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81.
Topographic–isostatic masses represent an important source of gravity field information, especially in the high-frequency
band, even if the detailed mass-density distribution inside the topographic masses is unknown. If this information is used
within a remove-restore procedure, then the instability problems in downward continuation of gravity observations from aircraft
or satellite altitudes can be reduced. In this article, integral formulae are derived for determination of gravitational effects
of topographic–isostatic masses on the first- and second-order derivatives of the gravitational potential for three topographic–isostatic
models. The application of these formulas is useful for airborne gravimetry/gradiometry and satellite gravity gradiometry.
The formulas are presented in spherical approximation by separating the 3D integration in an analytical integration in the
radial direction and 2D integration over the mean sphere. Therefore, spherical volume elements can be considered as being
approximated by mass-lines located at the centre of the discretization compartments (the mass of the tesseroid is condensed
mathematically along its vertical axis). The errors of this approximation are investigated for the second-order derivatives
of the topographic–isostatic gravitational potential in the vicinity of the Earth’s surface. The formulas are then applied
to various scenarios of airborne gravimetry/gradiometry and satellite gradiometry. The components of the gravitational vector
at aircraft altitudes of 4 and 10 km have been determined, as well as the gravitational tensor components at a satellite altitude
of 250 km envisaged for the forthcoming GOCE (gravity field and steady-state ocean-circulation explorer) mission. The numerical
computations are based on digital elevation models with a 5-arc-minute resolution for satellite gravity gradiometry and 1-arc-minute
resolution for airborne gravity/gradiometry. 相似文献
82.
Sean L. Bruinsma Christoph Förste Sandrine Mulet Marie-Hélène Rio Oleg Abrikosov Jean-Charles Marty 《Marine Geodesy》2016,39(3-4):238-255
The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy. 相似文献
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84.
Four new gravity field models from GOCE, two of them combined with GRACE, are compared here with EGM2008. The objectives are to look into the differences in consecutive ranges of the spherical harmonic expansion globally as well as in selected geographical regions and in the regions of the various data sources used for EGM2008. In general, GOCE is able to contribute to improved global gravity models in the spherical harmonic range between 120 and 200 (and above). The agreement between EGM2008 and the GOCE models is very good in well-surveyed regions such as North America, Europe and Australia, with geoid RMS-differences on the order of 4–6 cm. In other regions, where the surface gravity data available for the development of EGM2008 were poor, such as South America, Africa, South-East Asia or China the RMS-differences are on a level of 30 cm. Here GOCE leads to a significant improvement. These findings are confirmed by the analysis of the areas of the various EGM2008 data sources. In the regions of the so-called “fill-in” data of EGM2008 RMS-geoid height differences are high. In Antarctica GOCE also gives important improvements in terms of spatial resolution and accuracy. In general, the agreement between EGM2008 and the GOCE-models up to degree and order (d/o) 200 is good, with a global (excluding the polar gaps of GOCE orbits, throughout) geoid difference RMS of 11 cm, in the ocean areas 8 cm and 20 cm in the continental areas. GOCE models are better suited for ocean circulation studies because no prior ocean information enters into the data reduction process, as it is the case when deducing gravity anomalies from an altimetric mean sea surface. On the other hand, the good consistency between GOCE-models and EGM2008 in ocean areas very likely indicates that the influence of ocean circulation information on EGM2008 is rather small. The four tested GOCE models behave similarly except at the highest latitudes where GOCE lacks data due to its orbit inclination of 96.5° and some form of regularization which has to be applied. 相似文献
85.
为解决卫星重力梯度大尺度密度反演存在的平面模型误差、病态矩阵正则化、大型矩阵求逆、先验数据融合等问题,依托Tesseroid单元体模型,分别采用广义岭估计、代数重建(ART)、遗传算法完成了附加高斯白噪声的模拟异常体密度反演实验,并将反演结果与原始设定模型进行比较分析。 相似文献
86.
