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Combining EMI and GPR for non-invasive soil sensing at the Stonehenge World Heritage Site: the reconstruction of a WW1 practice trench

Timothy Saey UGent, Marc Van Meirvenne UGent, Philippe De Smedt UGent, Birger Stichelbaut UGent, Samuël Delefortrie, Eamon Baldwin and Vince Gaffney (2015) EUROPEAN JOURNAL OF SOIL SCIENCE. 66(1). p.166-178
abstract
Increasingly, conventional soil sampling procedures face restrictions because of their destructive character. Hence there is a growing interest in non-invasive techniques, on which proximal soil sensors are based. There is great interest in applying proximal soil sensing to improve the characterization of the buried heritage embedded in the soil landscape at sites such as the Stonehenge World Heritage Site, UK. Because calibration and validation procedures based on invasive practices are unconventional, we turned to the investigation of a well-documented practice trench dug during the First World War (WW1) close to the prehistoric Stonehenge monument. A methodology was tested that would simultaneously invert frequency-domain ground-penetrating radar (GPR) and multi-receiver electromagnetic induction (EMI) data, with the aim of reconstructing the trench network. This trench network could not be distinguished on the EMI apparent electrical conductivity (sigma(a)) measurements, but appeared on the apparent magnetic susceptibility ((a)) data. The GPR measurements showed the trench infilling as strong reflections contrasting with the surrounding soil. However, converting the two-way travel times to absolute depths requires knowledge of the relative permittivity (epsilon(r)). Because of the preference for non-invasive observation in this protected landscape, we developed a procedure integrating the GPR measurements with (a) measurements obtained with EMI. A fitting procedure, assuming a constant susceptibility and permittivity of the sub-surface layers, allowed us to estimate both the susceptibility of the trench fill and the surrounding soil material, and the epsilon(r) value of the material above and within the trench. This provided absolute depth values for the GPR reflection data, improving the lateral and vertical reconstruction of the trench system. Moreover, these results allowed depth slices to be determined from EMIa data. So, integrating both GPR and EMI measurements enabled the detailed reconstruction of the buried trench network at Stonehenge, offering new perspectives on the investigation of features buried within the soil of protected sites.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
FEATURES, AREA, CONDUCTIVITY, GROUND-PENETRATING RADAR, ELECTROMAGNETIC-INDUCTION
journal title
EUROPEAN JOURNAL OF SOIL SCIENCE
volume
66
issue
1
pages
166 - 178
Web of Science type
Article
Web of Science id
000348520600019
JCR category
SOIL SCIENCE
JCR impact factor
3.425 (2015)
JCR rank
3/34 (2015)
JCR quartile
1 (2015)
ISSN
1351-0754
DOI
10.1111/ejss.12177
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
5837923
handle
http://hdl.handle.net/1854/LU-5837923
date created
2015-02-04 16:07:24
date last changed
2016-12-19 15:39:47
@article{5837923,
  abstract     = {Increasingly, conventional soil sampling procedures face restrictions because of their destructive character. Hence there is a growing interest in non-invasive techniques, on which proximal soil sensors are based. There is great interest in applying proximal soil sensing to improve the characterization of the buried heritage embedded in the soil landscape at sites such as the Stonehenge World Heritage Site, UK. Because calibration and validation procedures based on invasive practices are unconventional, we turned to the investigation of a well-documented practice trench dug during the First World War (WW1) close to the prehistoric Stonehenge monument. A methodology was tested that would simultaneously invert frequency-domain ground-penetrating radar (GPR) and multi-receiver electromagnetic induction (EMI) data, with the aim of reconstructing the trench network. This trench network could not be distinguished on the EMI apparent electrical conductivity (sigma(a)) measurements, but appeared on the apparent magnetic susceptibility ((a)) data. The GPR measurements showed the trench infilling as strong reflections contrasting with the surrounding soil. However, converting the two-way travel times to absolute depths requires knowledge of the relative permittivity (epsilon(r)). Because of the preference for non-invasive observation in this protected landscape, we developed a procedure integrating the GPR measurements with (a) measurements obtained with EMI. A fitting procedure, assuming a constant susceptibility and permittivity of the sub-surface layers, allowed us to estimate both the susceptibility of the trench fill and the surrounding soil material, and the epsilon(r) value of the material above and within the trench. This provided absolute depth values for the GPR reflection data, improving the lateral and vertical reconstruction of the trench system. Moreover, these results allowed depth slices to be determined from EMIa data. So, integrating both GPR and EMI measurements enabled the detailed reconstruction of the buried trench network at Stonehenge, offering new perspectives on the investigation of features buried within the soil of protected sites.},
  author       = {Saey, Timothy and Van Meirvenne, Marc and De Smedt, Philippe and Stichelbaut, Birger and Delefortrie, Samu{\"e}l and Baldwin, Eamon and Gaffney, Vince},
  issn         = {1351-0754},
  journal      = {EUROPEAN JOURNAL OF SOIL SCIENCE},
  keyword      = {FEATURES,AREA,CONDUCTIVITY,GROUND-PENETRATING RADAR,ELECTROMAGNETIC-INDUCTION},
  language     = {eng},
  number       = {1},
  pages        = {166--178},
  title        = {Combining EMI and GPR for non-invasive soil sensing at the Stonehenge World Heritage Site: the reconstruction of a WW1 practice trench},
  url          = {http://dx.doi.org/10.1111/ejss.12177},
  volume       = {66},
  year         = {2015},
}

Chicago
Saey, Timothy, Marc Van Meirvenne, Philippe De Smedt, Birger Stichelbaut, Samuël Delefortrie, Eamon Baldwin, and Vince Gaffney. 2015. “Combining EMI and GPR for Non-invasive Soil Sensing at the Stonehenge World Heritage Site: The Reconstruction of a WW1 Practice Trench.” European Journal of Soil Science 66 (1): 166–178.
APA
Saey, T., Van Meirvenne, M., De Smedt, P., Stichelbaut, B., Delefortrie, S., Baldwin, E., & Gaffney, V. (2015). Combining EMI and GPR for non-invasive soil sensing at the Stonehenge World Heritage Site: the reconstruction of a WW1 practice trench. EUROPEAN JOURNAL OF SOIL SCIENCE, 66(1), 166–178.
Vancouver
1.
Saey T, Van Meirvenne M, De Smedt P, Stichelbaut B, Delefortrie S, Baldwin E, et al. Combining EMI and GPR for non-invasive soil sensing at the Stonehenge World Heritage Site: the reconstruction of a WW1 practice trench. EUROPEAN JOURNAL OF SOIL SCIENCE. 2015;66(1):166–78.
MLA
Saey, Timothy, Marc Van Meirvenne, Philippe De Smedt, et al. “Combining EMI and GPR for Non-invasive Soil Sensing at the Stonehenge World Heritage Site: The Reconstruction of a WW1 Practice Trench.” EUROPEAN JOURNAL OF SOIL SCIENCE 66.1 (2015): 166–178. Print.