Finding the Soil Surface in GPR Profiles: The Lift Test

Ground-penetrating radar (GPR) can be used to determine the depth to a subsurface layer if the user can identify where the ground surface is on the GPR trace. This study demonstrates a simple field procedure for unequivocally determining the ground surface in a GPR trace. A “lift test” was performed simply by raising the transceiving antenna unit off the ground and setting it back down while the GPR unit was recording. This procedure produced a distinct wave pattern on the GPR profile that clearly showed the soil surface. The lift test improved accuracy of depth estimates by approximately 10% in a GPR study to determine depths to moderately fine and fine textured horizons at a drained Carolina bay wetland restoration site. Though easy to perform, this procedure has apparently not been used in many GPR studies. The lift test provides an efficient means of determining the soil surface in GPR surveys, a necessity if accurate depth measurements are to be made.