Abstract: A method for locating and identifying search objects concealed in the gro under a ground surface is described. Preferred search objects are plastic mines, which inter alia contain a plastic body and at least one metallic part, particularly an igniter. Firstly the position of the metallic part is established, preferably with an eddy current probe. Then a search area surrounding the part is investigated by means of a ground probe, which produces a ground signal indicating the presence of ground material. The ground signal is evaluated in position discriminating manner. Preferably the ground probe and metal probe are identical, which is e.g. made possible by an operation of the eddy current probe with at least three different frequencies and a suitable signal evaluation. Prior to the investigation of the search area the electrical conductivity and/or magnetizability of the ground can be increased by impregnating with a liquid, which can contain salt water and/or magnetizable particles.

Abstract: A method for the operation and for the evaluation of signals of an eddy cent probe wherein a transmitting coil is supplied with alternating current with preferably three frequency components. The receiving coil signal corresponding to an a.c. voltage is broken down into corresponding frequency components and by phase-control rectification projection signals are formed corresponding to a real part or an imaginary part of the coil signal. From at least two, optionally individually amplified projection signals of the same type (real or imaginary signal) differential signals are formed. Finally, by the combination of at least two differential signals a combination signal is formed and evaluated. In particular, quotients and amount or value sums of differential signals are formed. The method offers decisive advantages in seeking mines in connection with the suppression of disturbing ground or soil signals and in the identification and classification of mines on the basis of signals from an eddy current probe.