Table of Content

31 January 2017, Volume 45 Issue S2

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Model and Performance Analysis of Tightly Combined BeiDou B2 and Galileo E5b Relative Positioning for Short Baseline

ZHANG Xiaohong, WU Mingkui, LIU Wanke

2016, 45(S2):  1-11.  doi:10.11947/j.AGCS.2016.F020

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With the modernization of GPS and GLONASS, and construction of Galileo and BeiDou, multi-frequency multi-GNSS is a trend. For the first time this paper investigates the model, algorithm, and performance of tightly combined relative positioning using BeiDou B2 and Galileo E5b observations for short baselines. The model and algorithm was first deduced in detail. Then the long stability of between-receivers differential inter-system bias (DISB) between BeiDou B2 and Galileo E5b observations was analyzed emphatically. It is shown that for baselines with identical receivers (the same firmware version), the DISB is close to zero; for baselines with different receiver types, the DISB is significant but with long stability, which allows for a-prior calibration of these DISBs. Finally, the performance of tightly combined positioning was evaluated using single frequency BeiDou B2 and Galileo E5b observations in an instantaneous approach. It is demonstrated that the DISB corrected tightly combined model can significantly improve the ambiguity resolution performance with respect to the loosely combined model. The improvement can be especially significant (10%~25%) under environments where the navigation signals are serious blocked or the observed satellite for each system is limited.

Study on a High-frequency Multi-GNSS Real-time Precise Clock Estimation Algorithm and Application in GNSS Augment System

CHEN Liang, HU Zhigang, GENG Changjiang, GE Maorong

2016, 45(S2):  12-21.  doi:10.11947/j.AGCS.2016.F021

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GNSS satellite-based differential augment system is based on real-time orbit and clock augment message. The multi-GNSS real-time precise clock error estimation model is studied, and then the parameters estimated in traditional un-difference model are optimized and a high-efficient real-time clock simplified model is proposed and realized. The real-time orbit data processing based on PANDA is also analyzed. The results indicate that the real-time orbit radial accuracy of GPS, BeiDou MEO and Galileo is 1~5 cm, and the radial accuracy of the BeiDou GEO/IGSO satellite is about 10 cm. It is found that the optimized real-time clock simplified model is more efficient in one epoch than un-difference model and can be applied to high-frequency (such as 1 Hz) updating of real-time clock augment message. The results show that the real-time clock error obtained by this model is absolute value and there is no constant bias. Based on the real-time orbit, the GPS real-time clock precision of the simplified model is about 0.24 ns, BeiDou GEO is about 0.50 ns, IGSO/MEO is about 0.22 ns and Galileo is about 0.32 ns. Using the multi-GNSS real-time data stream in GFZ, a multi-GNSS real-time augment prototype system is built and the real-time augment message is being broadcasted on the Internet. The real-time PPP centimeter-level service and meter-level navigation service based on pseudorange are realized based on this prototype system.

An Improved Semisoft Threshold Algorithm and Its Evaluation for Denoising Random Walk in GNSS Time Series

WU Hao, CAO Tingquan, HUA Xianghong, ZOU Jingui, SHI Wenzhong, LU Nan

2016, 45(S2):  22-30.  doi:10.11947/j.AGCS.2016.F022

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The differences in the satellite orbit and signal quality of global navigation satellite positioning system, resulting in the complexity of random walk noise in GNSS time series, has become a bottleneck problem in applying GNSS technology to the high precision deformation monitoring industry. For the complex characteristics of random walk noise, small magnitude, low frequency and low sensitivity, an improved semisoft threshold algorithm is presented. Then it forms a unified system of semisoft threshold function, so as to improve the adaptability of conventional semisoft threshold for random walk noise. In order to verify and evaluate the effect of improved semisoft threshold algorithm, MATLAB platform is used to generate a linear trend, periodic and random walk noise of the GNSS time series, a total of 1700 epochs. The results show that the improved semisoft threshold method is better than the classical method, and has better performance in the SNR and root mean square error. The evaluation results show that the morphological character has been performanced high consistency between the noise reduced by improved method with random walk noise. Further from the view of quantitative point, the evaluation results of spectral index analysis verify the applicability of the improved method for random walk noise.

