Local Gravity Research Articles

Multi-directional broad learning system for the unsupervised stereo matching method

The supervised stereo matching methods usually rely on ground truth disparity maps as the training labels, this limits its practical application in many situations. In this study, we propose a novel unsupervised stereo matching method based on a multi-directional broad learning system. A multi-directional broad learning system was constructed to generate multiple candidate disparity maps. During the generation of each candidate disparity map, an update criterion is proposed for the disparity value based on the maximum similarity of the inverse mapping region to remove the abnormal disparity values of the training samples. Subsequently, multi-direction consistency verification is performed to further eliminate abnormal disparity values, which are based on the uniqueness principle of disparity truth values at the same location. Finally, an invalid depth redefinition based on a local gravity weight method is introduced to select the appropriate disparity value to fill the invalid pixel positions from their neighborhood, which is calculated based on the local region of the color, matching cost, and geometric spaces in the stereo images. We provide the results of experiments on both indoor and outdoor scenarios to demonstrate the effectiveness and flexibility of our approach, including comparisons with state-of-the-art methods.

Determination of Spatial Scale in Martian Landscape Images Acquired by the Curiosity Rover, and Viewing Image Scale and Target Chemistry Using the ASIC Website

AbstractIn this paper we describe a method to compute spatial scales for images acquired by NASA's Mars Curiosity rover (Mars Science Laboratory, MSL). The method is based on the assumption that the rover stands on an infinite plane that may have any orientation with respect to the local gravity vector. While not new, it is the first time that this method is systematically applied to Martian images acquired by a lander. A continuously run software pipeline processes the images acquired by the rover within a 20 m radius, adds approximate scalebars to the raw images, and generates, whenever possible, rectified (warped) versions of those images. The products of this software pipeline and the chemical compositions of relevant rover science targets from NASA's Planetary Data System archive, are made available to the public via the Approximate Scale for Images and Chemistry website, which has been developed in collaboration with the Planetary Data System Analyst's Notebook for the MSL mission. Hyperlinks connect the two resources.

Features of Gravity Anomalies and Oil-Gas Distribution Rules in Central and Western Sichuan Basin, China

In order to explore the rules between gravity anomalies and oil-gas distribution characteristics in central and western Sichuan Basin, we divided the tectonic unit in central and western Sichuan basin on the base of the analysis of gravity anomaly characteristics, and studied the correlation between the oil–gas distribution and the local gravity anomaly in the study area. The results show that the variation in the range of the Bouguer gravity field in the interior of the basin is relatively small, and the southern part shows a clear gravity high zone, with gradual gravity gradient zones all around the basin periphery. The abnormal value of the residual gravity field in the basin is an obvious high–value gravity belt in the north and west, and the interior is arranged alternately with local high gravity and low gravity in the north–east direction. The tectonic units of the central and western Sichuan Basin can be divided into five regions, based on the characteristics of the Bouguer gravity field, namely, the Central Sichuan uplift zone, the West Sichuan depressional zone, the East Sichuan high steep zone, the South Sichuan low steep zone, and the North Sichuan low slow zone. Combined with geological data and Bouguer gravity anomaly processing results, the distribution of oil and gas fields in the central and western Sichuan Basin is certain correlated with the local gravity high zone and the transition zone between the local gravity high zone and the local gravity low zone. They are the major areas of oil and gas.

Insights into the Magmatic Feeding System of the 2021 Eruption at Cumbre Vieja (La Palma, Canary Islands) Inferred from Gravity Data Modeling

This study used spatiotemporal land gravity data to investigate the 2021 eruption that occurred in the Cumbre Vieja volcano (La Palma, Canary Islands). First, we produced a density model by inverting the local gravity field using data collected in July 2005 and July 2021. This model revealed a low-density body beneath the western flank of the volcano that explains a highly fractured and altered structure related to the active hydrothermal system. Then, we retrieved changes in gravity and GNSS vertical displacements from repeated measurements made in a local network before (July 2021) and after (January 2022) the eruption. After correcting the vertical surface displacements, the gravity changes produced by mass variation during the eruptive process were used to build a forward model of the magmatic feeding system consisting of dikes and sills based on an initial model defined by the paths of the earthquake hypocenters preceding the eruption. Our study provides a final model of the magma plumbing system, which establishes a spatiotemporal framework tracing the path of magma ascent from the crust–mantle boundary to the surface from 11–19 September 2021, where the shallowest magma path was strongly influenced by the low-density body identified in the inversion process.

