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With the rapid development of unmanned aerial vehicles (UAVs) technology, using UAVs for magnetic surveys is a booming branch. However, the magnetic interference generated by the UAV hinders the further application of UAV magnetic survey systems. In addition to the interference caused by the UAV maneuvering, the dynamic interference of airborne equipment has also been found and become one of the factors restricted by the detection accuracy of magnetic surveys. This paper proposes a multi-source two-channel linear time-invariant (MTLI) correlation model, considering the maneuvering magnetic interference and airborne equipment magnetic interference. The magnetic interference can be estimated and compensated by interference correlation without current sensors. Compared with the traditional aeromagnetic compensation process and other compensation methods considering the magnetic interference of airborne equipment, the proposed method can provide stable compensation effects in maneuvers and smooth flight, and the workflow is simple and fast. The actual flight experiment is conducted, and the results show that the two kinds of UAV interference fields are suppressed significantly with a root mean square error of 0.0062 and 0.0296 nT in smooth flight and maneuvering flight. [ABSTRACT FROM AUTHOR]

With the rapid development of unmanned aerial vehicles (UAVs) technology, using UAVs for magnetic surveys is a booming branch. However, the magnetic interference generated by the UAV hinders the further application of UAV magnetic survey systems. In addition to the interference caused by the UAV maneuvering, the dynamic interference of airborne equipment has also been found and become one of the factors restricted by the detection accuracy of magnetic surveys. This paper proposes a multi-source two-channel linear time-invariant (MTLI) correlation model, considering the maneuvering magnetic interference and airborne equipment magnetic interference. The magnetic interference can be estimated and compensated by interference correlation without current sensors. Compared with the traditional aeromagnetic compensation process and other compensation methods considering the magnetic interference of airborne equipment, the proposed method can provide stable compensation effects in maneuvers and smooth flight, and the workflow is simple and fast. The actual flight experiment is conducted, and the results show that the two kinds of UAV interference fields are suppressed significantly with a root mean square error of 0.0062 and 0.0296 nT in smooth flight and maneuvering flight.

In the past two decades, unmanned aerial vehicles (UAVs) have been used in many scientific research fields for various applications. In particular, the use of UAVs for magnetic surveys has become a hot spot and is expected to be actively applied in the future. A considerable amount of literature has been published on the use of UAVs for magnetic surveys, however, how to choose the platform and reduce the interference of UAV to the collected data have not been discussed systematically. There are two primary aims of this study: (1) To ascertain the basis of UAV platform selection and (2) to investigate the characteristics and suppression methods of UAV magnetic interference. Systematic reviews were performed to summarize the results of 70 academic studies (from 2005 to 2021) and outline the research tendencies for applying UAVs in magnetic surveys. This study found that multi-rotor UAVs have become the most widely used type of UAVs in recent years because of their advantages such as easiness to operate, low cost, and the ability of flying at a very low altitude, despite their late appearance. With the improvement of the payload capacity of UAVs, to use multiple magnetometers becomes popular since it can provide more abundant information. In addition, this study also found that the most commonly used method to reduce the effects of the UAV’s magnetic interference is to increase the distance between the sensors and the UAV, although this method will bring about other problems, e.g., the directional and positional errors of sensors caused by erratic movements, the increased risk of impact to the magnetometers. The pros and cons of different types of UAV, magnetic interference characteristics and suppression methods based on traditional aeromagnetic compensation and other methods are discussed in detail. This study contributes to the classification of current UAV applications as well as the data processing methods in magnetic surveys.

The compensation of magnetic and electromagnetic interference generated by drones is one of the main problems related to drone-borne magnetometry. The simplest solution is to suspend the magnetometer at a certain distance from the drone. However, this choice may compromise the flight stability or introduce periodic data variations generated by the oscillations of the magnetometer. We studied this problem by conducting two drone-borne magnetic surveys using a prototype system based on a cesium-vapor magnetometer with a 1000 Hz sampling frequency. First, the magnetometer was fixed to the drone landing-sled (at 0.5 m from the rotors), and then it was suspended 3 m below the drone. These two configurations illustrate endmembers of the possible solutions, favoring the stability of the system during flight or the minimization of the mobile platform noise. Drone-generated noise was filtered according to a CWT analysis, and both the spectral characteristics and the modelled source parameters resulted analogously to that of a ground magnetic dataset in the same area, which were here taken as a control dataset. This study demonstrates that careful processing can return high quality drone-borne data using both flight configurations. The optimal flight solution can be chosen depending on the survey target and flight conditions.

The relevance of the discussed issue is caused by the need to study the natural physical fields and their relations with the geological environment. The main aim of the work is to study the magnetic field and the nature of its changes on the typical Siberian sulfide quartz vein gold deposits Darasun. The methods used in the study: specialized experimental methodological field magnetic survey of various observational accuracy and detail of network measurement, laboratory determination of magnetic susceptibility of purposefully selected samples of rocks and ores, statistical analysis of the data, comparing them to known elements of the geological structure of ore-bearing area and its surroundings. The results. The authors have obtained the areal pattern of changes of magnetic induction increment within the ore field of Darasun deposit and its near neighborhood, determined the spectral composition of its changes, magnetic field and relationships with various elements of the geological structure of ore-bearing area Darasun, revealed physical and geological nature of various anomalous zones and provided a basis for assessing the possibilities of magnetic prospecting in solving various geological problems in the stages of prospecting and exploration of quartz-sulphide vein gold deposits in Siberia.