A Kalman Filter Method for BDS/GPS Short-term ISB Modelling and Prediction

ZHANG Hui, HAO Jinming, LIU Weiping, YU Heli, TIAN Yingguo

2016, 45(S2):  31-38.  doi:10.11947/j.AGCS.2016.F023

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Study of inter-system biases(ISB) is essential for the data processing of multi-constellation precise point positioning(PPP). When establishing BDS/GPS short-term ISB models, as equal-weight least square(LS) fails in taking the different weights of fitting ISB data into consideration, a method based on Kalman filter is proposed for the parameter estimation of ISB modelling, and the variance of fitting ISB data in Kalman filter is adjusted according to the distance between the data time and the forecast time. ISB models are established with ISB data over 7 days and the accuracy and applicability of ISB prediction for the 8th day is verified by static PPP experiments. The analysis result shows that the accuracy of ISB prediction generated by Kalman filter model is 29.7%, 11.5%, 43.5% and 32.0% higher than those generated by LS model at 4 stations, respectively. With the priori constraints of ISB prediction generated by Kalman filter model, the averaged RMS values of static PPP solutions are promoted by 2.7% and 0.9% higher in E and U components than those with priori constraints generated by LS model, and are promoted by 10.6%, 26.3% and 3.4% higher in E, N, U components than those without priori constraints, respectively.

Observation Weight Function Design for Fusing BDS/GPS Data to Estimate the Real-time Clock with Regard to the Orbit Errors

GU Shouzhou, SHI Chuang, DANG Yamin, MI jinzhong, XUE Shuqiang, ZHANG Longping

2016, 45(S2):  39-45.  doi:10.11947/j.AGCS.2016.F024

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The real-time clock product is one of the basis products for wide-area positioning service of high precision. Considering the difference between BDS orbit precision and GPS precision, we design a new observation weight function, in order to optimize the stochastic model of real time BDS/GPS clock estimation. The BDS/GPS observations of 78 MGEX global stations and 2 iGMAS stations were collected to generate the real time clock, and then the calculation results were compared with the final iGMAS precise clock product in two strategies (the old stochastic model and the new stochastic model).It shows that the method based the proposed stochastic model can improve the precision of satellite clock about 9% for GPS and 10%for BDS.

Combination and Assessment of GNSS Clock Products from iGMAS Analysis Centers

CHEN Kangkang, XU Tianhe, YANG Yuguo, CAI Hongliang, CHEN Guo

2016, 45(S2):  46-53.  doi:10.11947/j.AGCS.2016.F025

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The precise clock corrections are a prerequisite for applications of the GNSS positioning, navigation and timing (PNT) service. Therefore the combination and assessment for clock products is one of the important tasks of product integration and service center (ISC). First of all, it is introduced that the improved strategy and robust estimation of clock combination. The issues including nonlinear systematic error processing, alignment of clock reference and compensation of linear systematic error are highlighted. Furthermore, two combined products using epoch-wise clock alignment and the "three-step" alignment respectively are compared, and the clock products of recent two years from iGMAS are analyzed and evaluated in detail. Finally, in order to verify the accuracy and consistency of the combined products, PPP tests are implemented using static data from 5 IGS stations. The results show that the clock RMS of combined solutions is the best, which can be used as reference to assess the clock quality of analysis centers (ACs). The results of BDS only static PPP using the final combined products is within 4 cm, which is better than that of most ACs.

