共查询到20条相似文献，搜索用时 973 毫秒
1.
Mark Dransfield 《Geophysical Prospecting》2010,58(3):469-483
Gravity derived only from airborne gravity gradient measurements with a normal error distribution will have an error that increases with wavelength. It is straightforward in principle to use sparsely sampled regional gravimeter data to provide the long wavelength information, thereby conforming the derived gravity to the regional gravity. Regional surface or airborne gravimeter data are not always available and can be difficult and expensive to collect in many of the areas where an airborne gravity gradiometer survey is flown. However the recent release by the Danish National Space Centre of the DNSC08 global gravity anomaly data has provided regional gravity data for the entire earth of adequate quality for this purpose. Studies over three areas, including comparisons with ground, marine and airborne gravimetry, demonstrate the validity of this approach. Future improvements in global gravity anomaly data are expected, particularly as the product from the recently launched Gravity field and steady‐state Ocean Circulation Explorer (GOCE) satellite becomes available and these will lead directly to an improvement in the very wide bandwidth gravity available after conforming gravity derived from gravity gradiometry with the global gravity. 相似文献
2.
Gary Barnes 《Geophysical Prospecting》2014,62(3):646-657
When anomalous gravity gradient signals provide a large signal‐to‐noise ratio, airborne and marine surveys can be considered with wide line spacing. In these cases, spatial resolution and sampling requirements become the limiting factors for specifying the line spacing, rather than anomaly detectability. This situation is analysed by generating known signals from a geological model and then sub‐sampling them using a simulated airborne gravity gradient survey with a line spacing much wider than the characteristic anomaly size. The data are processed using an equivalent source inversion, which is used subsequently to predict and grid the field in‐between the survey lines by means of forward calculations. Spatial and spectral error analysis is used to quantify the accuracy and resolution of the processed data and the advantages of acquiring multiple gravity gradient components are demonstrated. With measurements of the full tensor along survey lines spaced at 4 × 4 km, it is shown that the vertical gravity gradient can be reconstructed accurately over a bandwidth of 2 km with spatial root‐mean square errors less than 30%. A real airborne full‐tensor gravity gradient survey is presented to confirm the synthetic analysis in a practical situation. 相似文献
3.
V. N. Koneshov V. B. Nepoklonov V. V. Pogorelov V. N. Solov’ev L. V. Afanas’eva 《Izvestiya Physics of the Solid Earth》2016,52(3):443-451
The application of the airborne gravimetry method for gravity measurements in the Arctic is considered. This method has been extensively employed in foreign studies for determining the figure of the Earth in high-latitude conditions. The possibility of conducting comparative studies along the extensive survey lines and the necessity of aerogravimetry studies for improving the global Earth’s gravity field (EGF) models are discussed. The possibility of the efficient application of the modern EGF models for estimating the systematical errors for different types of gravimetry surveys and exploring the influence of the anomalous far-zone field in the calculations of the plumb line deviations is demonstrated. 相似文献
4.
For airborne gravity gradiometry in rugged terrain, helicopters offer a significant advantage over fixed-wing aircraft: their ability to maintain much lower ground clearances. Crucially, this provides both better signal-to-noise and better spatial resolution than is possible with a fixed-wing survey in the same terrain. Comparing surveys over gentle terrain at Margaret Lake, Canada, and over rugged terrain at Mount Aso, Japan, demonstrates that there is some loss of spatial resolution in the more rugged terrain. The slightly higher altitudes forced by rugged terrain make the requirements for terrain correction easier than for gentle terrain. Transforming the curvature gradients measured by the Falcon gravity gradiometer into gravity and the complete set of tensor components is done by a Fourier method over gentle terrain and an equivalent source method for rugged terrain. The Fourier method is perfectly stable and uses iterative padding to improve the accuracy of the longer wavelengths. The equivalent source method relies on a smooth model inversion, and the source distribution must be designed to suit the survey design. 相似文献
5.
