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Journal articles on the topic 'Gravity gradiometers'

Author: Grafiati

Published: 4 June 2021

Last updated: 17 February 2022

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1

Qiang, Li-E., and Peng Xu. "Probing the post-newtonian physics of semi-conservative metric theories through secular tidal effects in satellite gradiometry missions." International Journal of Modern Physics D 25, no. 06 (May 2016): 1650070. http://dx.doi.org/10.1142/s021827181650070x.

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The existence of relativistic secular tidal effects along orbit motions will largely improve the measurement accuracies of relativistic gravitational gradients with orbiting gradiometers. With the continuous advances in technologies related to gradiometry and the improvements in their resolutions, it is feasible for future satellite gradiometry missions to carry out precision relativistic experiments and impose constraints on modern theories of gravity. In this work, we study the theoretical principles of measuring directly the secular post-Newtonian (PN) tidal effects in semi-conservative metric theories with satellite gradiometry missions. The isolations of the related PN parameters in the readouts of an orbiting three-axis gradiometer is discussed.

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2

Silvestrov, I. S., V. F. Fateev, and R. A. Davlatov. "Methods of metrological support of space gravity gradiometers." Izmeritel`naya Tekhnika, no. 1 (January 2020): 5–10. http://dx.doi.org/10.32446/0368-1025it.2020-1-5-10.

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An analysis is made of the known methods for calibrating and evaluating the parameters of implemented space gradiometers. There are 4 main stages: laboratory assessment of amendments, assessment of amendments during operation, assessment of amendments from independent data, calibration. A description of each step is provided. Two methods for calibrating space gradiometers are proposed: based on a complex of calibration sites and an onboard stand. The principles of building elements of a complex of calibration sites are investigated and their structure is formed. The analysis of the possibility of using the onboard mass on board the spacecraft for calibrating the space gradiometer is carried out. The main parameters of the onboard stand are highlighted. Scope: determination of metrological characteristics of space gravitational gradiometers.

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3

Zhao, Lin, Feng Ming Liu, Hai Jing Yuan, and Hong Bin Zhao. "The Design for Twelve-Accelerometer Gravity Gradiometer." Key Engineering Materials 419-420 (October 2009): 221–24. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.221.

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The design and manufacture for GGI are different and only several countries have the ability to produce it. Devising the feasible scheme for gravity gradiometer is the primary question.In this paper, a new type of GGI is designed using twelve accelerometers. First, the mathematical relationship between the accelerometer and GGI is derived and the method to separate the angular velocity and gravity gradient is disscussed. Second, the model of twelve-accelerometer gravity gradiometer is provided. Third, the estimation of angular velocity is analyzed when the GGI is installed in the form of strapdown or stabilized state. Finally, it is concluded that a new type of inertial navigation system using gravity gradiometers will be configured when it becomes possible to precisely measure gravity gradient.

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4

Evstifeev, M. I. "Dynamics of Onboard Gravity Gradiometers." Giroskopiya i Navigatsiya 27, no. 4 (2019): 69–87. http://dx.doi.org/10.17285/0869-7035.0015.

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5

Evstifeev, M. I. "Dynamics of Onboard Gravity Gradiometers." Gyroscopy and Navigation 11, no. 1 (January 2020): 13–24. http://dx.doi.org/10.1134/s207510872001006x.

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6

Dransfield, Mark H., and Asbjorn N. Christensen. "Performance of airborne gravity gradiometers." Leading Edge 32, no. 8 (August 2013): 908–22. http://dx.doi.org/10.1190/tle32080908.1.

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7

Karshakov, E. V., B. V. Pavlov, M. Yu Tkhorenko, and I. A. Papusha. "Promising Map-Aided Aircraft Navigation Systems." Giroskopiya i Navigatsiya 29, no. 1 (2021): 32–51. http://dx.doi.org/10.17285/0869-7035.0055.

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The paper analyses the development prospects for aircraft navigation systems using onboard geophysical field measurements. Prospective systems that are not widely applied yet are considered: magnetic gradiometers measuring the stationary magnetic field gradient, gravity gradiometers measuring the gravity field gradient, and electromagnetic systems measuring the alternating part of magnetic field. We discuss the main problems to be solved during airborne measurements of these parameters and give an overview of algorithms and hardware solutions. We analyse the results of onboard measurements and estimate the possible navigation accuracy.

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8

Bao, Qianzong, and Li-E. Qiang. "Null tests of nonlocal gravity with multi-axis gravity gradiometers in elliptic orbits: A theoretical study." Modern Physics Letters A 32, no. 25 (July 31, 2017): 1750131. http://dx.doi.org/10.1142/s0217732317501310.

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A theoretical study of testing nonlocal gravity in its Newtonian regime with gravity gradient measurements in space is given. For certain solutions of the modification to Newton’s law in nonlocal gravity, a null test and a lower bound on related parameters may be given with future high precision multi-axis gravity gradiometers along elliptic orbits.

