Improving crosshole ground‐penetrating radar full‐waveform inversion results by using progressively expanded bandwidths of the data

In the last decade, time-domain crosshole ground-penetrating radar full-waveform inversion has been applied to several different test sites and improved resolution reconstruction of subsurface properties. The requires diligent executed pre-processing steps guarantee a successful minimize risk being trapped in local minimum. Thereby, one important aspect is starting models inversion. Generally, adequate need fulfil half-wavelength criterion, which means that modelled data based on be within half wavelength measured entire investigation area. Ray-based approaches can provide such models, but presence high contrast layers, results do not always this criterion updated. Therefore, precise detailed processing good understanding experimental are necessary avoid erroneous results. Here, we introduce new approach, improves model problem able enhance medium approach tames non-linearity issue caused by complex media, applying bandpass filters with passband ranges during data. these considered for certain number iterations progressively expanded selected maximum frequency bandwidth. resulting permittivity update effective source wavelet used as an updated full bandwidth This electrical conductivity standard tested two synthetic case studies set. field were additionally compared cone penetration validation.