Methods for Determining Soil Moisture with Ground Penetrating Radar (GPR)

The soil water content has a dominant influence on the dielectric permittivity E of porous media because of the high permittivity of water compared with the matrix. The well known Maxwell’s relation which is valid for most natural soils combines the permittivity and the phase velocity v of electromagnetic waves where co is the velocity of light in vacuum, 1$$\varepsilon = \left( {\frac{{c_0 }} {\nu }} \right)^2 \cdot $$ Thus the water content can be quantified by determining this velocity. There exists a wide variety of possibilities to determine the phase velocity of the ground penetrating radar waves, whereby two of them will be introduced in the following section.