全球定位系统

2020 Vol. 45, No. 6

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Data/pilot joint tracking method of BeiDou B1C signal based on extended Kalman filter

ZHAO Lin, BAI Yaguo, DING Jicheng, ZHANG Xiaochun

2020, 45(6): 1-9. doi: 10.13442/j.gnss.1008-9268.2020.06.001

[Abstract](670) [PDF 972KB](51)

Abstract:
To improve the low tracking accuracy of BeiDou B1C signal under low carrier to noise ratio(CNR), we proposed a B1C signal data/pilot joint tracking method based on extended Kalman filter. By constructing a data/pilot dual channel joint tracking model, the utilization ratio of B1C signal is increased. To undermine the tracking errors introduced by discriminator and loop filter in traditional tracking loop, extended Kalman filter is applied on the basis of the proposed joint tracking model, which further improves the tracking performance of tracking loop for low carrier to noise ratio signal. The experimental results demonstrate that compared with the conventional single-pilot channel tracking method, single-pilot channel extended Kalman tracking method and joint tracking method, the proposed method can effectively enhance the tracking accuracy under low CNR.

A method of topology planning and simulation optimization of inter-satellite[JP]link(ISL) based on local laser high-speed node backbone network

DING Wen, ZUO Yong, YE Xiaozhou, LIU Wenxiang, SUN Guangfu

2020, 45(6): 10-15. doi: 10.13442/j.gnss.1008-9268.2020.06.002

[Abstract](412) [PDF 681KB](13)

Abstract:
The laser inter-satellite link has the technical characteristics of large transmission capacity and high transmission rate. The satellite node with the laser inter-satellite link function can be used as a high-speed backbone network node in the laser-microwave hybrid inter-satellite link network. How to deploy these high-speed nodes,so that,the constructed satellite network topology can reach the optimal goal. It is a research focus in the development of the inter-satellite link from microwave to laser transition. The application scenario is the navigation satellite constellation including 24 Medium orbit (MEO),3 Geochronous orbit(GEO) and 3 Inclined GeoSynchronous Orbit (IGSO) satellites. And the number of high-speed nodes is fixed Under the condition of, comprehensive geometric visibility, inter-satellite distance and engineering constraints and other constraints. With the minimum average end-to-end delay from the satellite network access node to the destination node as the optimization goal, a mathematical model is established. A high-speed node selection algorithm method based on multiple Source shortest path strategy hybrid inter-satellite link network is used to solve the optimal topology of the local laser high-speed node backbone network. Simulation results show that, the topological structure of local laser high-speed node backbone network can make the whole network transmission delay less and the communication performance is more effective.

Singular value correction method for ill conditioned least squares problem in survey adjustment

YANG Qiuwei, CHEN Hua, ZHOU Cong, LI Cuihong

2020, 45(6): 16-20. doi: 10.13442/j.gnss.1008-9268.2020.06.003

[Abstract](335) [PDF 500KB](15)

Abstract:
To solve the ill conditioned least squares problem in survey adjustment, a new singular value correction method is proposed in this paper based on a unified singular value correction formula. The proposed method overcomes the shortcomings of the existing methods, which need to determine the threshold value of singular value truncation or modification. The proposed method is simple and fast in calculation with high accuracy, and does not increase the amount of the computation cost. In addition, the proposed method has strong universality and no special requirements for the dimension and rank of the coefficient matrix of the system of equations. It can be applied to the solution of any type of linear system of equations. Two ill conditioned equations are taken as examples to verify the proposed method. The results are compared with the least square solution and the singular value truncation solution. It has been shown that the proposed method is simple and easy to use, and can obtain more accurate results than the singular value truncation method.