Marine gravimeters mounted on stabilized platforms are commonly used in aircraft to perform airborne gravity measurements. The role of the stabilized platform is to level the sensor mechanically, whatever the aircraft attitude. However, this compensation is generally insufficient due to the sensitivity of modern gravity sensors. Correcting the offlevel error requires that an offlevel correction calculated from positioning data be added to gravimeter measurements, which complicates not only the processing, but also the assessment of precision and resolution. This paper is a feasibility study describing the levelling of a completely strapped‐down LaCoste and Romberg gravimeter for airborne gravimetry operation, by means of GPS positioning data. It focuses on the calculation of the sensor offlevel correction needed for the complete gravity data processing. The precision of the offlevel correction that can be achieved, in terms of GPS data precision and gravity wavelengths, is theoretically studied and estimated using the gravity and GPS data acquired during the Alpine Swiss French airborne gravity survey carried out in 1998 over the French Western Alps. While a 1 cm precision of GPS‐determined baseline coordinates is sufficient to achieve a 5 mGal precision of the offlevel correction, we maintain that this precision has to reach 1 mm to ensure a 1 mGal precision of the offlevel correction at any wavelength. Without a stabilized platform, the onboard instrumentation becomes significantly lighter. Furthermore, the correction for the offlevel error is straightforward and calculated only from GPS data. Thus, the precision and the resolution of airborne gravity surveys should be estimated with a better accuracy. 相似文献
6.
我国在海域开展了大规模的航空重力勘探,这些资料对构建高精度大地水准面具有重要价值.基于此,本文提出一种利用海域航空重力测量数据快速构建大地水准面的方法.该方法基于移去-恢复法思想,利用位场最小曲率方法对航空重力数据进行高精度向下延拓并获取相应的扰动位,实现航空重力测量快速构建海域大地水准面.与斯托克斯积分计算相比,采用了处理效率更高的频率域位场转换,解决了向下延拓及垂向积分时航空重力异常数据空白及扩边问题,具有较高的位场转换精度.本文应用EGM2008模拟航空重力数据进行模型验证,计算结果与其给出的水准面的精度相当;同时,也选取GRAV-D计划的航空重力数据进行实际验证,计算结果与xGEOID18B水准面模型精度基本一致.模型验证和实际应用验证了本方法的实用性. 相似文献
7.
8.
The National Survey and Cadastre - Denmark (KMS) has for several years produced gravity anomaly maps over the oceans derived from satellite altimetry. During the last four years, KMS has also conducted airborne gravity surveys along the coast of Greenland dedicated to complement the existing onshore gravity coverage and fill in new data in the very-near coastal area, where altimetry data may contain gross errors. The airborne surveys extend from the coastline to approximately 100 km offshore, along 6000 km of coastline. An adequate merging of these different data sources is important for the use of gravity data especially, when computing geoid models in coastal regions.The presence of reliable marine gravity data for independent control offers an opportunity to study procedures for the merging of airborne and satellite data around Greenland. Two different merging techniques, both based on collocation, are investigated in this paper. Collocation offers a way of combining the individual airborne gravity observation with either the residual geoid observations derived from satellite altimetry or with gravity derived from these data using the inverse Stokes method implemented by Fast Fourier Transform (FFT). 相似文献
9.
V. N. Koneshov N. V. Drobyshev I. V. Koneshov 《Izvestiya Physics of the Solid Earth》2010,46(7):624-626
When processing the results of an airborne gravity survey flown in the Arctic at flight heights of 2000 to 3000 m, the authors
encountered conditions, when the values of the free-air anomaly of gravity exceeded the values taken from the anomaly map,
with a trend towards “heavier” values. The formula for calculation of the vertical gradient as a function of the latitude
of the locality has been refined. The tentative calculations reported in the paper also indicate that a free-air gravity anomaly
above the mountainous areas will contain additional positive systematic components, since only the effect of the vertical
gradient of the normal gravity field is taken into account here, and the flight’s height during an airborne gravity survey,
above a mountainous area, should be held constant, otherwise it would be necessary to take into account additional systematic
biases, obtained in different flights, which are caused by the different values of the vertical gradient at different heights. 相似文献
10.
