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1.
郭俊义 《武汉大学学报(信息科学版)》1993,(3)
本文提出了利用变分法解混合边值问题直接计算位系数的原理。根据这一原理可解第一、第二和第三边值问题的混合边值问题直接求得位系数。利用这一原理可较简单地联合利用经典重力测量(即重力点的平面位置由天文或三角测量确定,高程由水准或三角高程确定)、卫星重力测量(即利用卫星定位技术确定重力点的平面位置和大地高)以及卫星测高数据研究地球的重力场。 相似文献
2.
Geoid models from the new generation of satellite gravity missions, such as GRACE and GOCE, in combination with sea surface
from satellite altimetry allow to obtain absolute dynamic ocean topography with rather high spatial resolution and accuracy.
However, this implies combination of data with fundamentally different characteristics and different spatial resolutions.
Spectral consistency would imply the removal of the short-scale features of the altimetric sea surface height by filtering,
to provide altimetric data consistent with the resolution of the geoid field. The goal must be to lose as little as possible
from the high precision of the altimetric signal. Using a one-dimensional example we show how the spectrum is changing when
a function defined only on a limited domain (ocean in the real case) is extended or not as to cover the complete domain (the
whole sphere in the real case). The results depend on the spectral characteristics of the altimetric signal and of the applied
filter. Referring to the periodicity condition, as it is requested in the case of Fourier analysis, the action of the two
classical filters (Ideal Low Pass and Gauss filter) and of two alternative procedures (wavelets and Slepian) is studied. 相似文献
3.
物理大地测量面临着越来越多的数据:高程异常、垂线偏差、重力异常、重力梯度等,因此出现了超定边值问题,本文采用求解偏微分方程最简单而又最常用的差分法,对这一问题进行了初步的研究。 相似文献
4.
利用ENVISAT测高数据监测青海湖水位变化 总被引:2,自引:0,他引:2
使用2002年10月~2006年2月的ENVISAT SGDR数据,并利用重跟踪技术实施了距离等相关改正之后,计算了青海湖的水位变化;同时分别利用EGM96、青海省的似大地水准面模型计算了青海湖的正高和正常高相应水位变化,并与青海湖下社站的水文观测数据进行了验证.研究结果表明,利用波形重跟踪技术在某种程度上可以改进内陆水域的距离精度,能够较好地监测出青海湖的水位变化. 相似文献
5.
6.
海洋重力似大地水准面与区域测高似大地水准面的拟合问题 总被引:3,自引:0,他引:3
研究了将陆地重力似大地水准面与GPS水;住似大地水准面拟合的处理方法推广到海洋的问题.首先从理论上证明了当存在海面地形.则海洋大地水准面与似大地水准面不重合.导出了在海洋上大地水;住面差距与高程异常之间差值的公式.由此给出了求定平均海面相对于区域高程基准的正常高以及测高似大地水准面的计算公式。由于测高平均海面与GPS大地高有相近的精度.提出了将海洋重力似大地水准面与区域测高似大地水准面拟合的处理方法.并利用当前最新的海面地形模型和测高平均海面模型做了数值估计。 相似文献
7.
8.
2020珠峰高程测量,首次确定并发布了基于国际高程参考系统(IHRS)的珠峰正高。在珠峰地区实现国际高程参考系统,采用的方案是建立珠峰区域高精度重力大地水准面。利用地球重力场谱组合理论和基于数据驱动的谱权确定方法,测试优选参考重力场模型及其截断阶数和球冠积分半径等关键参数,联合航空和地面重力等数据建立了珠峰区域重力似大地水准面模型,61点高精度GNSS水准高程异常检核表明,模型精度达3.8 cm,加入航空重力数据后模型精度提升幅度达51.3%。提出顾及高差改正的峰顶高程异常内插方法,采用顾及地形质量影响的高程异常——大地水准面差距转换改正严密公式,使用峰顶实测地面重力数据,基于国际高程参考系统定义的重力位值W0和GRS80参考椭球,最终确定了国际高程参考系统中的高精度珠峰峰顶大地水准面差距。 相似文献
9.