Research on fast fixing algorithm of PPP-RTK ambiguity

SHANG Qinghua, CHENG Fang, SHEN Pengli, XIAO Xia

2020, 45(6): 21-26. doi: 10.13442/j.gnss.1008-9268.2020.06.004

[Abstract](728) [PDF 667KB](57)

Abstract:
The PPP-RTK technology, which combines the advantages of network RTK (NRTK) and precision point positioning (PPP) technology, has become a hotspot of current precision positioning research. This paper proposes a solution to quickly fix the ambiguity, Which can improves the reliability of ambiguity estimation. In the experiment, the measured data of the IGS station are used to perform PPP-RTK positioning solution, Statistics show that:When using this algorithm to locate the static data, it takes about 20 minutes for the data convergence time to reach the centimeter level. The accuracy of the positioning results has reached the centimeter level, The positioning accuracy in the plane position direction is better than 3 cm, and the positioning accuracy in the elevation direction is better than 5 cm.

Analysis on the effect of calibration of satellite accelerometers on smooth GRACE orbit dynamics

GAO Songtao, YOU Wei, FAN Dongming, YU Biao, SHENG Yongyun

2020, 45(6): 27-36. doi: 10.13442/j.gnss.1008-9268.2020.06.005

[Abstract](372) [PDF 968KB](20)

Abstract:
This paper takes the GRACE satellite reduced kinetic orbit published by JPL and the geometric orbit published by ITSG as observations, respectively. The influence of Calibration of onboard accelerometers on track smoothing results is studied by dynamic method. The arc length is fixed to 24 hours. The results show that the accuracy of the integral orbit can be improved by using the-first-order bias estimation strategy with 15-minute and the diagonal filling strategy of the scale model. The RMS values in X direction, Y direction and Z direction are 1.89 cm、1.76 cm and 1.56 cm, respectively.

Estimation of seismic elements from high-rate GPS observations

ZHANG Huanyu, LIN Jihang, CHEN Ting

2020, 45(6): 37-45. doi: 10.13442/j.gnss.1008-9268.2020.06.006

[Abstract](433) [PDF 1052KB](22)

Abstract:
In this paper, theories and methods of estimating seismic elements from the high-rate GPS observations were presented. Selecting July 4th, 2019 and July 6th, 2019 Ridgecrest earthquakes as the research object, kinematic precise point positioning (PPP) was used to obtain the time series of displacement, then S transform algorithm was chosen to eliminate the noise of displacement time series, and the amplitude and period of the seismic wave were extracted from the denoised time series, and then we came up with the double 3-sigma rules to pick up the arrival time of body waves and surface waves, at last estimated the location of epicenter, magnitude and origin time of the earthquakes. Compared with the seismic elements provided by USGS, the deviation of the epicenter was about 10 km, the magnitude deviation was around 0.2, and the deviation of origin time of earthquakes was within 20 s. The results showed that the high-rate GPS observations can be used to estimate the seismic elements accurately.

Fusion tropospheric model and its application in precise point positioning

CAI Shu, LAO Yuanji, LI Mengheng, QIN Tuanfa

2020, 45(6): 46-54. doi: 10.13442/j.gnss.1008-9268.2020.06.007

[Abstract](487) [PDF 975KB](20)

Abstract:
Limited by the measured meteorological parameters, the accuracy of the traditional tropospheric model using standard atmospheric parameters is not high. The precise tropospheric model using parameter estimation method increases the number of parameters to be estimated of the observation equation and affects the convergence rate. For the absence of measured meteorological parameters, a fusion tropospheric model is proposed. Two non-measured meteorological parameter models are used to calculate the meteorological parameters at the average sea level and at the station respectively, and then the Saastamoinen model empirical formula is used to solve the zenith tropospheric delay. Precise point positioning(PPP) experiments were performed on RTKLIB software. The proposed fusion tropospheric model is free from the limits of measured meteorological parameters. The results show that when this fusion troposphere model is used, the positioning accuracy in the east, north and up directions is improved by 16 mm、1 mm、2.2 mm, compared with the Saastamoinen model, respectively.And, the positioning accuracy in the east, north and up directions is improved by 13.8 mm、0.7 mm、1.6 mm compared with the MOPS model,respectively. The positioning accuracy in the east, north and up directions is improved by 2.9 mm、0.4 mm、0.7 mm compared with the GPT/UNB3m+Sa model,respectively. The positioning accuracy in the up and north direction is close to the parameter estimation model. The PPP positioning accuracy is improved by using the proposed fusion tropospheric model.

