GPR time-energy density analysis with complex wavelets for concrete data analysis

The ground penetration radar is a geophysical method that has achieved great progress in recent years in the inspection of concrete structures. It has been used to identify pathologies and estimate structure parameters. However, to analyze data from Ground Penetration Radar, an image-based analysis in time domain is commonly required. This requires a specialized operator to identify patterns, which increases the subjectivity of this methodology. The analysis of complex structures and the identification of weak signals become difficult with image-based analysis. Therefore, other analysis methodologies should be applied to improve the Ground Penetration Radar results. A possibility explored in this study is the use of Time Energy Density Analysis with Complex Wavelet Transform using Complex Morlet Wavelet to analyze concrete structure data. Using the absolute value of the complex analysis combined with the Time Energy Density analysis shows good results, which are cleaner than those from Real Wavelets. This facilitates the automation process and reduces the inspector's subjectivity. The method was tested in two different scenarios with different complexities and was able to locate rebars and estimate the concrete thickness, even for a shotcrete structure of a tunnel with considerable geometric variability.