Ground penetrating radar survey is a surface, non-destructive geophysical technique using electromagnetic radiations and detecting signals reflected from subsurface structures. GPR survey is used in engineering geology for pre-investment site characterization, location of cavities and voids, detection of buried objects, underground tunnels, for archaeological and environmental studies. 

GPR operates above the ground. The device  detects signals reflected from subsurface structures and produce cross-sectional image of the ground. The depth range of GPR measurements depends on some factors as a frequency of  emitted radio-wave, capability of the transmitting antenna  as well as electrical properties of the geological medium.