Analysis of influence of different saturated water vapor pressure models on GNSS inversion precipitable water

LI Deyan, YANG Weifang, GAO Zhiyu, LI Rongrong

2020, 45(6): 55-63. doi: 10.13442/j.gnss.1008-9268.2020.06.008

[Abstract](655) [PDF 1115KB](43)

Abstract:
Atmospheric weighted mean temperature (T_m) participation is required for ground-based GNSS water vapor inversion, and saturated water vapor (E_s) is an important variable in the calculation process of T_m that effects T_m, so e_swill be indirectly affect the inversion accuracy of Precipitable Water Vapor (PWV). In view of the three saturated water vapor pressure models (Magnus-Tetens model, BUCK model, Goff-Gratch model) established by different researchers commonly used in the research of ground-based GNSS water vapor inversion, this paper will research different saturated water vapor pressure models participate in the inversion Whether cause differences in results. Taking Hong Kong as the research area, using GAMIT to solve the Zenith Wet Delay (ZWD) of the dry and rainy season (February and July) in 2016, meanwhile using the sounding data of the King's park sounding station to calculate The T_m of the dry and rainy seasons (February and July) through the way of integrate numerical, and then calculating the PWV of the dry and rainy seasons (February and July) through programing with reference to the inversion steps.Thorough comparing and analyzing to get the effects and reasons of different saturated water vapor pressure models participating in the calculation on T_m and PWV. The results show that between the PWV calculated by the three saturated water vapor pressure models and the true value (PWV calculated by the sounding station) have no statistically significant differences, so all of them can be used to provide the saturated water vapor pressure e_s in the calculation of T_m, However, through comparative analysis, it is found that some researchers use the variable T in the BUCK model as the dew point temperature instead of the atmospheric temperature to make T_m produce a larger error. The analysis in this paper will provide a certain reference for the treatment of T_m in the subsequent research of ground-based GNSS water vapor inversion.

Analysis of the influence of different elevation mask angle on the accuracy of short baseline elevation direction

YE Kedong, XIONG Yongliang, XU Shaoguang, YUAN Zheng

2020, 45(6): 64-68. doi: 10.13442/j.gnss.1008-9268.2020.06.009

[Abstract](450) [PDF 594KB](30)

Abstract:
Based on the CORS network of the United States in 2018, data from four short baselines with length of about 11 km and different elevation difference between stations are selected for the experiment. In the case of estimating tropospheric delay, the baselines are solved by setting different elevation mask angles, and the results are compared by standardized root mean square error, baseline U-direction repeatability and baseline difference. The analysis results show that for the short baseline with elevation difference more than 100 m, the selection of elevation mask angle is not the main factor affecting the accuracy of elevation direction calculation; and the geodetic height of the station has a certain impact on the accuracy of short baseline elevation direction calculation.

Galileo dual/triple frequency SPP positioning accuracy analysis

LIU Haotian, LIU Chengyu, ZHAO Juan, WU Hao, CHENG Xi

2020, 45(6): 69-73. doi: 10.13442/j.gnss.1008-9268.2020.06.010

[Abstract](549) [PDF 503KB](26)

Abstract:
Aiming at the problem of analyzing the accuracy of the dual-frequency and triple-frequency combined SPP positioning of the Galileo system, this paper analyzes the dual-frequency and three-frequency combined SPP positioning accuracy of the Galileo system based on the measured data of the Galileo MEGX tracking station. It is found that the Galileo system E1/E5a and E1/E5b dual-frequency combination SPP positioning accuracy is higher, while the E5a/E5b and E1/E6 dual-frequency combination SPP positioning accuracy is too poor, not suitable for positioning. There is significant improvement in positioning accuracy of the three-frequency SPP than the dual-frequency combination. The positioning accuracy in the X and Y directions is better than 0.8 m, and the accuracy in the Z direction is better than 2.3 m, which can provide a certain reference for future research on the multi-frequency combined positioning of the Galileo system.

