Estimating Features of Underground Utilities: Hybrid GPR/GPS Approach

Abstract

Ground penetrating radar (GPR) is capable of detecting, locating, and characterizing underground utilities in a non-destructive manner. However, processing raw GPR scans to estimate the buried depth and radius of underground utilities remains a challenge in practice, which can be attributed to two main constraints: (1) the necessity of the GPR scanning trajectory being perpendicular to the centerline of the utility to be scanned and (2) the requirement of knowing either the velocity of the GPR electromagnetic (EM) waves traveling through heterogeneous soils or the range of the utility’s radius. This paper presents a novel method to overcome the two limitations by simultaneously estimating the radius and the buried depth of underground utilities based on GPR scans and auxiliary global positioning system (GPS) data. First, GPR scans are pre-processed to extract raw data points. Thereafter, a generic hyperbola equation is proposed to model GPR raw data, which incorporates the relative angles between buried utilities and GPR scanning trajectories. The very important point (VIP) algorithm then is developed to estimate the radius and depth utilizing auxiliary GPS data. The proposed new method was validated using GPR field scans obtained under various settings and was found to increase the accuracy of estimating the buried depth and radius under a general scanning condition (i.e., when both the EM wave velocity and the range of the radius are unknown and the GPR scanning trajectory is not perpendicular to the centerline of the buried utility).