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9

Deng, Zhongguang, Chenyuan Hu, Xiangqing Huang, Wenjie Wu, Fangjing Hu, Huafeng Liu, and Liangcheng Tu. "Scale Factor Calibration for a Rotating Accelerometer Gravity Gradiometer." Sensors 18, no. 12 (December 11, 2018): 4386. http://dx.doi.org/10.3390/s18124386.

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Rotating Accelerometer Gravity Gradiometers (RAGGs) play a significant role in applications such as resource exploration and gravity aided navigation. Scale factor calibration is an essential procedure for RAGG instruments before being used. In this paper, we propose a calibration system for a gravity gradiometer to obtain the scale factor effectively, even when there are mass disturbance surroundings. In this system, four metal spring-based accelerometers with a good consistency are orthogonally assembled onto a rotary table to measure the spatial variation of the gravity gradient. By changing the approaching pattern of the reference gravity gradient excitation object, the calibration results are generated. Experimental results show that the proposed method can efficiently and repetitively detect a gravity gradient excitation mass weighing 260 kg within a range of 1.6 m and the scale factor of RAGG can be obtained as (5.4 ± 0.2) E/μV, which is consistent with the theoretical simulation. Error analyses reveal that the performance of the proposed calibration scheme is mainly limited by positioning error of the excitation and can be improved by applying higher accuracy position rails. Furthermore, the RAGG is expected to perform more efficiently and reliably in field tests in the future.

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10

Evstifeev, M. I. "Onboard gravity gradiometers: current state of development." Giroskopiya i Navigatsiya 24, no. 3 (2016): 96–114. http://dx.doi.org/10.17285/0869-7035.2016.24.3.096-114.

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11

Paik, Ho Jung, and John M. Lumley. "Superconducting gravity gradiometers on STEP and GEM." Classical and Quantum Gravity 13, no. 11A (November 1, 1996): A119—A127. http://dx.doi.org/10.1088/0264-9381/13/11a/016.

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12

Bender, P. L., R. S. Nerem, and J. M. Wahr. "Possible Future Use of Laser Gravity Gradiometers." Space Science Reviews 108, no. 1/2 (2003): 385–92. http://dx.doi.org/10.1023/a:1026100130397.

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13

Nabighian, M. N., M. E. Ander, V. J. S. Grauch, R. O. Hansen, T. R. LaFehr, Y. Li, W. C. Pearson, J. W. Peirce, J. D. Phillips, and M. E. Ruder. "Historical development of the gravity method in exploration." GEOPHYSICS 70, no. 6 (November 2005): 63ND—89ND. http://dx.doi.org/10.1190/1.2133785.

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The gravity method was the first geophysical technique to be used in oil and gas exploration. Despite being eclipsed by seismology, it has continued to be an important and sometimes crucial constraint in a number of exploration areas. In oil exploration the gravity method is particularly applicable in salt provinces, overthrust and foothills belts, underexplored basins, and targets of interest that underlie high-velocity zones. The gravity method is used frequently in mining applications to map subsurface geology and to directly calculate ore reserves for some massive sulfide orebodies. There is also a modest increase in the use of gravity techniques in specialized investigations for shallow targets. Gravimeters have undergone continuous improvement during the past 25 years, particularly in their ability to function in a dynamic environment. This and the advent of global positioning systems (GPS) have led to a marked improvement in the quality of marine gravity and have transformed airborne gravity from a regional technique to a prospect-level exploration tool that is particularly applicable in remote areas or transition zones that are otherwise inaccessible. Recently, moving-platform gravity gradiometers have become available and promise to play an important role in future exploration. Data reduction, filtering, and visualization, together with low-cost, powerful personal computers and color graphics, have transformed the interpretation of gravity data. The state of the art is illustrated with three case histories: 3D modeling of gravity data to map aquifers in the Albuquerque Basin, the use of marine gravity gradiometry combined with 3D seismic data to map salt keels in the Gulf of Mexico, and the use of airborne gravity gradiometry in exploration for kimberlites in Canada.

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14

Sil’vestrov, I. S., V. F. Fateev, and R. A. Davlatov. "Methods for the Calibration of Space-Gravity Gradiometers." Measurement Techniques 63, no. 1 (April 2020): 1–6. http://dx.doi.org/10.1007/s11018-020-01741-z.

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15

Shimoda, Tomofumi, Kévin Juhel, Jean-Paul Ampuero, Jean-Paul Montagner, and Matteo Barsuglia. "Early earthquake detection capabilities of different types of future-generation gravity gradiometers." Geophysical Journal International 224, no. 1 (October 10, 2020): 533–42. http://dx.doi.org/10.1093/gji/ggaa486.

