What is the true time range of a GPR system?

Time range accuracy of GPR equipment is extremely important when quantitative target depth and wave propagation velocity information about the subsurface is required. It is common practice for GPR operators to accept the time range reported by the GPR system as being accurate. This can lead to inaccurate target depth estimates when repeating surveys with different time range settings or GPR equipment configurations. This paper formalizes a simple yet effective technique to measure the true time range of a GPR system based on a physical model. GPR operators can use the technique for system calibration and assess the time range accuracy of their equipment. The results of a comparison between the reported time range and measured time range values of some commercial GPR equipment are also presented.