Ground Probing Radar also known as Ground Penetrating Radar (GPR) is a high resolution, field-portable geophysical method that produces graphic sections of subsurface structure. Typical site investigation applications include accurate location of voids and buried obstructions; mapping subsurface soil and rock interfaces and defining buried archaeological structures. The method can also identify ancient landfill sites and detect buried hazardous waste.
Surveys are non-destructive and non-intrusive, revealing detailed information on subsurface ground conditions without requiring drilling or excavation. Results are presented in an an easy to understand engineering compatible format.
A typical GPR system comprises an antenna unit, control console, display monitor and graphic printer. The antenna unit is in direct ground contact, while the remaining equipment can be vehicle-mounted or stationary. Data is collected along accurately located profiles, usually set-out in a customised survey grid.
Variable frequency, interchangeable antenna units can be used with the GPR system, depending on the application. Low frequency units offer greater depth penetration and are generally better suited for civil engineering and geological site investigations. Small, portable, high frequency units are used for high resolution work involving NDT of concrete and masonry structures (check out GPR for NDT below).
Impulses of UHF/VHF frequency electromagnetic energy are emitted from the moving antenna and propagated downward into the ground. Reflections are generated at any subsurface boundary where an electrical contrast is present. The reflected signals are detected by the antenna receiver and digitally stored by the control console for post-survey processing and interpretation.
Data processing is carried out using specialised interactive software to optimise survey results. Data interpretation procedures correlate reflections on the GPR record with real physical interfaces such as soil or rock layering, voids, foundations and archaeological structures.
