Assessing the Precision of GPR Velocity and Vertical Two-way Travel Time Estimates

Accurate estimates of ground penetrating radar (GPR) traveltimes and velocities are essential to a number of civil engineering, agricultural and watershed management activities. This paper reports on a study to assess confidence limits on radar parameters using a sequence of high quality common midpoint (CMP) soundings collected on eight different days over the course of a year at a single location for a range of soil moisture conditions. On each day, a “repeat” CMP was acquired leading to a total of 16 independent CMP soundings. Two prominent reflections, present in all 16 independent CMP soundings, were analyzed to provide NMO velocities and vertical two-way traveltimes along with their associated 95% confidence limits estimated using Student’s t-test, accounting for both the appropriate number of observations and estimated parameters. Interval properties were then determined using the Dix relation. The radar velocity of the 1st interval has the largest variation observed, from 0.074(±0.002)m∕nsto0.146(...