Klobuchar-like Ionospheric Model for Different Scales Areas

LIU Chen, LIU Changjian, FENG Xu, XU Lingfeng, DU Ying

2016, 45(S2):  54-63.  doi:10.11947/j.AGCS.2016.F026

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Nowadays, Klobuchar is the most widely used ionospheric model in the positioning based on single-frequency terminal, and its different refined models have been proposed for a higher and higher accuracy of positioning. The variation of nighttime TEC with local time and the variation of TEC (total electron content) with latitude have been analyzed using GIMs. After summarizing the model refinement schemes with wide applications, we proposed a Klobuchar-like model for regions with different scales in this paper. The Klobuchar-like, 14-paramaters Klobuchar and 8-paramaters Klobuchar models were established for the small, large and global regions by GIMs (global ionospheric maps) in different solar activity periods and seasons, respectively. Klobuchar-like models, with the correction rates of 92.96%, 91.55% and 72.67% respectively in the small, large and global regions, have higher correction rates than 14-paramaters Klobuchar,8-paramaters Klobuchar and GPS Klobuchar models, which have verified the effectiveness and practicability of Klobuchar-like model.

Analysis and Application of BDS Broadcast Ephemeris Bias

ZHANG Yize, CHEN Junping, ZHOU Jianhua, YANG Sainan, WANG Bin, CHEN Qian, GONG Xiuqiang

2016, 45(S2):  64-71.  doi:10.11947/j.AGCS.2016.F027

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We analyze the BeiDou broadcast ephemeris biases starting from February 2014 to October 2016 by using the IGS post-processed precise orbit and clock as references. Results show that the bias of BeiDou broadcast ephemeris can reach up to 2 meter. To further verify this finding, we perform precise point positioning for about 18 MGEX stations using BeiDou broadcast ephemeris and wide-area differential correction parameters. Data of 97 days are analyzed and pseudo-range residuals of each frequency for each station are derived. Systematic biases are found in the residuals using broadcast ephemeris. Comparing the BEB applying the differential correction parameters with the TGD difference between IGS and BeiDou broadcast ephemeris, we find that the correlation coefficient of TGD differences and BEB values could reach up to 0.89. This proves that the BEB applying the differential correction parameters is mainly due to the biases of the TGD parameters in broadcast ephemeris. By correcting the biases into TGD parameters, we performed point positioning at different stations. Results show that after applying the biases, the pseudo-range error reduces much, and the positioning precision can improve about 14.9%, 28.4%, 15.5% in N,E,U, direction for dual-frequency users, respectively.

BeiDou/GPS Displacement Detection Using Robust Weighting Based on Moving Window

ZHANG Yunlong, YANG Songlin, LUO Xiaoyan, FANG Jianhong, QIU Dongwei

2016, 45(S2):  72-81.  doi:10.11947/j.AGCS.2016.F028

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The positioning accuracy of Kalman model under creep deformation condition is closely related to the observation variance, which can be affected by the accuracy of weight ratio of GPS and BDS observations. To improve displacement detection accuracy, shorten convergence time of initial coordinate and reduce monitoring cost, firstly the BDS/GPS single-frequency single-difference combination model is set up by using clock-synchronized dual-antenna BDS/GPS receiver. Then the equivalent weights of GPS and BDS observations are robustly determined respectively, and the Helmert variance component estimated by introducing time-correlated forgetting factor is used to achieve the precise weight ratio between GPS and BDS observations. Finally the coordinates are calculated using the extended Kalman filter by updating observed variance in real-time. According to the experiment, for the short baseline (1 km), BDS/GPS robust precise weighting Kalman method can shorten convergence time of initial coordinate significantly, which is suitable for monitoring the deformation body with creep characteristics, and the displacement detection accuracy can reach sub-millimeter level. Moreover the displacement convergence rate is inversely related to the length of moving window approximately.

Analysis and Optimization of BDS GEO/IGSO/MEO Ground Monitoring Stations Configuration for Determining GNSS Orbit

ZHANG Longping, DANG Yamin, CHENG Yingyan, XUE Shuqiang, GU Shouzhou, HAN Deqiang

