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131.
GIS中直线元内插点精度及对误差带的影响 总被引:1,自引:0,他引:1
基于误差传播定律,考虑参数r误差影响,推导了线元内插点的精度计算公式,讨论内插点精度对线元误差带的影响,并对影响的结果进行了分析,得到了一些有益的结论。 相似文献
132.
基于点重要度的地形LOD简化算法及精度 总被引:1,自引:0,他引:1
在分析、讨论目前关于3维地形模型简化与误差控制方法的基础上,提出了一种基于点重要度进行连续LOD模型简化的算法.并以5种典型地貌的实验数据作为运行实例,给出了点重要度与地貌类型之间的精度关系.这为今后连续LOD模型的合理建立提供了一种新思路和方法,也为模型的简化提供了科学依据. 相似文献
133.
基于MPI的机群并行计算系统平台构建 总被引:4,自引:1,他引:4
在高性能计算机领域,机群并行系统已成为一种重要的系统结构。这里介绍了机群并行系统的特点和发展现状;给出了将PC机或工作站通过高速以太网连接,使用TCP/IP作为标准的通信协议,利用MPI作为分布式的并行计算软件环境,在Windows平台和Unix平台上搭建用户自己的PC机群系统的两种方法;还给出了MPI安装中需要注意的关键步骤。实践表明,PC机群系统具有高性能、高可用性和极高的性价比。 相似文献
134.
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136.
The analysis of the time and space distribution of specular (reflecting) points in bistatic altimetry between GPS and CHAMP
satellites or SAC-C (taken as examples) is extended from Wagner and Klokočník (2003 J. Geod 77: 128–138). We demonstrate a
significantly higher number and density of reflecting points in bistatic altimetry in comparison with traditional monostatic
altimetry. After an outline of our older accuracy assessment for the vertical position of the reflecting point, we add a new
independent derivation and compare both approaches. We account for orbit errors of both the transmitters (GPS) and receiver
(CHAMP) satellites, and the measurement (delay) error. We found that the accuracy of the vertical position of the reflecting
point decreases only slowly with increasing off-nadir angle and that the orbit errors must be accounted for if decimeter and
better accuracy is required. In this paper, we do not study errors such as state of the ocean, technical parameters of the
receiving system, and atmospheric corrections. 相似文献
137.
Daniel G. Brown Rick Riolo Derek T. Robinson Michael North William Rand 《Journal of Geographical Systems》2005,7(1):25-47
The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, we identify four key relationships affecting how geographic data (fields and objects) and agent-based process models can interact: identity, causal, temporal and topological. We discuss approaches to implementing tight integration, focusing on a middleware approach that links existing GIS and ABM development platforms, and illustrate the need and approaches with example agent-based models. 相似文献
138.
R. Pail 《Journal of Geodesy》2005,79(4-5):231-241
In the recent design of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission, the gravity gradients are defined in the gradiometer reference frame (GRF), which deviates from the actual flight direction (local orbit reference frame, LORF) by up to 3–4°. The main objective of this paper is to investigate the effect of uncertainties in the knowledge of the gradiometer orientation due to attitude reconstitution errors on the gravity field solution. In the framework of several numerical simulations, which are based on a realistic mission configuration, different scenarios are investigated, to provide the accuracy requirements of the orientation information. It turns out that orientation errors have to be seriously considered, because they may represent a significant error component of the gravity field solution. While in a realistic mission scenario (colored gradiometer noise) the gravity field solutions are quite insensitive to small orientation biases, random noise applied to the attitude information can have a considerable impact on the accuracy of the resolved gravity field models. 相似文献
139.
B. Tapley J. Ries S. Bettadpur D. Chambers M. Cheng F. Condi B. Gunter Z. Kang P. Nagel R. Pastor T. Pekker S. Poole F. Wang 《Journal of Geodesy》2005,79(8):467-478
A new generation of Earth gravity field models called GGM02 are derived using approximately 14 months of data spanning from
April 2002 to December 2003 from the Gravity Recovery And Climate Experiment (GRACE). Relative to the preceding generation,
GGM01, there have been improvements to the data products, the gravity estimation methods and the background models. Based
on the calibrated covariances, GGM02 (both the GRACE-only model GGM02S and the combination model GGM02C) represents an improvement
greater than a factor of two over the previous GGM01 models. Error estimates indicate a cumulative error less than 1 cm geoid
height to spherical harmonic degree 70, which can be said to have met the GRACE minimum mission goals.
Electronic Supplementary Material Supplementary material is available in the online version of this article at 相似文献
140.
The problem of “global height datum unification” is solved in the gravity potential space based on: (1) high-resolution local
gravity field modeling, (2) geocentric coordinates of the reference benchmark, and (3) a known value of the geoid’s potential.
The high-resolution local gravity field model is derived based on a solution of the fixed-free two-boundary-value problem
of the Earth’s gravity field using (a) potential difference values (from precise leveling), (b) modulus of the gravity vector
(from gravimetry), (c) astronomical longitude and latitude (from geodetic astronomy and/or combination of (GNSS) Global Navigation
Satellite System observations with total station measurements), (d) and satellite altimetry. Knowing the height of the reference
benchmark in the national height system and its geocentric GNSS coordinates, and using the derived high-resolution local gravity
field model, the gravity potential value of the zero point of the height system is computed. The difference between the derived
gravity potential value of the zero point of the height system and the geoid’s potential value is computed. This potential
difference gives the offset of the zero point of the height system from geoid in the “potential space”, which is transferred
into “geometry space” using the transformation formula derived in this paper. The method was applied to the computation of
the offset of the zero point of the Iranian height datum from the geoid’s potential value W
0=62636855.8 m2/s2. According to the geometry space computations, the height datum of Iran is 0.09 m below the geoid. 相似文献