Airborne EM systems variety: what is the difference?

The challenge in developing airborne electromagnetic systems was followed by the appearance of a wide variety of different kinds of such systems. Even in the case of considering active inductive systems with only carried transmitters. Sometimes it seems that these different airborne electromagnetic systems are based on completely different laws of physics. But all of them, Time-Domain and Frequency-Domain, with different transmitter-receiver geometry, with use of different primary field waveform – are based on the same principles: time-variable magnetic field generated by any transmitter induces eddy currents in buried conductors and the secondary field of these currents measured by an inductive receiver can give us information about the geology structures. The objective of this paper is to review the variety of systems from different points, especially in terms of signal structure, to analyse advantages and limitations of many existing systems and to suggest an approach that can make possible the ability to use the achievements in all of them during developing a new one. An attempt to realize this lead to the appearance of the system EQUATOR. The practice of using the system EQUATOR in both isolating and conductive environment for different type of targets fully confirms effectiveness of this approach.