Influence of Earth curvature on the subsurface electromagnetic fields of a line source

The subsurface magnetic field produced by an oscillating line source of current on the Earth´s surface is considered. Particular attention is given to evaluating the effect of non-flatness of the ground on the structure of the field at the buried receiving point. It is indicated that the wave-tilt ratio will still be a useful parameter in contemplated schemes for direction-finding in mine rescue operations.