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SUMMARY Since gravity changes propagate at the speed of light, gravity perturbations induced by earthquake deformation have the potential to enable faster alerts than the current earthquake early warning systems based on seismic waves. Additionally, for large earthquakes (Mw > 8), gravity signals may allow for a more reliable magnitude estimation than seismic-based methods. Prompt elastogravity signals induced by earthquakes of magnitude larger than 7.9 have been previously detected with seismic arrays and superconducting gravimeters. For smaller earthquakes, down to Mw ≃ 7, it has been proposed that detection should be based on measurements of the gradient of the gravitational field, in order to mitigate seismic vibration noise and to avoid the cancelling effect of the ground motions induced by gravity signals. Here we simulate the five independent components of the gravity gradient signals induced by earthquakes of different focal mechanisms. We study their spatial amplitude distribution to determine what kind of detectors is preferred (which components of the gravity gradient are more informative), how detectors should be arranged and how earthquake source parameters can be estimated. The results show that early earthquake detections, within 10 s of the rupture onset, using only the horizontal gravity strain components are achievable up to about 140 km distance from the epicentre. Depending on the earthquake focal mechanism and on the detector location, additional measurement of the vertical gravity strain components can enhance the detectable range by 10–20 km. These results are essential for the design of gravity-based earthquake early warning systems.

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16

Dransfield, Mark. "Searchlights for gravity and magnetics." GEOPHYSICS 80, no. 1 (January 1, 2015): G27—G34. http://dx.doi.org/10.1190/geo2014-0256.1.

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The development of mental schemata is important in developing an understanding of physical phenomena and processes. Gravitational and magnetic fields are often visualized by geophysicists as equipotential surfaces (for gravity) and field lines (for magnetics). In these cases, the schemata treat the geology as the source of the field. In seismic and electromagnetic prospecting, one instead visualizes a field that is emitted by the instrument. Example schemata are traveling wavefronts (seismic) and smoke rings (electromagnetic induction in the dissipative limit). I carried this instrument-focused conceptualization over to potential field prospecting by a schema, which envisages the instrument as a probe, illuminating the earth in a manner analogous to a searchlight. Different potential-field instruments (potentiometers, gravimeters, magnetometers, and gradiometers) each have different beam characteristics and consequently illuminate the earth in different ways. This schema provides a new way of visualizing potential fields in prospecting with applications in instrument development, data acquisition and processing, and interpretation.

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17

Evstifeev, M. I. "The state of the art in the development of onboard gravity gradiometers." Gyroscopy and Navigation 8, no. 1 (January 2017): 68–79. http://dx.doi.org/10.1134/s2075108717010047.

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18

Gilavdary, I. Z., and N. N. Riznookaya. "STAGES OF DEVELOPMENT AND STATE OF ENGINEERING OF GRAVITY GRADIOMETERS FOR MOVING OBJECTS. (Review)." Devices and Methods of Measurements 7, no. 3 (January 1, 2016): 235–46. http://dx.doi.org/10.21122/2220-9506-2016-7-3-235-246.

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19

Zhang, Lu, Yuntao Qiu, Xikai Liu, Liang Chen, Ning Zhang, and Xiangdong Liu. "A horizontal linear vibrator for measuring the cross-coupling coefficient of superconducting gravity gradiometers." Measurement 174 (April 2021): 109083. http://dx.doi.org/10.1016/j.measurement.2021.109083.

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20

Schrama, Ernst J. O. "Gravity field error analysis: Applications of global positioning system receivers and gradiometers on low orbiting platforms." Journal of Geophysical Research: Solid Earth 96, B12 (November 10, 1991): 20041–51. http://dx.doi.org/10.1029/91jb01972.

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21

Qian, Xuewu, and Yanhua Zhu. "Self-Gradient Compensation of Full-Tensor Airborne Gravity Gradiometer." Sensors 19, no. 8 (April 25, 2019): 1950. http://dx.doi.org/10.3390/s19081950.

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In the process of airborne gravity gradiometry for the full-tensor airborne gravity gradiometer (FTAGG), the attitude of the carrier and the fuel mass will seriously affect the accuracy of gravity gradiometry. A self-gradient is the gravity gradient produced by the surrounding masses, and the surrounding masses include distribution mass for the carrier mass and fuel mass. In this paper, in order to improve the accuracy of airborne gravity gradiometry, a self-gradient compensation model is proposed for FTAGG. The self-gradient compensation model is a fuction of attitude for carrier and time, and it includes parameters ralated to the distribution mass for the carrier. The influence of carrier attitude and fuel mass on the self-gradient are simulated and analyzed. Simulation shows that the self-gradient tensor element Γ x x , Γ x y , Γ x z , Γ y z and Γ z z are greatly affected by the middle part of the carrier, and the self-gradient tensor element Γ y z is affected by the carrier’s fuel mass in three attitudes. Further simulation experiments show that the presented self-gradient compensation method is valid, and the error of the self-gradient compensation is within 0.1 Eu. Furthermore, this method can provide an important reference for improving the accuracy of aviation gravity gradiometry.

