UAV-based aeromagnetic gradient measurements and inversion

2021 ◽  
Author(s):  
Christian Kulüke ◽  
Christopher Virgil ◽  
Johannes Stoll ◽  
Andreas Hördt
Keyword(s):  
Magnetic Moment ◽  
General Rule ◽  
Magnetic Data ◽  
Measurement Unit ◽  
Fluxgate Magnetometer ◽  
Test Field ◽  
Horizontal Distance ◽  
Geographic Coordinate System ◽  
Gps Antenna ◽  
Sensor Positions

<p>Rotary wing UAV’s are used in aeromagnetic measurements for UXO detection. That way, contaminated areas can be mapped fast and with high resolution. Until today, only the total magnetic intensity (TMI) is evaluated, even when a three axis fluxgate magnetometer is flown. In this project, we use two three component fluxgate sensors, an inertial measurement unit (IMU) and a GPS antenna. The IMU allows for a projection of the magnetic data into the geographic coordinate system as well as the calculation of the sensor positions relative to the GPS antenna. With this system, it is possible for the first time to evaluate the component gradients between the magnetometers.</p><p>The sensors are attached to the UAV via a versatile, T-shaped boom hanging below the UAV with the sensors positioned in a horizontal distance of 50 cm. The total mass of the flight system is about 5 kg with an air time of 15 minutes.</p><p>For the inversion, we use a dipole model which calculates the magnetic data for all sensor positions. Because the sources of the magnetic anomalies are unknown as a general rule, there is no distinction between induced and remanent magnetisation. Instead, the three components of the magnetic moment are fitted alongside the positions of the anomaly sources. The number of dipoles to be fitted and their initial parameters are arbitrary. For the inversion, the TMI and component gradients between the sensors are considered.</p><p>In order to analyse the accuracy of the complete system, we conducted surveys over a test field of 100 x 20 m, separated into four sections with varying anomaly configurations. As anomaly sources, we used neodymium magnets which we characterised in laboratory measurements. For optimal coverage and to compare flight directions, the test field was surveyed both lengthways and crossways with a sensor height of 1.5 m above ground. Inversion results show that when component gradients are used, overlapping anomalies can be separated and parameterised. The mean errors of the derived anomaly positions are 5 cm, the total magnetic moment can be determined with an accuracy of 0.35 Am<sup>2</sup>, whereby the errors in direction (declination and inclination) are 4 ° and 2 °, respectively.</p>

Borehole magnetic surveys in weakly magnetic sediments (Chicxulub impact crater) versus strongly magnetic volcanics (Bathurst mining camp)

2019 ◽  
Vol 56 (5) ◽  
pp. 504-524
Author(s):  
William A. Morris ◽  
Sara-Lise Underhay ◽  
Hernan Ugalde ◽  
Bernd Milkereit
Keyword(s):  
Magnetic Property ◽  
Impact Crater ◽  
Magnetic Data ◽  
Coordinate Space ◽  
Systematic Change ◽  
Fluxgate Magnetometer ◽  
Magnetic Vector ◽  
Chicxulub Impact Crater ◽  
Bathurst Mining Camp ◽  
Chicxulub Impact

Borehole navigation surveys performed using a triaxial fluxgate magnetometer record the change in orientation of the magnetic vector versus depth. Variations in the orientation of the magnetic vector arise from either on- or off-hole magnetic sources. On-hole magnetic sources associated with magnetic property fluctuations in the immediate wall of the borehole (i.e., susceptibility) and (or) remanence polarity changes produce sharp-edged anomalies. Off-hole magnetic sources, caused by a magnetic body near, but not penetrated by, the borehole, produce broad smooth anomalies. Prior to the interpretation of borehole magnetic anomaly logs, data corrections must be applied. Data from each of the magnetic and tiltmeter sensors must be corrected for differential gain, base value offset, and nonorthogonality. By using a probe with two sets of triaxial fluxgates, it is possible to detect along hole magnetic field rotations, which compromise the borehole navigation calculations. After rotation into geographic coordinate space, borehole vector magnetic data from the Chicxulub impact crater in Mexico showed no evidence for any systematic change of magnetic property versus depth. What was originally interpreted as reversal stratigraphy has proved to be minor changes in borehole geometry. Borehole magnetic data from a borehole through the Stratmat deposit, located in the Bathurst mining camp, New Brunswick, show strong off-hole and on-hole anomalies associated with the pyrrhotite-rich ore bodies.

