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1.
Pavel Novák 《Surveys in Geophysics》2010,31(1):1-21
During the General Assembly of the European Geosciences Union in April 2008, the new Earth Gravitational Model 2008 (EGM08)
was released with fully-normalized coefficients in the spherical harmonic expansion of the Earth’s gravitational potential
complete to degree and order 2159 (for selected degrees up to 2190). EGM08 was derived through combination of a satellite-based
geopotential model and 5 arcmin mean ground gravity data. Spherical harmonic coefficients of the global height function, that
describes the surface of the solid Earth with the same angular resolution as EGM08, became available at the same time. This
global topographical model can be used for estimation of selected constituents of EGM08, namely the gravitational potentials
of the Earth’s atmosphere, ocean water (fluid masses below the geoid) and topographical masses (solid masses above the geoid),
which can be evaluated numerically through spherical harmonic expansions. The spectral properties of the respective potential
coefficients are studied in terms of power spectra and their relation to the EGM08 potential coefficients is analyzed by using
correlation coefficients. The power spectra of the topographical and sea water potentials exceed the power of the EGM08 potential
over substantial parts of the considered spectrum indicating large effects of global isostasy. The correlation analysis reveals
significant correlations of all three potentials with the EGM08 potential. The potential constituents (namely their functionals
such as directional derivatives) can be used for a step known in geodesy and geophysics as the gravity field reduction or
stripping. Removing from EGM08 known constituents will help to analyze the internal structure of the Earth (geophysics) as
well as to derive the Earth’s gravitational field harmonic outside the geoid (geodesy). 相似文献
2.
An alternative “direct method” to “mean dynamic topography” (MDT) computations using satellite altimetry-derived “mean sea
surface” (MSS) and “global geopotential model” (GGM), without direct application of the geoid, is devised. The developed approach,
which is based on derivation of an equipotential surface of the gravity field of the Earth that fits to global MSS in least
squares sense, is formulated via a constrained optimization problem. The validity of our method is numerically tested by computing
a global MDT model based on DNSC08 MSS model and EGM2008 GGM as input data. 相似文献
3.
The continuous efforts on establishment and modernization of the geodetic control in Turkey include a number of regional geoid
models that have been determined since 1976. The recently released gravimetric Geoid of Turkey, TG03, is used in geodetic
applications where GPS-heights need to be converted to the local vertical datum. To reach a regional geoid model with improved
accuracy, the selection of the appropriate global geopotential model is of primary importance. This study assesses the performance
of a number of recent satellite-only and combined global geopotential models (GGMs) derived from CHAMP and GRACE missions’
data in comparison to the older EGM96 model, which is the underlying reference model for TG03. In this respect, gravity anomalies
and geoid heights from the global geopotential models were compared with terrestrial gravity data and low-pass filtered GPS/levelling
data, respectively. Also, five new gravimetric geoid models, computed by the Fast Fourier Transform technique using terrestrial
gravity data and the geopotential models, were validated at the GPS/levelling benchmarks. The findings were also compared
with the validation results of the TG03 model.
The tests showed that as it was expected any of the high-degree combined models (EIGEN-CG03C, EIGEN-GL04C, EGM96) can be employed
for determining the gravity anomalies over Turkey. In the west of Turkey, EGM96 and EIGEN-CHAMP03S fit the GPS/levelling surface
better. However, all the tested GGMs revealed equal performance when they were employed in gravimetric geoid modelling after
de-trending the gravimetric geoid model with corrector surface fitting. The new geoid models have improved accuracy (after
fit) compared to TG03. 相似文献
4.
Angel Martin Ana Belén Anquela Jorge Padín José Luís Berné 《Studia Geophysica et Geodaetica》2010,54(3):347-366
A new generation of global geopotential models (GGM) is being developed. These solutions offer a file with fully-normalized
spherical harmonic coefficients of the Earth’s gravitational potential up to a degree greater than 2000 with very low commission
errors. This paper analyses the recent Earth Gravitational Model EGM2008, developed up to degree and order 2159 with additional
coefficients to degree 2190 and order 2159, which means recovering the gravitational field up to approximately 20 km wavelengths.
223 GPS/levelling points of the new Spanish High Precision Levelling Network in the Valencia region (Eastern Spain) are used
as external tool for evaluation in that particular region. The same evaluation has been performed to other different global
(EGM96 and EIGENCG03C), continental (EGG97), regional (IGG2005 and IBERGEO2006) and local (GCV07) geoid models for comparison
purposes only. These comparisons show that EGM2008 is the geoid model that best fits to the GPS/levelling data in that region. 相似文献
5.