Symmetry restoration in the vicinity of neutron stars with a nonminimal coupling

We propose a new model of scalarized neutron stars (NSs) realized by a self-interacting scalar field ϕ nonminimally coupled to the Ricci scalar R of the form F(ϕ)R. The scalar field has a self-interacting potential and sits at its vacuum expectation value ϕv far away from the source. Inside the NS, the dominance of a positive nonminimal coupling over a negative mass squared of the potential leads to a symmetry restoration with the central field value ϕc close to 0. This allows the existence of scalarized NS solutions connecting ϕv with ϕc whose difference is significant, whereas the field is located in the vicinity of ϕ=ϕv for weak gravitational stars. The Arnowitt-Deser-Misner mass and radius of NSs as well as the gravitational force around the NS surface can receive sizable corrections from the scalar hair, while satisfying local gravity constraints in the Solar system. Unlike the original scenario of spontaneous scalarization induced by a negative nonminimal coupling, the catastrophic instability of cosmological solutions can be avoided. We also study the cosmological dynamics from the inflationary epoch to today and show that the scalar field ϕ finally approaches the asymptotic value ϕv without spoiling a successful cosmological evolution. After ϕ starts to oscillate about the potential minimum, the same field can also be the source for cold dark matter.

Ore-controlling structures of the Qingchengzi Pb-Zn-Au-Ag orefield, northeastern China and significance for deep ore prospecting: Revealed from gravity and magnetic anomalies

Located in the middle of Liaodong Rift, the Qingchengzi orefield is an important Pb-Zn-Ag-Au polymetallic mining area in Northeast China. The Pb-Zn-Au-Ag mineralization mainly occurs in the Liaohe Group strata and is closely related to Indosinian and Yanshanian magmatic intrusive bodies. Currently the Qingchengzi orefield is poorly explored at depths greater than 1500 m, with no large deep concealed gold deposit being discovered yet. This study focused on delineating deep concealed ore-controlling structures from the local gravity and aeromagnetic anomalies in different wavelet orders acquired by the application of discrete wavelet transform (DWT), and evaluating their potential for undiscovered gold-rich polymetallic mineralization in the Qingchengzi orefield. We started from summarizing the characteristics of gravity and magnetic anomalies corresponding to the ore-controlling structures obtained from surface geology, exploration profiles and drilling results. Under the guidance of the correspondence, we interpreted the structural control factors of the tectonic-magmatic metallogenic system for the whole Qingchengzi orefield, such as faults, strata, magmatic bodies and mineralized alteration belts. Based on the spatial relationship between the known deposits and structural factors interpreted from gravity and magnetic anomalies, it is concluded that the gold-rich polymetallic deposits and mineralization are controlled by five major deep regional faults (two in the NE direction and three in the NW direction). Moreover, the borders of the Indosinian and Yanshanian concealed magmatic intrusions, as well as the intersections of deep regional faults are more favorable for the deposition of gold-rich polymetallic minerals. A NNE-trending concealed structure was found in the middle of our study area, connecting the Shuangdinggou, Qingchengzi, Xinling and Gujiagou intrusions, serving as a possible channel for magmatic activities in the Indosinian. The forward modeling results on the gravity and magnetic data of profile L1 indicates that the Liaohe Group strata and the possible Mesozoic concealed intrusion lies beneath the Paleoproterozoic Dadingzi granite. This finding supplements the traditional understanding that the Paleoproterozoic Dadingzi granite is the deepest boundary for ore prospecting, and provides new thoughts searching for deep-seated ore bodies for the Xiaotongjiapuzi ore deposits.