Pierre Keating 《Geophysical Prospecting》1995,43(4):569-580
Gravity data are often acquired over long periods of time using different instruments and various survey techniques, resulting in data sets of non-uniform accuracy. As station locations are inhomogeneously distributed, gravity values are interpolated on to a regular grid to allow further processing, such as computing horizontal or vertical gradients. Some interpolation techniques can estimate the interpolation error. Although estimation of the error due to interpolation is of importance, it is more useful to estimate the maximum gravity anomaly that may have gone undetected by a survey. This is equivalent to the determination of the maximum mass whose gravity anomaly will be undetected at any station location, given the data accuracy at each station. Assuming that the maximum density contrast present in the survey area is known or can be reasonably assumed from a knowledge of the geology, the proposed procedure is as follows: at every grid node, the maximum mass whose gravity anomaly does not disturb any of the surrounding observed gravity values by more than their accuracies is determined. A finite vertical cylinder is used as the mass model in the computations. The resulting map gives the maximum detection error and, as such, it is a worst-case scenario. Moreover, the map can be used to optimize future gravity surveys: new stations should be located at, or near, map maxima. The technique is applied to a set of gravity observations obtained from different surveys made over a period of more than 40 years in the Abitibi Greenstone Belt in eastern Canada. 相似文献
11.
Hasan Yildiz Rene Forsberg Carl Christian Tscherning Daniel Steinhage Graeme Eagles Johannes Bouman 《Studia Geophysica et Geodaetica》2017,61(1):53-68
An airborne gravity campaign was carried out at the Dome-C survey area in East Antarctica between the 17th and 22nd of January 2013, in order to provide data for an experiment to validate GOCE satellite gravity gradients. After typical filtering for airborne gravity data, the cross-over error statistics for the few crossing points are 11.3 mGal root mean square (rms) error, corresponding to an rms line error of 8.0 mGal. This number is relatively large due to the rough flight conditions, short lines and field handling procedures used. Comparison of the airborne gravity data with GOCE RL4 spherical harmonic models confirmed the quality of the airborne data and that they contain more high-frequency signal than the global models. First, the airborne gravity data were upward continued to GOCE altitude to predict gravity gradients in the local North-East-Up reference frame. In this step, the least squares collocation using the ITGGRACE2010S field to degree and order 90 as reference field, which is subtracted from both the airborne gravity and GOCE gravity gradients, was applied. Then, the predicted gradients were rotated to the gradiometer reference frame using level 1 attitude quaternion data. The validation with the airborne gravity data was limited to the accurate gradient anomalies (TXX, TYY, TZZ and TXZ) where the long-wavelength information of the GOCE gradients has been replaced with GOCO03s signal to avoid contamination with GOCE gradient errors at these wavelengths. The comparison shows standard deviations between the predicted and GOCE gradient anomalies TXX, TYY, TZZ and TXZ of 9.9, 11.5, 11.6 and 10.4 mE, respectively. A more precise airborne gravity survey of the southern polar gap which is not observed by GOCE would thus provide gradient predictions at a better accuracy, complementing the GOCE coverage in this region. 相似文献
12.
V. N. Koneshov I. V. Koneshov V. V. Klevtsov A. V. Makushin Yu. L. Smoller S. Sh. Yurist Yu. V. Bolotin A. A. Golovan 《Izvestiya Physics of the Solid Earth》2013,49(1):77-79
This work describes the different sets of instruments and methodic approaches for testing the models of gravity anomalies by repeated airborne gravimetric surveys in the polar cap regions of the Earth. The survey design including the specifications for flying the survey profiles and the arrangement of the base stations in polar areas is described, and the necessary modifications of the airborne gravity metering complexes for high-latitude measurements are suggested. 相似文献
13.
