Subterranean communications system and method

An underground wireless transmission system including:

• a sensor for sensing the underground environment and producing a corresponding data value;
• a data value transmission unit for transmitting the data value to the surface, the transmission unit providing an encoded low frequency magnetic oscillating field, modulated with the data value;
• a surface receiver unit including a magnetic sensor for sensing the encoded low frequency magnetic oscillating field and demodulating the data value from the field;
• and
• a surface control unit connected to the surface receiver unit for collation of the data values from one or more surface control units.

An underground low frequency wireless transmitter suitable for use in harsh environments comprising:

• a core electronics and battery formed in an elongated unit;
• an elongated hollow case formed from a high permeability material surrounding the core electronics;
• a low frequency oscillating electromagnetic field device;
• and
• at least one environmental sensor interconnected to the core electronics.