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22

Pail, R., and G. Plank. "Comparison of numerical solution strategies for gravity field recovery from GOCE SGG observations implemented on a parallel platform." Advances in Geosciences 1 (June 17, 2003): 39–45. http://dx.doi.org/10.5194/adgeo-1-39-2003.

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Abstract. The recovery of a full set of gravity field parameters from satellite gravity gradiometry (SGG) is a huge numerical and computational task. In practice, parallel computing has to be applied to estimate the more than 90 000 harmonic coefficients parameterizing the Earth’s gravity field up to a maximum spherical harmonic degree of 300. Three independent solution strategies, i.e. two iterative methods (preconditioned conjugate gradient method, semi-analytic approach) and a strict solver (Distributed Non-approximative Adjustment), which are operational on a parallel platform (‘Graz Beowulf Cluster’), are assessed and compared both theoretically and on the basis of a realistic-as-possible numerical simulation, regarding the accuracy of the results, as well as the computational effort. Special concern is given to the correct treatment of the coloured noise characteristics of the gradiometer. The numerical simulations show that there are no significant discrepancies among the solutions of the three methods. The newly proposed Distributed Nonapproximative Adjustment approach, which is the only one of the three methods that solves the inverse problem in a strict sense, also turns out to be a feasible method for practical applications.Key words. Spherical harmonics – satellite gravity gradiometry – GOCE – parallel computing – Beowulf cluster

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23

Dransfield, Mark, and Yi Zeng. "Airborne gravity gradiometry: Terrain corrections and elevation error." GEOPHYSICS 74, no. 5 (September 2009): I37—I42. http://dx.doi.org/10.1190/1.3170688.

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Terrain corrections for airborne gravity gradiometry data are calculated from a digital elevation model (DEM) grid. The relative proximity of the terrain to the gravity gradiometer and the relative magnitude of the density contrast often result in a terrain correction that is larger than the geologic signal of interest in resource exploration. Residual errors in the terrain correction can lead to errors in data interpretation. Such errors may emerge from a DEM that is too coarsely sampled, errors in the density assumed in the calculations, elevation errors in the DEM, or navigation errors in the aircraft position. Simple mathematical terrains lead to the heuristic proposition that terrain-correction errors from elevation errors in the DEM are linear in the elevation error but follow an inverse power law in the ground clearance of the aircraft. Simulations of the effect of elevation error on terrain-correction error over four measured DEMs support this proposition. This power-law relation may be used in selecting an optimum survey flying height over a known terrain, given a desired terrain-correction error.

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24

Bell, Robin E. "Gravity Gradiometry." Scientific American 278, no. 6 (June 1998): 74–79. http://dx.doi.org/10.1038/scientificamerican0698-74.

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25

Brzezowski, Steven J., and Warren G. Heller. "Gravity gradiometer survey errors." GEOPHYSICS 53, no. 10 (October 1988): 1355–61. http://dx.doi.org/10.1190/1.1442414.

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Gradiometer system noise, sampling effects, downward continuation, and limited data extent are the important contributors to moving‐base gravity gradiometer survey error. We apply a two‐dimensional frequency‐domain approach in simulations of several sets of airborne survey conditions to assess the significance of the first two sources. A special error allocation technique is used to account for the downward continuation and limited extent effects. These two sources cannot be modeled adequately as measurement noise in a linear error estimation algorithm. For a typical characterization of the Earth’s gravity field, our modeling indicates that limited data extent generally contributes about one‐half of the total error variance associated with recovery of the gravity disturbance vector at the Earth’s surface; gradiometer system noise typically contributes about one‐third. However, sampling effects are also very important (and are controlled through the survey track spacing). A 5 km track spacing provides a reasonable tradeoff between survey cost and errors due to track spacing. Furthermore, our results indicate that a moving‐base gravity gradiometer system can recover each component of the gravity disturbance vector with an rms accuracy better than 1.0 mGal.

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26

Vasco, D. W. "Resolution and variance operators of gravity and gravity gradiometry." GEOPHYSICS 54, no. 7 (July 1989): 889–99. http://dx.doi.org/10.1190/1.1442717.

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Gravity gradiometry represents a new potential field data set which may better constrain the density structure of the earth. Using singular value (spectral) decomposition of the gravity and gravity gradient kernels, the model parameter resolution and model parameter variance of the two data types are compared using data from the Defense Mapping Agency and a recently acquired collection of airborne gradient measurements from Bell Aerospace Textron’s Gravity Gradient Survey System (GGSS). The GGSS was flown over a portion of southwestern Oklahoma, where the gravitational anomaly from the buried Wichita basement rocks is over 60 mGal. The corresponding maximum vertical gravity gradient was found to be 46.2 Eötvös. The determination of the subsurface density structure is cast as a linear inverse problem and, for comparison, a nonlinear inverse problem. For both the linear and nonlinear inversions, the gravity gradients improve the resolution and result in smaller variances than the vertical component of gravity. The density resolution and variance were computed for a subset of tracks from an airborne gravity gradient survey made in the summer of 1987. For the linear inversion, the resolution of the density is not adequate below the second layer (20 km). Furthermore, the estimated error of the actual gradient observations for a resolution of 0.9 km is 10E, for which the maximum error of the density values is [Formula: see text]. The linearized resolution of the boundary perturbations is better, with most parameters being well resolved. The standard errors for the layer perturbations are less than 1 km for the shallower layer (5.0 km) when using the gradiometer data. For the deeper layer (25.0 km), the maximum error is larger, 4.3 km.

