全国天文大地网与空间大地网联合平差

天文大地网与空间大地网联合平差,对于检核、控制与加强天文大地网以及建立与扩展地心坐标系,都具有重要意义,全国天文大地网与全国ＧＰＳ大地网联合平差（Ｉ期）于１９９８年初完成,本文报告平差采用的原则和模型,并提出平差结果,通过联合平差,消除了天文大地网尺度的系统偏差,减弱了它的局部变形,改善了它的整体精度,更重要的是建立了由近５万个大地点坐标体现的地心参考系,其地心坐标的水平分量精度好于０．５ｍ。     

GPS高程拟合在地籍测量中的应用

在一般的地形测量中,GPS测量已成为获得点的平面坐标的最主要的方法。但是,GPS 3维坐标中测得的大地高未能在生产实际中发挥应有的作用。因此,需将GPS大地高转换成正常高。本文在实地的地形测量中,根据已有点的高程数据和联测的GPS高程数据,采用等值线图示法和平面拟合法对测区内进行GPS高程拟合,并对两种方法的拟合精度进行比较。最终认为在平坦地区等值线图示法要比平面拟合法更好些。     

ITRF2008框架下VLBI与GPS确定地心坐标的精度分析

为了解ITRF2008框架下VLBI和GPS两种空间技术确定地心坐标的真正实现精度,在并置站上对VLBI和GPS两种空间技术测定的地心坐标进行了比较,经过偏心改正和七参数转换之后,得到两种空间技术地心坐标不符值的加权中误差,其可以认为是这两种空间技术的真正实现精度,经比较分析这两种地心坐标三个坐标轴方向分量的外符精度都在10mm之内,说明VLBI和GPS确定的地心坐标精度已达到毫米级。     

基于克里金法的深圳似大地水准面插值研究

地面点的正常高可以通过GPS技术结合高精度、高分辨率的似大地水准面模型获得,以代替劳动强度大效率低的传统水准(或高程)测量。影响精度的因素有两个:GPS点大地高的测量精度和该点内插高程异常的精度。本文主要针对深圳市1km格网似大地水准面数据,利用克里金法内插拟合高程异常值,用实例说明克里金法在深圳市似大地水准面的应用中可以满足大比例尺数字化测图的需要。     

广阔范围内GPS网坐标系统转换模型的建立及精度分析

全球定位系统(GPS)技术己经在许多领域得到广泛的应用,由于GPS定位得到的观测成果通常是世界大地坐标系统WGS-84中的坐标或坐标差,但在实际应用中上需要的往往是地面点在国家坐标系或地方独立坐标系中的坐标.确立坐标系统转换模型并分析此模型的精度,根据至少3个公共点的两套大地坐标利用最小二乘法原理求出转换参数.本文以W...     

Mutual validation of GNSS height measurements and high-precision geometric-astronomical leveling

The method of geometric-astronomical leveling is presented as a suited technique for the validation of GNSS (Global Navigation Satellite System) heights. In geometric-astronomical leveling, the ellipsoidal height differences are obtained by combining conventional spirit leveling and astronomical leveling. Astronomical leveling with recently developed digital zenith camera systems is capable of providing the geometry of equipotential surfaces of the gravity field accurate to a few 0.1 mm per km. This is comparable to the accuracy of spirit leveling. Consequently, geometric-astronomical leveling yields accurate ellipsoidal height differences that may serve as an independent check on GNSS height measurements at local scales. A test was performed in a local geodetic network near Hanover. GPS observations were simultaneously carried out at five stations over a time span of 48 h and processed considering state-of-the-art techniques and sophisticated new approaches to reduce station-dependent errors. The comparison of GPS height differences with those from geometric-astronomical leveling shows a promising agreement of some millimeters. The experiment indicates the currently achievable accuracy level of GPS height measurements and demonstrates the practical applicability of the proposed approach for the validation of GNSS height measurements as well as the evaluation of GNSS height processing strategies.     

GPS测量坐标转换实用性问题的分析

针对ＧＰＳ测量坐标转换方法中存在的问题,提出了强制符合平面四参数法和多项式拟合法,这两种方法能够有效的克服高程系统以及椭球参数不一致造成的误差,比较适合于工程自由坐标之间的转换;同时本文给出了基于“全球大地水准面的几何中心地球质心相重合”这一假设之上的莫洛金斯坐标转换法,该法不需要联测公共点即可将ＷＧＳ－８４坐标转换成本地局部坐标。上述几种方法减少了额外联测的工作量,提高了ＧＰＳ的使用效率。     

A comparative analysis of GPS range,Doppler and interferometric observations for geodetic positioning

Geodetic positioning accuracies obtained from range, integrated Doppler and double differenced interferometric phase observations from a constellation of twenty-four Global Positioning System satellites are presented. It is demonstrated that GPS range and Doppler observations will provide sufficient accuracy for the estimation of geodetic coordinates. However the instability of the receiver atomic oscillator will limit the usefulness of these observations in providing rapid first-order baseline determination. Interferometric phase measurements twice differenced to eliminate clock error appear as an alternate procedure for providing such accuracies.     