2016, 45(S2):  82-92.  doi:10.11947/j.AGCS.2016.F029

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Orbit determination accuracy of GNSS satellites depends on the satellites dynamics models and GNSS orbit determination geometry. Because of the weak geometry, higher orbit height of GEO and IGSO and relatively low accuracy of the dynamics models, the geometry information may play an important role in improving the GNSS orbit. The method for analysis the configuration and the influence of BDS GEO/IGSO/MEO ground monitoring stations distribution are discussed. Firstly, based on the reduced-dynamic orbit determination theory, the precision improvement of GNSS orbit from multi-epoch geometry observations is revealed. Secondly, the geometric condition of an ideal configuration for BDS satellites orbit determination is studied and the influence factors (quantity, range, density) are obtained. Thirdly, the method based on the discrete probability distribution is proposed to analyse the configuration of the ground monitoring stations. Finally, the indicators of discrete probability density and configuration of BDS orbit determination are optimized by adding five Chinese regional stations. It is showed that the improvement of GEO and IGSO satellites is more significant relative to MEO satellites. The accuracy of GEO/IGSO/MEO satellites is improved by 10%, 16%, 4% respectively.

A Rapid Orbit Integration Algorithm for Multi-GNSS Satellites

FAN Lei, LI Min, SONG Weiwei, SHI Chuang, WANG Cheng

2016, 45(S2):  93-100.  doi:10.11947/j.AGCS.2016.F030

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A rapid and efficient orbit numerical integration algorithm with high accuracy is needed in multi-GNSS rapid precise orbit determination. In order to improve the compute efficiency, an adaptive step-changed Admas integration method and a synchronous integration algoritm for multi-GNSS satellites are developed in this paper. To validate the precision and efficiency of the proposed method, the multi-GNSS precise orbit products calculated by Wuhan University (WHU) and Center for Orbit Determination in Europe (CODE) are used for orbit fitting. Results show that, the average 3DRMS of GPS, GLONASS, BDS and Galileo satellites are all below 20 mm. Comparing with the traditional step-fixed orbit integraion method applied for each satellite separately, the computational efficiency of the proposed method is improved significantly:without damaging the accuracy, it takes only 0.09 s for a single satellite, which is 14 times faster than the traditional method. Besides, further improvement can be achieved when the number of satellites is increased.

Combining Regional Monitoring Stations with Space-based Data to Determine the MEO Satellite Orbit

WANG Le, ZHANG Qin, HUANG Guanwen, YAN Xingyuan, QIN Zhiwei

2016, 45(S2):  101-108.  doi:10.11947/j.AGCS.2016.F031

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The ground monitoring stations of BeiDou Navigation Satellite System (BDS) are regional distribution and the number of these stations is small. The more global ground stations cannot be built in the short term. The ground regional monitoring stations are difficult to observe the global Medium Earth Orbit Satellite (MEO) continuously, which leads to low precision of orbits in BDS real-time broadcast ephemeris. Based on the above problems, in view of real time satellite GNSS data of low earth orbit satellite can effectively make up the lack of regional monitoring stations in space overlay, a method is proposed that the GNSS receivers of LEO satellites used as high dynamic space-based monitoring stations combining with the data of the ground monitoring stations to calculate and forecast the MEO satellite orbits. The numeral results show that, using the data of seven regional monitoring stations add 1 to 3 LEO satellites, the precision of the MEO orbit determination can be increased by about 21%, 34% and 55% respectively. It also shows that, the ground regional monitoring stations combined with the data of LEO satellites can effectively improve the orbit precision of MEO satellite. It is suggested that using the data combined with ground stations and LEO satellites to improve the precision of broadcast ephemeris of MEO in BDS.

Analysis of the Accuracy of Beidou Combined Orbit Determination Enhanced by LEO and ISL

FENG Laiping, MAO Yue, SONG Xiaoyong, SUN Bijiao

2016, 45(S2):  109-115.  doi:10.11947/j.AGCS.2016.F032

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In order to improve the precision of BeiDou orbit determination under the conditions of regional ground monitoring station and make good use of increasingly rich on-board data and upcoming ISL technology, a method of BeiDou precision orbit determination is proposed which combines the use of ground monitoring stations data, low earth orbit satellite(LEOs) data and Inter-Satellite Link(ISL) data. The effects of assisting data of LEOs and ISL on the precision orbit determination of navigation satellite are discussed. Simulation analysis is carried out mainly from the number of LEOs, orbit slot configuration and ISL. The results show that the orbit precision of BeiDou will greatly improve about 73% with a small number of LEOs, while improvement of clock bias is not remarkable; the uniform orbit slot configuration of the same number of LEOs has a modest effect on the accuracy of combined orbit determination; compared with LEOs, the increase of ISL will significantly improve the accuracy of orbit determination with a higher efficiency.

