Time filter

Source Type

Feng X.,China National Administration of GNSS and Applications | Wang H.,Xian Research Institute of Surveying and Mapping
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2011

In this paper, using narrow correlation and double delta correlation techniques, the running average of weighted multipath error envelope of BPSK(1) and BOC(1, 1) is simulated in different pre-correlation bandwidth and correlator spacing. The result shows that multipath performance becomes better when correlator spacing decreases, but it's not obvious when correlator spacing is 0.1 chip, and there is a least multipath error when pre-correlation bandwidth increases.

Yang Y.,China National Administration of GNSS and Applications | Yang Y.,Xian Research Institute of Surveying and Mapping | Xu T.,Xian Research Institute of Surveying and Mapping
International Association of Geodesy Symposia | Year: 2015

The quality of kinematic positioning and navigation depends on the quality of the kinematic model describing the vehicle movements and the reliability of the measurements. A series of adaptive Kalman filters have been studied in recent years. The main principles of four kinds of adaptive filters are summarized, i.e. fading Kalman filter, adaptive Sage windowing filter, robust filter and adaptively robust filter. Some of the developed equivalent weight functions and the adaptive factors including the fading factors are also introduced. Some applications are mentioned. © Springer International Publishing Switzerland 2015.

Li J.,Zhengzhou University | Yang Y.,China National Administration of GNSS and Applications | Xu J.,Zhengzhou University
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2011

In case of triple-frequency signals, there are many combination observations with longer wavelength, smaller noise, smaller ionosphere effect, which may improve the precision of cycle-slip detection and repair. The threshold for cycle-slip detection is deduced, and the success rate of cycle-slip determination is proposed. Criterions and methods for selecting code-phase combination are presented in order to enhance the success rate of cycle-slip determination. At last, experiments are carried out to test the performance of the method using GPS triple-frequency observations. The result shows that optimal code-phase combinations selected by proposed criterions can detect and repair all cycle-slips of triple-frequency un-differenced observations, when ionosphere error between-epoch can be ignored in case of high data rate.

Huang G.,Chang'an University | Yang Y.,China National Administration of GNSS and Applications | Yang Y.,State Key Laboratory of Geographic Information Engineering | Liu C.,Chang'an University | And 2 more authors.
Lecture Notes in Electrical Engineering | Year: 2013

The standard GNSS combined PPP algorithm cannot be used satisfactorily in the real-time and high frequency precise positioning because of its low compute efficiency. A new algorithm based on the parameter equivalent reduction principle is proposed. First, the observations equation and the normal equation which belong to the single navigation system can be solved independently. Second, the normal equations of overlapping parameters between the different systems can be obtained by using parameter equivalent reduction principle. At last, the combined PPP resolutions can be computed easily by using the Least Squares method. The proposed algorithm can improve the calculating efficiency immensely. In addition, an adaptively combined method which can automatically adjusts the contributed weight of different GNSS systems is also proposed in this paper. The numerical examples using the data set of three IGS stations, show that the PPP precisions and efficiencies based on the proposed model have been improved significantly compared with those of standard model. This proposed principle can also be applied in the GNSS precise satellite clock determination and the indifference baseline network adjustment plus the GNSS time offset monitoring. © 2013 Springer-Verlag Berlin Heidelberg.

Song Y.,Beijing Institute of Technology | Zhou H.,China National Administration of GNSS and Applications | Zeng T.,Beijing Institute of Technology | Zhang L.,Beijing Institute of Technology
Institute of Navigation - International Technical Meeting 2010, ITM 2010 | Year: 2010

Under the circumstances of satellite out of orbit or experiment test in laboratory, in order to validate performance of satellite positioning system, satellite signal simulator is needed to simulate real satellite signal at various conditions. Relative high speed movement between satellite and receiver makes the carrier and code frequency of received signal changed in dynamic environment. Doppler frequency shift simulation is a key technique that must be solved for the high dynamic satellite signal simulator. The satellite signal simulation architecture (e.g. computer + DSP + FPGA + DAC + RF module) based on Software Define Radio is widely used nowadays. Digital intermediate frequency satellite modulation signal is generated by FPGA. The precision of approximation to Doppler frequency implemented on FPGA determines performance of high dynamic simulator. This paper proposes a three-stage cascaded DDS Doppler implementation architecture according to real high dynamic model with acceleration and jerk. The new architecture overcomes the disadvantages of traditional DDS, and can be used in the accurate simulation of Doppler frequency. In section 2, the problem definition of simulated GNSS signal under high dynamic condition is given and traditional DDS architecture is described. Section 3 presents the third-order DDS model and gives the derivation of its output phase expression step by step. The corresponding relationships between the design parameters of DDS and signal Doppler are analyzed and a guide line to choose proper parameters is provided. Simulation instances in high dynamic motion with acceleration and jerk are discussed in section 4. The performance of third-order DDS is verified by software simulation and hardware test. Section 5 are conclusions and future work.

