Radio-detection uses the principles of electromagnetic to detect underground utilities. This principle works on the basis that a current flowing along a conductor creates a magnetic field, which extends around the conductor in concentric circles. A receiver coil can be used to detect the amplitude of this magnetic field. The amplitude varies depending on the position and orientation of the receiver within the field. The amplitude is maximum when the receiver is in line with the field and directly above the conductor. Moving the receiver from side to side it is possible to follow the maximum signal response and, therefore, the line of the buried service. More...