Improving BDS Autonomous Orbit Determination Performance Using Onboard Accelerometers

QIAO Jing, CHEN Wu

2016, 45(S2):  116-131.  doi:10.11947/j.AGCS.2016.F033

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Autonomous orbit determination is a crucial step for GNSS development to improve GNSS vulnerability, integrity, reliability and robustness. The newly launched BeiDou (BD) satellites are capable of conducting satellite to satellite tracking (SST), which can be used for autonomous orbit determination. However, using SST data only, the BD satellite system (BDS) will have whole constellation rotation in the absence of absolute constraints from ground or other celestial body over time, due to various force perturbations. The perturbations can be categorized into conservative forces and non-conservative forces. The conservative forces, such as the Earth non-spherical perturbations, tidal perturbation, the solar, lunar and other third-body perturbations, can be precisely modeled with latest force models. The non-conservative forces (i.e. Solar Radiation Pressure (SRP)), on the other hand, are difficult to be modeled precisely, which are the main factors affecting satellite orbit determination accuracy. In recent years, accelerometers onboard satellites have been used to directly measure the non-conservative forces for gravity recovery and atmosphere study, such as GRACE, CHAMP, and GOCE missions. This study investigates the feasibility to use accelerometers onboard BD satellites to improve BD autonomous orbit determination accuracy and service span. Using simulated BD orbit and SST data, together with the error models of existing space-borne accelerometers, the orbit determination accuracy for BD constellation is evaluated using either SST data only or SST data with accelerometers. An empirical SRP model is used to extract non-conservative forces. The simulation results show that the orbit determination accuracy using SST with accelerometers is significantly better than that with SST data only. Assuming 0.33 m random noises and decimeter level signal transponder system biases in SST data, IGSO and MEO satellites decimeter level orbit accuracy can be achieved over a service life of two months using SST data and accelerometers. If only SST data are used, the orbit accuracy is 3~6 m with the same time period, which is an order worse.

The Prediction of BeiDou Satellite Clock Bias Based on Periodic Term and Starting Point Deviation Correction

AI Qingsong, XU Tianhe, SUN Dawei, REN Lei

2016, 45(S2):  132-138.  doi:10.11947/j.AGCS.2016.F034

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According to the physical characteristics of the BDS on-board atomic clocks, a spectral analysis method is used to detect the periodicity based on the products published by the IGS data Center of Wuhan University from January 1, 2016 to November 1, 2016. The results show that there are periodic fluctuations in the three types of satellite clocks. The main period of GEO and IGSO satellite clock bias is relatively obvious. The testing with nearly a year data showed that the main periods of GEO are 12, 24, 8 and 6 h, but for IGSO are 24, 12, 8 and 6 h, while those for MEO are 12.9, 6.4 and 24 h. Based on the periodic characteristics of different types of clocks and the correction of the starting point deviation of the clock bias, a modified prediction method of satellite clock bias is used to forecast the BeiDou satellite clock bias. The results show that the modified method can significantly improve the prediction accuracy, the 24 h, 12 h, 6 h average forecast accuracy can reach 6.55 ns, 3.17 ns and 1.76 ns respectively.

Ionospheric Anomaly before Kyushu|Japan Earthquake

YANG Li, ZHAO Haishan, DONG Ming, Xu Shiy, NAN Tianhao

2016, 45(S2):  139-146.  doi:10.11947/j.AGCS.2016.F035

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GIM data released by IGS is used in the article and a new method of combining the Sliding Time Window Method and the Ionospheric TEC correlation analysis method of adjacent grid points is proposed to study the relationship between pre-earthquake ionospheric anomalies and earthquake. By analyzing the abnormal change of TEC in the 5 grid points around the seismic region, the abnormal change of ionospheric TEC is found before the earthquake and the correlation between the TEC sequences of lattice points is significantly affected by earthquake. Based on the analysis of the spatial distribution of TEC anomaly, anomalies of 6 h, 12 h and 6 h were found near the epicenter three days before the earthquake. Finally, ionospheric tomographic technology is used to do tomographic inversion on electron density. And the distribution of the electron density in the ionospheric anomaly is further analyzed.

