The main objective of this project is to develop and field test an induction system and estimator algorithm for remote determination (at the surface) of the location, shape and size of underground coal burn voids. Field measurements were conducted with a wideband loop-loop induction system at the Hanna Underground Coal Gasification Site of the LERC during July, August and October of 1976. Field data were processed on the new Fourier Analyzer System and 3-dimensional response maps were plotted via the central computing system in both time and frequency domains. Strong anomalies at 5 kHz were observed on traverses over both burns at Hanna II. Computer programs for generation of induction responses of 3 different buried conducting bodies have been written and tested. The effects of conducting wells and the air-earth interface were explored. A Bayes statistical estimation procedure was developed to interpret induction responses for shape and size information. An analytic and a numerical minimum mean-square-error algorithm were developed for the estimation of the radius of a cylindrical conductor. Performance of the general numerical algorithm was shown to be nearly identical to that of the analytic algorithm.