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27

Jekeli, Christopher. "A review of gravity gradiometer survey system data analyses." GEOPHYSICS 58, no. 4 (April 1993): 508–14. http://dx.doi.org/10.1190/1.1443433.

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The Gravity Gradiometer Survey System (GGSS) was designed to measure the local and regional gravity field from a ground or airborne moving platform. With the first and only airborne field test, the GGSS was able to recover five‐arcminute by five‐arcminute mean gravity anomalies to an accuracy of a few mGal. These results were obtained by flying the system, with an operational precision of about 10 Eötvös (ten‐second average), on a grid of orthogonal tracks spaced 5 km apart at an altitude of about 700 m above the terrain. Despite perpetual navigation problems with the Global Positioning System and several periods of excessive system noise, the results of a performance analysis on 19 out of 128 tracks demonstrated the potential accuracy and efficiency of the GGSS as an airborne gravity mapping system. The ground tests (both road and railway), suffering from undue vehicle vibrations and from a lack of ground truth data, were correspondingly less successful, but they also showed no surprises in the system corrupted by these adverse conditions. Unfortunately, the GGSS program has terminated; and it is appropriate to reflect on its accomplishments. Without going into technical details, this somewhat historical review summarizes the field tests, the data reduction algorithms, and the test results, which together portray the breadth of expertise the program engendered in the area of gravity gradiometry.

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28

Reitz, Anya, Richard Krahenbuhl, and Yaoguo Li. "Feasibility of time-lapse gravity and gravity gradiometry monitoring for steam-assisted gravity drainage reservoirs." GEOPHYSICS 80, no. 2 (March 1, 2015): WA99—WA111. http://dx.doi.org/10.1190/geo2014-0217.1.

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There is presently an increased need to monitor production efficiency as heavy oil reservoirs become more economically viable. We present a feasibility study of monitoring steam-assisted gravity drainage (SAGD) reservoirs using time-lapse gravimetry and gravity gradiometry. Even though time-lapse seismic has historically shown great success for SAGD monitoring, the gravimetry and gravity gradiometry methods offer a low-cost interseismic alternative that can complement the seismic method, increase the survey frequency, and decrease the cost of monitoring. In addition, both gravity-based methods are directly sensitive to the density changes that occur as a result of the replacement of heavy oil by steam. Advances in technologies have made both methods viable candidates for consideration in time-lapse reservoir monitoring, and we have numerically evaluated their potential application in monitoring SAGD production. The results indicate that SAGD production should produce a strong anomaly for both methods at typical SAGD reservoir depths. However, the level of detail for steam-chamber geometries and separations that can be recovered from the gravimetry and gravity gradiometry data is site dependent. Gravity gradiometry shows improved monitoring ability, such as better recovery of nonuniform steam movement due to reservoir heterogeneity, at shallower production reservoirs. Gravimetry has the ability to detect SAGD steam-chamber growth to greater depths than does gravity gradiometry, although with decreasing resolution of the expanding steam chambers.

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29

Gao, Duanyang, Baiqing Hu, Lubin Chang, Fangjun Qin, and Xu Lyu. "An Aided Navigation Method Based on Strapdown Gravity Gradiometer." Sensors 21, no. 3 (January 27, 2021): 829. http://dx.doi.org/10.3390/s21030829.

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The gravity gradient is the second derivative of gravity potential. A gravity gradiometer can measure the small change of gravity at two points, which contains more abundant navigation and positioning information than gravity. In order to solve the problem of passive autonomous, long-voyage, and high-precision navigation and positioning of submarines, an aided navigation method based on strapdown gravity gradiometer is proposed. The unscented Kalman filter framework is used to realize the fusion of inertial navigation and gravity gradient information. The performance of aided navigation is analyzed and evaluated from six aspects: long voyage, measurement update period, measurement noise, database noise, initial error, and inertial navigation system device level. When the parameters are set according to the benchmark parameters and after about 10 h of simulation, the results show that the attitude error, velocity error, and position error of the gravity gradiometer aided navigation system are less than 1 arcmin, 0.1 m/s, and 33 m, respectively.

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30

Lee, James B. "Falcon Gravity Gradiometer Technology." Exploration Geophysics 32, no. 3-4 (September 2001): 247–50. http://dx.doi.org/10.1071/eg01247.

