Abstract: An apparatus and method for locating an underground object or structure by employment of a radar-like probe and detection technique is disclosed. The underground structure is provided with a device which generates a specific signature signal in response to a probe signal transmitted from above the ground. Cooperative action between the probe signal transmitter at ground level and the signature signal generating device provided on the underground object provides for accurate detection of the subsurface object, despite the presence of a large background noise signal. The depth and, if desired, orientation of the underground object may also be determined using the signature signal generated by the signature signal generating device mounted to the underground object. Orientation information may be encoded on the signature signal or transmitted as an information signal separate from the signature signal. The probe signal may be microwave or acoustic.

Abstract: An apparatus and method for locating an underground boring tool using a radar-like probe and detection technique. A boring tool is provided with a device which generates a specific signature signal in response to a probe signal transmitted from above the ground. Cooperative operation between the probe signal transmitter at ground level and a signature signal generator disposed within the boring tool provides for the accurate locating of the boring tool, despite the presence of a large background signal. The signature signal produced by the boring tool may be generated either passively or actively, and in a manner which differs from the probe signal in one or more ways, including timing, frequency content, or polarization. A survey of a boring site, made either prior to or during the boring operation, provides data related to the characteristics of the ground medium subjected to the survey and the identification of underground hazards, such as buried utilities.