Electromagnetic wave method for mapping subterranean earth formations

A method for mapping anomalies in a subterranean coal bed prior to in situ gasification of the coal bed and for providing the description of the continually changing characteristics and position of a burn front resulting during the in situ gasification of the coal bed, comprising the steps of emplacing a highly directional electromagnetic wave transmitting means and an electromagnetic wave receiving means including a voltage standing wave ratio meter in each of a plurality of vertical directionally oriented bores penetrating the coal bed, transmitting electromagnetic waves at a different selected frequency up to 10,000 MHz over a selected azimuth angle in each of said bores for effecting a reflection of the electromagnetic waves upon encountering an electrical anomaly indicative of at least one of a solid-gas interface indicative of the burn front, a solid-liquid interface, and a solid-solid interface where the electrical properties of the solids defined in the solid-solid interface differ, and providing a polar plot of the magnitude of the reflected waves and the ratio of the power of the reflected waves to the power of the incident waves at each selected frequency and correlating the dielectric constant of the coal bed and tangent loss at each transmitted frequency with each other for providing the mapping of the anomlies in the coal bed and the description and position of the burn front in the coal bed.