Auto-picking and phase assessment by means of attribute analysis applied to GPR pavement inspection

We propose an automated procedure, based on attribute analysis, to quickly and objectively detect and characterize reflections along GPR profiles. The process uses the cosine of the instantaneous phase to mark as a horizon any event that shows lateral phase continuity, defining its time-space positions and peak amplitudes, to be used in interpretation and inversion processes. Such attribute allows to efficiently track even the weakest events, as well as those showing large lateral amplitude variations. Furthermore, the algorithm is able to extract the polarity of each reflection, by identifying their actual initial phase. This analysis is done by assessing the behavior of the cosine phase in the vicinity of each picked horizon, searching for other sub-parallel horizons that can be grouped into the same event. The proposed procedure is mostly independent from the interpreter, except for a few required thresholds. Moreover, since it uses only the cosine phase, it can be applied to data sets after basic processing without the need of any amplitude recovery, which introduces a certain degree of subjectivity on the results and prevents further quantitative analyses and data inversion. In this paper we validate the method and discuss its accuracy, as well as its limitations and possible applications. The algorithm successfully tracked events with lateral phase continuity in the tests performed on GPR data acquired on an airport runway.