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31

Lee, James B. "FALCON gravity gradiometer technology." ASEG Extended Abstracts 2001, no. 1 (December 2001): 1–4. http://dx.doi.org/10.1071/aseg2001ab068.

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32

Barnes, Gary, and John Lumley. "Processing gravity gradient data." GEOPHYSICS 76, no. 2 (March 2011): I33—I47. http://dx.doi.org/10.1190/1.3548548.

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As the demand for high-resolution gravity gradient data increases and surveys are undertaken over larger areas, new challenges for data processing have emerged. In the case of full-tensor gradiometry, the processor is faced with multiple derivative measurements of the gravity field with useful signal content down to a few hundred meters’ wavelength. Ideally, all measurement data should be processed together in a joint scheme to exploit the fact that all components derive from a common source. We have investigated two methods used in commercial practice to process airborne full-tensor gravity gradient data; the methods result in enhanced, noise-reduced estimates of the tensor. The first is based around Fourier operators that perform integration and differentiation in the spatial frequency domain. By transforming the tensor measurements to a common component, the data can be combined in a way that reduces noise. The second method is based on the equivalent-source technique, where all measurements are inverted into a single density distribution. This technique incorporates a model that accommodates low-order drift in the measurements, thereby making the inversion less susceptible to correlated time-domain noise. A leveling stage is therefore not required in processing. In our work, using data generated from a geologic model along with noise and survey patterns taken from a real survey, we have analyzed the difference between the processed data and the known signal to show that, when considering the Gzz component, the modified equivalent-source processing method can reduce the noise level by a factor of 2.4. The technique has proven useful for processing data from airborne gradiometer surveys over mountainous terrain where the flight lines tend to be flown at vastly differing heights.

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33

Bell, Robin E., Roger Anderson, and Lincoln Pratson. "Gravity gradiometry resurfaces." Leading Edge 16, no. 1 (January 1997): 55–59. http://dx.doi.org/10.1190/1.1437431.

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34

Nekut, A. G. "Borehole gravity gradiometry." GEOPHYSICS 54, no. 2 (February 1989): 225–34. http://dx.doi.org/10.1190/1.1442646.

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Gravity gradients measured in a borehole are of interest due to their direct, simple relation to the density of the formations surrounding the hole. Borehole gravity meters (BHGMs) are used to measure gravity differences along the borehole and from these differences, we compute averaged values for a linear combination of the gravity gradient tensor elements. One way to implement a borehole gravity gradiometer (BHGGM) is to measure the torque exerted on a pair of masses separated by a beam. A BHGGM directly measures all the elements of the gravity gradient tensor. Knowledge of these elements provides information about the direction to density anomalies in the vicinity of the borehole and enhances the analysis of dipping beds. The BHGGM may be superior to the BHGM for resolving the density of thin beds. Density variations remote from the borehole are best detected and characterized by joint interpretation of BHGM and BHGGM data.

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35

Müller, J., and M. Wermut. "GOCE gradients in various reference frames and their accuracies." Advances in Geosciences 1 (June 17, 2003): 33–38. http://dx.doi.org/10.5194/adgeo-1-33-2003.

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Abstract. The objective of GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) is the determination of the Earth’s gravity field with high spatial resolution. The main science sensor (the gradiometer) measures differential accelerations, from which the gravitational gradients, i.e. the matrix of the second derivatives of the gravitational potential, are derived. Some of them (the diagonal components of the gravitational tensor) are observed with highest accuracy, 4 mE/√Hz in a frequency range from 5 mHz to 100 mHz, whereas the off-diagonals are obtained less accurately. The gradients will be observed in the instrument frame, which approximates the along-track oriented, local orbital frame. For the transformation of the gradients in other frames (e.g. in the strictly earth-pointing frame or a local geodetic frame), the transformation parameters (orientation angles) and all components of the gravity tensor have to be known with sufficient accuracy. We show how the elements of the gravitational tensor and their accuracies look like in the various frames as well as their spectral behaviour, if only the GOCE observations are used for the transformation. Only V'zz keeps approximately its original accuracy in all frames discussed, except in the earth-fixed frame ITRF (International Terrestrial Reference Frame). Therefore we recommend to analyse the gradients as ‘close’ as possible in the observation frame.Key words. Satellite gradiometry, GOCE mission, reference frames, transformation errors

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Zieliński, J. B., and M. S. Petrovskaya. "The possibility of the calibration/validation of the GOCE data with the balloon-borne gradiometer." Advances in Geosciences 1 (October 2, 2003): 149–53. http://dx.doi.org/10.5194/adgeo-1-149-2003.

