To study the electric resistance of rock-call closed chandin and spread of coal layers. I've explored the coal mining Geophysics with various electrode placement.
To study the electrical resistance of the soil - rock and roll off the pile of coal. I had mine with a geophysical survey methods and electrode placement.
To study the electrical resistivity of soil - stone off the accumulation and spread of coal. I used to survey coal mining by means of geophysical electrode placement models.