Correction of GPR wave velocity with distorted hyperbolic reflection in underground utility's GPR survey

A validation study was conducted over a fixed alignment of underground utilities to study the effects of GPR traverse directions on GPR wave velocity estimation of utilities. The experiment was carried out on a 0.98 m deep underground drainage pipe in the campus of Hong Kong PolyU. During the changes of GPR traverse directions relative to the fixed and known utility alignments at an angle 90°, 75°, 60°, and 45°, we studied the variation of GPR wave velocities estimated through the hyperbolic fitting process of the pipe's reflection, and correct it with a simple algorithm. Errors of velocity estimation would result in errors of depth estimation of buried utilities and variation of material properties.