GPR System to Inspect Underground Distribution Systems

Abstract

Laboratory experiments were used to investigate the potential of using ground penetrating radar (GPR) to detect problems in the underground distribution system. Surface geophysical methods are noninvasive, trenchless tools used to characterize the physical properties of the subsurface material. This characterization is then used to interpret the geologic and hydro geologic conditions of the subsurface. Many geophysical techniques have been suggested among them Ground penetrating radar (GPR) is one of the common sensor systems for underground inspection. GPR is a reflection technique which uses high frequency electromagnetic waves to acquire subsurface information. GPR responds to changes in electrical properties, which are a function of soil and rock material and moisture content. It emits electromagnetic signals which can pass through objects are recorded, digitized and then, the B-scan images are formed. Depending upon the properties of scanning object, GPR creates different intensity values on the object regions. Thus, these changes in signal represent the properties of scanning object. This paper proposes a three step method to detect and discriminate buried pipes : N-row average-subtraction (NRAS), Min-max normalization and image scaling. Proposed method has been tested using three common algorithms from the literature. Results shows increased object detection ratio and positive object discrimination (POD) significantly.