finally, an experimental analysis was performed regarding the effect of soil surface roughness on the GPR signal.
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Lambot, S., Weihermüller, L., Huisman, S., Vanclooster, M., & Slob, E. (2005). Identifying surface water content from full wave inversion of off-ground monostatic ground penetrating radar signal. Internat. workshop “Measuring soil water contents at different scales”, Forschungzentrum Jülich (Germany). https://hdl.handle.net/2078.5/152989