A. V. Sokolov A. A. Krasnov V. N. Koneshov V. V. Glazko 《Izvestiya Physics of the Solid Earth》2016,52(2):254-258
The experience with conducting a marine gravity survey onboard a surface vessel under complicated ice conditions at high latitude is described. In 2014, a high-precision marine gravity survey with two modifications of the Chekan-AM gravimeter was carried out in the North Pole region. The measurements were conducted during two months from aboard the Akademik Fedorov research vessel on a given grid with a total length of 10000 km of the routes. As a result, 70000 gravity points at Arctic latitudes including the region of the geographical North Pole itself are acquired. In this paper, we discuss the methodical aspects of conducting the survey and present the accuracy estimates of the gravity measurements. The comparison of the obtained results with the Earth’s gravity models demonstrates the absence of systematic errors and the higher spatial resolution of the measurements with the Chekan-AM gravimeters. 相似文献
14.
航空重力测量受到各种各样的高频噪声干扰,因此,低通滤波是提取重力信号的重要环节,其关键在于设计性能优越的低通滤波器.目前航空重力测量中常用FIR（Finite Impulse Response）低通滤波方法存在明显的滤波边缘效应,导致不得不舍弃边缘部分数据.针对这一问题,本文引入一种可以有效抑制边缘效应的新方法——傅里叶基追踪低通滤波方法（Fourier Basis Pursuit Low Pass Filter,FBPLPF）.该方法通过基追踪准则,选择全局优化,采用凸优化中的内点算法,将低频信号挤压在低频上,实现低频信号与高频信号的有效分离,能够有效减少有限时间序列造成的谱污染和谱泄漏.最后利用仿真实验和实测数据对该方法进行了验证,均方根误差（RMS）东西测线为0.7×10-5 m·s-2,南北测线为1.4×10-5 m·s-2,与FIR低通滤波方法舍弃边缘数据后统计的均方根误差相当.表明该方法可以不舍弃或者舍弃少量边缘数据,提高航空重力数据的利用率. 相似文献
15.
N. V. Drobyshev V. N. Koneshov V. V. Pogorelov Yu. E. Rozhkov V. N. Solov’ev 《Izvestiya Physics of the Solid Earth》2009,45(8):656-660
Specific features of the technique of airborne gravity surveys in the Arctic are considered. The main requirements for aerogravimetric complexes used for such surveys and for reference GPS stations located at high latitudes are formulated, as well as the conditions necessary for converting an aircraft into an aircraft-laboratory. Specific features of the planning of measurements of aerogravimetric profiles in the Arctic are described. The need in the operations necessary for the rapid estimation of the results is substantiated. The obtained regional gravimetric map on a 1:200000 scale is presented as an example. 相似文献
16.
The possibility of applying the global positioning system (GPS) data for calculating the corrections for variations in the sea level to the results of a gravity survey and for improving the accuracy of marine gravity measurements is discussed. 相似文献
17.
全张量测量技术是在空中或海上用加载了多个加速度计的移动平台技术测量位场的五个独立分量.各张量分量包含不同方向的地下地质体信息,水平张量分量T_(xx)、T_(yy)、T_(xy)、T_(xz)、T_(yz)通常用于识别和映射与地质构造或地层变化有关的测量区域中的目标,垂直张量分量Tzz用于估计深度.然而,这些分量传统上是彼此分开解释,经常遇到错失关键信息的风险.本文所用全张量欧拉反褶积是在单独z方向的欧拉反演基础上发展而来的,它融合了重力异常垂直分量以及其三个方向导数、水平分量以及其三个方向导数.全张量数据信息得以有效应用的同时,欧拉反褶积结果也比常规欧拉反褶积结果更加收敛.最后,结合美国墨西哥湾地区实测航空FTG数据,用重力梯度张量数据进行联合欧拉三维反演研究,有效的识别岩盖的边界信息,划分岩盖范围,为进一步研究盖层底下深部复杂地质情况提供可靠的解释结果. 相似文献
18.
