An investigation into underground navigation using electromagnetic waves

This thesis explores the possibility of measuring the movement of an underground transmitter using electromagnetic waves. The displacement of the transmitter was estimated based on the magnitude and phase of the received electromagnetic wave, using receiver antennas at fixed locations. Electromagnetic wave propagation underground was dependent on the frequency used, soil type, soil moisture content and environmental conditions. An extensive investigation has been conducted in measuring the soil dielectric constant and conductivity. When the sample moisture was increased, its dielectric constant increased, being disperse for clays, but fairly linear for sands. Clays show a higher conductivity. The optimum antennas to use underground were dielectric loaded electric monopole and dipole antennas. A method was developed to predict the admittance of insulated monopole antennas in soil using measured data of the ambient medium. [Continues.]