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Abstract. A new calibration/validation experiment for GOCE mission is proposed. Simultaneously with the satellite mission another gradiometer will be flown on the board of the stratospheric balloon on the altitude 20–40 km. The measurements can be compared with satellite data. The advantage of this method is that the same functionals are compared – gravity gradients. The post-mission external calibration/ validation is possible more directly than through the comparison with the ground truth gravity anomalies or geoid undulation. The calibrating gradiometer is less sensitive, but thanks to the altitude difference, compatible in precision with the orbiting GOCE gradiometer. Analytical procedure of the downward continuation is presented which permits comparison of these observables, supported by numerical examples. The threshold for the precision of the calibrating gradiometer is indicated. Similar comparison can be done between GOCE and GRACE missions.

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Sorokin, N. A. "Earth's gravity field parameters determination by the space geodesy dynamical approach." Geodesy and Cartography 919, no. 1 (February 20, 2017): 7–12. http://dx.doi.org/10.22389/0016-7126-2017-919-1-7-12.

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The method of the geopotential parameters determination with the use of the gradiometry data is considered. The second derivative of the gravitational potential in the correction equation on the rectangular coordinates x, y, z is used as a measured variable. For the calculated value of the measured quantity required for the formation of a free member of the correction equation, the the Cunningham polynomials were used. We give algorithms for computing the second derivatives of the Cunningham polynomials on rectangular coordinates x, y, z, which allow to calculate the second derivatives of the geopotential at the rectangular coordinates x, y, z.Then we convert derivatives obtained from the Cartesian coordinate system in the coordinate system of the gradiometer, which allow to calculate the free term of the correction equation. Afterwards the correction equation coefficients are calculated by differentiating the formula for calculating the second derivative of the gravitational potential on the rectangular coordinates x, y, z. The result is a coefficient matrix of the correction equations and corrections vector of the free members of equations for each component of the tensor of the geopotential. As the number of conditional equations is much more than the number of the specified parameters, we go to the drawing up of the system of normal equations, from which solutions we determine the required corrections to the harmonic coefficients.

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Bobojć, A., and A. Drożyner. "Satellite orbit determination using satellite gravity gradiometry observations in GOCE mission perspective." Advances in Geosciences 1 (June 30, 2003): 109–12. http://dx.doi.org/10.5194/adgeo-1-109-2003.

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Abstract. Between the years 2004 and 2005 the launch of the first gradiometric satellite is planned. This satellite will be an important element of the Gravity Field and Steady – State Ocean Circulation Explorer Mission (GOCE). This mission is one of the reasons for performing the simulation research of the Satellite Gravity Gradiometry. Our work contains the theory description and simulation results of the satellite orbit determination using the gravity tensor observations. In the process of the satellite orbit determination the initial dynamic state vector corrections are obtained. These corrections are estimated by means of the gravity gradiometry measurements. The performed simulations confirm the possibility of satellite orbit determination by means of the gravity tensor observations.Key words. satellite geodesy, satellite gradiometry, satellite orbits

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Zhdanov, Michael S., and Wei Lin. "Adaptive multinary inversion of gravity and gravity gradiometry data." GEOPHYSICS 82, no. 6 (November 1, 2017): G101—G114. http://dx.doi.org/10.1190/geo2016-0451.1.

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We have developed a novel approach for inversion of gravity and gravity gradiometry data based on multinary transformation of the model parameters. This concept is a generalization of binary density inversion to the models described by any number of discrete model parameters. The multinary inversion makes it possible to explicitly exploit the sharp contrasts of the density between the host media and anomalous targets in the inversion of gravity and gravity gradiometry data. In the framework of the multinary inversion method, we use the given values of density and error functions to transform the density distribution into the desired step-function distribution. To accommodate a possible deviation of the densities from the fixed discrete values, we develop an adaptive technique for selecting the corresponding standard deviations, guided by the inversion process. The novel adaptive multinary inversion algorithm is demonstrated to be effective in determining the shape, location, and densities of the anomalous targets. We find that this method can be effectively applied for the inversion of the full tensor gravity gradiometry (FTG) data computer simulated for the SEG salt density model and for the field FTG data collected in the Nordkapp Basin, Barents Sea.

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van Kann, F., C. Edwards, M. Buckingham, and R. Penny. "A prototype superconducting gravity gradiometer." IEEE Transactions on Magnetics 21, no. 2 (March 1985): 610–13. http://dx.doi.org/10.1109/tmag.1985.1063855.

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Arabelos, D., and I. N. Tziavos. "Gravity field approximation using airborne gravity gradiometer data." Journal of Geophysical Research 97, B5 (1992): 7097. http://dx.doi.org/10.1029/92jb00106.

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Paik, Ho Jung, Jurn-Sun Leung, Samuel H. Morgan, and Joseph Parker. "Global gravity survey by an orbiting gravity gradiometer." Eos, Transactions American Geophysical Union 69, no. 48 (1988): 1601. http://dx.doi.org/10.1029/88eo01211.

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de Oliveira Lyrio, Julio Cesar Soares, Luis Tenorio, and Yaoguo Li. "Efficient automatic denoising of gravity gradiometry data." GEOPHYSICS 69, no. 3 (May 2004): 772–82. http://dx.doi.org/10.1190/1.1759463.

