Analytical studies of the vertical array-Differential Target Antenna Coupling (DTAC) method for rapid sensing and imaging of subsurface targets

2017

JEEG

Self Cite

We have tested the Vertical-Array Differential Target Antenna Coupling (DTAC) system over a variety of well-characterized, buried targets. The DTAC system produces a primary field in the frequency range of 10 Hz to 10 kHz and records secondary magnetic fields from subsurface targets, relative to a reference frequency. The current DTAC system has higher power, compared with our earlier tests, and this system is suitable for either ground or airborne mapping of a wide variety of near-surface targets, which might be encountered in civil engineering, water resources, environmental characterization, mining, and other natural-resource exploration. Profiles over three well-characterized targets show a close agreement between the measured DTAC response and model simulations. Conventional field measurements using induced magnetic fields are also displayed and they do not show nearly as effective mapping of the targets. Another profile shows that the DTAC method has greatly reduced sensitivity to surface clutter, compared to conventional measurements.

Section: Horizontal-array Dtac Methodsmentioning

confidence: 99%

Section: Objective Of This Papermentioning

confidence: 99%

Field Tests of the Vertical-Array Differential Target Antenna Coupling (DTAC) System

Feng

2017

JEEG

Self Cite

“…To investigate the feasibility of such a system, in Dvorak and Sternberg (2014) we study the extension of the DTAC method to the moving, vertical TX/RX array that is shown in Fig. 2 in that paper.…”

Section: Background On the Vertical Array-dtac Methodsmentioning

confidence: 99%

“…Since a moving array requires the field components to be measured simultaneously, Dvorak and Sternberg (2014) show that a two-axis RX that simultaneously measures only the two horizontal field components is adequate for the vertical array. Dvorak and Sternberg (2014) also develop the theoretical basis for the vertical array-DTAC method and then employ this analysis along with numerical examples to explain the physical phenomenology behind the vertical DTAC method.…”

Section: Background On the Vertical Array-dtac Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Studies and Verification of the Vertical Array-Differential Target Antenna Coupling (DTAC) Method for Rapid Sensing and Imaging of Subsurface Targets

Feng

Dvorak

et al. 2015

JEEG

Self Cite

We have developed a new electromagnetic geophysical system that has significantly improved target sensing and imaging capabilities compared to conventional measurements. In a previous series of papers, we described a new measurement technology called the Differential Target Antenna Coupling (DTAC) method, which used a magnetic-field transmitter (TX) and a magneticfield receiver (RX), oriented in a horizontal array, with separation distances of the order of tens of meters, and up to tens of kilometers. In the present paper, we use the DTAC method in a verticalarray configuration, with the TX coil directly above two null-coupled RX coils. This vertical array provides a number of important advantages over the large-offset horizontal array for some applications. For example, the vertical array-DTAC method can be adapted to rapidly moving measurements, such as from a helicopter. In addition, the vertical array-DTAC method also suppresses surface clutter, such as fences, steel buildings, and parked vehicles.The DTAC method uses at least two frequencies. One frequency is used as a reference signal to establish the null direction at that frequency, and then a different frequency is used to measure the change in the null at the new frequency. We can also use an arbitrary number of frequencies with just one reference frequency for wide-bandwidth spectral measurements. We first describe the vertical array-DTAC measurement system and discuss the calibration procedure for the instrumentation. Next, we discuss the methods employed for scale-model testing of the system. We validate the vertical array-DTAC method using small-scale controlled tests and demonstrate the enhanced resolution and sensitivity of the vertical array-DTAC method. Suitable TX moments and frequency ranges can be selected for effective study of nearsurface targets (civil engineering, water resource, and environmental characterization) as well as deep targets (mining and other natural-resource exploration).

Differential Target Antenna Coupling (DTAC) EM Surveying with Stationary Transmitter Loop and Moving In-Loop Receivers

2020

JEEG

Following our previous studies of the Differential Target Antenna Coupling (DTAC) method with horizontal and vertical arrays for EM surveys, in this paper we study the application of the DTAC method to a different configuration, where a large, stationary transmitter loop is on the ground surface. We then run profile lines inside this loop. The DTAC method is effective in eliminating errors due to the large variations in the primary field along profile lines within the transmitting loop. Operational tests show that we obtain more diagnostic DTAC anomalies over buried targets than using just the B x and B y data. The DTAC method also produces smaller false-alarm targets due to background geology variations, compared with B z measurements. The DTAC method can be used with either time- or frequency-domain data and the receiver can be moved on the ground or deployed from an airborne vehicle, such as a drone.