"The main objective of this research project is to develop and field test an induction system and estimator algorithm for remote determination of the shape and size of underground coal burn voids. During the first quarter the newly configured induction system was field tested on several traverses at Hanna. A computer program was written and tested for generation of induction responses of buried conducting boxes. During the second quarter field tests were continued . Hanna II, Phase 1 was completely characterized with 4 traverses. Hanna II, Phases 2 and 3, Traverse I was rerun to spot-check for changes that might have occurred in 1 1/2 months since the original traverse wns run. Only slight changes in response were ted. Field data for this later site was processed on the new Fourier Analyzer System and 3-dimcnsional response maps were plotted via the central computing system in both time and frequency domains. The magnitude frequency response exhibited a ]00-to-1 anomaly at 25 kHz as the system was moved across this site. Two Bayes estimator algorithms were derived for the radius of an infinitely long cylinder. A Monte Carlo simulation demonstrated that the numerical algorithm performed nearly identical to the analytic algorithm at various signal-to-noise ratios. Optional conducting wells were added to the computer program for responses of buried conducting boxes. However, this modeling docs not produce significant response anomalies commensurate with those obtained by field measurements. Consequently the air/earth interface effect will be included next."