Topographic correction for ground penetrating radar for enhanced detection of dike subsurface anomalies

Dikes are critical components of flood control infrastructure in China. Ground-penetrating radar (GPR) is widely used for non-destructive detection of subsurface anomalies (e.g., cavities, seepage paths, and soil loosening) in dikes. Conventional GPR surveys are typically conducted along longitudinal lines on the dike crest, which limits comprehensive cross-sectional assessment. This study introduces a novel trapezoidal survey layout that integrates data from upstream/downstream slopes and the crest, coupled with a terrain-correction algorithm. The method projects slope-acquired radar signals onto a topographic model, enabling fused visualization of subsurface anomalies and dike morphology. Validated via borehole and cone penetration tests (CPT) at a Yellow River dike site, the corrected GPR profiles accurately delineated soil stratification and localized a loose-soil zone at the downstream slope foot. This approach significantly enhances interpretability for dike safety assessments.