scholarly journals DESMEX: A novel system development for semi-airborne electromagnetic exploration

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. E253-E267 ◽  
Author(s):  
M. Becken ◽  
C. G. Nittinger ◽  
M. Smirnova ◽  
A. Steuer ◽  
T. Martin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transfer Functions ◽  
System Development ◽  
Low Noise ◽  
Raw Material ◽  
Measurement Unit ◽  
Fluxgate Magnetometer ◽  
Low Frequencies ◽  
Airborne Electromagnetic ◽  
Fixed Reference

There is a clear demand to increase detection depths in the context of raw material exploration programs. Semi-airborne electromagnetic (semi-AEM) methods can address these demands by combining the advantages of powerful transmitters deployed on the ground with efficient helicopter-borne mapping of the magnetic field response in the air. The penetration depth can exceed those of classic airborne EM systems because low frequencies and large transmitter-receiver offsets can be realized in practice. A novel system has been developed that combines high-moment horizontal electric bipole transmitters on the ground with low-noise three-axis induction coil magnetometers, a three-axis fluxgate magnetometer, and a laser gyro inertial measurement unit integrated within a helicopter-towed airborne platform. The attitude data are used to correct the time series for motional noise and subsequently to rotate into an earth-fixed reference frame. In a second processing step, and as opposed to existing semi-AEM systems, we transform the data into the frequency domain and estimate the complex-valued transfer functions between the received magnetic field components and the synchronously recorded injection current by regression analysis. This approach is similar to the procedure used in controlled-source EM. For typical source bipole moments of 20–40 kAm and for rectangular current waveforms with a fundamental frequency of approximately 10 Hz, we can estimate reliable three-component (3C) transfer functions in the frequency range from 10 to 5000 Hz over a measurement area of [Formula: see text] for a single source installation. The system has the potential to be used for focused exploration of deep targets.

scholarly journals One second vector and scalar magnetic measurements at low latitude observatory, CPL

2017 ◽  
Author(s):  
Phani Chandrasekhar Nelapatla ◽  
Sai Vijay Kumar Potharaju ◽  
Kusumita Arora ◽  
Chandra Shakhar Rao Kasuba ◽  
Leonid Rakhlin ◽  
...  
Keyword(s):  
Real Time ◽  
Magnetic Measurements ◽  
Low Frequency ◽  
Magnetic Data ◽  
Magnetic Observatory ◽  
Fluxgate Magnetometer ◽  
Main Concern ◽  
Low Latitude ◽  
Time Space ◽  
New Instrument

