空间技术实现地心坐标的精度检测与分析

为评价GPS、VLBI、SLR三种空间技术确定地心坐标的实现精度,选择使用三种技术并置站上的坐标数据,在经历元统一、偏心改正和七参数转换之后,计算了这三种技术实现的参考架的转换参数,得到了任意两种技术地心坐标不符值的加权中误差,以此作为外符精度。经分析可知VLBI与GPS实现的地心坐标比SLR高一些,可达到毫米级。     

国际地球参考框架ITRF2020的定义和实现

国际地球参考框架(ITRF)是目前理论背景最完善、构建方法最全面、实现精度最高的全球地心基准,也是世界各国在建立区域地心基准时的重要参考。给出了国际地球自转与参考系统服务组织(IERS)最新发布的ITRF2020的理论定义,重点讨论了各专业技术组织提供的数据资源和计算模型,以及IERS在数据整合时的处理策略,并对基于震后形变(PSD)模型的位置计算进行了讨论,给出了相对于ITRF2014的改进和转换参数。ITRF2020首次区分了地球的质量中心和形状中心,并考虑了PSD模型的季节性信号,提高了坐标框架精度,为地球科学研究和应用提供了统一基准,对精化和维持我国地心参考框架具有重要参考意义。     

GPS测量中偏心距较大时的归心改正计算方法

在分析规范中GPS归心改正计算公式的基础上,考虑地球弯曲差等因素的影响,推导出了偏心距较大时GPS归心改正计算的严密公式.采用该公式计算了多组实验数据,并与采用规范公式和严密导线平差的计算结果进行了比较.结果表明,偏心距较大时,采用该公式的计算精度远远高于规范公式,在1 500m以内可以达到严密导线平差的精度水平.     

最新国际地球参考框架ITRF2014的分析与评述

介绍ITRF2014的定义、测站分布、输入数据、分析策略以及与ITRF2008的转换参数,并分析ITRF2014相对于ITRF2008的改进。ITRF2014是国际地球参考框架ITRF的最近一次更新,它是基于四种空间大地测量技术(VLBI、SLR、GNSS和DORIS)重新处理解实现的。相较于ITRF2008,ITRF2014不仅在观测数据和测站数量上有所增加,还改善了对非线性运动的处理,包括对周期性信号的估计以及对震后形变(post-seismic deformation,PSD)的改正,并提供了PSD模型和地球质心运动模型两个新产品。ITRF2014为地球科学等相关领域的研究与应用提供了统一的空间基准,也为其他坐标框架的维持与精化提供了参考。     

利用伪卫星技术提高GPS定位质量的方法

差分GPS定位(DGPS)可显著提高GPS导航、定位的精度。但在卫星几何分布图形不良或个别方向卫星信号失锁的情况下,DGPS将失去其作用。若将发布差分改正信息的基准站看成伪GPS卫星(简称伪卫星),则可极大地改善差分定位的精度。本文结合国外的试验成果,将这一技术作一介绍,可对我国建立海上差分GPS观测模式时参考。     

RTK布设高精度控制点的可行性分析

GPS RTK可以实时获取流动站的坐标,但无法确定点位坐标精度的可靠性。利用高精度基线检定场对RTK测量成果的精度估计进行了研究,证明在具备高等级已知点位成果时RTK测量可用于获取较高精度的控制点。     

GAMIT软件中不同星历对GPS/BDS数据定位的影响

为掌握星历误差对GAMIT软件解算GPS/BDS数据定位的影响,选取不同精密星历分析长基线和短基线条件下,获得基线解算精度和点位坐标精度,结果表明:①不同的精密星历对GPS解算和短基线的BDS解算影响不大,可采用超快速精密星历;②对于长基线的BDS解算,要顾及北斗参考站数据的质量以及站间的兼容性和空间位置,需要调整站点...     

起算点精度对GPS基线解算质量的影响

基线处理时要求知道一个点的坐标,其精度对GPS基线的解算结果有影响。采用实测数据研究起算点精度对GPS基线解算质量的影响,得出了其影响规律,同时给出了提高起算点精度的方法。     

两种电离层延迟改正方法的对比研究

从模型改正法和双频改正法两个方面阐述了目前对于在GPS数据处理中关于电离层延迟改正的两种思路,主要整理了Klobuchar模型的解算步骤,给出了双频改正的具体方法。并结合实测数据,分别用这两种方法对电离层延迟进行改正,然后与不用任何方法改正的解算结果进行比较,通过对比这两种方法对电离层延迟的改正效果,得出有益的结论。     

WGS—84与BJZ54两坐标系转换参数的精度

随着我国GPS一级网的成功建立及GPS二级网工作的顺利展开,建立我国高精度地心坐标系统的条件已日臻成熟。目前为了满足某些工程测量的需要,利用现有的全国高精度GPS一级网及天文大地网资料,求得了WGS—84坐标系与BJZ54坐标系(整体平差转换值)的转换参数,该转换参数的出现,已引起有关专家及应用部门的关注。     

Absolute Calibration of the Jason-1 Altimeter Using UK Tide Gauges

This article describes an “absolute” calibration of Jason-1 (J-1) altimeter sea surface height bias using a method developed for TOPEX/Poseidon (T/P) bias determination reported previously. The method makes use of U.K. tide gauges equipped with Global Positioning System (GPS) receivers to measure sea surface heights at the same time, and in the same geocentric reference frame, as Jason-1 altimetric heights recorded in the nearby ocean. The main time-dependent components of the observed altimeter-minus-gauge height-difference time series are due to the slightly different ocean tides at the gauge and in the ocean. The main harmonic coefficients of the tide differences are calculated from analysis of the copious TOPEX data set and then applied to the determination of T, P, and J-1 bias in turn. Datum connections between the tide gauge and altimetric sea surface heights are made by means of precise, local geoid differences from the EGG97 model. By these means, we have estimated Jason-1 altimeter bias determined from Geophysical Data Record (GDR) data for cycles 1–61 to be 12.9 cm, with an accuracy estimated to be approximately 3 cm on the basis of our earlier work. This J-1 bias value is in close agreement with those determined by other groups, which provides a further confirmation of the validity of our method and of its potential for application in other parts of the world where suitable tide gauge, GPS, and geoid information exist.     