A detailed gravimetric geoid in the North Atlantic Ocean, named DGGNA-77, has been computed, based on a satellite and gravimetry
derived earth potential model (consisting in spherical harmonic coefficients up to degree and order 30) and mean free air
surface gravity anomalies (35180 1°×1° mean values and 245000 4′×4′ mean values). The long wavelength undulations were computed
from the spherical harmonics of the reference potential model and the details were obtained by integrating the residual gravity
anomalies through the Stokes formula: from 0 to 5° with the 4′×4′ data, and from 5° to 20° with the 1°×1° data. For computer
time reasons the final grid was computed with half a degree spacing only. This grid extends from the Gulf of Mexico to the
European and African coasts.
Comparisons have been made with Geos 3 altimetry derived geoid heights and with the 5′×5′ gravimetric geoid derived byMarsh andChang [8] in the northwestern part of the Atlantic Ocean, which show a good agreement in most places apart from some tilts which
porbably come from the satellite orbit recovery. 相似文献
10.
11.
Rüdiger Lehmann 《Journal of Geodesy》1993,67(1):31-40
Gravity data inversion methods using spatial source distributions are frequently investigated and applied in Geodesy. Nearly all of them construct a fixed geometry for the sources. It was shown that this is not at all necessary. We give an approach to the problem of geoid determination based on free-positioned point masses. The algorithm available is extended and refined in order to make it applicable to more ill-designed and complex problems than addressed so far. We introduce concepts to handle different data accuracies, non-uniform data coverages, and different data types. The Gulf of Bothnia serves as an area of investigation. We determine a pure gravimetric geoid solution as well as a combined solution based on gravimetric and altimetric data. The problem of gross error detection in the altimetry is treated. The prediction accuracies obtained prove the method to be suitable for such a problem. 相似文献
12.
Quasi-stationary sea surface topography estimation by the multiple input/output method 总被引:1,自引:0,他引:1
Multiple input/multiple output system theory (MIMOST) is briefly presented, and the application of the method to the quasi-stationary
sea surface topography (QSST) estimation and the filtering of the input observations are discussed. The repeat character of
satellite altimetry missions provides more than one sample of the measured sea surface height (SSH) field, and an approximation
of the input signal and error power spectral densities can be determined using this successive information. A case study in
the Labrador Sea is considered using SSHs from ERS1 phases C and G, ERS1-GM, ERS2 phase A and TOPEX/POSEIDON altimetric missions
in combination with shipborne gravity anomalies. The time period of the observations in this study is from 1993 to 1998. Some
comparisons between the techniques used for the power spectral density approximation are carried out and some remarks on the
properties of the estimated QSST are presented.
Received: 19 October 1999 / Accepted: 23 October 2000 相似文献
13.
14.
Retracking considerations in spaceborne GNSS-R altimetry 总被引:1,自引:0,他引:1
Hyuk Park Adriano Camps Enric Valencia Nereida Rodriguez-Alvarez Xavier Bosch-Lluis Isaac Ramos-Perez Hugo Carreno-Luengo 《GPS Solutions》2012,16(4):507-518
The European Space Agency Passive Reflectometry and Interferometry System In-orbit Demonstrator (IoD) aims to perform mesoscale altimetric observations by measuring the Global Navigation Satellite System (GNSS) opportunity signals reflected over the sea surface. Altimetry based on GNSS reflectometry (GNSS-R) is significantly affected by satellite motion, since it requires relatively long integration times to reduce noise. We present the impact of the satellite motion on the GNSS-R observables and the need to retrack the waveforms. By using a detailed GNSS-R space mission simulator, the change of delay difference between the direct and the reflected signals during the incoherent averaging of the waveform has been investigated. Their effects on the waveform shape and the altimetric performance are presented comparing the aligned and non-aligned waveforms. Results show that the performance of spaceborne GNSS-R altimeter is seriously degraded without a proper alignment of the waveform samples. 相似文献
15.
Xiaopeng Li 《Journal of Geodesy》2018,92(5):471-485
Radial basis functions (RBFs) have been used extensively in satellite geodetic applications. However, to the author’s knowledge, their role in processing and modeling airborne gravity data has not yet been fully advocated or extensively investigated in detail. Compared with satellite missions, the airborne data are more suitable for these kinds of localized basis functions especially considering the following facts: (1) Unlike the satellite missions that can provide global or near global data coverage, airborne gravity data are usually geographically limited. (2) It is also band limited in the frequency domain. (3) It is straightforward to formulate the RBF observation equations from an airborne gravimetric system. In this study, a set of band-limited RBF is developed to model and downward continue the airborne gravity data for local geoid improvement. First, EIGEN6c4 coefficients are used to simulate a harmonic field to test the performances of RBF on various sampling, noise, and flight height levels, in order to gain certain guidelines for processing the real data. Here, the RBF method not only successfully recovers the harmonic field but also presents filtering properties due to its particular design in the frequency domain. Next, the software was tested for the GSVS14 (Geoid Slope Validation Survey 2014) area in Iowa as well as for the area around Puerto Rico and the US Virgin Islands by use of the real airborne gravity data from the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) project. By fully utilizing the three-dimensional correlation information among the flight tracks, the RBF can also be used as a data cleaning tool for airborne gravity data adjustment and cleaning. This property is further extended to surface gravity data cleaning, where conventional approaches have various limitations. All the related numerical results clearly show the importance and contribution of the use of the RBF for high- resolution local gravity field modeling. 相似文献
16.