Abstract. There is increasing demand from the global geomagnetic community for the recording of 1 second vector and scalar magnetic datain lieu of the traditional of the 1 minute data, as the 1 second magnetic data would be more compatible with measurements made from low-earth orbiting satellites and the increased detectability threshold, would contribute to: (i) understanding the global scale ultra-low frequency (ULF) waves, sudden impulses and other processes in the ionosphere & magnetosphere: (ii) development of real-time space weather forecasts. The combination of ground and satellite data opens a new pathway in understanding many underlying physical processes in the lower-middle atmospheric dynamics, which has not been accurately understood so far. The International Real-time Magnetic ObservatoryNetwork (INTERMAGNET)observatories (IMO-s) have taken a lead in this direction and many IMO-s now produce both 1 minute and 1 second data. Being affordable, rugged, compact as well as having low power consumption, fluxgate magnetometers are the staple vector sensors of IMO-s.The increased order of noise in these sensors with increasing frequencies, is the main concern and work has been going on for the last decade towards development of suitable instruments (Courtillot and Chulliat, 2008; Korepanov et al. 2006, 2009; Pedersen and Merenyi, 2016 and references therein, Dobrodnyak, 2014; Logvinov, 2014) and techniques for the evaluation and elimination of noise from the data is also being pursued (Turbitt et al. 2013). At the new Magnetic Observatory of CSIR-NGRI in Choutuppal (CPL) campus, 1 second magnetic measurements commenced in the year 2016 using the newly developed Observatory grade 1 second fluxgate magnetometer, GEOMAG-02MO, from GEOMAGNET Ukraine and the Overhauser Proton Precession Magnetometer along with the data acquisition system, MAGREC-4B. The processes of commissioning of this setup in low-latitude conditions, with the aim to finally produce 1 second definitive data (the standards of which are still under discussion with INTERMAGNET) and the characteristics of the data from this new instrument are presented in this work.

scholarly journals Synthesis, characterization and antimicrobial activities of heteroleptic metal chelates of isoniazid and 2,2’-bipyridine

2021 ◽  
Vol 34 (3) ◽  
pp. 471-478
Author(s):  
O. F. Akinyele ◽  
E. G. Fakola ◽  
L. M. Durosinmi ◽  
T. A. Ajayeoba ◽  
A. O. Ayeni
Keyword(s):  
Antimicrobial Activity ◽  
Magnetic Moment ◽  
Antibacterial Activities ◽  
Antimicrobial Activities ◽  
Carbonyl Oxygen ◽  
Bidentate Ligand ◽  
Magnetic Data ◽  
Diffusion Method ◽  
Vis Spectroscopy ◽  
Structure Geometry

The Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of isoniazid (L1) mixed with 2,2-bipyridine (L2) were synthesized and characterized by solubility studies, percentage metal analysis, UV-Vis spectroscopy, IR spectroscopy, conductivity measurements and magnetic moment measurements. The IR spectra revealed that the isoniazid coordinated as a bidentate ligand. In Co(II) and Ni(II) complex it coordinated  via the carbonyl oxygen (C=O) and the amide nitrogen, while in the Cu(II), Mn(II) and Zn(II) complexes it coordinated using the amide and carbonyl oxygen via enolization. Bipyridine also bonded to the metals as a bidentate ligand through the pyridinic nitrogen atoms. The magnetic data showed that all the complexes were paramagnetic with values ranging from 1.70 to 5.0 B.M., except [Zn(Is)(Bipy)(H2O)Cl2] which was diamagnetic. The conductivity results revealed that the Cu(II), Mn(II), Zn(II) complexes were 1:1 electrolytes while Co(II) was 1:2 electrolyte and [Ni(Is)(Bipy)Cl2] was non-electrolytic in nature. The antibacterial activities of the ligands and the complexes as evaluated via the agar diffusion method showed that the complexes displayed moderately high antimicrobial activity in comparison with the free ligands when tested against ten strains of bacteria.                     KEY WORDS: Isoniazid, Electronic structure, Geometry, Antimicrobial activity, Electrolytic nature, Magnetic moment   Bull. Chem. Soc. Ethiop. 2020, 34(3), 471-478. DOI: https://dx.doi.org/10.4314/bcse.v34i3.4

scholarly journals METHOD OF NOISE DETECTION IN MAGNETIC DATA

2019 ◽  
pp. 87-97
Author(s):  
С.Ю. Папшева ◽  
О.В. Мандрикова ◽  
С.Ю. Хомутов
Keyword(s):  
Wavelet Transformation ◽  
Magnetic Data ◽  
Fluxgate Magnetometer ◽  
Noise Detection ◽  
Natural Sources ◽  
Time Frequency ◽  
Threshold Functions ◽  
Frequency Structure ◽  
Kamchatka Region ◽  
Scale Levels