Interpolation analysis of BDS precision ephemeris based on sliding Fourier series

LIAO Yiping, DENG Jian, CHEN Runjing, JIANG Zelin

2020, 45(6): 74-79. doi: 10.13442/j.gnss.1008-9268.2020.06.011

[Abstract](617) [PDF 651KB](21)

Abstract:
The interpolation of precise ephemeris is one of the important tasks of GNSS data processing, and its interpolation accuracy also directly affects the positioning accuracy. This paper integrates sliding interpolation theory and Fourier series algorithm, and uses different orders of Fourier series and 9th-order Chebyshev polynomials to fit and interpolate The precision ephemeris of GEO satellite, IGSO satellite, MEO satellite in BDS so as to analyze the interpolation effect of Fourier series interpolation in BDS precision ephemeris interpolation. Experiments show that GEO satellites and IGSO satellites have the highest degree of accuracy when the order of Fourier series is 3, reaching millimeter accuracy. And MEO satellites have the highest accuracy when the order is 4, reaching centimeter accuracy. Compared result shows that 9-order chebyshev fitting in precise ephemeris of GEO satellites and IGSO satellites has higher accuracy, while Fourier series interpolation in that of MEO satellites has higher accuracy.

Research on port vehicle combined positioning method based on fuzzy Kalman filter

YANG Yongsheng, CHI Jingcheng, YAO Haiqing

2020, 45(6): 80-85. doi: 10.13442/j.gnss.1008-9268.2020.06.012

[Abstract](390) [PDF 627KB](19)

Abstract:
Aiming at the problems of BDS/INS integrated navigation system positioning failure in the obstructed environment, by analyzing the impact of sensor status changes in the integrated navigation system on positioning accuracy, we design a fuzzy logic inference system based on the status of the system, combined with the Kalman filter algorithm, the positioning accuracy is improved by real-time adjustment of the noise variance of the system measurement. Finally, experiments were carried out on unmanned vehicles in a port environment. Experiment shows that the proposed method can effectively improve the positioning accuracy of unmanned vehicles in an occluded environment, and has good robustness.

Non-linear variation analysis of height time series of north China GNSS reference stations

CHEN An, WU Yijiang, LIN Hongdong, WANG Le, SU Xiaokui, HE Shunji

2020, 45(6): 86-91. doi: 10.13442/j.gnss.1008-9268.2020.06.013

[Abstract](415) [PDF 694KB](24)

Abstract:
The non-linear variation analysis of height time series of GNSS reference Stations in North China is studied by using power spectral analysis and least-squares method based on the GNSS observations of the CMONOC network, and the effects of different environmental loads are also analyzed. The results show that there are obvious annual and semi-annual cycle features in the height time series of the GNSS reference station in North China, and the annual feature is more significant than the semi-annual feature. There are differences in the periodic amplitudes and phases of the reference stations located in different regions, and the annual amplitudes are larger in the southern part of the North China than in the northern part. The overall annual variation in North China reached its maximum in the autumn season. The effect of different environmental loading effects on the GNSS height displacement of the North China is inconsistent. Results of correcting the GNSS time series using three environmental loads, So that, the hydrological loads have the best corrections, followed by the non-tidal atmospheric loads, and non-tidal ocean loads have poor corrections.

GNSS leveling method research suitable for third and fourth order level requirements in engineering surveying

LI Shanjun, LIU Hui, SU Yong, DUAN Taisheng

2020, 45(6): 92-99. doi: 10.13442/j.gnss.1008-9268.2020.06.014

[Abstract](423) [PDF 849KB](27)

Abstract:
In response to the problem of traditional level measurement being inefficient and the geodetic heights obtained from static GNSS measurement being left unused, this paper investigates the methods and relevant measures to improve the accuracy of elevation measurement. The author initially develops the dual model software for calculating height anomaly through the selection of model combinations. Then, the author proposes the corresponding observation requirements in satellite positioning static measurement on the basis of the technical standards of the third and fourth order leveling, and achieves the third order level accuracy in satellite static measurement through on-site verifications in multiple places across the country. The experimental results of the study show that, for elevation control measurement tasks of third order level accuracy and below in the field of engineering measurement, the dual model height anomaly calculation software can conveniently facilitate the completion of such measurement tasks together with plane control measurement and fulfil the static measurement requirements specified in this paper.

