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171.
用球谐函数方法(SHM)计算了由Schwiderski海潮图和日本海海潮图引起的M2,S2,K1和O1各分潮波的综合海潮负荷参数.计算中采用了Pagiatakis(1990)地球模型的负荷Love数.结果表明SHM具有更高的计算效率和计算精度.为了真正实现±毫米的VLBI地壳运动测定精度和±0.1微伽的绝对重力测量精度,对未来海潮图模型,特别是日本海的海潮图模型的精度要求作了讨论.计算结果还表明不同地球模型的负荷Love数对计算的测站位移之差为0.7毫米,在目前测量精度下尚可以不作考虑.中国近海的海潮M2波对台北,上海,Daejeon,Okinawa,和Kagosima站的径向和水平分量位移影响可分别达±22.4~±1.0毫米和±05-±5.5毫米,表明中国近海高精度的海潮图模型对东亚测站的地壳运动高精度测量是十分重要的. 相似文献
172.
利用球冠谐分析方法提取不同波长重力场异常 总被引:2,自引:0,他引:2
介绍球冠谐分析方法在重力场研究中的基本理论和计算方法。探讨了球冠谐系数与波长的关系,以及利用球冠谐分析方法提取不同波长的重量场力场异常,进而研究深部地壳结构的问题,最后给出一个实例。 相似文献
173.
The satellite mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer), the first Core Mission of the Earth Explorer Programme funded by ESA (European Space Agency), is dedicated to the precise modelling of the Earth's gravity field, with its launch planned for 2006. The mathematical models for parameterizing the Earth's gravity field are based on a series expansion into spherical harmonics, yielding a huge number of unknown coefficients. Their computation leads to the solution of very large normal equation systems. An efficient way to handle these equation systems is the so-called semianalytic or lumped coefficients approach, which theoretically requires an uninterrupted, continuous time series of observations, recorded along an exact circular repeat orbit. In this paper the consequences of violating these conditions are analyzed. The effects of an interrupted observation stream onto the estimated spherical harmonic coefficients are demonstrated, and an iterative strategy, which reduces the negative influence depending on the characteristics of the data gaps, is proposed. Additionally, the impact of an imperfectly closing orbit (non-repeat orbit) on the gravity field model is analyzed, and a strategy to minimize the corresponding errors is presented. The applicability of the semianalytic approach also to a joint inversion of satellite-to-satellite tracking data in high-low mode (hl-SST) and satellite gravity gradiometry (SGG) observations is demonstrated, where the analysis of the former component is based on the energy conservation law. Several realistic case studies prove that the semianalytic approach is a feasible tool to generate quick-look gravity solutions, i.e. fast coefficient estimates using only partial data sets. This quick-look analysis shall be able to detect potential distortions of statistical significance (e.g. systematic errors) in the input data, and to give a fast feedback to the GOCE mission control. 相似文献
174.
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 (preconditioned
conjugate gradient method, semi-analytic approach, and distributed non-approximative adjustment), which are based on different
concepts, 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 the three methods deliver nearly identical
results—even in the case of large data gaps in the observation time series. The newly proposed distributed non-approximative
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.
Received: 17 December 2001 / Accepted: 17 July 2002
Acknowledgments. We would like to thank Prof. W.-D. Schuh, Institute of Theoretical Geodesy, University of Bonn, for providing us with the
serial version of the PCGMA algorithm, which forms the basis for the parallel PCGMA package developed at our institute. This
study was partially performed in the course of the GOCE project `From E?tv?s to mGal+', funded by the European Space Agency
(ESA) under contract No. 14287/00/NL/DC.
Correspondence to: R. Pail 相似文献
175.
Yoshiaki Ohsawa Hirofumi Kagaya Takeshi Koshizuka 《Journal of Geographical Systems》2002,4(3):325-342
When demand points are given as a planar map where projection method is explicitly stated, we usually know the latitudes
and longitudes of these points from the map. Then we can solve the Weber problem on the globe, and we do not suffer from errors.
This paper analyses how cylindrical projections cause distortion in the Weber problem when demands are distributed on the
Northern Hemisphere. First, we demonstrate that planar solutions are always located south of the spherical solution if the
Mercator projection, the equirectangular projections with standard parallels near the demands, or the equal-area projection
with the same characteristic is chosen. Second, we verify that this geographical tendency is inclined to hold when the demand
points, are distributed symmetrically, widely or toward the north.
Received: 15 August 2001 / Accepted: 20 April 2002
This paper was partially written while the first author was visiting the Department of Geography at the Catholic University
of Louvain, Louvain-la-Neuve, Belgium [1993–1994]. He is grateful for the hospitality of this department. An earlier version
of this paper was presented in 1994 at the Seventh Meeting of the European Operational Research Working Group on Locational
Analysis in Brussels, and in 1996 at the Fifth World Congress of the Regional Science Association International in Tokyo.
The authors would also like to thank the participants as well as three anonymous referees for their constructive comments. 相似文献
176.
G. Ramillien 《Journal of Geodesy》2002,76(3):139-149
A fast spherical harmonic approach enables the computation of gravitational or magnetic potential created by a non-uniform
shell of material bounded by uneven topographies. The resulting field can be evaluated outside or inside the sphere, assuming
that density of the shell varies with latitude, longitude, and radial distance. To simplify, the density (or magnetization)
source inside the sphere is assumed to be the product of a surface function and a power series expansion of the radial distance.
This formalism is applied to compute the gravity signal of a steady, dry atmosphere. It provides geoid/gravity maps at sea
level as well as satellite altitude. Results of this application agree closely with those of earlier studies, where the atmosphere
contribution to the Earth's gravity field was determined using more time-consuming methods.
Received: 14 August 2000 / Accepted: 19 March 2001 相似文献
177.
Simplified techniques for high-degree spherical harmonic synthesis are extended to include gravitational potential second
derivatives with respect to latitude.
Received: 23 July 2001 / Accepted: 12 April 2002
Acknowledgement. The authors would like to thank Christian Tscherning for recommending Laplace's equation as an accuracy test. Our use of
Legendre's differential equation, as the most direct means for extending our simplified synthesis methods to second-order
derivatives, was a direct result of this suggestion.
Correspondence to: S. A. Holmes 相似文献
178.
通过弹性球面波的势函数求得了爆炸应力波BSW模型中弹性球面波的径向应力、质点振速等的显式解析解,并据此通过数值模拟得出实际计算中将球面波按平面波近似处理的误差及该误差随爆源距离,泊松比等的变化而产生变化的曲线。分析结果表明:距离是影响误差的决定性因素;在此条件下,当距离大于2-5m时,弹性球面波即可近似按平面波处理,其误差不超过5%,当距离小于此范围时,误差较大。 相似文献
179.
推导了运用地球重力场模型计算单点、格网点以及格网平均的扰动重力梯度复组合分量的公式;提出了广义球谐函数及其定积分的新算法,并利用EGM96地球重力场模型试算了全球地区卫星轨道面上的重力梯度分量的格网平均观测值;通过对角线分量满足Laplace方程的精度,验证了该算法的有效性和实用性。 相似文献
180.