Co-seismic Displacement of the 25 April 2015 Nepal Ms8.1 Earthquake Effects on the China's Mount Everest Area Derived from GNSS Data Using the PPP Network Solution by UPD Ambiguity Fixed Technology

WANG Hu, LI Jiancheng, DANG Yamin, Cheng Yingyan, WANG Jiexian, YANG Qiang, XU Changhui, ZHANG Shoujian

2016, 45(S2):  147-155.  doi:10.11947/j.AGCS.2016.F036

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Co-seismic displacement of the GNSS stations in areas surrounding the earthquake are accurately obtained using UPD (uncalibrated phase delay) ambiguity fixed technology without having to consider the effects of earthquake on the GNSS baseline calculating. During the 25 April 2015 Nepal Ms8.1 seismological GNSS data from the National Datum Engineering of China, the Crustal Movement Observation Network of China and the Mount Everest GNSS stations are calculated using UPD ambiguity fixed technology, then co-seismic displacement field of the China's Mount Everest and surrounding areas are derived and analyzed. Firstly, the UPD of wide-lane and narrow lane are estimated using the uniform distribution National GNSS and the surrounding IGS stability stations away from the seismic zones. Secondly, the float carrier phase ambiguities from each GNSS station in the seismic zones are fixed using the UPD of wide-lane and narrow until all the GNSS station are completed. Then whole network GNSS station coordinates are just only estimated using the accurately phase observations without ambiguity form all the GNSS stations. The GNSS data from IGS stations are used to verify the precision of the above method. Finally, Co-seismic displacement field of the China's Mount Everest are derived and particularly analyzed. From 2005 to 2015 year the displacement of China's Mount Everest are showed. Meanwhlile, this paper provides a precise and reliable method to monitor earthquake.

Weights of Multiscale Ionospheric Tomography Determination Method Based on Mixed Penalty Function

YU Longfei, HU Wusheng, HAN Lixiang, ZHENG Dunyong

2016, 45(S2):  156-164.  doi:10.11947/j.AGCS.2016.F037

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For the ionospheric electron density (IED) distribution based on GNSS, multi-scale ionospheric tomography (MST) is a simultaneous application of many overlapping single-scale tomography (SST) with different pixel sizes by using the weight factor. MST can effectively solve the problem of the final IED distortion and the inadaptable problem in SST. In MST, the weight between different SST models is an important factor to influence the final ionospheric tomography accuracy. In order to obtain a high accuracy of MST model, considering the existence of equality and inequality constraints between the weights,the penalty function method is applied to the weights determination. Based on GNSS Observations for the tomographic reconstruction of IED distribution, the experimental results show that the accuracy of MST model obtained by the penalty function method is the highest than other methods. It is proved that the accuracy of the ionospheric tomography model can be effectively improved by using the appropriate weight factor.

The BDS Triple Frequency Pseudo-range Correlated Stochastic Model of Single Station Modeling Method

HUANG Lingyong, LÜ Zhiping, LÜ Hao, GONG Yisong

2016, 45(S2):  165-171.  doi:10.11947/j.AGCS.2016.F038

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In order to provide a reliable pseudo-range stochastic model, a method is studied to estimate the BDS triple-frequency pseudo-range related stochastic model based on three BDS triple-frequency pseudo-range minus carrier (GIF) combinations using the data of a single station. In this algorithm, the low order polynomial fitting method is used to fit the GIF combination in order to eliminate the error and other constants except non pseudo noise at first. And then, multiple linear regression analysis method is used to model the stochastic function of three linearly independent GIF combinations. Finally the related stochastic model of the original BDS triple-frequency pseudo-range observations is obtained by linear transformation. The BDS triple-frequency data verification results show that this algorithm can get a single station related stochastic model of BDS triple-frequency pseudo-range observation, and it is advantageous to provide accurate stochastic model for navigation and positioning and integrity monitoring.