Multi-scale Physical Properties of NGC 6334 as Revealed by Local Relative Orientations between Magnetic Fields, Density Gradients, Velocity Gradients, and Gravity

We present ALMA dust polarization and molecular line observations toward four clumps (I(N), I, IV, and V) in the massive star-forming region NGC 6334. In conjunction with large-scale dust polarization and molecular line data from JCMT, Planck, and NANTEN2, we make a synergistic analysis of relative orientations between magnetic fields (θ B), column density gradients (θ NG), local gravity (θ LG), and velocity gradients (θ VG) to investigate the multi-scale (from ∼30 to 0.003 pc) physical properties in NGC 6334. We find that the relative orientation between θ B and θ NG changes from statistically more perpendicular to parallel as column density () increases, which is a signature of trans-to-sub-Alfvénic turbulence at complex/cloud scales as revealed by previous numerical studies. Because θ NG and θ LG are preferentially aligned within the NGC 6334 cloud, we suggest that the more parallel alignment between θ B and θ NG at higher is because the magnetic field line is dragged by gravity. At even higher , the angle between θ B and θ NG or θ LG transits back to having no preferred orientation, or statistically slightly more perpendicular, suggesting that the magnetic field structure is impacted by star formation activities. A statistically more perpendicular alignment is found between θ B and θ VG throughout our studied range, which indicates a trans-to-sub-Alfvénic state at small scales as well, and this signifies that magnetic field has an important role in the star formation process in NGC 6334. The normalized mass-to-flux ratio derived from the polarization-intensity gradient (KTH) method increases with , but the KTH method may fail at high due to the impact of star formation feedback.

Local gravity field modeling using gravity difference observations along the line of sight of the GRACE-FO satellites and adjusted spherical cap harmonic basis functions

Local gravity field modeling using gravity difference observations along the line of sight of the GRACE-FO satellites and adjusted spherical cap harmonic basis functions

Key nodes mining for complex networks based on local gravity model

Identification of key nodes in complex networks can effectively speed up the spread of favourable information or prevent the spread of rumours and diseases. An algorithm based on local gravity model is proposed to mine the key spreaders in complex networks. The existing algorithms based on gravity model consider the shortest distance between nodes. However, nodes not only influence each other through the shortest path, which will lead the loss of information between nodes. Different from the existing gravity model, the distance considered in this model is not the shortest distance between nodes, but the reciprocal of the number of feasible paths between nodes. Conveniently, the model is called FPLGM (Local Gravity Model Based on Feasible Paths). Ten different networks are utilised to verify the effectiveness of FPLGM. Results show that the FPLGM performs best in comparison with the well-known state-of-the-art methods.

The European GeoMetre project: developing enhanced large-scale dimensional metrology for geodesy

We provide a survey on the joint European research project “GeoMetre”, which explores novel technologies and their inclusion to existing surveying strategies to improve the traceability of geodetic reference frames to the SI definition of the metre. This work includes the development of novel distance meters with a range of up to 5 km, the realisation of optical multilateration systems for large structure monitoring at an operation distance of 50 m and beyond, and a novel strategy for GNSS-based distance determination. Different methods for refractivity compensation, based on classical sensors, on dispersion, on spectroscopic thermometry, and on the speed of sound to reduce the meteorological uncertainties in precise distance measurements, are developed further and characterised. These systems are validated at and applied to the novel European standard baseline EURO5000 at the Pieniny Kippen Belt, Poland, which was completely refurbished and intensely studied in this project. We use our novel instruments for a reduced uncertainty of the scale in the surveillance networks solutions for local tie measurements at space-geodetic co-location stations. We also investigate novel approaches like close-range photogrammetry to reference point determination of space-geodetic telescopes. Finally, we also investigate the inclusion of the local gravity field to consider the deviations of the vertical in the data analysis and to reduce the uncertainty of coordinate transformations in this complex problem.