Предложен вычислительный метод обнаружения помех в геомагнитных данных, основанный на вейвлет-преобразовании и пороговых функциях. Эффективность метода показана на примере обработки результатов измерений с помощью вариационного феррозондового магнитометра FGE-DTU (обсерватория Паратунка , Камчатский край, ИКИР ДВО РАН). Рассмотрены некоторые виды помех от естественных источников (при землетрясениях на Камчатке) и техногенных помех, связанных с работой ионозонда. Детально изучена частотно-временная структура помех в вариациях Z- и D-составляющих геомагнитного поля (частота измерений 2 Гц). Для рассмотренного вида помех определены информативные масштабные уровни вейвлет-преобразования и оценены параметры алгоритма реализации метода. The method of detection of noise in magnetic data based on wavelet transformation and threshold functions is considered. Efficiency is shown by the results of analysis of fluxgate magnetometer FGE-DTU measurements at Observatory Paratunka, Kamchatka, IKIR FEB RAS. The noise from natural sources such as earthquakes in Kamchatka region and from artificial sources such as the vertical sounding of ionosphere by the ionosonde near Observatory is considered. Detailed time-frequency structure of noise in 2 Hz records of Z and D components is investigated. To automation the method for considered examples of noise the informative scale levels of wavelet-transformation are determined and parameters of threshold functions appreciated.

scholarly journals Synthetic Case Study: Discrimination of Unexploded Ordnance (UXO) and non-UXO Sources with varying Remanent Magnetization Strength using Magnetic Data

2021 ◽  
Author(s):  
Mark David Wigh ◽  
Thomas Mejer Hansen ◽  
Arne Døssing
Keyword(s):  
Magnetic Moment ◽  
Remanent Magnetization ◽  
Prior Information ◽  
Forward Model ◽  
Magnetic Data ◽  
Unexploded Ordnance ◽  
The North ◽  
Discrimination Rate ◽  
High Discrimination

Summary We investigate if it is theoretically possible to discriminate between unexploded ordnance (UXO) and non-UXO sources by modelling the magnetic dipole moment for ferrous objects of different shapes and sizes. This is carried out by approximating the volumetric demagnetization factors of rectangular prisms, representing shapes similar to a long rod or flat steel plate. By modelling different UXO as prolate spheroids the demagnetization factors can be determined which can be compared with the magnetic response of a prism. The inversion is carried out in a probabilistic framework, where the UXO forward model and the non-UXO forward model are assigned individual prior models in terms of shape, size, orientation and remanent magnetization of the object. 95 independent realizations of the prism prior model are generated to make 95 synthetic anomalies exemplifying non-UXO objects, which are inverted for using the UXO model. It is investigated if an identical magnetic moment can be produced between the two models and how well resolved the magnetic moment is in terms of the measured anomaly. The case study is carried out in two steps where we first have little prior information of expected UXO properties and another where a UXO prior is introduced with expected values of aspect ratio and size of 24 different UXO, that are often encountered in the North Sea. With no prior information of expected UXO, discrimination is at many times implausible, unless elongated rod prism objects are considered, where the magnetic moment often can not be reproduced by a spheroid. Introducing the UXO prior we achieve a much better discrimination rate when using the list of expected UXO properties. By using the UXO prior we can account for a much higher remanent magnetization allowed in the prior, and still achieve high discrimination capabilities in comparison to a case with no UXO prior.

scholarly journals Magnetic properties of CHAMP and their effects on in-orbit calibration

2013 ◽  
Vol 2 (1) ◽  
pp. 9-17 ◽  
Author(s):  
H. Lühr ◽  
F. Yin ◽  
R. Bock
Keyword(s):  
Magnetic Field ◽  
Magnetic Moment ◽  
Field Data ◽  
Field Vector ◽  
Current Strength ◽  
Fluxgate Magnetometer ◽  
Vector Data ◽  
Magnetic Field Data ◽  
Average Current

