A multipath reduction algorithm based on GPS/BDS measurement is proposed in this paper.With pseudorange and Doppler observations of BDS/BDS,the availability of observations is enhanced.In addition,combined with the robust adaptive Kalman filter,the multipath errors caused by high buildings in urban areas can be efficiently reduced and thus the accuracy and reliability of satellite navigation is improved.Results from a car driving test show that position error is reduced from 4.9 m to 4.3 m with GPS and GPS/BDS point positioning respectively.When the robust filter method is adopted,the position error has been further reduced from 4.3 m to 3.4 m.

As one significant error source,the receiver antenna and GPS satellite antenna PCO/PCV must be corrected in high accuracy data processing.In this paper,the influence of receiver antenna and GPS satellite antenna PCO/PCV is analyzed for baseline processing.The result shows that the effects of receiver antenna PCO/PCV for long and very long baseline in components and length can reach 101mm.The effects of satellite antenna PCO/PCV for long baseline in components and length are in millimeter level,the maximum is less than 4mm,for very long baseline,the effects in components and length can reach 40mm.

In the generalised total least squares (GTLS) problem, observations can be perturbed by random errors that are dependently, inconsistently and normally distributed with a non-zero mean, and the coefficient matrix can hold any structure. In this contribution, a set of formulae for GTLS adjustment is derived using a pseudo-observation method. Based on the derived results, an iterative algorithm (algorithm 1) only for the estimation of parameters and a two-loop iterative algorithm (algorithm 2) for the estimation of parameters and variance factors are developed. Moreover, the derivative of a vector is introduced to deal with the structured TLS problem. A straight line fitting and a simulated 2D affine transformation experiment are performed to verify the applicability of the developed algorithms. The results show that algorithm1 can be used to simultaneously handle the structured coefficient matrix, correlated error and non-zero expectation problem, while algorithm 2 can be utilised to manage the variance component estimation problem with the non-zero expectation assumption. Under the identical statistical assumptions, the suggested algorithm can achieve the same results as the solutions of Schaffrin (2008), Shen (2011), Fang (2013) and Amiri-Simkooei (2013).

以水汽辐射计(WVR)精确测定的天顶方向延迟值作为参考,评估Saastamoinen、GPT2、EGNOS、UNB3M四种常用对流层模型在上海地区的改正精度;并将WVR观测值及以上4种对流层模型计算的对流层延迟值作为真值应用到GNSS精密单点定位(PPP)中,评估其对定位精度的影响.比较发现,GPT2模型的对流层改正精度比其余3种要好,其天顶干延迟(ZHD)的偏差均值与中误差分别为-0.11 cm、±0.75 cm,天顶湿延迟(ZWD)的平均偏差与中误差分别为-2.34 cm、±7.67 cm;和传统的PPP结果相比,采用WVR对流层观测值的定位精度提高了16％.

This study presents validation of BeiDou measurements in un-differenced standalone mode and experimental results of its application for real data. A reparameterized form of the unknowns in a geometry-free observation model was used. Observations from each satellite are independently screened using a local modeling approach. Main advantages include that there is no need for computation of inter-system biases and no satellite navigation information are needed.Validation of the triple-frequency BeiDou data was performed in static and kinematic modes, the former at two continuously operating reference stations in Australia using data that span two consecutive days and the later in a walking mode for three hours. The use of the validation method parameters for numerical and graphical diagnostics of the multi-frequency BeiDou observations are discussed. The precision of the system's observations was estimated using an empirical method that utilizes the characteristics of the validation statistics. The capability of the proposed method is demonstrated in detection and identification of artificial errors inserted in the static BeiDou data and when implemented in a single point positioning processing of the kinematic test.

Under poor observation conditions, single navigation system usually has lower visibility and declined positioning accuracy. Combined navigation system can improve the satellite visibility and improve positioning accuracy. Beidou navigation system has already been available for primary navigation and positioning. Test is an indispensable part in the development of positioning software. Its goal is to find and eliminate potential errors in the software, so as to improve software quality and meet the design and requirements. We introduce a test program of GPS and Beidou positioning software with an example of actual test. Achievement evaluation index has been given in the paper according to the design demand.