GOCE Downward Continuation to the Earth’s Surface and Improvements to Local Geoid Modeling by FFT and LSC

One of the main applications of the gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite data is their combination with local gravity anomalies for geoid and gravity field modeling purposes. The aim of the present paper was the determination of an improved geoid model for the wider Hellenic area, using original GOCE SGG data filtered to retain only useful signals inside the measurement bandwidth (MBW) of the satellite. The filtered SGGs, originally at the satellite altitude, were projected to a mean orbit (MO) and then downward continued to the Earth’s surface (ES) in order to be combined with local gravity anomalies. For the projection to an MO, grids of disturbing gravity gradients from a global geopotential model (GGM) were used, computed per 1 km from the maximum satellite altitude to that of the MO. The downward continuation process was then undertaken using an iterative Monte Carlo (MC) simulated annealing method with GGM gravity anomalies on the ES used as ground truth data. The final geoid model over the wider Hellenic area was estimated, employing the remove–compute–restore method and both Fast Fourier Transform (FFT) and Least Squares Collocation (LSC). Gravity-only, GOCE-only and combined models using local gravity and GOCE data were determined and evaluation of the results was carried out against available GNSS/levelling data in the study area. From the results achieved, it was concluded that even when FFT is used, so that a combined grid of local gravity and GOCE data is used, improvements to the differences regarding GNSS/levelling data by 14.53% to 27.78% can be achieved. The geoid determination with LSC was focused on three different areas over Greece, with different characteristics in the topography and gravity variability. From these results, improvements from 14.73%, for the well-surveyed local data of Thessaly, to 32.88%, over the mountainous area of Pindos, and 57.10% for the island of Crete for 57.10% were found.

Cosmology in theories with spontaneous scalarization of neutron stars

In a model of spontaneous scalarization of neutron stars proposed by Damour and Esposito-Farese, a general relativistic branch becomes unstable to trigger tachyonic growth of a scalar field $\ensuremath{\phi}$ toward a scalarized branch. Applying this scenario to cosmology, there is fatal tachyonic instability of $\ensuremath{\phi}$ during inflation and matter dominance being incompatible with solar-system constraints on today's field value ${\ensuremath{\phi}}_{0}$. In the presence of a four-point coupling ${g}^{2}{\ensuremath{\phi}}^{2}{\ensuremath{\chi}}^{2}/2$ between $\ensuremath{\phi}$ and an inflaton field $\ensuremath{\chi}$, it was argued by Anson et al. that a positive mass squared heavier than the square of a Hubble expansion rate leads to the exponential suppression of $\ensuremath{\phi}$ during inflation and that ${\ensuremath{\phi}}_{0}$ can remain small even with the growth of $\ensuremath{\phi}$ after the radiation-dominated epoch. For several inflaton potentials approximated as $V(\ensuremath{\chi})={m}^{2}{\ensuremath{\chi}}^{2}/2$ about the potential minimum, we study the dynamics of $\ensuremath{\phi}$ during reheating as well as other cosmological epochs in detail. For certain ranges of the coupling $g$, the homogeneous field $\ensuremath{\phi}$ can be amplified by parametric resonance during a coherent oscillation of the inflaton. Incorporating the backreaction of created particles under a Hartree approximation, the maximum values of $\ensuremath{\phi}$ reached during preheating are significantly smaller than those obtained without the backreaction. We also find that the minimum values of $g$ consistent with solar system bounds on $\ensuremath{\phi}$ at the end of reheating are of order ${10}^{\ensuremath{-}5}$ and hence there is a wide range of acceptable values of $g$. Thus, the scenario proposed by Anson et al. naturally leads to the viable cosmological evolution of $\ensuremath{\phi}$ consistent with local gravity constraints, without modifying the property of scalarized neutron stars.

Early stage internal short circuit fault diagnosis for lithium-ion batteries based on local-outlier detection

Internal short circuit (ISC) is considered to be one of the main causes of battery thermal runaway, which is a critical obstacle to the application of lithium-ion batteries for energy storage. Aiming at inconspicuous characteristics and slow detection speed of early stage ISC faults, this paper proposes a fast diagnostic method for ISC based on local-gravitation outlier detection. In the serial battery module, the cell terminal voltages are normalized to characterize voltage trends that are more sensitive to faults than voltage magnitudes, which improves the speed of fault diagnosis. The normalized voltages are then evaluated by a local gravity outlier detection algorithm to detect faults, by which the anomalies caused by the faults are amplified to achieve the ability to diagnose early ISC faults. The performance of the method is validated under the Urban Dynamometer Driving Schedule test, where several sets of experimental results for ISC faults of varying severity showed that the proposed method could detect them accurately and rapidly even when the fault characteristics are not obvious.