我国建立现代大地基准的思考

提出了现代大地基准要考虑和顾及高精度、涵盖全部国土、三维、地心、动态、国际接轨等6个要素。建议在国家GPS2000网的基础上，进一步加密GPS网点和永外性跟踪站，构建有足够数量和密度合理分布的新的大地坐标框架点。现代大地基准应为用户在我国任何地点、任何时间测定高精度的三维地心坐标提供可靠的地理空间基础框架。     

GPS常用水准方法研究及精度分析

GPS全球定位系统是随着现代科技发展而建立起来的高精密卫星导航定位系统。GPS测量具有很多传统测量方式所不具备的优点,如无须通视、高精度、全天候、操作简便、自动化高等,因此GPS测量可以极大地提高生产效率。水准测量是GPS应用的一个重要方面,用水准拟合方法将GPS测量所得到的大地高转化为我国所通用的正常高已经成为我国GPS研究的重要方面。本文通过实验来比较GPS水准不同的拟合方法和拟合点的分布对GPS水准面拟合精度的影响。     

Precise Point Positioning Using IGS Orbit and Clock Products

The contribution details a post-processing approach that used undifferentiated dual-frequency pseudorange and carrier phase observations along with IGS procise orbit products, for stand-alone precise geodetic point positioning (static or kinematic) with cm precision. This is possible if one takes advantage of the satellite clock estimates available with the satellite coordinates in the IGS precise orbit products and models systematic effects that cause cm variations in the satelite to user range. This paper will describe the approach, summarize the adjustment procedure, and specify the earth- and space-based models that must be implementetd to achieve cm-level positioning in static mode. Furthermore, station tropospheric zenth path delays with cm precision and GPS receiver clock estimates procise to 0.1 ns are also obtained. ? 2001 John Wiley & Sons, Inc.     

南宁CORS系统基准站地心大地坐标精确测定的方法与实践

采用地心坐标系已成为国际测量界的总趋势,而利用GPS连续运行参考站建立地心坐标框架最为普遍。利用GAM IT软件,采用有基准算法对南宁市全球导航连续运行参考站网络系统(NNCORS)的南宁基准站NANN的观测资料进行了归算,结果表明该基准站观测资料的质量是可靠的,并获得了该站在ITRF2000中毫米级精度的地心大地坐标。     

基于区域与分区拟合似大地水准面方法研究

与传统测量方式比较,全球定位系统(global positioning system,GPS)测量具有定位精度高、测量时间短、操作简单、全天候作业等优势,利用GPS观测得到的大地高拟合成正常高可以大大提高测绘效率。研究了二次曲面法拟合似大地水准面模型,以豫北某区域为研究区,分别作整体区域二次曲面拟合和分区二次曲面拟合,并进行精度分析,结论如下:通过提高GPS测量的大地高精度和选用高精度的联测水准点,能够有效提高拟合后的高程精度;测区面积较大和测区地形起伏较大时,采用分区拟合高程的精度相对于整体区域拟合的精度会大大提高。     

清远市清城区似大地水准面的精密确定

利用GPS技术可获得精度优于1 cm的大地高,若能够获得相应点的高精度似大地水准面(高程异常),则可将大地高转换为相应精度的正常高,从而代替相应等级的水准测量.文中介绍了清远市清城区似大地水准面的计算方法,并对计算结果进行了分析和评价.结果表明,清远市清城区1 km格网似大地水准面的精度为1.3 cm.     

利用北斗系统建立和维持国家大地坐标参考框架的方法研究

2000中国大地坐标系统（China Geodetic Coordinate System 2000,CGCS2000）的建立和维持主要依赖于GPS技术,不利于保障国家时空信息安全。中国北斗卫星导航系统（BeiDou navigation satellite system,BDS）提供亚太区域服务,可满足中国及周边地区高精度定位导航应用需求,对建立和维持国家大地坐标参考框架具有重要意义。研究利用已建成的北斗基准站网观测数据,实现基于BDS技术、并与国际地球参考框架（International Terrestrial Reference Frame,ITRF）一致的国家大地坐标参考框架,为今后国家级和全球性北斗坐标参考框架（BeiDou Terrestrial Reference Frame,BTRF）的建立和维持提供理论基础和方法支撑。初步计算结果表明,积累2 a以上的观测数据,利用单独BDS数据可以获得与GPS精度相当的水平速度场,精度约为2~3 mm/a。基于单独BDS数据,测站残差平面和高程的重复性分别可优于0.8 cm和1.7 cm。利用BDS数据已可监测到测站高程方向的季节性变化。此外,还对单独BDS与GPS数据计算的坐标可能存在的与经纬度相关的系统误差进行了分析。总体来说,目前的北斗系统可满足建立和维持中国cm级大地坐标框架的需求。     

