Authors

B Jafrasteh, N Fathianpour, SH Tabatabaei

Description

Ground Penetration Radar (GPR) as a nondestructive method for identifying underground objects has been successfully applied to different fields of science such as geotechnical investigations, oil and gas exploration, geology, pipe detection and archeology investigations. Metallic and nonmetallic objects can be identified by this method. The depth of penetration is dictated by the GPR antennas. Low frequency antennas (from 25-200 MHz) explore materials from deeper depths in the low cost resolutions. High-frequency antenna (> 200 MHz) obtains reflections from shallow depths with higher resolutions. Ground penetrating radar is considered as the most suitable approach to detect shallow buried objects. Transmitter and receiver antenna are closely spaced together and can detect changes in the electromagnetic properties of an object. Electromagnetic waves are transmitted through an antenna and the reflected waves form various buried objects or contacts between different materials are received and stored in digital control unit. Antenna shielding is performed to eliminate interferences from other intruder sources. Electromagnetic waves are emitted by the transmitting antenna and distorted by the soil conductivity variation, dielectric permittivity, and magnetic permeability. The reflected waves are recorded by the receiving antenna in nanoseconds. The shape of GPR radargrams, vertical map of the radar reflection returned from subsurface objects, of cylindrical objects is similar to a hyperbola. Interpretation of acquired GPR data needs an expert geoscientist with a lot of knowledge and time.