本文通过分析陆地实测空间重力异常数据、海洋船载测量空间重力异常数据、卫星测高重力异常,布格重力异常数据、EGM2008地球重力模型数据等多种来源数据的性质和精度,并对相关数据进行对比,研究了编制1:500万中国海陆空间重力异常图的数据使用方案和技术方法.在地形较为平坦、实测数据分布均匀的陆区,使用实测数据,在地形复杂,实测数据稀少以及没有实测数据的陆区或岛屿,利用布格重力异常反推空间异常的方法合成平均空间重力数据,西藏地区的数据对比实验证明合成平均空间重力异常数据是一种有效的数据补充.利用三观测列方差分解法在南海地区对船载测量空间重力数据和美国SS系列及丹麦DNSC08GRA卫星重力数据进行了方差分解计算,结果表明不同来源的卫星测高重力数据具有很大的一致性,数据精度较以往有了很大的提高.海区空间重力数据使用原则是在船载重力测量数据校准下,全面使用卫星测高重力数据进行编图.海陆过渡区的异常处理应以EGM2008地球重力模型重力场为基准参考场,实现海陆异常平缓过渡,无缝连接.对中国海陆空间重力异常场进行了小波变换处理,对空间重力异常场进行了解读,勾画出三横四竖的一级重力梯级带及其所围限的8个一级重力异常区,并划分了二级重力异常区和梯级带,为块体构造学体系中大地构造格架的建立提供了地球物理证据. 相似文献
6.
V. N. Koneshov V. B. Nepoklonov O. V. Polovnev 《Izvestiya Physics of the Solid Earth》2017,53(1):108-115
The results of the theoretical and experimental research on the technique for refining the global Earth geopotential models such as EGM2008 in the continental regions are presented. The discussed technique is based on the high-resolution satellite data for the Earth’s surface topography which enables the allowance for the fine structure of the Earth’s gravitational field without the additional gravimetry data. The experimental studies are conducted by the example of the new GGMplus global gravity model of the Earth with a resolution about 0.5 km, which is obtained by expanding the EGM2008 model to degree 2190 with the corrections for the topograohy calculated from the SRTM data. The GGMplus and EGM2008 models are compared with the regional geoid models in 21 regions of North America, Australia, Africa, and Europe. The obtained estimates largely support the possibility of refining the global geopotential models such as EGM2008 by the procedure implemented in GGMplus, particularly in the regions with relatively high elevation difference. 相似文献
7.
Robert Tenzer Pavel Novák Ilya Prutkin Artu Ellmann Peter Vajda 《Studia Geophysica et Geodaetica》2009,53(2):157-167
To reduce the numerical complexity of inverse solutions to large systems of discretised integral equations in gravimetric
geoid/quasigeoid modelling, the surface domain of Green’s integrals is subdivided into the near-zone and far-zone integration
sub-domains. The inversion is performed for the near zone using regional detailed gravity data. The farzone contributions
to the gravity field quantities are estimated from an available global geopotential model using techniques for a spherical
harmonic analysis of the gravity field. For computing the far-zone contributions by means of Green’s integrals, truncation
coefficients are applied. Different forms of truncation coefficients have been derived depending on a type of integrals in
solving various geodetic boundary-value problems. In this study, we utilise Molodensky’s truncation coefficients to Green’s
integrals for computing the far-zone contributions to the disturbing potential, the gravity disturbance, and the gravity anomaly.
We also demonstrate that Molodensky’s truncation coefficients can be uniformly applied to all types of Green’s integrals used
in solving the boundaryvalue problems. The numerical example of the far-zone contributions to the gravity field quantities
is given over the area of study which comprises the Canadian Rocky Mountains. The coefficients of a global geopotential model
and a detailed digital terrain model are used as input data. 相似文献
8.
P. Novák 《Studia Geophysica et Geodaetica》2007,51(3):351-367
Satellite missions CHAMP and GRACE dedicated to global mapping of the Earth’s gravity field yield accurate satellite-to-satellite
tracking (SST) data used for recovery of global geopotential models usually in a form of a finite set of Stokes’s coefficients.
The US-German Gravity Recovery And Climate Experiment (GRACE) yields SST data in both the high-low and low-low mode. Observed
satellite positions and changes in the intersatellite range can be inverted through the Newtonian equation of motion into
values of the unknown geopotential. The geopotential is usually approximated in observation equations by a truncated harmonic
series with unknown coefficients. An alternative approach based on integral inversion of the SST data of type GRACE into discrete
values of the geopotential at a geocentric sphere is discussed in this article. In this approach, observation equations have
a form of Green’s surface integrals with scalar-valued integral kernels. Despite their higher complexity, the kernel functions
exhibit features typical for other integral kernels used in geodesy for inversion of gravity field data. The two approaches
are discussed and compared based on their relative advantages and intended applications. The combination of heterogeneous
gravity data through integral equations is also outlined in the article.
panovak@kma.zcu.cz 相似文献
9.
