| 摘要 |
The invention concerns a method and apparatus (10) for conducting electromagnetic exploration of the earth's surface. At least one primary coil (12) is provided. The primary coil(s) is or are powered to generate a primary electromagnetic field and the earth's surface is exposed to this primary field. A receiver is provided to detect a secondary field generated by the earth as a result of currents generated therein by the primary field. Spaced apart nulling coils (14) are powered in such a manner as to null the primary field in a three-dimensional volume surrounding the receiver, thereby enabling the receiver to detect the secondary field vectorially. |
