Electromagnetic Cave-To-Surface Mapping System

The principle, design, and construction of an instrument for remote location of position<br>and depth of a transmitter in a cave will be presented. Two people can use the system to<br>map a cave location on the ground surface. The instrument consists of an EM dipole<br>transmitter/receiver configuration. The vertical component of the transmitted field reaches<br>a maximum at the point where the transmitter and receiver are vertically collinear. At this<br>position the horizontal component of the field reaches a minimum. A survey procedure is<br>developed and tested to efficiently locate this position.<br>Results of calibration work done at MIT and a field test of the system at Indian Echo<br>Caverns, in Hershey, Pennsylvania are presented. We were able to verify theoretical<br>results with the calibrations. The system was subsequently able to successfully map the<br>cave system at Indian Echo Caverns.