Abstract: A process for geotechnic exploration comprising the steps of:(a) Emitting one or more brief electromagnetic pulses or waves from an airborne platform at regular intervals based on the airspeed of the platform and the area being surveyed;(b) The wavelengths, frequencies and cyclicity of the waves being selected to provide, upon reflection, satisfactory indicia of the physical characteristics of the area being measured;(c) Receiving the reflections of said waves at said platform;(d) Amplifying said reflected waves to a readily processable level;(e) Processing said waves to enhance the spatial resolution of images produced therefrom;(f) Further processing said waves by selecting those variables represented by the waves that are deemed relevant;(g) Displaying said waves in visual form representing a cross-section of an area;(h) If desired, storing in recoverable form the signals representing said variables; and(i) Repeating said process as often as desired.

Abstract: The secondary signals induced in the receiver coils of two or three transmitter-receiver coil-pairs flown over terrain to be surveyed are combined to provide additional data relating to the terrain. One of the coil-pairs is arranged in a whaletail configuration, and the other or others in standard and/or fishtail configurations. The inphase and/or quadrature secondary whaletail and standard or fishtail signals are combined in such a manner as to cancel responses due to conductive overburden and distributed magnetite, and the whaletail and standard (or fishtail) signals are compared to differentiate anomalies caused by thin and thick steeply dipping conductive layers.

Abstract: This invention relates to electromagnetic mapping wherein magnetic fields of two or three different and normally audio frequencies may be transmitted or received efficiently using induction coils with the same orientation and essentially the same spatial location. Flat, air cored coils are used and are overlapped so as to have essentially zero mutual inductance between pairs.