GPR Bscan Change Detection Network for Structural Defect Evolution

Shape change detection is crucial for monitoring structural defect evolution. However, variations in temperature and precipitation dynamically alter the dielectric properties of structural defects and underground soil media, impacting the position and shape of scattering curves in ground penetrating radar (GPR) Bscan. This poses a challenge in determining the shape of the changing area by using dual-time GPR Bscan comparisons. To extract the structural defect features and shape change detection under changing backgrounds, this paper proposes a change detection network based on GPR Bscan (GPR CDNet). This method includes an encoder-decoder structure. In the encoder, we design a multi-scale and multi-dilated convolution (MSMDconv) to construct a pseudo-Siamese backbone feature extraction network to enhance contextual understanding and capture fine-grained details. Furthermore, to improve the accuracy of reconstructing the shape of the changing region, the feature transformation module (FTM) is designed to convert Bscan features into spatial model features to enhance the representation of change feature information. The Bscan features are then fused with the spatial model features and input into the decoder to reconstruct the shape of the changing area. In addition, this paper conducts experiments in the background medium and structural defect relative permittivity changes, rebar shielding, and actual sandbox scenarios. The results show that the network can adapt to the changes in the background medium’s relative permittivity and the structural defects’ relative permittivity and reconstruct the regional shape of structural defects that change over time with better
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performance and less computational complexity.