In the classical geodetic data processing, a non- linear problem always can be converted to a linear least squares adjustment. However, the errors in Jacob matrix are often not being considered when using the least square method to estimate the optimal parameters from a system of equations. Furthermore, the identity weight matrix may not suitable for each element in Jacob matrix. The weighted total least squares method has been frequently applied in geodetic data processing for the case that the observation vector and the coefficient matrix are perturbed by random errors, which are zero mean and statistically in- dependent with inequality variance. In this contribution, we suggested an approach that employ the weighted total least squares to solve the nonlinear problems and to mitigate the affection of noise in Jacob matrix. The weight matrix of the vector from Jacob matrix is derived by the law of nonlinear error propagation. Two numerical examples, one is the triangulation adjustment and another is a simulation experiment, are given at last to validate the feasibility of the developed method.

The possibility of Real-Time Precise Point Positioning directly in the Australian GDA94 datum has become possible through the availability of Real-Time Broadcast Corrections (BCs) provided by the IGS Real-Time Pilot-Project. Generation of BCs for the GDA94 datum has some pitfalls which are identified in this contribution. It is shown that it is impossible to obtain identical positioning results using either the BCs in ITRF or BCs in GDA94 due to scale differences between both systems. A new user-friendly RBC-approach is introduced, which deals with the scale-induced biases in the current approach. The user-friendly RBC-approach eliminates the user-need of having to apply the ITRF-to-GDA94 transformation, while still giving correct horizontal PPP positions in GDA94. For users that additionally require precise height information in GDA94 as well, a simple constant height-correction, valid for the complete Australian continent, is all that is needed to obtain the correct full 3D PPP position.

在不同约束条件下,分别利用中国区域附近11个GPS基准站,和全球230个GPS基准站一个月的双频实测数据,通过建立球谐函数模型同时解算电离层电子含量、GPS卫星和接收机的DCB.将其结果与CODE提供的结果进行比较,表明电子含量、GPS卫星与接收机的DCB组合不受约束条件的影响,且精度能达到2 ns,垂直电子含量相对于CODE能改正90％.同时本文利用AR模型对球谐系数进行预报,根据预报系数得到的垂直电子含量相对准确率能达到80％以上,采用卫星DCB和时得到的垂直电子含量准确率略高于采用某颗卫星DCB固定.

The IGS Real-time Pilot Project (IGS-RTPP) provides real-time precise orbits and clocks, which support real-time positioning for single stations over large areas using the Precise Point Positioning (PPP) technique. This paper investigates the impact of real-time orbits, network configuration, and analysis strategies on real-time PPP implementation and demonstrates the real-time PPP performance. One month of data from the IGS network is analyzed in a real-time simulation mode. Results reveal the following: (1) In clock estimation, differential approaches are much more efficient than the zero-differenced approach. (2) The precision of IGS Ultra rapid (IGU) orbits could meet the IGS-RTPP requirement for precise clock estimation and PPP positioning. (3) Considering efficiency and precision, a network with 50 stations is recommended for the IGS-RTPP. It is demonstrated that the real-time satellite clock precision is 0.1 ns supporting hourly static PPP with a mean precision of 2–3 cm in the North component and 3–4 cm in the other components. Kinematic PPP assessed with onboard GPS data collected from a buoy provided mean coordinate precision of 2.2, 4.2, 6.1 cm in the North, East and Up directions, compared to the RTK solutions.

As a result of the Real-Time IGS Pilot Project (RT-IGS) and the EUREF Real-Time Analysis Project (EUREF-RT), real-time GNSS satellite orbit and clock corrections to broadcast ephemeris, the so-called real-time broadcast corrections (BC), have become available for the application in precise point positioning (PPP). The real-time BCs are currently available in global as well as in regional reference frames. In this contribution the PPP usage and performances of these global and regional BCs are analysed for the Australian continent. We identify the limitations of the current regional BCs, which results in scale-induced biases, and show how they can be improved. We also present an alternative, more user friendly, approach for regional BCs. It provides PPP users with simple means to correct for the biases of the regional approach.

为了消弱对流层对GPS高精度定位的影响,UNB(University of New Brunswick)发布了最新的格网天顶对流层延迟。本文介绍该数据模型的内插改正方法,采用全球12个IGS站比较内插精度,结果显示大部分测站的中误差小于±5 cm,可以为卫星定位和对流层延迟估计提供较为准确的初值。

Positioning results may be influenced by different unavoidable errors such as space correlation errors,time correlation errors and so on,though ionosphere-free combination model can somewhat diminish the effects of ionosphere delay,and the orbit error can be modified more or less by the precise orbit.Based on the theory of precise point positioning,the paper presents a dscussion on the characterization of troposphere delay by adopting the data collected in different sample intervals,and also analyses of the variation of epoch-difference values of troposphere delay with the variation of sample intervals.Finally,the paper presents a study of the effects of troposphere delay on the observation of epoch-difference,the effects of residual errors on the position-difference and observation combination,and the variation of residual errors with time.