Liu Q.,China National Administration of GNSS and Applications | Tian S.,PLA University of Science and Technology
Proceedings of 2nd International Conference on Computer Science and Network Technology, ICCSNT 2012 | Year: 2012

The paper focuses on the Receiver Autonomous Integrity Monitoring (RAIM) performance of Compass augmentation using a proposed LEO satellite system. The Compass satellite system is briefly reviewed. RAIM algorithm is analyzed, in addition, the measurement equation in the joint Compass/LEO system is constructed. The RAIM performance is analyzed using the rates of fault detection and identification. Based on the authors' previous work, the performance of the augmented scheme is demonstrated through in-depth numerical simulations. Results show that the augmentation with LEO satellite system will improve the performance of RAIM. © 2012 IEEE.

Yang Y.,China National Administration of GNSS and Applications | Li J.,Zhengzhou University | Xu J.,Zhengzhou University | Tang J.,China National Administration of GNSS and Applications
Journal of Navigation | Year: 2011

Integrated navigation using multiple Global Navigation Satellite Systems (GNSS) is beneficial to increase the number of observable satellites, alleviate the effects of systematic errors and improve the accuracy of positioning, navigation and timing (PNT). When multiple constellations and multiple frequency measurements are employed, the functional and stochastic models as well as the estimation principle for PNT may be different. Therefore, the commonly used definition of dilution of precision (DOP) based on the least squares (LS) estimation and unified functional and stochastic models will be not applicable anymore. In this paper, three types of generalised DOPs are defined. The first type of generalised DOP is based on the error influence function (IF) of pseudo-ranges that reflects the geometry strength of the measurements, error magnitude and the estimation risk criteria. When the least squares estimation is used, the first type of generalised DOP is identical to the one commonly used. In order to define the first type of generalised DOP, an IF of signal-in-space (SIS) errors on the parameter estimates of PNT is derived. The second type of generalised DOP is defined based on the functional model with additional systematic parameters induced by the compatibility and interoperability problems among different GNSS systems. The third type of generalised DOP is defined based on Bayesian estimation in which the a priori information of the model parameters is taken into account. This is suitable for evaluating the precision of kinematic positioning or navigation. Different types of generalised DOPs are suitable for different PNT scenarios and an example for the calculation of these DOPs for multi-GNSS systems including GPS, GLONASS, Compass and Galileo is given. New observation equations of Compass and GLONASS that may contain additional parameters for interoperability are specifically investigated. It shows that if the interoperability of multi-GNSS is not fulfilled, the increased number of satellites will not significantly reduce the generalised DOP value. Furthermore, the outlying measurements will not change the original DOP, but will change the first type of generalised DOP which includes a robust error IF. A priori information of the model parameters will also reduce the DOP. Copyright © The Royal Institute of Navigation 2011.

Huang G.,Chang'an University | Yang Y.,China National Administration of GNSS and Applications | Zhang Q.,Chang'an University
Acta Geodaetica et Cartographica Sinica | Year: 2011

Is proposed that a novel clock error estimation and prediction algorithm - adaptively robust sequential adjustment with classified adaptive factors based on opening windows. The main ideas are firstly one dimensional clock error series are processed to eliminate the gross errors with robust equivalence weight estimation in opening windows, where adaptive factors are used between windows to reduce the anomaly of clock errors. Secondly, as for the different satellite clocks, based on their different error characteristics, the classified adaptive factors are adapted to mitigate the effects form clock outliers. Tests indicate as for the fitting precision and prediction precision, the new proposed algorithm can improve 78. 9% and 60. 4% respectively by comparing with no robust estimation method. Besides, even for the robust estimation, classified factors method are better than single factor method, tests show about 4. 3% and 29. 2% improvement in fitting precision and prediction precision respectively.

Yang Y.,China National Administration of GNSS and Applications
Acta Geodaetica et Cartographica Sinica | Year: 2010

Satellite navigation has stepped into the era of a hundred flowers in bloom. The progress, application, contribution and challenges of Compass/Beidou satellite system is reviewed and analyzed. Firstly, the construction principles and development steps are Introduced. Secondly, the general realizations of signal frequency and the coordinate system as well as the time system of Beidou satellite navigation system In the frame of compatibility and interoperability are described. Thirdly, In the concept of redundancy, the main contributions of Beidou system are analyzed. At last, the applications and the main challenges of Beidou system are reviewed.

Cui X.-Q.,Chang'an University | Yang Y.-X.,China National Administration of GNSS and Applications | Wu X.-B.,Chang'an University | Wu X.-B.,Xian Research Institute of Surveying and Mapping
Yuhang Xuebao/Journal of Astronautics | Year: 2012

Reliable fitting of broadcast ephemeris parameters is a key technique to build the satellite navigation system. The efficiency of user navigation and positioning is directly lying on the briefness and high efficiency of the ephemeris user algorithm. The broadcast ephemeris parameter fitting of GEO satellites is a difficult problem urgent to be solved in Compass system construction. The influence formula of the orbital plane rotation angle on the broadcast ephemeris parameters is deduced and main factors determining the calculated value of the influence function are analyzed based on the least square fitting solution of the broadcast ephemeris parameters. And the effect of the orbital plane rotation angle on the ephemeris fitting algorithm stability is analyzed. The calculation results show that not only the overrange problem of the GEO satellite broadcast ephemeris parameters can be solved but also accuracy and reliability of the broadcast ephemeris parameter fitting algorithm can be insured by increasing the orbital plane rotation angle.

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