Pitfalls in GPR data interpretation: Differentiating stratigraphy and buried objects from periodic antenna and target effects

Periodic events in ground penetrating radar (GPR) data may result from antenna and target effects rather than reflections from geologic features. One of the most common pitfalls in GPR data interpretation is to identify each event on a radar cross-section as scattering from a discrete horizon, without considering other possible sources of these events. Soil electrical properties and surface roughness affect ground penetrating radar antenna radiation and waveform characteristics. An impedance mismatch occurs over soils with electrical properties different than those for which the antennas were designed to perform optimally over, and results in periodic ring-down, which can be misinterpreted as stratigraphy or multiple reflections. In addition, target resonance can introduce additional periodic features that can lead to misinterpretation in regards to the number of targets present. Co-pole and cross-pole antenna configurations can be combined with polarization dependent scattering characteristics of subsurface objects to recognize and reduce antenna ring-down for improved imaging and interpretation.