为解决世界各国高程基准差异的问题,提出联合卫星重力场模型、地面重力数据、GNSS大地高、局部高程基准的正高或正常高,按大地边值问题法确定局部高程基准重力位差的方法。首先推导了利用传统地面"有偏"重力异常确定高程基准重力位差的方法;接着利用改化Stokes核函数削弱"有偏"重力异常的影响,并联合卫星重力场模型和地面"有偏"重力数据,得到独立于任何局部高程基准的重力水准面,以此来确定局部高程基准重力位差;最后利用GNSS+水准数据和重力大地水准面确定了美国高程基准与全球高程基准W0的重力位差为-4.82±0.05 m2s-2。 相似文献
17.
论高精度卫星重力场模型和厘米级区域大地水准面的确定及水文学时变重力效应 总被引:3,自引:2,他引:1
阐述了联全新一代卫星重力测量数据、卫星测高数据及全球陆地重力数据确定高精度180阶全球重力场模型、以全球重力场模型为框架参考场、利用我国地面重力数据、GPS水准资料、数值高程模型和地形密度信息确定高分辨率cm级区域大地水准面的思想。指出了一个重点发展方向:利用GRACE卫星每30天的重力位模型分析时变重力场,联系合卫星测高同时相平均海面以及水文、气候和海洋模型,分析我国黄河流域和海洋地区水储量分布和海流季节性变化,并解释与气候要素变化的相关性。 相似文献
18.
J. Y. Chen 《Journal of Geodesy》1982,56(1):9-26
Summary The application of combined data (satellite and terrestrial data) to the practical computation of height anomalies or the
deflections of the vertical was originally suggested by (Molodensky et al. 1962). This idea usually leads to the modification
of Stokes' or Vening-Meinesz' functions in the integration procedure. In the recent decade there were various suggestions
in this regard especially for the computation of height anomalies. For example, a considerable mathematical insight into the
modification of Stokes' function and the truncation of its integral has been provided by (Meissl 1971, Houtze et al. 1979,
Rapp 1980, Jekeli 1980).
Five different methods for computing deflections of the vertical by modifying Vening-Meinesz' function are studied and compared
with each other. The corresponding formulae, the values of the coefficients in each method and the estimations of their corresponding
potential coefficient error and truncation error are given in this article.
This paper was written at the Institut f. Angewandte Geod?sie, Technische Universit?t Graz, Austria. 相似文献
19.
H. Nahavandchi 《Journal of Geodesy》2002,76(6-7):345-352
It is suggested that a spherical harmonic representation of the geoidal heights using global Earth gravity models (EGM) might
be accurate enough for many applications, although we know that some short-wavelength signals are missing in a potential coefficient
model. A `direct' method of geoidal height determination from a global Earth gravity model coefficient alone and an `indirect'
approach of geoidal height determination through height anomaly computed from a global gravity model are investigated. In
both methods, suitable correction terms are applied. The results of computations in two test areas show that the direct and
indirect approaches of geoid height determination yield good agreement with the classical gravimetric geoidal heights which
are determined from Stokes' formula. Surprisingly, the results of the indirect method of geoidal height determination yield
better agreement with the global positioning system (GPS)-levelling derived geoid heights, which are used to demonstrate such
improvements, than the results of gravimetric geoid heights at to the same GPS stations. It has been demonstrated that the
application of correction terms in both methods improves the agreement of geoidal heights at GPS-levelling stations. It is
also found that the correction terms in the direct method of geoidal height determination are mostly similar to the correction
terms used for the indirect determination of geoidal heights from height anomalies.
Received: 26 July 2001 / Accepted: 21 February 2002 相似文献
20.
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