Change detection in remote sensing images combined with intuitionistic fuzzy clustering and change vector analysis

JI Xinran, HUANG Liang, CHEN Pengdi

2020, 45(6): 100-106. doi: 10.13442/j.gnss.1008-9268.2020.06.015

[Abstract](395) [PDF 863KB](9)

Abstract:
Aiming at the problems of multi-temporal remote sensing images change detection with data uncertainty and low detection accuracy, a multi-temporal remote sensing images change detection method combined with change vector analysis (CVA) and intuitionistic fuzzy C-means clustering algorithm (IFCM) is proposed. Firstly, the difference image of bi-temporal remote sensing images is obtained by change vector analysis method. Then the difference image is clustered by the intuitionistic fuzzy C-means clustering algorithm to obtain the change areas and the non-change areas. Finally, the change detection results are binarized and the accuracy is evaluated. The bi-temporal Gaofeng-1 remote sensing images and Szada image data sets were selected as experimental data. The experimental results show that the proposed method can effectively solve the data uncertainty problem existing in the traditional method, it is a feasible remote sensing images change detection method. The overall accuracy of change detection achieved 95.92% and 92.70%. The research results can be used for forest dynamic change monitoring, land reclamation utilization planning change analysis and damage assessment.

Maximum likelihood estimators for rigid body localization using DOA measurement

YAO Xiaofeng, WU Shenglan, ZHOU Biao, PANG Min

2020, 45(6): 107-114. doi: 10.13442/j.gnss.1008-9268.2020.06.016

[Abstract](262) [PDF 862KB](15)

Abstract:
Rigid body localization (RBL) not only estimates the position of the target, but also obtains the attitude information of the target. The RBL framework of single base station is studied in three-dimensional space. This framework uses a single base station to measure the direction of arrival (DOA) of signal from small-scale wireless sensor network signal installed on the rigid target surface, and then fuses the DOA measurement with the network topology information, and finally proposes two maximum likelihood estimators (MLE) for RBL purpose. The improved Gauss Newton algorithm is adopted to optimize the MLEs of rotation matrix and translation vector and the three-dimensional position and attitude of the object are estimated. The simulation results show that the proposed MLEs can approach the theoretical Cramer Rao Lower Bound, and have better performance with respect to convergence success rate and computation cost.

Prediction of tropospheric delay based on the LSTM model of Keras platform

SHI Yaojia, WU Fei, ZHU Hai, HAN Xuefa

2020, 45(6): 115-122. doi: 10.13442/j.gnss.1008-9268.2020.06.017

[Abstract](416) [PDF 857KB](27)

Abstract:
Tropospheric delay is a vital factor that influence the measurement accuracy of GNSS. To solve the problems of poor stability and low accuracy of existing tropospheric delay model, a prediction model of tropospheric delay based on the Long-Short Term Memory neural network (LSTM) of Keras platform is proposed in the absence of measured meteorological parameters. Eight stations evenly distributed around the world were selected to use their 42-day hourly tropospheric delay data from the 90th to 131st day of 2016 to predict their hourly data of 132nd to 136th day. Based on the troposphere products provided by International GNSS Service (IGS) center, the prediction effects of LSTM model and back propagation neural network (BP) model were analyzed and compared. The result shows that the root mean square error of LSTM model basically reaches mm level, and the mean absolute error and mean absolute percentage error of LSTM model are lower than those of BP model, and the accuracy and stability of LSTM model are significantly improved compared with BP model. LSTM model has an average RMSE of 7.82 mm in mid and high latitude, which shows it is more suitable for mid and high latitude.