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Gravity gradiometry data are prized for the high frequency information they provide. However, as any other geophysical data, gravity gradient measurements are contaminated by high‐frequency noise. Separation of the high‐frequency signal from noise is a crucial component of data processing. The separation can be performed in the frequency domain, which usually requires tuning filter parameters at each survey line to obtain optimal results. Because a modern gradiometry survey generates more data than a traditional gravity survey, such time‐consuming manual operations are not very practical. In addition, they may also introduce subjectivity into the process. To address this difficulty, we propose an automatic, data‐adaptive 1D wavelet filtering technique specially designed to process gravity gradiometry data. The method is based on the thresholding of the wavelet coefficients to filter out high‐frequency noise while preserving localized sharp signal features. We use an energy analysis across scales (specific for gravity gradiometry data) to select denoising thresholds and to identify sharp features of interest. We compare the proposed method with traditional Fourier‐domain filters by applying them to synthetic data sets contaminated with either correlated or uncorrelated noise. The results demonstrate that the proposed filter is efficient and, when applied in the fully automated mode, produces results that are comparable to the best results achievable through frequency‐domain filters. We further illustrate the method by applying it to a set of gravity gradiometry data acquired in the Gulf of Mexico and by characterizing the removed noise. Both synthetic and field examples show that the proposed method is an efficient and better alternative to other traditional frequency domain methods.

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Moody, M. Vol, Ho Jung Paik, and Edgar R. Canavan. "Three-axis superconducting gravity gradiometer for sensitive gravity experiments." Review of Scientific Instruments 73, no. 11 (November 2002): 3957–74. http://dx.doi.org/10.1063/1.1511798.

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Chan, H. A., and H. J. Paik. "Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory." Physical Review D 35, no. 12 (June 15, 1987): 3551–71. http://dx.doi.org/10.1103/physrevd.35.3551.

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Chan, H. A., M. V. Moody, and H. J. Paik. "Superconducting gravity gradiometer for sensitive gravity measurements. II. Experiment." Physical Review D 35, no. 12 (June 15, 1987): 3572–97. http://dx.doi.org/10.1103/physrevd.35.3572.

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Qian, Xuewu, Liye Zhao, Weiming Liu, and Jianqiang Sun. "Frequency Domain Analysis of Partial-Tensor Rotating Accelerometer Gravity Gradiometer." Sensors 21, no. 5 (March 9, 2021): 1925. http://dx.doi.org/10.3390/s21051925.

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The output model of a rotating accelerometer gravity gradiometer (RAGG) established by the inertial dynamics method cannot reflect the change of signal frequency, and calibration sensitivity and self-gradient compensation effect for the RAGG is a very important stage in the development process that cannot be omitted. In this study, a model based on the outputs of accelerometers on the disc of RGAA is established to calculate the gravity gradient corresponding to the distance, through the study of the RAGG output influenced by a surrounding mass in the frequency domain. Taking particle, sphere, and cuboid as examples, the input-output models of gravity gradiometer are established based on the center gradient and four accelerometers, respectively. Simulation results show that, if the scale factors of the four accelerometers on the disk are the same, the output signal of the RAGG only contains (4k+2)ω (ω is the spin frequency of disc for RAGG) harmonic components, and its amplitude is related to the orientation of the surrounding mass. Based on the results of numerical simulation of the three models, if the surrounding mass is close to the RAGG, the input-output models of gravity gradiometer are more accurate based on the four accelerometers. Finally, some advantages and disadvantages of cuboid and sphere are compared and some suggestions related to calibration and self-gradient compensation are given.

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Cevallos, Carlos, Peter Kovac, and Sharon J. Lowe. "Application of curvatures to airborne gravity gradient data in oil exploration." GEOPHYSICS 78, no. 4 (July 1, 2013): G81—G88. http://dx.doi.org/10.1190/geo2012-0315.1.

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We apply equipotential surface curvatures to airborne gravity gradient data. The mean and differential curvature of the equipotential surface, the curvature of the gravity field line, the zero contour of the Gaussian curvature, and the shape index improve the understanding and geologic interpretation of gravity gradient data. Their use is illustrated in model data and applied to FALCON airborne gravity gradiometer data from the Canning Basin, Australia.

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Charkin, Victor A., and Alexander E. Pischits. "Gravity gradiometer with coupled superconducting suspensions." Cryogenics 32 (January 1992): 521–24. http://dx.doi.org/10.1016/0011-2275(92)90220-5.

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DiFrancesco, Daniel, Andy Grierson, Dan Kaputa, and Thomas Meyer. "Gravity gradiometer systems - advances and challenges." Geophysical Prospecting 57, no. 4 (July 2009): 615–23. http://dx.doi.org/10.1111/j.1365-2478.2008.00764.x.

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