The SSA+FBPF Method and Its Application on Extracting the Periodic Term from BeiDou Satellite Clock Bais

XIAO Shenghong, WANG Guocheng, TU Yi

2016, 45(S2):  172-178.  doi:10.11947/j.AGCS.2016.F039

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The frequency aliasing often exists when reconstructing the periodic signals using the singular spectrum analysis (SSA) method, the precision of the boundary value extracting by Fourier band-pass filtering (FBPF) is often not precise enough because of the influence of the residual trend term. In view of these kinds of situation, a combined method that joints SSA and Fourier band-pass filter method (SSA+FBPF) is proposed, the signal reconstructed by SSA is filtered by Fourier band-pass filter after SSA. The simulation results show that the reconstruction precision using SSA+FBPF method can improve 35% and 26% relative to that using the SSA and FBPF methods, respectively, in the case SNR is 0.017. These demonstrate that the SSA+FBPF method can reduce greatly the edge effect and has good robustness. The amplitudes of the 24 h terms obtained by the SSA+FBPF method from the BeiDou satellite clock PC06 and PC07 show that they have significantly variation.

Inertial Aided Cycle-slip Detection and Repair for BDS Triple-frequency Signal in Severe Multipath Environment

NING Yipeng, WANG Jian, HU Xuanxuan, WANG Shida

2016, 45(S2):  179-187.  doi:10.11947/j.AGCS.2016.F040

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Inertial information has been proposed to improve the success rate and repair rate for BDS triple-frequency cycle-slip detection in severe environment with multipath effects.At the same time, a BDS/INS loose coupled model has been developed. An innovative INS aided BDS triple-frequency combination method was developed which based on the traditional method of code-phase combination and geometry-free linear combination. The INS aided cycle-slip detection monitoring value was established and the effect of INS positioning error on cycle-slip capacity was analyzed. The proposed method overcomes the shortcoming of cycle-slip detection capacity influenced by the pseudorange observation precision. It also realizes small cycle-slips detection for BDS in severe multipath effects environment. At last, a field test was analysised with INS/BDS triple-frequency integrated positioning system onboard. The results indicate that the method proposed in this paper shows a high cycle-slip detection success rate and repair rate, when traditional triple-frequency detection model losed efficacy above water surface with multipath effects, and it also can be effective in low frequency sampling data.

The Positioning Performance Analysis of BeiDou/Pseudolites Collaboration by CNMC Method

FU Jingyang, ZHOU Jianhua, LI Guangyun

2016, 45(S2):  188-193.  doi:10.11947/j.AGCS.2016.F041

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At present, the number of orbit satellites is limited for the Beidou satellite navigation system. In special terrain like “city Canyon” and other special circumstances, the signal of Beidou is easy to be blocked, which reduces positioning accuracy or interrupts positioning continuity of users. Joining pseudolites can effectively solve the problem of the insufficient number of BeiDou satellites visible to users. During cooperative positioning of Beidou satellites and pseudolites, the multi-path problem in pseudo-range observation values of the BeiDou satellite and the pseudolite shall be properly handled to obtain better positioning accuracy. The CNMC method (Code Noise and Multi-path Correction) can effectively reduce the multi-path effect of the BeiDou satellite's pseudo-range observation value, but cannot be applied directly to pseudo-range data processing of the pseudolite due to different observation error characteristics caused by different signal propagation paths. To solve the multi-path processing problem of pseudolites, the CNMC method is improved in this paper. The BeiDou/Pseudolite dynamic cooperative positioning experiments were conducted in the actual field of pseudolites. The test results show that the three-dimensional positioning accuracy is increased from 2.326 m to 1.936 m with enhanced positioning stability after pseudo-range observation values of the BeiDou satellite and the ground pseudolite are processed by the CNMC method.