Though Ground Penetrating Radar serves as an insightful and comprehensive subsurface imaging tool, functionality and readings can vary widely due to site conditions. Though GPR equipment may not perform optimally in all conditions, it can perform basic functions in a wide variety of sites. The chart included here demonstrates the potential depth for GPR.
As you can see, ground penetrating radar can reach depths of up to 100 feet (30 meters) in low conductivity materials such as dry sand or granite. Moist clays, shale, and other high conductivity materials, may attenuate or absorb GPR signals, greatly decreasing the depth of penetration to 3 feet (1 meter) or less.