Effect of positional inaccuracies on multielectrode results

Szalai, S.; Koppán, András; Szarka, László

doi:10.1556/ageod.43.2008.1.3

Cited by 11 publications

(13 citation statements)

References 3 publications

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“…This shows that the greater the offline electrode distance the more the effect. This outcome is contrary to that of Szalai et al (2008), who found that offline electrodes effect on 2-D ERT result was insignificant. More so, the low resistivity zone or saturated zone along the distance (12 m -27 m) at a depth of 4 m and beyond (Figure 8a), decrease to 13 m -24 m for WA-2EO survey at 1.2 m offline electrodes distance (Figure 8g).…”

Section: Wenner Array With Two Electrodes Offline (Wa-2eo)contrasting

confidence: 99%

“…But, due to surface constraint associated with most survey areas, it is rarely possible to conduct a two-dimensional resistivity survey on a straight line. To this end, Szalai et al (2008) investigated the effect of electrode positioning error on the inverted pseudo-section of a 2-D ERT survey. They found the positioning error to be insignificant except for a very rocky field.…”

Section: Introductionmentioning

confidence: 99%

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Solution of Collinearity Problem in Two-Dimensional Electrical Resistivity Tomography using Wenner Array

Mohammed¹,

Muztaza²,

Saad³

2021

JST

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Two-dimensional electrical resistivity tomography (2-D ERT) is one of the most common geophysical tools employed to satisfy the ever-growing need for obtaining subsurface information. Most of the conventional electrode arrays used for 2-D ERT survey are built with the theoretical assumption that the survey lines are straight to guarantee four collinear electrodes at every point of measurement. However, due to surface constraint associated with most survey areas, it is rarely possible to conduct a two-dimensional resistivity survey on a straight line. Therefore, 2-D ERT survey conducted on a surface constraint field requires shifting one or more electrodes off the survey line, which contrasts with the underlying assumption. Consequently, the result might be prone to false anomalies. Thus, this study aimed to device a new approach that could mitigate the false anomalies posed by non-collinearity of electrodes in 2-D ERT result. In view of this, ABEM Terrameter SAS4000 using Wenner array configuration was adopted for the survey. The data was acquired with all electrodes inline and one or more electrodes offline at stepwise distances, respectively. Based on the result obtained, the new approach mitigates the offline electrodes effect, as the inverse resistivity tomograms resolves the geometries of the true model reasonably well. More so, it has high R-value >90% which is an indication of proximity to the true model. Hence, it is concluded that the new approach is effective in mitigating offline electrode effect on a 2-D ERT result.

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Section: Wenner Array With Two Electrodes Offline (Wa-2eo)contrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solution of Collinearity Problem in Two-Dimensional Electrical Resistivity Tomography using Wenner Array

Mohammed¹,

Muztaza²,

Saad³

2021

JST

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“…While it is well known that inaccurate electrode positions lead to severe artifacts in the inverted resistivity models [ Zhou and Dahlin , ; Oldenborger et al ., ; Szalai et al ., ; Wilkinson et al ., , , ], conventional time‐lapse inversion methodologies, such as difference, ratio, or 4‐D inversion [e.g., LaBrecque and Yang , ; Daily et al ., ; Kim et al ., ], have not previously allowed for changing electrode positions with time. Thus, a new methodology has been developed to incorporate electrode movements into a time‐lapse inversion workflow (Figure ).…”

Section: Geoelectrical Monitoring Methodologymentioning

confidence: 99%

“…When landslides move, the electrode positions vary with time. Several studies have shown that misplaced electrodes cause significant distortions in the resistivity models [ Zhou and Dahlin , ; Oldenborger et al ., ; Szalai et al ., ; Wilkinson et al ., , , , ; Uhlemann et al ., ]. At the studied landslide, Uhlemann et al .…”