星载BDS/GPS低轨卫星定轨精度分析

针对低轨卫星搭载BDS/GPS接收机实现定轨将成为定轨领域热点的现状,该文讨论了基于星载BDS/GPS实时定轨和精密定轨需要考虑的数学模型,阐述了实时定轨和精密定轨的模型差异。基于自主研发程序,利用高动态信号仿真器仿真的星载BDS/GPS数据研究了基于星载BDS/GPS实时定轨和精密定轨的可行性及其能达到的精度。试验结果表明,星载BDS/GPS实时定轨位置精度为1.19m,速度精度为2.35mm/s。GPS信号发生中断时即仅采用BDS观测数据进行实时定轨时,三维位置误差达到3.73m;星载BDS/GPS精密定轨位置精度为2.30cm,仅采用BDS观测数据进行精密定轨时,三维位置误差可达到8.26cm。     

Adjustment of geodetic measurements with mixed multiplicative and additive random errors

Adjustment has been based on the assumption that random errors of measurements are added to functional models. In geodetic practice, we know that accuracy formulae of modern geodetic measurements often consist of two parts: one proportional to the measured quantity and the other constant. From the statistical point of view, such measurements are of mixed multiplicative and additive random errors. However, almost no adjustment has been developed to strictly address geodetic data contaminated by mixed multiplicative and additive random errors from the statistical point of view. We systematically develop adjustment methods for geodetic data contaminated with multiplicative and additive errors. More precisely, we discuss the ordinary least squares (LS) and weighted LS methods and extend the bias-corrected weighted LS method of Xu and Shimada (Commun Stat B29:83–96, 2000) to the case of mixed multiplicative and additive random errors. The first order approximation of accuracy for all these three methods is derived. We derive the biases of weighted LS estimates. The three methods are then demonstrated and compared with a synthetic example of surface interpolation. The bias-corrected weighted LS estimate is unbiased up to the second order approximation and is of the best accuracy. Although the LS method can warrant an unbiased estimate for a linear model with multiplicative and additive errors, it is less accurate and always produces a very poor estimate of the variance of unit weight.     

矢量GIS图上地理曲线的定位误差模型

为了分析ＧＩＳ图上地理曲线的定位精度,首先探讨地理曲线的表达与定位误差,区分“数字曲线”和“连续曲线”两个概念;然后结合由数字曲线生成连续曲线的ＧＩＳ算法,建立连续曲线的误差带模型,并导出地理曲线长度的误差估计公式;最后通过算例说明地理曲线误差带的可视化方法和曲线长度误差估计公式的应用。     

Reducing the draconitic errors in GNSS geodetic products

Systematic errors at harmonics of the GPS draconitic year have been found in diverse GPS-derived geodetic products like the geocenter $Z$ -component, station coordinates, $Y$ -pole rate and orbits (i.e. orbit overlaps). The GPS draconitic year is the repeat period of the GPS constellation w.r.t. the Sun which is about 351 days. Different error sources have been proposed which could generate these spurious signals at the draconitic harmonics. In this study, we focus on one of these error sources, namely the radiation pressure orbit modeling deficiencies. For this purpose, three GPS+GLONASS solutions of 8 years (2004–2011) were computed which differ only in the solar radiation pressure (SRP) and satellite attitude models. The models employed in the solutions are: (1) the CODE (5-parameter) radiation pressure model widely used within the International GNSS Service community, (2) the adjustable box-wing model for SRP impacting GPS (and GLONASS) satellites, and (3) the adjustable box-wing model upgraded to use non-nominal yaw attitude, specially for satellites in eclipse seasons. When comparing the first solution with the third one we achieved the following in the GNSS geodetic products. Orbits: the draconitic errors in the orbit overlaps are reduced for the GPS satellites in all the harmonics on average 46, 38 and 57 % for the radial, along-track and cross-track components, while for GLONASS satellites they are mainly reduced in the cross-track component by 39 %. Geocenter $Z$ -component: all the odd draconitic harmonics found when the CODE model is used show a very important reduction (almost disappearing with a 92 % average reduction) with the new radiation pressure models. Earth orientation parameters: the draconitic errors are reduced for the $X$ -pole rate and especially for the $Y$ -pole rate by 24 and 50 % respectively. Station coordinates: all the draconitic harmonics (except the 2nd harmonic in the North component) are reduced in the North, East and Height components, with average reductions of 41, 39 and 35 % respectively. This shows, that part of the draconitic errors currently found in GNSS geodetic products are definitely induced by the CODE radiation pressure orbit modeling deficiencies.     

GPS在精密高程测量中的运用

全球卫星定位系统GPS是具有全球性、全天候、全能性优势的导航定位系统，其可以提供三维坐标的优越性目前还未能得到充分发挥。分析了GPS高程测量中影响精度的主要因素，以及解决这些影响的一些方法；在GPS高程转换为正常的过程中，介绍两种转换方法即加权平均法和平差转换法；提出了提高GPS高程测量精度必须注意的几个方面。