Combining ground-penetrating radar sections with different antenna frequencies including time-frequency domain noise suppression filters

Abstract

Ground-penetrating radar (GPR) is one of the most useful geophysical methods that rapidly and efficiently provide high-resolution subsurface images depending on antenna frequencies and target depth. Recently, to enrich the interpretation of GPR sections, multifrequency sections have been combined at deeper and shallower levels in a profile. In this context, the techniques of combination and image quality improving processes of GPR data also have gained importance. For this, simple summation (SS) and time-shifted balanced summation (TSBS) techniques, frequency-domain local mean notch filter (FDLMNF), frequency-space ( f- x) filter, and automatic gain control (AGC) processes are sequentially applied within a workflow. Although the FDLMNF is used to effectively remove single-frequency spike-like noises without distortion around the notch frequency, the f- x filter is applied to suppress the random noise and improve the lateral traceability of the section, and AGC provides a statistically based gain recovery. In the proposed workflow, after generating synthetic and field GPR data with 100 and 250 MHz frequencies, data were combined using SS and TSBS techniques. Finally, FDLMNF, f- x, and AGC were applied to increase the image quality of this combined section. The result sections were evaluated and compared using the Fourier average amplitude and f- k spectra. According to the spectra, the TSBS technique provides good spectral balancing and offers wider spectral content. At the same time, it was observed that the image quality of the combined GPR sections increased significantly after applying FDLMNF, f- x, and AGC processes. As a result, when the sections resulting from SS and TSBS techniques are examined, the image enhancement processes that protect and strengthen the spectral bandwidth of the data are successful. Thus, the temporal resolution and spatial continuity of GPR sections also will be increased, and a better quality interpretation will be provided.