A review of high-performance MEMS sensors for resource exploration and geophysical applications

MEMS sensors have the advantages of small volume, lightweight, and low cost, therefore, have been widely used in the fields of consumer electronics, industry, health, defence, and aerospace. With their ever-improving performance, MEMS sensors have also started to be used in resource exploration and geophysical applications. However, the requirements of high-precision MEMS sensors for geophysical applications have not been specified in detail. Therefore, this paper systematically analyzes the requirements of high-performance MEMS sensors for prospecting and geophysical applications, including seismic surveillance, Earth tide, volcanic activity monitoring for natural disasters; seismic, gravity, and magnetic resource prospecting; drilling process monitoring and local gravity measurement for gravity aided navigation. Focusing on the above applications, this paper summarizes the state-of-the-art of research on high-performance MEMS sensors for resource exploration and geophysical applications. Several off-the-shelf MEMS sensors have been used for earthquake monitoring, seismic exploration and drilling process monitoring, and a range of MEMS research prototype sensors have successfully been employed for Earth tides measurement and are promising to be used for gravity exploration. MEMS magnetometers should have a lower noise floor to meet the demand for magnetic exploration. MEMS gravity gradiometers are still under early development and will not be deployable in short-term. High-performance MEMS sensors hold the advantages of low-cost, high integration, and capability of working in extreme environments; therefore, they are likely to gradually replace some conventional geophysical instruments in some application areas.

Transmission and reflection of three-dimensional Boussinesq internal gravity wave packets in nonuniform retrograde shear flow

Simulated fully localized internal gravity wave packets with moderately large initial amplitude exhibit finite transmission across a reflection level, due to the combined effects of the wave-induced shear locally cancelling the retrograde background shear, modulational instability, and the nonlinear generation and evolution of secondary wave packets.

A Multiscale Picture of the Magnetic Field and Gravity from a Large-scale Filamentary Envelope to Core-accreting Dust Lanes in the High-mass Star-forming Region W51

We present 230 GHz continuum polarization observations with the Atacama Large Millimeter/Submillimeter Array at a resolution of 0.″1 (∼540 au) in the high-mass star-forming regions W51 e2 and e8. These observations resolve a network of core-connecting dust lanes, marking a departure from earlier coarser, more spherical continuum structures. At the same time, the cores do not appear to fragment further. Polarized dust emission is clearly detected. The inferred magnetic field orientations are prevailingly parallel to dust lanes. This key structural feature is analyzed together with the local gravitational vector field. The direction of local gravity is found to typically align with dust lanes. With these findings, we derive a stability criterion that defines a maximum magnetic field strength that can be overcome by an observed magnetic field–gravity configuration. Equivalently, this defines a minimum field strength that can stabilize dust lanes against a radial collapse. We find that the detected dust lanes in W51 e2 and e8 are stable, hence possibly making them a fundamental component in the accretion onto central sources, providing support for massive star formation models without the need of large accretion disks. When comparing to coarser resolutions, covering the scales of envelope, global, and local collapse, we find recurring similarities in the magnetic field structures and their corresponding gravitational vector fields. These self-similar structures point at a multiscale collapse-within-collapse scenario until finally the scale of core-accreting dust lanes is reached where gravity is entraining the magnetic field and aligning it with the dust lanes.

APPROXIMATION OF GRAVITATIONAL CALCULATION BASED ON ANALYTICAL MODELS

Gravity meters can be used to measure all effects that make up the Earth’s gravity field. Many of these effects are caused by known sources such as the Earth’s rotation, distance from the Earth’s center, topographic relief, and tidal variation. Physical fields are the main component of many centuries of the paradigm of all of Earth Sciences. The changing gravitational field is very important subject of research in the scientific aspect and practical. This paper applies two analytical models to simplify the gravitation calculation, which are sphere and cone models. Examples and finite element applications for the two models are studied also and discussed. The results of this study reveal that the possibility of using the proposed method with using presented analytical, finite element and numerical models to estimate the better determination of the characteristics of the local gravity of natural and man-made objects of sizes up to several tens of kilometers.

