INSTALLATION AND DETECTION METHOD FOR CONCEALED OBJECTS

摘要

A method for installation and subsequent location of a concealed object such as an underground cable or pipe comprises locating on or near the object a detection element formed of a ferromagnetic alloy having a high permeability and low coercivity for providing a characteristic magnetic response to an interrogating magnetic field whereby the object can be subsequently located. A detecting apparatus produces an interrogating magnetic field, and incorporates means for detecting a returned signal in accordance with the magnetic response of the element.