Fig. 3. Different modes of permittivity analysis are outlined in the waveform transformation process. Travel time analysis (TTA) yields permittivities in the time domain using longer probes in non-saline soils. Discrete fast Fourier transform (DFFT) of the input [v_o(t)] and response [r(t)] function waveforms provide the scatter function [S₁₁(f)] from the transformed frequency-dependent functions V_o(f) and R(f). Permittivity estimates are obtained from scatter function fitting (SFF) utilizing Debye (1929) model parameterization or from resonant frequency analysis (RFA) giving permittivity estimates based on the resonant or half-wavelength frequency (f*).