Autonomous navigation for lunar final approach based on gravity gradient measurements

Lunar final approach navigation is critical for pin-point lunar landing in future missions. This study investigates the use of lunar gravity gradient measurements for autonomous navigation of a lunar probe during the final approach phase. As the spacecraft approaches the Moon, the strength of gravity gradient signals improves. A spaceborne gravity gradiometer can precisely measure local gravity gradients, and the latest lunar gravity model GL1500E is used to provide reference values. The employed truncation degree and order of the gravity model are increased stepwise considering the decreasing altitude of the spacecraft in order to reach a compromise between computational costs and model accuracy. An iterative Kalman filter is developed for coupled orbit and attitude estimation using gravity gradient measurements and attitude quaternions obtained from star sensors. A simulated spacecraft with a gradiometer noise level of 0.01 E is considered. Simulation results show that the spacecraft’s position converges rapidly and achieves an accuracy of less than 100 m at the last epoch.

Effect of flow direction on heat transfer characteristics of supercritical CO2 in a heating serpentine micro-tube

The combined effect of gravitational buoyancy, centrifugal force and centrifugal buoyancy on the heat transfer of supercritical CO2 in a serpentine micro-tube under different flow directions is numerically studied. The comprehensive heat transfer performance in the four flow directions is vertical upward flow (VU), horizontal flow vertical bend (HV), horizontal flow horizontal bend (HH) and vertical downward flow (VD) in ascending order. Considering the angle between gravity and centrifugal force and the angle between gravity and local flow direction, Richardson number can better reflect the effect degree of buoyancy under different flow directions. In VU, VD and HV, the gravitational buoyancy at low mass flux can weaken the local heat transfer deterioration at the turning point, but the gravitational buoyancy at high mass flux can only weaken the local heat transfer deterioration at the turning point when the heat transfer of tube section is enhanced. In HH, the local flow direction, gravity and centrifugal force are perpendicular to each other, and the location of local heat transfer deterioration at the turning point is affected by the ratio of centrifugal force to gravity.

Geodynamic hazards and risk assessment at the Karachaganak oil, gas, and condensate field

The geodynamic hazards and risk assessment at the Karachaganak oil, gas, and condensate field (KOGCF) were explored on the northern board of the Pre-Caspian Basin to predict the consequences of the long-term exploitation of this field. We integrate multiple measurements, including repeated accurate leveling, Global Positioning System (GPS) measurements, and high precision gravimetric and seismological monitoring at the KOGCF. The results of geodynamic monitoring at the KOGCF for the first time made it possible to prove noticeable seismic deformation processes in the sedimentary cover under the influence of hydrocarbon production. The vertical displacements and horizontal movement along faults, changes in local gravity anomalies, and earthquake sources at depths comparable to hydrocarbon production intervals at the KOGCF have been identified. The maximum amplitudes of modern vertical movement of the earth's surface and the minimum values of the differently oriented horizontal movement were revealed within the projection on the ground surface of the crest of the carbonate massif (Upper Devonian-Lower Permian age). The results suggest the expansion of uneven compression in the crest of the KOGCF while tension processes occur on its periphery. There is a decrease in gravity variations in relation to the slopes of this massif in areas with active hydrocarbon production. An extended zone of high-gradient steps of ΔGa anomalies, spatially coinciding with the position of fault zones, is mapped along the periphery of the contour of production wells. In the northeastern part of the KOGCF, seismic events were registered practically in the depth intervals of the productive horizons from which hydrocarbons are produced. A spatial relationship between the seismic events and the anomalous deformation activity in the northeast KOGCF has been revealed. Consequently, the field development has provoked both intense deformation of the earth's surface and weak local seismicity.