Method for monitoring an area of the surface of the earth

A method using a central data processor and a plurality of memory units for monitoring an area of the surface of the earth to determine the self potential at a plurality of probes relative to a base probe comprising the steps of

• embedding a base probe in the surface to be monitored, embedding a plurality of non-polarizable measurement probes in a grid pattern in the surface to be monitored,
• interrogating the measurement probes repeatedly to determine measured values of self-potential,
• repeatedly measuring the earth resistance between pairs of probes including at least one of the measurement probes and the base probe immediately adjacent in time to a measurement of the self-potential at the at least one measurement probe, successive measurements of the earth resistance and of the self-potentials being made between the same probe pairs,
• each pair of measurement probes being operatively associated with a memory unit, the method further including
• repeatedly substantially simultaneously detecting and transmitting self-potential values in analog form from the measurement probes to the associated memory unit,
• buffer storing the transmitted self-potential values in the memory units,
• measuring the earth resistance between successive measurements of self-potential values,
• transmitting the earth resistance measurements in analog form to the memory unit,
• buffer storing the earth resistance measurements in the memory units,
• converting buffer-stored data from analog to digital form, and repeatedly interrogating the buffer stored data of all probe groups with the central data processor.