47 research outputs found
A lightweight prototype of a magnetometric system for unmanned aerial vehicles
Detection of the Earth’s magnetic field anomalies is the basis of many types of studies in the field of earth sciences and archaeology. These surveys require different ways to carry out the measures but they have in common that they can be very tiring or expensive. There are now several lightweight commercially available magnetic sensors that allow light-UAVs to be equipped to perform airborne measurements for a wide range of scenarios. In this work, the realization and functioning of an airborne magnetometer prototype were presented and discussed. Tests and measures for the validation of the experimental setup for some applications were reported. The flight sessions, appropriately programmed for different types of measurements, made it possible to evaluate the performance of this detection methodology, highlighting the advantages and drawbacks or limitations and future developments. From the results obtained it was possible to verify that the measurement system is capable of carrying out local and potentially archaeological magnetometric measurements with the necessary precautions
INFACT technology watch report
This research has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement nº 776487. Furthermore, some of the authors (B.J. and V.H.-S.) were supported by the Spanish Ministry of Science Innovation and Universities under the framework of the R&D project RTI2018-098966-B-I00.Summary: This report presents a bibliometric study on patents and scientific publications related to the following technologies involved in INFACT: airborne electromagnetic methods, airborne gravity gradiometry, airborne magnetometry and drone-borne hyperspectral imaging. A statistical analysis of the documents reveals the main players, technology trends and collaboration patterns via bibliometric techniques
Absolute Positioning Using the Earth\u27s Magnetic Anomaly Field
Achieving worldwide alternatives to GPS is a challenging engineering problem. Current GPS alternatives often suffer from limitations such as where and when the systems can operate. Navigation using the Earth\u27s magnetic anomaly field, which is globally available at all times, shows promise to overcome many of these limitations. We present a navigation filter which uses the Earth\u27s magnetic anomaly field as a navigation signal to aid an inertial navigation system (INS) in an aircraft. The filter utilizes highly-accurate optically pumped cesium (OPC) magnetometers to make scalar measurements of the Earth\u27s magnetic field and compare them to a map using a marginalized particle filter approach. We demonstrate navigation accuracy of 13 meters DRMS with a high quality magnetic anomaly map at low altitudes with real flight data. We conduct a simulation over the continental United States to predict accuracies with respect to variables like location and altitude. Finally, we address the problem of map availability by presenting a method for a self-building magnetic anomaly model
Metalliferous mining geophysics — State of the art after a decade in the new millennium
This paper is © 2019 Society of Exploration Geophysicists. The posting is available free of charge and its use is subject to the SEG terms and conditions: https://seg.org/Terms-of-UseMining exploration was very active during the first decade of the twenty-first century because there were numerous advances in the science and technology that geophysicists were using for mineral exploration. Development came from different sources: instrumentation improvements, new numerical algorithms, and cross-fertilization with the seismic industry. In gravity, gradiometry kept its promise and is on the cusp of becoming a key technology for mining exploration. In potential-field methods in general, numerous techniques have been developed for automatic interpretation, and 3D inversion schemes came into frequent use. These inversions will have even greater use when geologic constraints can be applied easily. In airborne electromagnetic (EM) methods, the development of time-domain helicopter EM systems changed the industry. In parallel, improvements in EM modeling and interpretation occurred; in particular, the strengths and weaknesses of the various algorithms became better understood. Simpler imaging schemes came into standard use, whereas layered inversion seldom is used in the mining industry today. Improvements in ground EM methods were associated with the development of SQUID technology and distributed-acquisition systems; the latter also impacted ground induced-polarization (IP) methods. Developments in borehole geophysics for mining and exploration were numerous. Borehole logging to measure physical properties received significant interest. Perhaps one reason for that interest was the desire to develop links between geophysical and geologic results, which also is a topic of great importance to mining geologists and geophysicists
