Mineral exploration with the AeroTEM system

Balch, S.J.; Boyko, W.P.; Black, G.; Pedersen, Rolf N.

doi:10.1190/1.1817437

Cited by 6 publications

(3 citation statements)

References 2 publications

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“…The frequency‐domain helicopter‐borne electromagnetic (EM) method (Sengpiel and Siemon ; Siemon ; Tølbøll and Christensen ) and airborne transient systems (Balch et al . ; Eaton et al . ; Macnae ), including the recent SkyTEM system (Sørensen and Auken ), have been used for mining purposes, in hydrogeophysical and geotechnical investigations, and for mapping salt water intrusion, capping clays, etc.…”

Section: Introductionmentioning

confidence: 99%

Strictly horizontal lateral parameter correlation for 1D inverse modelling of large datasets

Christensen

2016

Near Surface Geophysics

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This paper presents new developments to the lateral parameter correlation method, a method that can be used to invoke lateral smoothness in model sections of one‐dimensional inversion models. The lateral parameter correlation method has three steps. First, all datasets are inverted individually. Next, a laterally smooth version of each model parameter is found by solving a simple constrained inversion problem by postulating identity between the uncorrelated and correlated parameters and solving the equations including a model covariance matrix that ensures lateral smoothness. As a final step, all sounding data are reinverted with the correlated model parameter values as a priori values to produce models that better fit the data. Because the method separates inversion and correlation, it is much faster than methods where the inversion and correlation are solved simultaneously. The new development to the lateral parameter correlation method presented in this paper is an option to perform a strictly horizontal correlation, thereby avoiding the model artefacts sometimes seen when correlating along layers, namely that formations tend to follow the topography. Furthermore, a solution to the intractable computation times arising with large datasets is formulated, employing a tessellation of the plane and an averaging scheme within the subareas that reduces the size of the numerical lateral parameter correlation inversion problem while maintaining correct correlation within a very large area. In a field example, correlation along layers and the new strictly horizontal correlation are compared, and it is demonstrated that the horizontal correlation removes the above mentioned artefacts that can appear when correlating along layers. The lateral parameter correlation method is very flexible and is capable of correlating models from inversion of different data types, including information from boreholes, and it lends itself easily to “embarrassingly parallel” computation.

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Section: Introductionmentioning

confidence: 99%

Strictly horizontal lateral parameter correlation for 1D inverse modelling of large datasets

Christensen

2016

Near Surface Geophysics

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“…Airborne systems in both frequency and time‐domain, today often helicopter‐borne, are finding increased use. The frequency domain HEM method (Sengpiel and Siemon 2000; Siemon 2001; Tølbøll and Christensen 2006) and airborne transient systems (Balch et al 2002; Eaton et al 2002), including the recent SkyTEM system (Sørensen and Auken 2004), have been used in hydrogeophysical investigations to map deep, buried valley aquifers, salt water intrusion, capping clays, etc. A general characteristic of continuous methods is that they produce very large data sets and quantitative inversion of the data becomes time consuming.…”

Section: Introductionmentioning

confidence: 99%

A lateral model parameter correlation procedure for one‐dimensional inverse modelling

Christensen

Tølbøll

2009

Geophysical Prospecting

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A B S T R A C TWe present a new, fast and versatile method, the lateral parameter correlation method, of invoking lateral smoothness in model sections of one-dimensional (1D) models. Modern, continuous electrical and electromagnetic methods are capable of recording very large data sets and except for a few cases, standard inversion methodology still relies on 1D models. In environments where the lateral rate of change of resistivity is small, 1D inversion can be justified but model sections of concatenated 1D models do not necessarily display the expected lateral smoothness.The lateral parameter correlation method has three steps. First, all sounding data are inverted individually. Next, a laterally smooth version of each model parameter, one at a time, is found by solving a simple constrained inversion problem. Identity is postulated between the uncorrelated and correlated parameters and the equations are solved including a model covariance matrix. As a last step, all sounding data are inverted again to produce models that better fit the data, now subject to constraints by including the correlated parameter values as a priori values. Because the method separates the inversion from the correlation it is much faster than methods where the inversion and correlation are solved simultaneously, typically with a factor of 200-500.Theoretical examples show that the method produces laterally smooth model sections where the main influence comes from the well-determined parameters in such a way that problems with equivalence and poor resolution are alleviated. A field example is presented, demonstrating the improved resolution obtained with the lateral parameter correlation method. The method is very flexible and is capable of coupling models from inversion of different data types and information from boreholes.

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“…In the decades leading towards the millennium both methods where further developed and refined, while the fundamental principles stayed untouched (Fountain, 1998). The new millennium saw the development of a trade off between the high resolution of fdEM and large penetration of tdEM, with the introduction of helicopter towed tdEM (HTEM) systems such as SkyTEM (Sørensen and Auken, 2004), AeroTEM (Balch et al, 2002) or VTEM (Witherly et al, 2004). As of today these HTEM systems are the by far most used platform and HEM has become a niche method for a limited number of applications that demand the comparably high frequencies and in-phase measurements possible with HEM.…”

Section: Introductionmentioning

confidence: 99%

Not extinct yet: innovations in frequency domain HEM triggered by sea ice studies

Pfaffhuber

Hendricks

2015

Exploration Geophysics

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Abstract. The last 15 years have brought major innovations in helicopter towed time domain electromagnetics (EM), while few further developments have been made within the classic frequency domain segment. Operational use of frequency domain EM for sea ice thickness mapping acted as a driving force to develop new concepts such as the system under our consideration. Since its introduction we have implemented new concepts aiming at noise reduction and drift elimination. We decreased signal noise base levels by one to two orders of magnitude with changes to the signal transmission concept. Further, we increased the receiver coil dynamic range creating an EM setup without the need for primary field bucking. Finally, we implemented control signals inside the receiver coils to potentially eliminate system drift. Ground tests demonstrate the desired noise reduction and demonstrate drift control, leading to essentially drift free data. Airborne field data confirm these results, yet also show that the procedures can still be improved. The remaining quest is whether these specialised system improvements could also be implemented in exploration helicopter EM (HEM) systems to increase accuracy and efficiency.

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Mineral exploration with the AeroTEM system

Cited by 6 publications

References 2 publications

Strictly horizontal lateral parameter correlation for 1D inverse modelling of large datasets

Strictly horizontal lateral parameter correlation for 1D inverse modelling of large datasets

A lateral model parameter correlation procedure for one‐dimensional inverse modelling

Not extinct yet: innovations in frequency domain HEM triggered by sea ice studies

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