The BGR helicopter (Sikorsky S-76B) is used for airborne geophysical surveying of the Earth’s subsurface. The standard equipment comprises the methods electromagnetics, magnetics and radiometrics. The active multi-frequency, helicopter-borne electromagnetic (HEM) measuring system consists of circular (diameter about 0,5 m) transmitter and receiver coils (horizontal separation about 8 m) housed by a flying tube (bird) about 40 m beneath the helicopter. The ratio of received and transmitted signal yields to the electrical conductivity down to 50/150 m depth in case of conductive/resistive subsurface. The results are displayed as apparent resistivity (= half-space resistivity) and centroid depth at each of the six system frequencies ranging from 0.4 to 130 kHz. Furthermore, vertical and horizontal resistivity (= inverse of conductivity) sections are derived from multi-layer inversion results (1D resistivity-depth models).