现代大地测量参考系统

概述现代大地测量参考系统的定义及不同参考系统之间的关系.主要讨论我国当代大地测量界常使用的3种用以表示几何位置的参考系统1980年国家大地坐标系、全球大地测量系统 1984 (WGS 84)、国际地球参考系统(ITRS),和一种用以表示物理位置,高程的参考系统1985年国家高程基准.并讨论大地测量中框架和基准的概念.     

台湾的地心参考系统

大地测量的基本目标之一就是要精密地确定点在地球表面上的位置，这就必须建立一个定义明确的大地基准以供大地测量观测和定位计算使用，近来，应用GPS并参照ITRF所建立的一组坐标可作为一个国家的三维地心参考系统。台湾于1997年开始建立并于1998年实现了这种基于全新概念的地心参考系统，利用GPS可有效地建立新的国家参考系统，同时这些分布好的定义明确的GPS点，还有益于方便地进行坐标系统的维护。     

CORS坐标参考框架更新探讨

CORS系统运行过程中,由于站点的相对沉降、搬迁、天线更换等原因,导致基准站/网坐标发生了明显变化,必须进行局部站点或站网更新。本文阐述了CORS坐标参考框架的更新原则、方法,针对广东省CORS改造升级过程基准站坐标变化情况,发现了引起基准站坐标变化的天线罩问题,并研究了“偏心观测量”的处理方案;研究解决了个别基准站坐标更新及基准站网坐标参考框架更新问题,保证了广东省CORS系统的持续、高精度运行及站网坐标参考框架的延续。     

现代大地测量参考系统

概述现代大地测量参考系统的定义及不同参考系统之间的关系。主要讨论我国当代大地测量界常使用的3种用以表示几何位置的参考系统－1980年国家大地坐标系、全球大地测量系统1984（WGS84）、国际地球参考系统（ITRS），和一种用以表示物理位置，高程的参考系统－1985年国家高程基准。并讨论大地测量中框架和基准的概念。     

基于多技术全球参考框架的维持及应用分析

全球基准从参与构建框架的方式来说分为长期框架和短期框架(历元框架),由于框架点运动的非线性特性,长期框架构建的基准无法描述毫米级地球表面运动,常会采用短期框架来描述。短期框架实现时严格说应该保证空基(卫星轨道)和地基(ITRF、IGS)的一致性,再者,空间大地测量技术综合框架与单一技术基准在构建和维持上同样存在差异,这些不一致都将导致地面站坐标表达的差异。不同时期长期框架维持差异性及精度也是我国框架维持需考虑的问题,该文就以上各类框架构建策略不同对实际点位的影响进行了比较分析并给出结论,供我国高精度基准建设参考。     

基于GPS卫星跟踪站的高精度单机定位精度分析

本文根据海洋８６３课题要求,就建立海陆一体大地测量控制网的基准选择、扩网方案等问题进行了探讨,并以陆地实际测量数据按所确定方案进行了数据处理和精度分析,提出适合目前条件下的海陆一体建网的作业方案。     

参考框架、坐标变换和地壳运动

讨论参考框架、坐标变换和地壳运动的关系,说明主要由于地壳运动使得参考框架的问题变得十分复杂,而只有通过连续观测,如GPS等连续观测,和对地壳运动的观测与深入研究,才能有效地维持参考框架。简要介绍ITRF(国际地球参考框架)框架的发展与现状,介绍层次不同的三种ITRF2000框架和时空效果不同的三种参考框架,说明这些框架之间的关系。相似变换不仅用于坐标变换,还用于研究不同参考框架(或位移基准)下的相对运动,特别是区域内的相对运动。由于地壳水平和垂直运动有不同的特点,在研究相对运动时应分别作相似变换处理。坐标变换也必须考虑地壳水平和垂直运动的不同特点,分别作变换,以避免垂直运动对水平坐标分量的影响,使得到的坐标变换参数有时效性。建立GNNS等连续观测站是维持参考框架的最有效途径。     

基于GPS卫星跟踪站的高精度单机定位精度分析

本文根据海洋８６３课题要求,就建立海陆一体大地测量控制网的基准选择、扩网方案等问题进行了探讨,并以陆地实际测量数据按所确定方案进行了数据处理和精度分析,提出适合目前条件下的海陆一体建网的作业方案。     

空间数据基础设施中的坐标参考框架

论述了坐标参考框架在空间数据基础设施中的作用和职责，作为该领域的新动向，介绍了美国和加拿大近年实施的国家空间参考系计划。在分析我国坐标参考框架现状的基础上，提出了当前要着重解决的几个问题。     

国际大地测量参考框架技术进展

结合2007年7月意大利佩鲁贾(Perugia)第24届IUGG大会上世界各国科学家在国际大地测量参考框架方面的学术交流,全面回顾了自2003年以来全球参考框架领域的技术进展。具体针对全球参考框架,欧洲、北美、非洲等区域参考框架的技术进展,详细介绍了过去四年里世界各国在地心参考框架和全球垂直参考系统等方面所做的工作,对我国开展大地测量参考框架领域的研究具有非常重要的参考价值。     

日本大地基准及其现代化的思考

介绍了日本曾采用了百余年的大地基准TD1918,阐述了它不能适应当前日本的经济、社会和军事发展的需求,日本于2002年开始采用新的地心三维大地基准JGD2000.概要介绍了JGD2000大地系统的定义及其框架,最后给出了这两个新老大地基准的转换.     