Modeling and inversion of airborne full tensor magnetic gradiometry data in the Thuringian basin and forest
The recent development of airborne full tensor magnetic gradiometer (FTMG) systems, based on superconducting quantum interference devices (SQUID), allows to obtain the full magnetic gradient tensor of the Earth's magnetic field of large areas (10x10 km). This system allows acquiring all components of the magnetic gradient tensor. This tensor exhibits some advantages over conventional airborne magnetic field data, e.g. a higher spatial resolution and additional directional sensitivity. In this work a FTMG system was applied in the framework of the multidisciplinary INFLUINS project (Integrated fluid dynamics in sedimentary basins) in order investigate different areas in the Thuringian Basin and the neighboring highlands. Main goal was to map magnetic lineaments along major fault zones and to demonstrate the advantages of airborne FTMG. Full tensor data sets have been acquired with very low system noise of only 60 (pT/m). Two different case studies are presented: In the first case study a strong magnetic anomaly in the center of the Thuringian Forest, caused by the magmatic intrusion of the Höhenberger dolerite is analyzed, which exhibits indications of a significant remanent magnetization. Multiple magnetization vector inversions were performed using either the full magnetic gradient tensor or only the total field anomaly data. The inversion results are evaluated using magnetization directions acquired by paleomagnetic sampling and available geological information. In the second case study, a small magnetic anomaly was investigated. It was discovered while mapping magnetic anomalies along the Eichenberg-Gotha-Saalfeld fault zone, which is one of the major fault zones in the Thuringian Basin. The detected lineament is interpreted using the components of the magnetic gradient tensor, additional ground based geo-electrical data and available geological information. The inversion of the magnetic gradients revealed a steeply dipping zone of mostly induced magnetization
Gravity modelling in the western Bushveld Complex, South Africa, using integrated geophysical data
A 10 km x 10 km study area in the western Bushveld Complex, south of the Pilanesberg Complex, was selected for testing the inversion of vertical component gravity (Gz) data to determine the geometry of the Bushveld Complex/Transvaal Supergroup contact. This contact has a density contrast of ~0.350 g.cm-3 making it a suitable target for gravity inversion. The resulting 3D gravity model agrees well with the 3D seismic interpretation, indicating that the depths determined from the seismic data are appropriate. The gravity inversion could be extended laterally to investigate regions without seismic data coverage. This methodology may prove useful where upwellings in the floor of the Bushveld Complex distort seismic data, but can be imaged by gravity inversions.
The Gz dataset was created from converted Airborne Gradient Gravity (AGG) data, combined with upward continued ground Gz gravity data, providing extensive coverage. This combined dataset was used in an interactive, iterative 3D gravity inversion methodology used to model the geometry of the Bushveld Complex/Transvaal Supergroup contact and densities of the Bushveld Complex, Transvaal Supergroup and Iron-Rich Ultramafic Pegmatoids (IRUPs). The resulting 3D gravity model provides an acceptable first-pass model of the Bushveld Complex/Transvaal Supergroup contact. In the shallow south-west region of the study area, the steeply dipping contact was determined from borehole intersections. 3D seismic data was the only constraint towards the north-east, where the contact flattens out to a sub-parallel contact, at ~2 000 m depth. In the north-western section, the Bushveld Complex/Transvaal Supergroup contact is fault-bounded by a conjugate set of the Rustenburg Fault, causing the Bushveld to onlap the Transvaal sediments. In the southern region, the contact changes as the conjugate fault dies out, and the Bushveld Complex becomes layered/sub-parallel to Transvaal sediments. This, and other geological features (e.g. faulting, folding, dykes), can be explained in relation to the regional tectonic history, relating to motion along the Thabazimbi-Murchison Lineament (TML). Pre-Bushveld emplacement NW-SE far-field stress caused NW trending extensional features in the region (e.g. Rustenburg Fault). Re-orientation of the compressive force to NE-SW, in syn- to post-emplacement, caused compressive features in the region (e.g. open folds with axes trending NW).