Abstract. CHAMP has so far been the most successful magnetic field mission. For achieving that, special effort had to be invested in building a magnetically clean spacecraft. The magnetic moment of the spacecraft is about 1 Am2. In this article we introduce a new method that allows the determination of the magnetic moment during the mission from the average current strength of the magneto-torquers. In order to achieve precise field vector data, the readings of the fluxgate magnetometer are routinely calibrated against the absolute Overhauser measurements. A reanalysis of all the magnetic field data is performed which takes also into account small disturbances from the power system. Uncertainties of the final magnetic field data are estimated to be of the order of 0.1 nT.

scholarly journals Automated observatory in Antarctica: real-time data transfer on constrained networks in practice

2017 ◽  
Vol 6 (2) ◽  
pp. 285-292 ◽  
Author(s):  
Stephan Bracke ◽  
Alexandre Gonsette ◽  
Jean Rasson ◽  
Antoine Poncelet ◽  
Olivier Hendrickx
Keyword(s):  
Real Time ◽  
Data Transfer ◽  
Extreme Values ◽  
Magnetic Data ◽  
Magnetic Observatory ◽  
Fluxgate Magnetometer ◽  
File Transfer ◽  
Time Data ◽  
Vector Magnetometer ◽  
Minimum Power Consumption

Abstract. In 2013 a project was started by the geophysical centre in Dourbes to install a fully automated magnetic observatory in Antarctica. This isolated place comes with specific requirements: unmanned station during 6 months, low temperatures with extreme values down to −50 °C, minimum power consumption and satellite bandwidth limited to 56 Kbit s−1. The ultimate aim is to transfer real-time magnetic data every second: vector data from a LEMI-25 vector magnetometer, absolute F measurements from a GEM Systems scalar proton magnetometer and absolute magnetic inclination–declination (DI) measurements (five times a day) with an automated DI-fluxgate magnetometer. Traditional file transfer protocols (for instance File Transfer Protocol (FTP), email, rsync) show severe limitations when it comes to real-time capability. After evaluation of pro and cons of the available real-time Internet of things (IoT) protocols and seismic software solutions, we chose to use Message Queuing Telemetry Transport (MQTT) and receive the 1 s data with a negligible latency cost and no loss of data. Each individual instrument sends the magnetic data immediately after capturing, and the data arrive approximately 300 ms after being sent, which corresponds with the normal satellite latency.

scholarly journals Accuracy of An Algorithm Using Motion Data Of Five Wearable IMU Sensors For Estimating Lifting Duration And Lifting Risk Factors

2019 ◽  
Vol 63 (1) ◽  
pp. 1105-1111 ◽  
Author(s):  
Menekse S. Barim ◽  
Ming-Lun Lu ◽  
Shuo Feng ◽  
Grant Hughes ◽  
Marie Hayden ◽  
...  
Keyword(s):  
Ground Truth ◽  
The Body ◽  
Measurement Unit ◽  
Horizontal Distance ◽  
Dominant Hand ◽  
Trunk Flexion ◽  
Left Wrist ◽  
Motion Data ◽  
Optical Motion ◽  
Optical Motion Capture

The objective of this study was to assess the accuracy of an algorithm for processing data from five inertial measurement unit (IMU) sensors for measuring the vertical distance (V) and horizontal distance (H) of two handed lifting, trunk flexion angle (T) and lifting duration (LD). The sensors were placed on five body segments including the left wrist, right wrist, upper arm of the dominant hand, upper back, and thigh of the dominant leg. A laboratory-grade optical motion capture system was used as the ground truth for the assessment. Data were collected on ten subjects that performed 12 two-handed lifting tasks varying in height of the hands and horizontal distance between the body and the lifted object. Results showed that the algorithm performed well for determining the LD (~1 sec error) and T (~2° error). The average errors for V and H were about 33 and 6.5 cm, respectively.

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