So far the recent Earth's gravity model, EGM08, has been successfully applied for different geophysical and geodetic purposes. In this paper, we show that the computation of geoid and gravity anomaly on the reference ellipsoid is of essential importance but error propagation of EGM08 on this surface is not successful due to downward continuation of the errors. Also we illustrate that some artefacts appear in the computed geoid and gravity anomaly to lower degree and order than 2190. This means that the role of higher degree harmonics than 2160 is to remove these artefacts from the results. Consequently, EGM08 must be always used to degree and order 2190 to avoid the numerical problems. 相似文献
10.
Jitka Hájková 《Studia Geophysica et Geodaetica》2011,55(3):515-528
A mathematical model used for determination of a local geoid model by combining airborne gravity disturbances and the Earth
Gravitational Model 2008 (EGM08) is shortly reviewed. The precision of the estimated local geoid model of Taiwan is tested
by its comparison with the “real” geoid at Global Satellite Navigation Systems (GNSS)/levelling points. The same comparison
at GNSS/levelling points is done for the geoid evaluated only by using EGM08. Conclusions concerning a rate of improvement
of the “global” geoid from EGM08 using the “local” geoid from airborne gravity data are presented. 相似文献
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14.
The elasto-gravitational deformation response of the Earth’s solid parts to the perturbations of the pressure and gravity
on the core-mantle boundary (CMB) and the solid inner core boundary (ICB), due to the dynamical behaviors of the fluid outer
core (FOC), is discussed. The internal load Love numbers, which are formulized in a general form in this study, are employed
to describe the Earth’s deformation. The preliminary reference Earth model (PREM) is used as an example to calculate the internal
load Love numbers on the Earth’s surface, CMB and ICB, respectively. The characteristics of the Earth’s deformation variation
with the depth and the perturbation periods on the boundaries of the FOC are also investigated. The numerical results indicate
that the internal load Love numbers decrease quickly with the increasing degree of the spherical harmonics of the displacement
and depend strongly on the perturbation frequencies, especially on the high frequencies. The results, obtained in this work,
can be used to construct the boundary conditions for the core dynamics of the long-period oscillations of the Earth’s fluid
outer core.
Foundation item: State Natural Science Foundation of China (40174022 and 49925411) and the Projects from Chinese Academy of Sciences (KZCX2-106
and KZ952-J1-411). 相似文献
15.
高精度高程基准重力位的确定往往依赖于高精度全球重力场模型,其对全球和区域高程基准的高精度统一非常关键,GRACE、GOCE卫星重力计划极大地提高了全球重力场模型中长波的精度.本文首先对GRACE/GOCE卫星重力场模型的内符合和外符合精度进行讨论分析,结果说明卫星重力模型的截断误差影响可达到分米级水平,在确定高程基准重力位时该影响不可忽略.利用EGM2008模型扩展GRACE/GOCE卫星重力场模型至2190阶,可有效减弱卫星重力模型的截断误差影响,但不同模型扩展时的最优拼接阶次不同,其中DIR-1、DIR-5模型对应的最优拼接阶次分别为180阶和220阶,以GPS水准数据检验,扩展模型在中国区域的精度均优于18cm.最后,基于最优拼接阶次获得的扩展重力场模型对我国1985高程基准重力位进行了估计,DIR-5和TIM-5模型对应数值分别为62636853.47m~2·s~(-2)和62636853.49m~2·s~(-2),精度均为1.51m~2·s~(-2);发现在中国区域模型大地水准面与GPS/水准数据的差值存在微弱的系统性倾斜,东西向倾斜约为9cm,南北向倾斜约为1.4cm,考虑倾斜改正后基于DIR-5和TIM-5模型估计我国1985高程基准重力位的精度提高了0.16m~2·s~(-2). 相似文献
16.
The Mohorovičić discontinuity is the boundary between the Earth’s crust and mantle. Several isostatic hypotheses exist for
estimating the crustal thickness and density variation of the Earth’s crust from gravity anomalies. 相似文献
17.
