An evaluation of optimization strategies to automatically select the optimal set of array configurations for 2D electrical imaging surveys

Alfouzan, Fouzan; Loke, M.H.; Adlan, Mohd Nordin

doi:10.1088/1742-2132/7/3/011

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…Most recent studies on ERT measurement optimization make use of the model resolution matrix (Alfouzan et al, 2010;Loke et al, 2015bLoke et al, , 2014Loke et al, , 2010Stummer et al, 2004;Wagner et al, 2015;Wilkinson et al, 2015Wilkinson et al, , 2012Wilkinson et al, , 2006. In comparison to sensitivity based optimization strategies (Athanasiou et al, 2009;Tsakirrbaloglou et al, 2016;Tsourlos et al, 2016), the model resolution accounts for linear (in)dependency between measurement configurations, and is therefore used here as well.…”

Section: Methodsmentioning

confidence: 99%

Optimized survey design for electrical resistivity tomography: combined optimization of measurement configuration and electrode placement

Uhlemann

Wilkinson

Maurer

et al. 2018

Geophysical Journal International

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Within geoelectrical imaging, the choice of measurement configurations and electrode locations is known to control the image resolution. Previous work has shown that optimized survey designs can provide a model resolution that is superior to standard survey designs. This paper demonstrates a methodology to optimize resolution within a target area, while limiting the number of required electrodes, thereby selecting optimal electrode locations. This is achieved by extending previous work on the 'Compare-R' algorithm, which by calculating updates to the resolution matrix optimizes the model resolution in a target area. Here, an additional weighting factor is introduced that allows to preferentially adding measurement configurations that can be acquired on a given set of electrodes. The performance of the optimization is tested on two synthetic examples and verified with a laboratory study. The effect of the weighting factor is investigated using an acquisition layout comprising a single line of electrodes. The results show that an increasing weight decreases the area of improved resolution, but leads to a smaller number of electrode positions. Imaging results superior to a standard survey design were achieved using 56 % fewer electrodes. The performance was also tested on a 3D acquisition grid, where superior resolution within a target at the base of an embankment was achieved using 22 % fewer electrodes than a comparable standard survey. The effect of the underlying resistivity distribution on the performance of the optimization was investigated and it was shown that even strong resistivity contrasts only have minor impact. The synthetic results were verified in a laboratory tank experiment, where notable image improvements were achieved. This work shows that optimized surveys can be designed that have a resolution superior to standard survey designs, while requiring significantly fewer electrodes. This methodology thereby provides a means for improving the efficiency of geoelectrical imaging.

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Section: Methodsmentioning

confidence: 99%

Optimized survey design for electrical resistivity tomography: combined optimization of measurement configuration and electrode placement

Uhlemann

Wilkinson

Maurer

et al. 2018

Geophysical Journal International

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“…The composition of sand and gravel varies from fine to coarse. The second layer is the bedrock of granite and this was encountered at a depth of about 42 m (Alfouzan et al, 2010).…”

Section: Site and Target Descriptionsmentioning

confidence: 99%

Effects of Electrode Spacing and Inversion Techniques on the Efficacy of 2d Resistivity Imaging to Delineate Subsurface Features

J.¹

2013

American Journal of Applied Sciences

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In this study, the effect of the choice of appropriate electrode spacing and inversion algorithms on the efficacy of 2D imaging to map subsurface features was investigated. The target being investigated was the drainage concrete pipe buried at approximately 0.3 m into the subsurface. A profile perpendicular to the strike of the pipe was established. 2D resistivity data was separately collected with the electrode spacings of 1.5 m and 0.5 m. using the Dipole-Dipole, the Wenner and the Wenner-Schlumberger array configurations. The results obtained showed that when the electrode spacing of 1.5 m was used for the investigations, none of the three array types was able to map the target with either of the two inversion techniques. The results further show that the attainment of RMS error of less about 10% which usually gives the indication of a good subsurface model is not a guarantee that subsurface features are successfully mapped. On the other hand, when the electrode spacing of 0.5 m was used for the data collection, the results obtained with the standard constrains inversion technique showed that all the three array configurations mapped the target however, only the dipole-dipole array was able to resolve the boundary between the concrete pipe and the entrapped air. With the robust constrain inversion technique; the target was also successfully mapped by all the three array types. In addition to this, the boundary between the entrapped air and the concrete pipe was resolved by all the three array types. This suggests that if there is a significant contrast in the subsurface layers' resistivities, the robust constrain inversion algorithm technique gives better boundaries resolution irrespective of the array types used for the survey. The inversion of the 3D data gave 3D resistivity sections which were presented as horizontal depth slices. The result obtained from the inversion of the 3D data has assisted us in getting information about the dimension and orientation of the target. The study revealed that a miniature subsurface feature can only be effectively delineated if the feature is not deeply buried into the subsurface.

