Subsurface target identification using phase profiling of impulse GPR data

The problem of target discrimination in ground penetrating radar data (GPR) is addressed in this study. Formerly developed frequency-domain technique based on building separate amplitude and phase profiles for every A-scan has been modified to be suitable also for impulse GPR data. To this end, impulse radar data have been preprocessed and transformed to frequency domain. The rest of the algorithm is rather similar to the case of frequency-domain radar data. The method yields a phase profile as a function of depth that is related to the phase shift occurring in the act of reflection of the wave from inhomogeneity existing at given depth. This phase shift depends on the contrast between the target and surrounding medium and thus can be used for target characterization. The technique was used to interpret data collected over a test site, where metal bars and a plastic pipe were buried inside sand and gravel. The radar data was collected with Malâ´s CX11 Concrete Imaging System operating at the 1600 MHz central frequency. The images built with the use of the novel signal processing technique demonstrate its validity for recognition of some buried objects.