This work presents a validation study of global geopotential models (GGM) in the region of Fagnano Lake, located in the southern Andes. This is an excellent area for this type of validation because it is surrounded by the Andes Mountains, and there is no terrestrial gravity or GNSS/levelling data. However, there are mean lake level (MLL) observations, and its surface is assumed to be almost equipotential. Furthermore, in this article, we propose improved geoid solutions through the Residual Terrain Modelling (RTM) approach. Using a global geopotential model, the results achieved allow us to conclude that it is possible to use this technique to extend an existing geoid model to those regions that lack any information (neither gravimetric nor GNSS/levelling observations). As GGMs have evolved, our results have improved progressively. While the validation of EGM2008 with MLL data shows a standard deviation of 35 cm, GOCO05C shows a deviation of 13 cm, similar to the results obtained on land. 相似文献
18.
The EGM08 geopotential model complete to degree and order 2159 was used in a remove-compute-restore (RCR) method for the geoid
computation in the State of Rio de Janeiro, Brazil. Terrain and indirect effect corrections were computed using a 6-arcsec
resolution DTE, derived from the TOPODATA Project (Shuttle Radar Topography Mission data) raised by the National Institute
for Space Research. INPE, Brazil. We applied Voronoi/Delaunay discretisations for discrete Stokes integration. In these schemes,
target area is partitioned into polygons/triangles, respectively, and the computation is carried out by point-wise numerical
integration and no gridding is mandatory. For both procedures, the cells were produced using either observed gravity data
combined with gridded Bouguer derived information. Particularly in Delaunay scheme, as the gravity anomalies are interpolated
into the triangular cells, and geoid undulations are computed for their vertices, Stokes function singularity was gone. Externally
estimated errors resulting from a comparison with GPS/leveling data were presented for both the schemes and classical ones,
as well as for the EGM08 undulations. They yielded RMS differences equal to 0.105 m, 0.110 m, 0.110 m, 0.115 m and 0.228 m,
respectively, for Voronoi, Delaunay, Voronoi/Delaunay with gridded-data alone and EGM08, computed between 32 GPS/leveling
points. 相似文献
19.
We investigate the roughness of and the correlation with topography of the observed, topographically corrected (T), and bathymetrically
and topographically corrected (BT) gravity disturbances. The numerical investigation is carried out for the gravity disturbances
at the Earth’s surface and for the upward continued gravity disturbances at different altitudes. The area of study comprises
a rough part of the Canadian Rockies surrounded by flat regions. The smoothest at the Earth’s surface are the BT gravity disturbances.
The evolution of roughness with altitude shows an interesting phenomenon, diverse for the three types of gravity disturbances.
The correlation with topography over the study area of the observed gravity disturbances is bellow 0.6, and of the BT gravity
disturbances approximately −0.6. The largest absolute value, of about −0.75, is found between the topography and the T gravity
disturbances. This large negative correlation indicates a presence of the isostatic compensation in mountainous regions of
the Canadian west coast. 相似文献
20.
Ali Kiliçoğlu Ahmet Direnç Hasan Yildiz Murat Bölme Bahadir Aktuğ Mehmet Simav Onur Lenk 《Studia Geophysica et Geodaetica》2011,55(4):557-578
Turkish regional geoid models have been developed by employing a reference earth gravitational model, surface gravity observations
and digital terrain models. The gravimetric geoid models provide a ready transformation from ellipsoidal heights to the orthometric
heights through the use of GPS/leveling geoid heights determined through the national geodetic networks. The recent gravimetric
models for Turkish territory were computed depending on OSU91 (TG-91) and EGM96 (TG-03) earth gravitational models. The release
of the Earth Gravitational Model 2008 (EGM08), the collection of new surface gravity observations, the advanced satellite
altimetry-derived gravity over the sea, and the availability of the high resolution digital terrain model have encouraged
us to compute a new geoid model for Turkey. We used the Remove-Restore procedure based on EGM08 and applied Residual Terrain
Model (RTM) reduction of the surface gravity data. Fast Fourier Transformation (FFT) was then used to obtain the residual
quasigeoid from the reduced gravity. We restored the individual contributions of EGM08 and RTM to the whole quasi-geoid height
(TQG-09). Since the Helmert orthometric height system is adopted in Turkey, the quasi-geoid model (TQG-09) was then converted
to the geoid model (TG-09) by making use of Bouguer gravity anomalies and digital terrain model. After all we combined a gravimetric
geoid model with GPS/leveling geoid heights in order to obtain a hybrid geoid model (THG-09) (or a transformation surface)
to be used in GPS applications. The RMS of the post-fit residuals after the combination was found to be ± 0.95 cm, which represents
the internal precision of the final combination. And finally, we tested the hybrid geoid model with GPS/leveling data, which
were not used in the combination, to assess the external accuracy. Results show that the external accuracy of the THG-09 model
is ± 8.4 cm, a precision previously not achieved in Turkey until this study. 相似文献