Low frequency inductive airborne electromagnetic surveying systems DIP-4A (for airplanes) and EM-4H (for helicopters) simultaneously register the elements of an electromagnetic field, which determine the value of bedrock conductivity, at the frequencies of 130, 520, 2080 and 8360 Hz, using the method of dipole induction profiling (DIP, Frequency Domain EM). A more than sixty-fold difference between a low and a high frequency provide for effective penetration and an ability to distinguish deep features at various sections of low or high conductivity.
A transmitter coil is mounted onto an aircraft (a plane or a helicopter) and a receiver is towed behind in a “bird”. A GPS sensor and a magnetic detector sensor are also in the “bird”. You can see an airborne electromagnetic surveying system EM-4H, installed on a MI-8 helicopter, in the picture below.