Geophysical prospecting method and apparatus utilizing correlation of received waveforms with stored reference waveforms

Claim 1

Geophysical prospecting apparatus comprising: a. means for generating a primary electromagnetic field and coupling said primary field with an area of the earth, said primary field being defined by a pre-determined, periodic, time varying waveform containing a plurality of frequency components sufficient to permit the identification of mineral deposits which may be located in said area, said primary field causing eddy currents to be induced in conductive deposits present in said area which are intersected by said primary field, which eddy currents result in the formation of secondary electromagnetic fields, b. means for receiving electromagnetic signals emanating from the earth which are responsive in phase and amplitude to said secondary electromagnetic fields, said eleCtromagnetic signals being received in the presence of said primary field and during intervals when said primary field is not time varying, c. means for storing a plurality of reference waveforms which respectively are related in a pre-determined manner to a plurality of different pre-determined geophysical conditions, said reference waveforms comprising mathematically derived functions representing geophysical conductors of a plurality of time constants and being selected from the group consisting of (a) a conductive loop, (b) a conductive sheet and (c) a conductive sphere, and d. means for correlating said received electromagnetic signals with said stored reference waveforms and for indicating the particular reference waveform which provides an optimum match therewith.