15 October 1999 Electromagnetic location system for trapped miners
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Electromagnetic signals in the very low frequency range (VLF, below 10 kHz) can penetrate rock sufficiently far for miner's location with nearly no distribution of the field structure, if the near field condition is fulfilled. The relevant solutions of the Maxwell's equations for a magnetic dipole (transmitting antenna to be carried by the miner) in a dissipative medium then are independent of the medium. From these equations the magnetic field strength in any point of reception can be calculated. The key for the location method is the inverse distance function (locus curve), describing the possible location of the dipole from the measured field strength and direction in a point of reception (performed by the rescue team). At least two of these measurements give locus curves intersecting in two points, the correct solution can be found by means of an additional direction information calculated in the points of interest. A system has been built and successfully tested with miner's transmitters which can be activated by a coded signal on the rescue team, a receiver device measuring the field amplitude and field direction and a software package to calculate the miner's location on a notebook directly in the mine.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Norbert H. Nessler, Norbert H. Nessler, } "Electromagnetic location system for trapped miners", Proc. SPIE 3752, Subsurface Sensors and Applications, (15 October 1999); doi: 10.1117/12.365706; https://doi.org/10.1117/12.365706

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