根据GOCE和EGM08重力场模型的频谱互补性,利用Wenzel加权谱组合法构建了GOCE和EGM08的组合重力场模型。累积大地水准面误差表明,组合重力场模型具有明显的优势。美国实测GPS/水准检验结果表明,Dir4+EGM08的组合模型精度最高,比EGM08模型精度提高了8%。 相似文献
87.
国际重力卫星研究进展和我国将来卫星重力测量计划 总被引：12，自引：3，他引：9
本文首先分别介绍了国际已经成功发射的专用地球重力测量卫星CHAMP、GRACE以及即将发射的GOCE、GRACE Follow-On和专用月球重力探测卫星GRAIL的研制机构、轨道参数、关键载荷、跟踪模式、测量原理、科学目标和技术特征;其次,阐述了当前相关学科对地球重力场测量精度的需求;最后,建议我国在将来实施的卫星重力测量计划中首选卫星跟踪卫星高低\低低模式,尽快开展轨道参数优化选取的定量系统研究论证和重力卫星系统的误差分析,依据匹配精度指标先期开展重力卫星各关键载荷的研制以及尽早启动卫星重力测量系统的虚拟仿真研究。 相似文献
88.
???????????????????????????????????????????????????????????????????????????????о??????????????????????GOCE????????????????????????????210?????GO_CONS_GCF_2_DIR_R4???????GO_CONS_GCF_2_SPW_R1????????????8.883??????250?????GO_CONS_GCF_2_DIR_R4???????GO_CONS_GCF_2_TIM_R1????????????4.388?????????????????????κ???????????????????????????????????????????????????? 相似文献
89.
重力梯度仪校准参数的确定是GOCE重力梯度观测数据处理的关键环节。本文对GOCE卫星重力梯度观测值中的时变信号与粗差进行了分析,利用高精度全球重力场模型,确定了GOCE重力梯度观测值各分量的尺度因子与偏差,并对校准结果进行了精度评定。结果表明,在测量带宽内,海潮对重力梯度观测值影响在mE量级,与重力梯度仪的精度水平相当,陆地水等非潮汐重力场时变信号略小于海潮,量级约为10-4E;各分量重力梯度观测值的粗差比例均大于0.2%;除EGM96模型外的其他模型对GOCE重力梯度仪进行校准后,Vxx、Vyy、Vzz、Vyz分量上尺度因子的稳定性均在10-4量级,Vxz分量能达到10-5量级,Vxy分量为10-2量级,这与梯度观测值各分量的精度水平一致。 相似文献
90.
The determination of local geoid models has traditionally been carried out on land and at sea using gravity anomaly and satellite
altimetry data, while it will be aided by the data expected from satellite missions such as those from the Gravity field and
steady-state ocean circulation explorer (GOCE). To assess the performance of heterogeneous data combination to local geoid
determination, simulated data for the central Mediterranean Sea are analyzed. These data include marine and land gravity anomalies,
altimetric sea surface heights, and GOCE observations processed with the space-wise approach. A spectral analysis of the aforementioned
data shows their complementary character. GOCE data cover long wavelengths and account for the lack of such information from
gravity anomalies. This is exploited for the estimation of local covariance function models, where it is seen that models
computed with GOCE data and gravity anomaly empirical covariance functions perform better than models computed without GOCE
data. The geoid is estimated by different data combinations and the results show that GOCE data improve the solutions for
areas covered poorly with other data types, while also accounting for any long wavelength errors of the adopted reference
model that exist even when the ground gravity data are dense. At sea, the altimetric data provide the dominant geoid information.
However, the geoid accuracy is sensitive to orbit calibration errors and unmodeled sea surface topography (SST) effects. If
such effects are present, the combination of GOCE and gravity anomaly data can improve the geoid accuracy. The present work
also presents results from simulations for the recovery of the stationary SST, which show that the combination of geoid heights
obtained from a spherical harmonic geopotential model derived from GOCE with satellite altimetry data can provide SST models
with some centimeters of error. However, combining data from GOCE with gravity anomalies in a collocation approach can result
in the estimation of a higher resolution geoid, more suitable for high resolution mean dynamic SST modeling. Such simulations
can be performed toward the development and evaluation of SST recovery methods. 相似文献