Section: Introductionmentioning

confidence: 99%

Four‐dimensional imaging of moisture dynamics during landslide reactivation

et al. 2017

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Landslides pose significant risks to communities and infrastructure, and mitigating these risks relies on understanding landslide causes and triggering processes. It has been shown that geophysical surveys can significantly contribute to the characterization of unstable slopes. However, hydrological processes can be temporally and spatially heterogeneous, requiring their related properties to be monitored over time. Geoelectrical monitoring can provide temporal and volumetric distributions of electrical resistivity, which are directly related to moisture content. To date, studies demonstrating this capability have been restricted to 2‐D sections, which are insufficient to capture the full degree of spatial heterogeneity. This study is the first to employ 4‐D (i.e., 3‐D time lapse) resistivity imaging on an active landslide, providing long‐term data (3 years) highlighting the evolution of moisture content prior to landslide reactivation and showing its decline post reactivation. Crucially, the time‐lapse inversion methodology employed here incorporates movements of the electrodes on the unstable surface. Although seasonal characteristics dominate the shallow moisture dynamics during the first 2 years with surficial drying in summer and wetting in winter, in the months preceding reactivation, moisture content increased by more than 45% throughout the slope. This is in agreement with independent data showing a significant rise in piezometric heads and shallow soil moisture contents as a result of prolonged and intense rainfall. Based on these results, remediation measures could be designed and early‐warning systems implemented. Thus, resistivity monitoring that can allow for moving electrodes provides a new means for the effective mitigation of landslide risk.

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“…errors, originating from a possible incorrect positioning of electrodes), and the effect of these errors on various multielectrode arrays (Szalai et al 2007(Szalai et al , 2008a.…”

Section: Studying Of Errors Due To Incorrect Positioning Of Electrodementioning

confidence: 99%

Non-conventional geoelectric arrays — Practical results of the OTKA project K49604

Szalai¹,

Varga²,

Novák³

et al. 2011

Acta Geodaetica et Geophysica Hungarica

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In this paper we provide a comprehensive summary about the practical results of the OTKA project K49604. 1. We calculated the consequences of incorrect positioning of the electrodes for various multielectrode systems. In practice these effects were found to be negligible. The only exception is the case of rocky surface, where it is impossible to put the electrodes in the desired positions. The errors can however be kept within an acceptable range, if the electrodes of the linear arrays are put off-set, at right angles from the measuring line. A five-six times larger off-set has less effect than a certain mis-position along the line, connecting the electrodes. 2. We carried out tensorial geoelectric measurements around the Cistercian Monastery at Pilisszentkereszt. Areal measurements provide much more detailed and unambiguous anomalies than 2D profile measurements, and the tensor invariant representation of apparent resistivity anomalies provides a realistic picture about the lateral variation of the subsurface resistivity, even in field circumstances. 3. We tested the applicability of 3D electrical resistivity tomography (ERT) technique to detect landmines in different soil conditions and at various depths. Metallic and non-metallic landmines buried in wet and dry soils had been synthetically modeled. According to the inverted resistivity data using the dipole axial array in wet environment, it was possible to locate the metallic and non-metallic landmines as long as the noise level was about 5%. 4. We elaborated moreover a geoelectrical procedure which is able to map multidirectional fissure systems by combining geoelectrical profiling and geoelectrical azimuthal measurements. Results received by using both the so-called null-, and traditional arrays were jointly interpreted. The humidity of the fissures affects the measured results significantly, and in a meaningful way. 5. We presented the socalled standardized pricking probe (PP) surveying technique and demonstrated its usefulness in an archaeological study. The PP images proved to be definitely more close to the realistic shape of the buried chapel than the geoelectric and magnetic measurements, and they also revealed more details about the subsurface than the georadar. The optimum PP parameters: horizontal interval, pricking depth, observable quantity and its way of presentation were optimized through field experiments. For more details see the cited publications. The figures ever published in Hungarian journals are not reproduced here.

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Effect of positional inaccuracies on multielectrode results

Cited by 11 publications

References 3 publications

Solution of Collinearity Problem in Two-Dimensional Electrical Resistivity Tomography using Wenner Array

Solution of Collinearity Problem in Two-Dimensional Electrical Resistivity Tomography using Wenner Array

Four‐dimensional imaging of moisture dynamics during landslide reactivation

Non-conventional geoelectric arrays — Practical results of the OTKA project K49604

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