介绍距离算法和时间算法,可以优化筛选GPS点,减少GPS点数,但不失去描述路径的重要信息.该算法在道路密集,道路形状复杂等复杂路段具有计算快、可靠性高的特点.最后通过一个导航试验实例,对优化筛选后的GPS点描绘的路径和原始数据路径相比较,进行评价,得到满意的结果.

Network based real-time precise point positioning system includes two stages, i.e. real-time estimation of satellite clocks based on a reference network and real-time precise point positioning thereafter. In this paper, a satellite- and epoch-differenced approach, adopted from what is introduced by Han et al. (2001), is presented for the determination of satellite clocks and for the precise point positioning. One important refinement of our approach is the implementation of the robust clock estimation. A prototype software system is developed, and data from the European Reference Frame Permanent Network on September 19, 2009 is used to evaluate the approach. Results show that our approach is 3 times and 90 times faster than the epoch-difference approach and the zero-difference approach, respectively, which demonstrates a significant improvement in the computation efficiency. The RMS of the estimated clocks is at the level of 0.1ns (3cm) compared to the IGS final clocks. The clocks estimates are then applied to the precise point positioning in both kinematic and static mode. In static mode, the 2-h estimated coordinates have a mean accuracy of 3.08, 5.79, 6.32cm in the North, East and Up directions. In kinematic mode, the mean kinematic coordinates accuracy is of 4.63, 5.82, 9.20cm.

The ambiguity free model of precise pointing can eliminate the ambiguity parameter,because the method of Epoch-difference of phase is used. The estimation parameters of this model are the position difference. Based on the robust estimation,this paper discusses the analyses the effects of the sample interval on the results of position-difference. The characterization of position-difference error is studied using wavelet analysis. According to the characterization of errors,some key problems that happen using the method of Epoch-difference to position are also studied.

Based on the regional GNSS (Global Navigation Satellite System) network, the real-time epoch-differenced values of relative clock are estimated using the algorithm of epoch-differential and satellite-differential derived model. On account of the character of precise real-time clocks, the estimation model of real-time precise point positioning is deduced by a satellite-differential algorithm. Comparing the epoch-differenced values of relative clock and the IGS final products, the accuracy can be at 0. 08 ns. The hourly data was processed using the real-time precise point positioning algorithm based on the estimated real-time precise clocks. In static mode, the hourly positioning accuracy in the N, E and U directions are 1. 47, 3. 62, 4. 09 cm respectively. The kinematic positioning accuracy in the N, E and U directions are 2. 63, 3. 82, 5. 20 cm respectively. The accuracy of real-time solution is better than the precise point positioning using the IGS final orbits and clocks in the N, E and U three directions.

A method of beam forming for processing high-rate GPS data and extracting seismic wave information is introduced.Simulated seismic waves of each GPS station are synthesized by adding simulated Rayleigh waves into vertical component of GPS coordinates series.The capacity of beam forming to extract seismic wave information of different SNR(signal to noise ratio) is analyzed.The results indicate that,the correct value of slowness cannot be obtained when the SNR is 1.5,while it is close to the theoretical value when the SNR ratio is 3.

To ensure reliable ambiguity resolution, ambiguity validation is an indispensable step. It has been a challenge for many years and is far from being resolved. Over the past years, various ambiguity validation methods have been proposed, such as F-ratio test, R-ratio test, difference test, projector test, ellipsoidal integer aperture (EIA) estimator and penalized integer aperture (PIA) estimator. In this paper, through analysis and testing, we find that, when the aperture region of EIA is not allowed to be overlapped, the efficiency of ambiguity resolution with EIA is low and it is not applicable to fast static positioning or real-time kinematic (RTK) applications. Then EIA with overlapped aperture regions is recommended and the resulted fail-rate becomes upper bound of the actual one. After that, it is suggested that combined use of overlapped EIA and R-ratio test can increase the reliability of ambiguity resolution. Finally, numerical tests are carried out based on practical buoy data and simulated Galileo data.