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“…Alfouzan et al . () compare the methods proposed by Stummer et al . () and two methods proposed by Wilkinson et al .…”

Section: Optimized Designmentioning

confidence: 99%

“…More recent work by Loke et al . () on one of the methods presented by Wilkinson et al . () has greatly improved the efficiency.…”

Section: Optimized Designmentioning

confidence: 99%

“…While the above studies focus on four-electrode arrays, other studies have considered experimental design for multichannel systems or the use of novel search algorithms to speed the optimization (Xu and Noel 1993;Stummer et al 2002;Stummer et al 2004;Wilkinson et al 2006a;Coles and Morgan 2009). Alfouzan et al (2010) compare the methods proposed by Stummer et al (2004) and two methods proposed by Wilkinson et al (2006a); they find the methods of Wilkinson et al (2006a) provide greater resolution but are also time-intensive. More recent work by Loke et al (2010) on one of the methods presented by Wilkinson et al (2006a) has greatly improved the efficiency.…”

Section: Optimized Designmentioning

confidence: 99%

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Informed experimental design for electrical resistivity imaging

Nenna

Pidlisecky

Knight

2011

Near Surface Geophysics

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Electrical resistivity imaging has been successfully used to monitor near‐surface hydrologic processes but use of standard measurement arrays may not provide the greatest data sensitivity to the imaged region. We present a method of experimental design based on the concept of informed imaging for creating an electrical resistivity imaging experiment to monitor flow beneath a recharge pond. Informed imaging is the integration of all available data about a site into the acquisition, inversion and interpretation of electrical resistivity data. Informed experimental design uses all available information to develop an a priori model of the subsurface conductivity structure that guides the selection of measurement arrays for an electrical resistivity imaging experiment given spatial and temporal constraints on the acquisition. Selection of arrays focuses on maximizing the amount of unique information acquired with each source pair. We apply the method to the selection of arrays for imaging the top 5 m of the subsurface beneath a recharge pond in Northern California, which is part of an aquifer storage and recovery project. Decreasing infiltration rates over time reduce the effectiveness of the recharge pond. We seek to monitor infiltration processes at the contact between a fines‐rich sand layer and coarser sand layer in an effort to understand the hydrologic controls on infiltration. The performance of the arrays selected using informed experimental design relative to two standard arrays (Wenner and dipole‐dipole) is validated on two synthetic subsurface conductivity models, which are representative of conductivity structures that may arise during an infiltration event. Performance is evaluated in terms of a singular value decomposition of the sensitivity matrix produced by the three types of arrays, as well as a measure of the region of investigation. Results demonstrate that arrays selected using informed experimental design provide independent information about the imaged region and are robust in the presence of noise, improving the ability to image changes in a conductivity structure that result from infiltration processes.

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An evaluation of optimization strategies to automatically select the optimal set of array configurations for 2D electrical imaging surveys

Cited by 4 publications

References 11 publications

Optimized survey design for electrical resistivity tomography: combined optimization of measurement configuration and electrode placement

Optimized survey design for electrical resistivity tomography: combined optimization of measurement configuration and electrode placement

Effects of Electrode Spacing and Inversion Techniques on the Efficacy of 2d Resistivity Imaging to Delineate Subsurface Features

Informed experimental design for electrical resistivity imaging

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