A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant from cycle to cycle, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

The invention relates to a dual detector with a detection head (10), comprising:—a platform (11) and—an induction sensor fastened to the platform (11) and comprising a transmitter coil (12) and a receiver coil (13), the transmitter coil (12) and the receiver coil (13) each forming a loop, the loop of the transmitter coil (12) overlapping the loop of the receiver coil (13) at least partially so as to form a coupling zone (14), the coupling zone (14) being elongated in a first longitudinal direction defining a first axis (X.sub.1), the handle (20) extending in a plan (P.sub.1) normal to the platform (11) and the first axis (X.sub.1) of the coupling zone (14) being transverse to this plane (X.sub.1).

A method for improving a performance of a metal detector, including: determining positions of a sensor head of the metal detector with respect to a coordinate system as the sensor head is moved on top of a ground; processing a receive signal received by the sensor head to produce a substantially ground balanced signal that is substantially insensitive to signals due to the ground; and actively controlling the step of processing based on one or more of the determined positions as the metal detector is moved on top of the ground; wherein, during a continuous use of the metal detector, the determined positions are processed to control, without any instruction or indication from an operator of the metal detector to do so, the step of processing the receive signal to produce the substantially ground balanced signal.

A method for improving a performance of a metal detector, including: determining positions of a sensor head of the metal detector with respect to a coordinate system as the sensor head is moved on top of a ground; processing a receive signal received by the sensor head to produce a substantially ground balanced signal that is substantially insensitive to signals due to the ground; and actively controlling the step of processing based on one or more of the determined positions as the metal detector is moved on top of the ground; wherein, during a continuous use of the metal detector, the determined positions are processed to control, without any instruction or indication from an operator of the metal detector to do so, the step of processing the receive signal to produce the substantially ground balanced signal.

A calibration method for calibrating an underground beacon and tracker system for use with horizontal directional drilling. The beacon emits a magnetic field, which is received at an above-ground receiving antenna. The antenna is used to locate front and rear null points in the emitted field. The vertical and horizontal offset between the null points is determined to locate the beacon. Then, the magnetic field strength is determined at one of the null points. This value may be used to calculate or update a calibration constant. The calibration constant is then used in subsequent locating step while the characteristics of the underground environment surrounding the beacon remain similar.

A method for detecting a moisture damage on an asphalt pavement based on adaptive selection of a penetrating radar (GPR) image grayscale includes the following steps: step 1: obtaining a moisture damage GPR image dataset through asphalt pavement investigation by using a ground GPR, where a GPR image with an appropriate plot scale is selected according to an adaptive GPR image selection method; step 2: adjusting image resolution, specifically, scaling a resolution of an initial GPR image dataset of a damage directly to 224×224 to obtain a BD dataset; step 3: inputting the dataset into a recognition model, specifically, inputting the BD dataset obtained in step 2 into the recognition model, performing operation by the recognition model, and performing step 4; and step 4: outputting a moisture damage result. The new method truly realizes automatic and intelligent target detection based on the GPR.

The invention is related to a vehicle mounted metal and mine detector, which is used in the operations with military or humanitarian purposes regarding the clearance or removal of landmines for detecting mines with high metal content and plastic mines with a minimum content of metal that are near the ground surface or buried underground, as well as any improvised explosive devices, ammunitions and explosives; in the archaeological researches for determining the location of the buried archaeological remains without damaging them; in the geophysical studies for the exploration of mineral deposits, industrial minerals and rock formations; and in the detection of infrastructure elements such as underground pipelines and cables. The system is comprised of a manned or unmanned ground vehicle (8), a lower arm (2) and an upper arm (3) that are connected to the lower shell (7) of the vehicle by means of rotating links, a search head (1) in which electromagnetic interference (EMI) sensor coils and ground penetrating radar (GPR) antennas are arranged to be nested inside one another, fore arms (9) that are fastened directly on the search head (1) or into the ribs (13) placed on the search head and that enable the search head (1) to be connected to the lower arm (2) and to the upper arm (3) by means of the quick-connect rotating connection components, a linear actuator (5) and a lever arm (4) that are connected to either one of the lower arm (2) and the upper arm (3) with rotating links for adjusting the height of the search head (1) from the ground, and an upper shell (6) covering the last-mentioned mechanisms for protecting them against external factors. While adjusting the height of the search head (1) from the ground, at the same time, it is kept parallel to the ground, and these two functions are carried out by using only one linear actuator (3). Through the arrangement of the sensors in the search head such that the sensors are arrayed in pairs nested one another, the dimensions of the search head are kept as small as possible, providing the ease of use in narrow areas where the detection operation is carried out. When the search head is damaged, the connection components are broken off by themselves and the search head is broken off from the vehicle due to the connection of the search head (1) to the lower arm (2) and the upper arm (3) by means of the quick-connect connection components, which prevents the rest of the vehicle from being damaged by protecting it against the damaging effects. Furthermore, the dam

The invention is related to a vehicle mounted metal and mine detector, which is used in the operations with military or humanitarian purposes regarding the clearance or removal of landmines for detecting mines with high metal content and plastic mines with a minimum content of metal that are near the ground surface or buried underground, as well as any improvised explosive devices, ammunitions and explosives; in the archaeological researches for determining the location of the buried archaeological remains without damaging them; in the geophysical studies for the exploration of mineral deposits, industrial minerals and rock formations; and in the detection of infrastructure elements such as underground pipelines and cables. The system is comprised of a manned or unmanned ground vehicle (8), a lower arm (2) and an upper arm (3) that are connected to the lower shell (7) of the vehicle by means of rotating links, a search head (1) in which electromagnetic interference (EMI) sensor coils and ground penetrating radar (GPR) antennas are arranged to be nested inside one another, fore arms (9) that are fastened directly on the search head (1) or into the ribs (13) placed on the search head and that enable the search head (1) to be connected to the lower arm (2) and to the upper arm (3) by means of the quick-connect rotating connection components, a linear actuator (5) and a lever arm (4) that are connected to either one of the lower arm (2) and the upper arm (3) with rotating links for adjusting the height of the search head (1) from the ground, and an upper shell (6) covering the last-mentioned mechanisms for protecting them against external factors. While adjusting the height of the search head (1) from the ground, at the same time, it is kept parallel to the ground, and these two functions are carried out by using only one linear actuator (3). Through the arrangement of the sensors in the search head such that the sensors are arrayed in pairs nested one another, the dimensions of the search head are kept as small as possible, providing the ease of use in narrow areas where the detection operation is carried out. When the search head is damaged, the connection components are broken off by themselves and the search head is broken off from the vehicle due to the connection of the search head (1) to the lower arm (2) and the upper arm (3) by means of the quick-connect connection components, which prevents the rest of the vehicle from being damaged by protecting it against the damaging effects. Furthermore, the dam

An antenna arrangement for a locating device. The antenna arrangement includes two sets of coaxial antennas, where the sets are vertically displaced from one another. The arrangement may also include a phase reference antenna. Each antenna is parallel to each of the others. Each antenna detects the electromagnetic field, emanating from below-ground utilities, at an above ground location. Such detection may enable an operator of the arrangement to determine the presence and location of multiple underground lines.

The present disclosure relates to systems and methods for uniquely identifying buried utilities in a multi-utility region by sensing magnetic fields emitted from the buried utilities.