The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has systematically undertaken the task of making measurements of the Earth's magnetic field in Italy. By tradition and because of the elongated geometric shape of our peninsula and islands, in Italy, a grid of more than 110 points, called the first order repeat stations, with an average spacing around 55-60 km, is in operation. Over this grid the measurements are repeated regularly, every 5 years. A survey of 131 repeat stations of the Italian Magnetic Network (including 2 observatories, 11 stations in Albania, 3 stations in Corsica and 1 in Malta) was carried out between 2009 and 2010 with the main purpose of updating our magnetic cartography. We describe the characteristics of magnetic first and second order networks, the magnetic measurements and the data reduction procedure. In agreement with the recommendations of MagNetE Committee, we report new repeat station data measured and reduced at 2010.0. An analytical expression, a second order polynomial, in latitude and longitude for the field elements, was determined, and coefficients for 2010.0 and average secular variation over the period 2005-2010, were obtained. The new maps for Italy, for D, F, H and Z at the epoch 2010.0, are shown. A selection of stations from the Italian Magnetic Network, based on their low values of anomaly with respect to a 'normal' field, is also proposed for future surveys.

Unexploded ordnance (UXO) is military ordnance that was fired, dropped, or emplaced but failed to function as intended and thus constitutes an explosive hazard. UXO is a worldwide problem that kills or maims thousands of civilians each year. Magnetic surveys are an efficient means of locating UXO containing ferrous metal when geologic conditions are sufficiently free of magnetic soil and rock. However, discrimination of UXO from non-UXO is complicated by the fact that UXO is often associated with high levels of clutter from ordnance fragmentation. To date, magnetic modeling of UXO has been based on calculations for a simple body of revolution geometry (prolate spheroids). We conducted an investigation to show how numerical modeling, in particular, finite-element modeling of more realistic geometries, compares to prolate spheroid results. Our results show that the calculated dipole moment response for complex models resembling actual UXO is up to 50% higher than the dipole moments for the prolate spheroid model. We also found that altering the shape of a model from a prolate spheroid to a complex shape has a greater effect on dipole moment than maintaining the same shape and altering the volume. Finally, in comparing the surface response from our models to real total field magnetic data, we find that complex models more closely match actual field data than prolate spheroid models. We suggest that modeling and, ultimately, discrimination using more realistic UXO shapes could result in significant improvements in distinguishing UXO from magnetic clutter and geology. [ABSTRACT FROM AUTHOR]

We present high-resolution gravity and magnetic field survey results over the 85-km- diameter Chesapeake Bay impact structure. Whereas a continuous melt sheet is anticipated at a crater this size, shallow-source magnetic field anomalies of ∼100 nT instead suggest that impact melt pooled in kilometer-scaled pockets surrounding the base of a central peak. A central anomaly of ∼300 nT may represent additional melt or rock that underwent shock-induced remagnetization. Models predict that the total volume of the melt ranges from ∼0.4 to 10 km3, a quantity that is several orders of magnitude smaller than expected for an impact structure this size. However, this volume is within predictions given a transient crater of diameter of 20-40 km for a target covered with water and sedimentary deposits such that melt fragments were widely dispersed at the time of impact Gravity data delineate a gently sloping inner basin and a central peak via a contrast between crystalline and sedimentary rock. Both features are ovoid, oriented parallel to larger preimpact basement structures. Conceptual models suggest how lateral differences in rock strength due to these preimpact structures helped to shape the crater's morphology during transient-crater modification. [ABSTRACT FROM AUTHOR]

A pennanent geomagnetic observatory is always the ideal reference station for monitoring geomagnetic activity during airborne, marine or ground magnetic surveying, especially in Antarctica, where logistic difficulties are an important factor even for the deployment of temporary base stations. The utility of the magnetic observatory records for the correct reduction of the survey data is reinforced if both their spatial homogeneity and their particular anomaly biases are assessed. This, combined with data from the magnetic surveys themselves, can yield information on the crustal contribution to the Earth's magnetic field from a remote and poorly understood region. With these objectives in mind, we present a new geomagnetic observatory in the South Shetland Islands, where (because of the complex regional tectonic characteristics) magnetic surveys on one or another structure are conducted from time to time. An evaluation of the observatory representativeness and a look at the crustal magnetic anomaly ambience are also given.

The compensation of magnetic and electromagnetic interference generated by drones is one of the main problems related to drone-borne magnetometry. The simplest solution is to suspend the magnetometer at a certain distance from the drone. However, this choice may compromise the flight stability or introduce periodic data variations generated by the oscillations of the magnetometer. We studied this problem by conducting two drone-borne magnetic surveys using a prototype system based on a cesium-vapor magnetometer with a 1000 Hz sampling frequency. First, the magnetometer was fixed to the drone landing-sled (at 0.5 m from the rotors), and then it was suspended 3 m below the drone. These two configurations illustrate endmembers of the possible solutions, favoring the stability of the system during flight or the minimization of the mobile platform noise. Drone-generated noise was filtered according to a CWT analysis, and both the spectral characteristics and the modelled source parameters resulted analogously to that of a ground magnetic dataset in the same area, which were here taken as a control dataset. This study demonstrates that careful processing can return high quality drone-borne data using both flight configurations. The optimal flight solution can be chosen depending on the survey target and flight conditions. [ABSTRACT FROM AUTHOR]