Ground gravity data (100 m x 100 m station- and line-spacing) were also inverted to obtain a 3D model of the overburden, constrained by borehole data. However, the inversion failed to satisfy the gravity data and borehole data simultaneously, relating to difficulties in modelling the regional gravity field and the gradational nature of the weathered contact. Several rapid variations in overburden thickness were mapped, with particular success in the high frequency ground gravity survey (30 m x 30 m station- and line-spacing) with the identification of a deeply weathered (~10 m deep) channel relating to an mapped fault
The High Resolution Airborne Resource and Environmental Survey- (Phase 1) (HiRES-1): background, data processing and dissemination and future prospects
This report provides an overview of the HiRES-1 airborne
geophysical survey of Central England. The BGS and World
Geoscience (UK) Ltd. carried out the survey jointly in 1998.
The three main survey data sets acquired were magnetic,
radiometric (gamma ray spectrometry) and Very Low
Frequency (VLF) electromagnetic. The main aim of the report
is to provide information on the acquisition, processing and
storage of the final data and map products produced by the
HiRES-1 project. Additional descriptions of ground truthing
activities, data licensing and dissemination are also provided.
A significant aspect of the project was the assessment of the
potential of, and issues raised by, modern, multi-parameter,
regional-scale airborne geophysical surveys in the UK
context. Some of the main issues outlined in the report are:
• The practical difficulties of conducting extensive low
level, fixed-wing geophysical surveying in the UK.
Issues discussed include CAA regulatory permissions,
flight height adjustments above conurbations and
surveying near areas with dense air traffic.
• The processing challenges introduced by cultural (nongeological)
influences on high resolution airborne
magnetic data sets in the UK.
• The significant amounts of detailed geological and
environmental information contained within the
radiometric data.
• The weak application potential provided by passive
(i.e. VLF) measurements, in contrast to active airborne
electromagnetic techniques.
The future prospects for regional-scale, airborne geophysical
surveys in the UK are considered. Such prospects are also
influenced by a further set of trial airborne data, obtained in
1999, but not described here.
Further detail of the HiRES-1 survey, productivity,
technical specifications and data pre-processing are contained
in the survey logistics report prepared by WGL: ‘British
Geological Survey “Hi-Res Phase One” Airborne Geophysical
Survey (Survey Details, Technical Specifications &
Processing Summary)’ (WGL 2000)
APPLICATION OF THE KALMAN FILTER ON FULL TENSOR GRAVITY GRADIOMETRY DATA AROUND THE VINTON SALT DOME, LOUISIANA
Full tensor gravity (FTG) data are known for their high resolution but also for higher noise in its components due to the dynamic nature of the platform used for data acquisition. Although a review of the literature suggests steady increase in the success of gravity gradiometry, we still cannot take advantage of the full potential of the method, mostly because of the noise with the same amplitude and wavenumber characteristics as the signal that affects these data. Smoothing from common low pass filters removes small wavelength features and makes it difficult to detect structural features and other density variations of interest to exploration. In Kalman filtering the components of the FTG are continuously updated to calculate the best estimation of the state. The most important advantage of the Kalman filter is that it can be applied on gravity gradiometry components simultaneously. In addition, one can incorporate constraints. We use the Laplace’s equation that is the most meaningful constraint for potential field data to extract signal from noise and improve the detection and continuity of density variations. We apply the Kalman filter on the FTG data acquired by Bell Geospace over the Vinton salt dome in southwest Louisiana
A Comparative Overview of Geophysical Methods
This report was prepared with support from the Air Force Research Laboratory, under contract FA8718-07-C-0021.The shallow subsurface structure of the Earth is important to understand for many economic and safety reasons. The
problem is usually difficult due to complexity of the earth’s subsurface processes especially near the surface. A
number of geophysical methods are used for this purpose using different physical characteristics of the Earth
materials. A particular geophysical method illuminates part of the problem, but a reliable solution can only be found
by combining results of different methods. In order to synthesize information from different geophysical methods, it
is important to understand their similarities and differences. The aim of this study is to correlate the basic principles
of geophysical methods side-by-side starting from fundamental equations. This study reveals that many analogies
exist among these methods both in their mathematical formulation, and sometimes, in ways they are used in the
geophysical applications