Man-portable locator systems for locating buried or otherwise inaccessible pipes, conduits, cables, wires and inserted transmitters using detector arrays and stochastic signal processing and similar techniques to analyze and display multiple target objects at differing frequencies in a layered user interface (UI) are disclosed.

An electromagnetic (EM) receiver system for measuring EM signals. The EM receiver system includes a platform; a coil for measuring EM signals; and first to third suspension mechanisms located between the platform and the coil so that the coil oscillates relative to the platform, and the first to third suspension mechanisms attenuate motion induced noise introduced by towing the receiver system above ground.

Methods and apparatus according to the invention include inductive units or apparatus such as magnetic metal detectors comprising multiple electromagnetic coils and circuit boards such as electronic printed circuit boards (PCBs) so that the circuit boards, while containing metallic surfaces and layers, are positioned in such a way as to reduce or eliminate their effect on the metal detector's coils. The apparatus comprising: a plurality of electromagnetic coils and a plurality of circuit boards, and wherein at least one of said circuit boards is positioned so that its thickness direction is orthogonal to the magnetic field of at least one of said coils.

Front-end circuits that combine inductive and capacitive sensing are described. In one embodiment, an apparatus includes a plurality of inductive elements, an inductive measurement circuit, and a frequency divider circuit. The inductive measurement circuit is to output a first signal with a first frequency. The first signal is associated with an inductance change of one of the inductive elements. A feedback circuit can maintain the sinusoidal operation of the first signal. The frequency divider circuit can generate a second signal with a second frequency that is lower than the first frequency.

An electromagnetic induction (EMI) system for characterizing geophysical (e.g. subterranean) environments, includes: (a) a transmitter module including a transmission coil and signal transmission electronics; and (b) at least one receiver module including a receiver coil and signal reception electronics wherein the at least one receiver module is physically separated from the transmitter module without a wired signal connection between them, wherein phase information of signals sent by the transmitter module and those received by at least one receiver module are preserved such that phase information of received signals may be determined and used in characterizing the geophysical environment. In some systems, signal preservation uses a pair of correlated, stable, high frequency clocks.

A measurement vehicle includes a geophysical sensor. One or more operational sensors are configured to detect operational data related to operation of the measurement vehicle. A driving system is configured to move the measurement vehicle in a travel direction relative to a measurement point. A controller is configured to receive information from the geophysical sensor and the operational sensors, and to control the driving system based on the information.