Advanced inversion methods for airborne electromagnetic exploration

Sengpiel, Klaus-Peter; Siemon, B.

doi:10.1190/1.1444882

Cited by 95 publications

(71 citation statements)

References 16 publications

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“…A few authors have suggested to perform a full inversion of the EMI data without assuming the LIN approximation [29][30][31], but it is our impression that this is not common practice. For airborne instruments of a similar type, the industry standard has been to perform a full processing and inversion of the data [32,33].…”

Section: Introductionmentioning

confidence: 99%

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

et al. 2016

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Increasingly, electromagnetic induction methods (EMI) are being used within the area of archaeological prospecting for mapping soil structures or for studying paleo-landscapes. Recent hardware developments have made fast data acquisition, combined with precise positioning, possible, thus providing interesting possibilities for archaeological prospecting. However, it is commonly assumed that the instrument operates in what is referred to as Low Induction Number, or LIN. Here, we detail the problems of the approximations while discussing a best practice for EMI measurements, data processing, and inversion for understanding a paleo-landscape at an Iron Age human bone depositional site (Alken Enge) in Denmark. On synthetic as well as field data we show that soil mapping based on EMI instruments can be improved by applying data processing methodologies from adjacent scientific fields. Data from a 10 hectare study site was collected with a line spacing of 1-4 m, resulting in roughly 13,000 processed soundings, which were inverted with a full non-linear algorithm. The models had higher dynamic range in the retrieved resistivity values, as well as sharper contrasts between structural elements than we could obtain by looking at data alone. We show that the pre-excavation EMI mapping facilitated an archaeological prospecting where traditional trenching could be replaced by a few test pits at selected sites, hereby increasing the chance of finding human bones. In a general context we show that (1) dedicated processing of EMI data is necessary to remove coupling from anthropogenic structures (fences, phone cables, paved roads, etc.), and (2) that carrying out a dedicated full non-linear inversion with spatial coherency constraints improves the accuracy of resistivities and structures over using the data as they are or using the Low Induction Number (LIN) approximation.

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Section: Introductionmentioning

confidence: 99%

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

et al. 2016

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“…A comparison of several 1-D inversion procedures is presented by [19]. In this paper, the procedures described by [7] are used.…”

Section: Calculation Of Resistivity Modelsmentioning

confidence: 99%

“…To interpret the AEM data in terms of layered-earth resistivity models the Marquardt-Levenberg 1-D inversion technique [6] and [7] is used.…”

Section: Instrumentation For Airborne Em Surveysmentioning

confidence: 99%

Relevance of AEM and TEM to Detect the Groundwater Aquifer at Faiyum Oasis Area, Faiyum, Egypt

Basheer¹,

Taha²,

El-Kotb³

et al. 2014

IJG

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This study investigates the groundwater aquifer located in Fayuim oasis. In this study, two of the electromagnetic measurement methods have been used in determining the hydrological situation in the Fayoum oasis. The first is airborne electromagnetic (AEM) which, sometimes is referred to as Helicopter electromagnetic (HEM) and the second is ground Time-domain Electromagnetic method (TEM). The subsurface consists of four geoelectrical layers with a rough slope towards the center. The third and the fourth layers in the succession are suggested to be the two-groundwater aquifers. The third layer saturates with fresh water overlying saline water which exists in the bottom of the second one. It is worth mentioning that the depth of the fresh water surface undulates between the surface level in two lakes in the study area and 57 meters below the ground, whereas the thickness of the fresh water aquifer varies from 13 to 36 meters. The depth of the saline water surface undulates between 59 and 81 meters below the ground. In general, airborne electromagnetic surveying has the advantage of fast resistivity mapping with high lateral resolution. Groundbased geophysical surveys are often more accurate, but they are definitely slower than airborne surveys. It depends on targets of interest, time, budget, and manpower available by the method or the combination of methods that will be chosen. A combination of different methods is useful to obtain a detailed understanding of the subsurface resistivity distribution.

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“…The algorithm provides dual interpretation parameters (apparent resistivity and apparent depth) at each frequency. Formal (non-linear, least-squares) inversion of AEM data is becoming more widespread (Sengpiel and Siemon, 2000) and a multilayer inversion (Beamish, 2002b), restricted to a half-space assessment, is used here to provide models of the subsurface resistivity distribution.…”

Section: The Airborne Em Techniquementioning

confidence: 99%

Time-Lapse Airborne EM Surveys Across a Municipal Landfill

Beamish

Mattsson

2003

JEEG

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In contrast to the majority of historical landfills, modern municipal landfills are highly engineered and follow a contain and seal strategy of leachate management. The purpose of the management system is to render the waste products inert and environmentally safe. A requirement for monitoring and assessment of the installation on the scale of decades is a consequence of the strategy. Data obtained from two repeated fixed-wing airborne electromagnetic surveys across an active, municipal solid waste landfill are considered here. The time interval between the surveys is 4 years. In theory such data may be used to both test the isolation performance of the installation and to monitor mass (leachate) transport behaviour within the landfill structure. Single frequency (3.1 kHz) data obtained at a similar density (100 m flight line spacing) over the 4 year span are presented and compared. These data have an expected mean depth of investigation of about 15 m within the landfill. Half-space conductivity models are determined from the survey data by an inversion procedure. Conductivities within the landfill are observed to be three orders of magnitude above background. From the initial survey data, a specific distribution of high conductivity material can be identified in three of the landfill cells (peak values of 170 mS/m). Four years later, a considerable redistribution of material is apparent in the results obtained across two of the cells (peak values of 317 mS/m). A third cell shows no change. A subtraction of the two time-lapse conductivity models allows the dynamic components of the conductivity distribution (all increases with time) to be mapped within individual cells. All larger conductivity increases (e.g. > 20 mS/m) are confined to the operational landfill.2

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Advanced inversion methods for airborne electromagnetic exploration

Cited by 95 publications

References 16 publications

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

Improved Geoarchaeological Mapping with Electromagnetic Induction Instruments from Dedicated Processing and Inversion

Relevance of AEM and TEM to Detect the Groundwater Aquifer at Faiyum Oasis Area, Faiyum, Egypt

Time-Lapse Airborne EM Surveys Across a Municipal Landfill

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