Gaussian rough surfaces can be characterized by two roughness parameters, the root-mean-square height and correlation length. For accurate estimation of these parameters from measured surface height-profile, data samples with sufficiently long record length are necessary. In this letter, an expression of correlation length in terms of a surface slope function is introduced in order to estimate correlation length and analytical expression of the data record length required for accurate estimation is derived. The result shows that the method using the slope function can reduce the data record length approximately 60% as compared to the commonly employed method using the correlation function. In order to check the result, a Monte Carlo simulation is also carried out and the validity of the result is confirmed.

A method of calibration for GPR responses is introduced in order to extract a target response from GPR data. This calibration procedure eliminates undesirable waveform distortion that is caused by antenna characteristics and multiple scattering effects between the antennas and the ground surface. An application result to measured GPR data shows that undesirable late-time responses caused by the antenna characteristics and multiple scattering effects are removed, and that the target response is clearly reconstructed. This result demonstrates that the waveform calibration of GPR data is significant and essential for reliable target identification.

This brief paper proposes a method for calibration of GPR pulse waveforms that is effective for identification of buried objects in the ground and/or in concrete structures. This approach is based on the inverse filtering operation that eliminates the influence of GPR antenna characteristics, and a response from a flat metal plate is employed as a reference data for calibration. In order to evaluate the effectiveness of this approach, it is applied to actual experimental data measured by the UWB-GPR antennas. The results show the validity of the method and importance of the waveform calibration for target identification.