基于单组广播星历的GPS卫星在轨位置的拟合计算

对只接收到一组GPS卫星广播星历的情况下应用广播星历拟合计算卫星在轨位置的方法进行了研究,通过与精密星历进行比较,对拟合计算的精度进行了说明。     

Fast BDS Positioning Convergence Based on the Contribution of GPS Observations

Comparing to single BeiDou Navigation Satellite System (BDS) Precise Point Positioning (PPP), a method which can more quicklydetermine the ambiguity parameters of BDS through applying the contribution of GPS observations is proposed and analyzed in this article. The numerical examples and analysis show that the ionosphere-free ambiguities of BDS satellites can be determined and converged more quickly because of the contribution of GPS observations. The average improvement of the convergent speed of positioning is 18.5% and its positioning accuracy in N, E, and U components are improved by 29.4, 30.3, and 34.4%, respectively, with the contribution of the a priori coordinates obtained from GPS observations. This method is useful for single BDS system positioning when there is a priori information provided by GPS or other sensors which be replaced by and can be applied at the beginning of the computation.     

GPS positioning accuracy using precise real‐time ephemeris and clock correction

Global positioning system (GPS) has found applications in various areas including marine geodesy. GPS positioning accuracy, however, is greatly degraded by GPS ephemeris and clock errors, particularly errors due to Selective Availability (SA). Thus, it is crucial to use precise ephemeris and clock corrections for users who require high position accuracy. Presently, precise ephemeris and clock corrections are available only in post‐mission. This paper investigates the generation of precise real‐time ephemeris and clock corrections and the positioning accuracy using them. In this research, precise real‐time ephemeris is generated from accurate dynamic orbit prediction and clock corrections are calculated using instantaneous GPS measurements. Numerical analysis using data from an actual GPS tracking network is performed that indicates use of precise ephemeris and clock corrections can improve the positioning accuracy to the one meter level. This accuracy is attainable in real‐time as the precise real‐time ephemeris and clock corrections become available in the future.     

Absolute Calibration of the Jason-1 Altimeter Using UK Tide Gauges

This article describes an “absolute” calibration of Jason-1 (J-1) altimeter sea surface height bias using a method developed for TOPEX/Poseidon (T/P) bias determination reported previously. The method makes use of U.K. tide gauges equipped with Global Positioning System (GPS) receivers to measure sea surface heights at the same time, and in the same geocentric reference frame, as Jason-1 altimetric heights recorded in the nearby ocean. The main time-dependent components of the observed altimeter-minus-gauge height-difference time series are due to the slightly different ocean tides at the gauge and in the ocean. The main harmonic coefficients of the tide differences are calculated from analysis of the copious TOPEX data set and then applied to the determination of T, P, and J-1 bias in turn. Datum connections between the tide gauge and altimetric sea surface heights are made by means of precise, local geoid differences from the EGG97 model. By these means, we have estimated Jason-1 altimeter bias determined from Geophysical Data Record (GDR) data for cycles 1-61 to be 12.9 cm, with an accuracy estimated to be approximately 3 cm on the basis of our earlier work. This J-1 bias value is in close agreement with those determined by other groups, which provides a further confirmation of the validity of our method and of its potential for application in other parts of the world where suitable tide gauge, GPS, and geoid information exist.     

航天测量船坞内标校基准计算的新方法

GPS测量直接获得点位的精确三维坐标,通过空间直角坐标系、大地坐标系、站心地平直角坐标系、站心极坐标系等一系列转换,再加入大气折光差改正和垂线偏差改正,就可以快速获得设备标校所需的精确基准。与采用常规测量方法、分别计算设备标校基准相比,不仅大大减少了工作量,还提高了计算结果的精度。     

利用JPL行星/月球星历计算遥感水汽中的地球固体潮改正

简要介绍GPS遥感水汽的原理,详细讨论了计算地球固体潮改正模型的理论公式。介绍获取JPL星历的方法,以及如何利用JPL行星/月球星历来计算太阳和月亮的坐标,并逐步计算出地球固体潮改正。举例计算了地球固体潮改正,分析了其对水汽的影响,比较了太阳距离、月亮距离与地球固体潮改正的关系。     

远海航渡式水深测量水位改正方法研究

针对远海航渡式水深测量作业中的潮汐改正难题,基于全球潮汐场DTU10模型及GPS无验潮测深两种改正模式,通过潮汐场预报精度评估、验潮站实测数据比对分析以及GPS大地高计算潮汐值等多种手段,开展了大范围、长时段、单测线情况下水深测量水位改正研究,形成了一套适用性强的航渡水深测量水位改正方法与流程,为面向全球的海洋水深测量资料处理提供了潮汐、垂直基准和水位归算的方法和技术支持。