An improved procedure for the determination of ground parameters using level difference measurements

Attenborough has developed a theory to predict the ground impedance from four physical parameters; the flow resistivity (σ), the tortuosity (T), the porosity (Ω), and the pore shape factor (sp). This theory has been used to determine the flow resistivity, tortuosity, and effective flow resistivity (sp2σΩ) by fitting level difference measurements above the soil surface to the theory [Soil Sci. Soc. Am. J. 54, 658–672 (1990)]. Subsequent work indicated that this procedure may be indeterminate. A numerical and analytic study is performed to identify and remove the indeterminacy. A new form of the Attenborough four parameter model which is a function of two independent variables is developed and is shown to be determinate for simulated data and for data published previously. These new variables are the reduced flow resistivity and reduced tortuosity. Since there are only two independent variables, an additional measurement is required to determine σeff, T, and Ω. Two measurements are suggested to remove the indeterminacy.