The ability to augment local gravity surveys with additional gravity stations from easily accessible national databases can greatly increase the areal coverage and spatial resolution of a survey. It is, however, necessary to integrate such data seamlessly with the local survey. One challenge to overcome in integrating data from national databases is that these data are typically of unknown quality. This study presents a procedure for the evaluation and seamless integration of gravity data of unknown quality from a national database with data from a local Global Positioning System (GPS)-based survey. The starting components include the latitude, longitude, elevation and observed gravity at each station location. Interpolated surfaces of the complete Bouguer anomaly are used as a means of quality control and comparison. The result is an integrated dataset of varying quality with many stations having GPS accuracy and other reliable stations of unknown origin, yielding a wider coverage and greater spatial resolution than either survey alone. 相似文献
19.
Variations of gravity before and after the Haicheng earthquake, 1975, and the Tangshan earthquake, 1976 总被引：2，自引：0，他引：2
《Physics of the Earth and Planetary Interiors》1979,18(4):330-338
Before and after the Haicheng earthquake of magnitude 7.3 which occurred on February 4, 1975, five repeated gravimeter surveys were carried out, three before and two after the earthquake, along a northwest-southeast profile of about 250 km in length not far on the west of the epicenter. The mean-square error of the measurements of the gravity differences between two consecutive points on the profile is less than 40 μGal. From June, 1972 to May, 1973, within a period of about one year, the results of three surveys indicated a clear decrease of the gravity values at points on the southeastern portion of the profile, amounting to about 352 μGal. After the earthquake, the fourth survey, which was carried out in March, 1975, revealed that the gravity values had recovered to the levels of the first survey and continued to increase as was shown by a fifth survey carried out in July of the same year.Variations of gravity were also observed before and after the Tangshan earthquake of magnitude 7.8 which occurred on July 28, 1976, but in this case, gravity was increasing instead of decreasing before the earthquake. Along an east-west profile of about 270 km in length and not far on the north of the epicenter, two gravity surveys were made before and two after the earthquake. The results showed that after the main shock, the gravity values of the whole profile, especially at those points closer to Tangshan, tended to return gradually to their values of the first survey before the earthquake.From these results, there seems to be a close relationship between these gravity variations and the occurrences of earthquakes. Based on results of repeated levelling work done in these regions, the estimated amount of gravity change caused by the change of elevation of the ground surface is far too small to account for the observed value. Therefore we speculate that some large earthquakes might be associated with some sort of mass transfer under ground, within the crust or in the upper mantle. This transfer would cause a large part of the gravity variation observed. We have made a theoretical analysis of this effect and attempted to obtain some estimate of the magnitude of this mass transfer, even though we are not yet clear about the physics of it. 相似文献
20.
通过联合全球重力位模型(EGM2008)、航空重力扰动数据和剩余地形模型(RTM)数据,基于频谱域(二维FFT变换)和空间域(Stokes数值积分)算法对毛乌素测区GT-2A航空重力测量系统采集的空中测线后处理重力扰动数据进行解算,构建了该地区的航空重力梯度扰动全张量.(1)残余航空重力扰动延拓结果表明:残余航空重力扰动经向下延拓至大地水准面,再向上延拓至航空高度后与原数据差值的标准差为1.0078 mGal,考虑边缘效应后,内缩计算范围得到的差值标准差减小至0.1269 mGal.(2)基于残余重力扰动数据(原航空高度数据及向下延拓数据),通过不同方案解算得到的梯度扰动结果表明:两种方案得到的研究区域重力梯度扰动各分量之差的最大标准差为6.4798E(Γ_(yz)分量),最小标准差为2.6968E(Γ_(xy)分量),内缩计算范围后得到的差值标准差最大值为1.8307E(Γ_(zz)分量),最小值为0.7223E(Γ_(yz)分量).本文的思路和方法可为未来我国自主构建航空重力梯度标定场提供参考. 相似文献