地球参考标架和动态地球

本文首先对天球参考标架和地球参考标架作了一般叙述。其次较详细地说明地球参考标架究竟是什么,它是如何形成的,直到现在它的发展情况。最后说明了地球参考标架在有关学科中的应用。     

New global positioning system reference station in Brazil

Co-located very long baseline interferometry (VLBI) and global positioning system (GPS) reference stations were installed near Fortaleza, Brazil, in 1993. Both have been important in the realization and maintenance of the International Terrestrial Reference Frame. A new-generation GPS system was installed in 2005 to replace the original station. Experience gained in the prior 12 years was used to improve the design of the GPS antenna mount. Preliminary indications are greatly improved data quality from the new station. Simultaneous observations from the nearly half-year of overlapping operation have been used to determine the local tie between the new and old GPS reference points to about 1 mm accuracy. This can be used to update the 1993 survey tie between the original GPS and the VLBI points, although there are questions about the accuracy of that measurement based on a comparison with space geodetic data. A test of removing the conical radome over the old GPS antenna indicates that it has biased the station height by about 16 mm downward, which probably accounts for most of the previous survey discrepancy.     

多普勒系统对历元地球参考框架的影响研究

针对历元地球参考框架在确定站点高频非线性运动和季节性变化方面具有国际地球参考框架不具备的优势问题,该文通过比较两种技术间组合策略建立的多源融合历元地球参考框架的精度,研究DORIS对于多源融合历元地球参考框架的影响。通过基于坐标的法方程叠加方法进行技术内法方程叠加和技术间组合,并利用并置站条件联系不同技术的法方程,从而建立多源融合历元地球参考框架。结果表明,DORIS的引入并不会对多源融合历元地球参考框架的基准定义或其他3种技术站点的点位精度产生较大的影响,同时能够体现4种技术中精度较差的DORIS对于ETRF的精度及稳定性的影响。     

EPN coordinate time series monitoring for reference frame maintenance

The EUREF permanent network (EPN) is a network of continuously operating global navigation satellite system (GNSS) stations, primarily installed for reference frame maintenance. In order to ensure the long term reliability of the EPN products, a thorough station performance monitoring has been initiated and carried out in addition to the routine GNSS data management, processing and analysis. This paper addresses the main factors influencing the quality of the coordinate time series in a permanent GNSS network. Relevant examples, based on the EPN experience are given, the analysis strategy is introduced, the estimated coordinate offsets are published and the importance of this analysis for site velocity estimation is demonstrated. The results are derived from the analysis of the EPN weekly combined solutions covering the period from 1996 to 2003. Our target is the identification, interpretation and elimination of offsets and outliers present in the EPN coordinate time series in order to estimate reliable coordinates and velocities and consequently maintain a high quality kinematic reference network.

Effect of the selection of reference radio sources on geodetic estimates from VLBI observations

This paper evaluates the effect of the accuracy of reference radio sources on the daily estimates of station positions, nutation angle offsets, and the estimated site coordinates determined by very long baseline interferometry (VLBI), which are used for the realization of the international terrestrial reference frame (ITRF). Five global VLBI solutions, based on VLBI data collected between 1979 and 2006, are compared. The reference solution comprises all observed radio sources, which are treated as global parameters. Four other solutions, comprising different sub-sets of radio sources, were computed. The daily station positions for all VLBI sites and the corrections to the nutation offset angles were estimated for these five solutions. The solution statistics are mainly affected by the positional instabilities of reference radio sources, whereas the instabilities of geodetic and astrometric time-series are caused by an insufficient number of observed reference radio sources. A mean offset of the three positional components (Up, North, East) between any two solutions was calculated for each VLBI site. From a comparison of the geodetic results, no significant discrepancies between the respective geodetic solutions for all VLBI sites in the Northern Hemisphere were found. In contrast, the Southern Hemisphere sites were more sensitive to the selected set of reference radio sources. The largest estimated mean offset of the vertical component between two solutions for the Australian VLBI site at Hobart was 4 mm. In the worst case (if a weak VLBI network observed a limited number of reference radio sources) the daily offsets of the estimated height component at Hobart exceeded 100 mm. The exclusion of the extended radio sources from the list of reference sources improved the solution statistics and made the geodetic and astrometric time-series more consistent. The problem with the large Hobart height component offset is magnified by a comparatively small number of observations due to the low slewing rate of the VLBI dish (1°/ s). Unless a minimum of 200 scans are performed per 24-h VLBI experiment, the daily vertical positions at Hobart do not achieve 10 mm accuracy. Improving the slew rate at Hobart and/or having an increased number of new sites in the Southern Hemisphere is essential for further improvement of geodetic VLBI results for Southern Hemisphere sites.     

地球参考框架联合解算方法

地球参考框架是地球坐标系统的实现,本文系统介绍了地球参考框架的确定方法,结合ITRF2005参考框架,详细介绍了地球参考框架联合解算的方法,并对地球参考框架的质量分析方法进行了探讨。