Not extinct yet: innovations in frequency domain HEM triggered by sea ice studies
Andreas A. Pfaffhuber 1 3 Stefan Hendricks 21 Norwegian Geotechnical Institute (NGI), Sognsveien 72, 0806 Oslo, Norway.
2 Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), Bussestrasse 24, 27570 Bremerhaven, Germany.
3 Corresponding author. Email: aap@ngi.no
Exploration Geophysics 46(1) 64-73 https://doi.org/10.1071/EG14034
Submitted: 21 March 2014 Accepted: 21 August 2014 Published: 17 October 2014
Journal Compilation © ASEG 2015
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.
Key words: AEM, drift, frequency domain, HEM, sea ice.
References
Balch, S., Boyko, W., Black, G., and Pedersen, R., 2002, Mineral exploration with the AeroTEM system: 72nd Annual International Meeting, SEG, Expanded Abstracts, 9–12.Coillot, C., Moutoussamy, J., Lebourgeois, R., Ruocco, S., and Chanteur, G., 2010, Principle and performance of a dual-band search coil magnetometer: a new instrument to investigate fluctuating magnetic fields in space: IEEE Sensors Journal, 10, 255–260
| Principle and performance of a dual-band search coil magnetometer: a new instrument to investigate fluctuating magnetic fields in space:Crossref | GoogleScholarGoogle Scholar |
Fountain, D., 1998, Airborne electromagnetic systems – 50 years of development: Exploration Geophysics, 29, 1–11
| Airborne electromagnetic systems – 50 years of development:Crossref | GoogleScholarGoogle Scholar |
Haas, C., Goebell, S., Hendricks, S., Martin, T., Pfaffling, A., and von Saldern, C., 2006, Airborne electromagnetic measurements of sea ice thickness: methods and applications, in P. Wadhams, and G. Amanatidis, eds., Arctic sea ice thickness: past, present and future: European Commission, Climate Change and Natural Hazards series, 1–14 .
Hodges, G., Amine, D., and Annison, C., 2010, The power of frequency domain EM: principles and case histories: ASEG 2010 (Sydney), Extended Abstracts, 1–4.
Kovacs, A., and Holladay, J. S., 1990, Sea ice thickness measurement using a small airborne electromagnetic sounding system: Geophysics, 55, 1327–1337
| Sea ice thickness measurement using a small airborne electromagnetic sounding system:Crossref | GoogleScholarGoogle Scholar |
Pfaffhuber, A. A., and Hendricks, S., 2012, First data from MAiSIE, a multi-sensor airborne sea ice explorer: Remote Sensing Workshop (EAGE), Paris, France, 3–5 September, RS14.
Pfaffhuber, A. A., Hendricks, S., and Kvistedal, Y., 2012a, Progressing from 1D to 2D and 3D near surface airborne electromagnetic mapping with a multi-sensor airborne sea ice explorer: Geophysics, 77, WB109–WB117
| Progressing from 1D to 2D and 3D near surface airborne electromagnetic mapping with a multi-sensor airborne sea ice explorer:Crossref | GoogleScholarGoogle Scholar |
Pfaffhuber, A. A., Hendricks, S., Hunkeler, P., and Kvistedal, Y., 2012b, Introducing a new generation mulit-sensor airborne system for mapping sea ice cover of polar oceans: First Break, 30, 83–88
Pfaffling, A., and Reid, J. E., 2009, Sea ice as an evaluation target for HEM modeling and inversion: Journal of Applied Geophysics, 67, 242–249
| Sea ice as an evaluation target for HEM modeling and inversion:Crossref | GoogleScholarGoogle Scholar |
Schuchman, L., 1964, Dither signals and their effect on quantization noise: IEEE Transactions on Communication Technology, 12, 162–165
| Dither signals and their effect on quantization noise:Crossref | GoogleScholarGoogle Scholar |
Sørensen, K. I., and Auken, E., 2004, SkyTEM – a new high-resolution helicopter transient electromagnetic system: Exploration Geophysics, 35, 191–199
Witherly, K., Irvine, R., and Morrison, E. 2004, The Geotech VTEM time domain helicopter EM system: ASEG 2004, Extended Abstracts, 1–4.
Won, I. J., Oren, A., and Funak, F., 2003, GEM-2A: a programmable broadband helicopter-towed electromagnetic sensor: Geophysics, 68, 1888–1895
| GEM-2A: a programmable broadband helicopter-towed electromagnetic sensor:Crossref | GoogleScholarGoogle Scholar |
