GNSS World of China

Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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Remote sensing image change detection based on cyclic convolution projection and EM algorithm
ZHANG Zelong, LI Jiatian, YANG Ruchun, YANG Chao, LU Dajin
 doi: 10.12265/j.gnss.2022010
[Abstract](69) [FullText HTML](31) [PDF 3018KB](13)
The detection of changes in remote sensing images in different tenses has become a challenging research topic in rapid remote sensing damage assessment. Aiming at the problem of how to determine the appropriate change threshold of pixel difference images in different temporal remote sensing images, this paper proposes a remote sensing image change detection method based on cyclic convolution projection and Expectation-Maximization algorithm (EM). First, the two temporal images are projected into their respective imaging modalities based on cyclic convolution, so that the projected image and the target image have the same statistics, and the pixel difference image between the two images can be obtained by subtracting pixel by pixel; secondly, based on the Bayesian minimum error rate theory and the distribution characteristics of the pixel difference image histogram, it is assumed that the pixel difference image obeys the generalized Gaussian distribution; finally, the maximum expectation algorithm is used to iteratively obtain the various parameters of the generalized Gaussian distribution. If the conditional probability of the pixel and the unchanged pixel are equal, the optimal change threshold can be obtained, and the adaptive change detection process can be completed. Experiments were performed on multiple pairs of remote sensing images collected under different imaging methods, resolutions and different types of changes. The results show that the detection accuracy of this method on the experimental data set is 2.55% higher than the comparison method on average, and the FM comprehensive evaluation index is increased by 0.086 on the average compared with the comparison method. It can detect the change area more accurately and has strong robustness.
2023, 48(2): 1-2.  
[Abstract](0) [FullText HTML](0) [PDF 2014KB](0)
Discussion on data processing technology about precise time transfer based on GNSS carrier phase observation
TU Rui, ZHANG Pengfei, ZHANG Rui, FAN Lihong, HAN Junqiang, WANG Siyao, LU Xiaochun
2023, 48(2): 1-9.   doi: 10.12265/j.gnss.2023003
[Abstract](11) [FullText HTML](3) [PDF 2254KB](1)
Precise time transfer is one of the most fundamental works in the field of time frequency. GNSS has become an important means of precise time transfer due to its advantages. In particular, the time transfer technology based on high-precision carrier phase observations developed in recent years has become a research hotspot in the GNSS based time-frequency field. This study comprehensively summarizes the research on GNSS carrier phase precise time transfer, expatiates on the observation model and ambiguity resolution method, and discusses the key technical issues such as precision, consistency, robustness, continuity, real-time, and integrity which are involved in the data processing. It is pointed out that this field should focus on the unity of un-differenced and differenced processing models, the unity of time service by integrating different mechanisms, and the seamless time service of sky, earth, sea and underground.
Review of GNSS direct position estimation techniques
ZHOU Zhijian, RAN Chengxin, DAI Zhiqiang, CHEN Zhengkun, XU Yiyu, ZHU Xiangwei
2023, 48(2): 10-21.   doi: 10.12265/j.gnss.2022199
[Abstract](50) [FullText HTML](15) [PDF 2912KB](18)
The direct position estimation (DPE) technology is robust to weak signals and multipath interference, which can overcome the shortcomings of traditional two-step methods that can not work normally in complex environments such as cities with tall buildings and indoors. This paper summarizes and analyzes the research status of the direct position estimation technology from three aspects: theory, implementation and application. According to previous researches, the problems of huge amount of computation, low positioning accuracy, and the need for initialization are summed up in the realization of direct position estimation. A receiver design framework in complex environments is presented in the application layer. The receiver judges whether to use DPE for navigation and positioning according to the signal availability, which can improve the positioning performance of the receiver in complex environments with minimal computational resources.
Theory and Discussion
Real-time orbit determination of Beidou satellite based on square root information filtering
YAO Xia, ZHENG Hongjie, YUAN Yongqiang
2023, 48(2): 22-29.   doi: 10.12265/j.gnss.2023031
[Abstract](24) [FullText HTML](12) [PDF 4015KB](7)
Continuous, stable and high-precision real-time satellite orbit products are essential for the international, scale and intelligent application of the BeiDou system. Current BDS real-time precise orbit products, which rely on “batch processing solution + orbit prediction”, suffer from poor continuity, low stability and low accuracy. Therefore, we introduce the square root information filtering method to perform real-time epoch-by-epoch solutions for the precise orbit of BeiDou satellites. Experimental results demonstrate that the BDS orbits generated by real-time filtering method outperform the ultra-rapid orbit products by effectively avoiding boundary jumps, improving continuity and stability. Moreover, the real-time filtering precise orbit determination method can significantly improve the orbit accuracy of BeiDou satellites, reducing the 3D orbit errors of MEO and IGSO satellites by 46% and 68%, respectively. Also, the validation by satellite laser ranging shows that the orbit accuracy of real-time filtering method is generally better than that of the predicted orbit.
Performance analysis of BDS-3 PPP/INS tightly-coupled positioning
SONG Debiao, SUN Fuping, XIAO Kai, KE Ye, SHANG Xiangyong, YU Yuan
2023, 48(2): 30-35.   doi: 10.12265/j.gnss.2022196
[Abstract](18) [FullText HTML](9) [PDF 4612KB](0)
With the completion of BDS-3 in China, the requirements of high-precision positioning and attitude determination based on BDS-3 is increasingly urgent. This paper derives the BDS-3 precise point positioning(PPP)model with ionosphere-free combination and inertial navigation system(INS)error equation in geocentric fixed coordinate system , and constructs the BDS-3 PPP/INS tight combination filtering model. This paper evaluates the positioning performance of BDS-3 PPP, BDS-3 PPP/INS loose combination model and BDS-3 PPP/INS tight combination model. The results of the experiment show that the position accuracy of BDS-3 PPP/INS loose combination is basically the same as that of BDS-3 PPP, the position accuracy of BDS-3 PPP/INS tight combination model in the east, north and sky directions is 7.9 cm, 9.3 cm and 9.4 cm, which is higher than that of BDS-3 PPP/INS loose combination model by 38.3%, 33.1% and 35.6%; the speed is improved by 27.3%, 45.8% and 12% respectively in three directions; the attitude accuracy of both is equal.
Comparison and analysis of GNSS precision point positioning performance based on DCB and OSB products
LIU Honghui, WANG Qianxin, YU Zhihao, WANG Maolei, LIU Yongliang
2023, 48(2): 36-42.   doi: 10.12265/j.gnss.2022191
[Abstract](39) [FullText HTML](9) [PDF 2594KB](10)
With the development of the Global Navigation Satellite System (GNSS), the channels and frequencies used for precision point positioning (PPP) are gradually diversified. Therefore, based on the original observation equations, this study derived the dual-frequency ionosphere-free (IF) PPP model for differential code bias (DCB) and observable-specific signal bias (OSB) products, respectively, and used 10-day continuous observation data collected from 50 Multi-GNSS Experiment (MGEX) stations to analyze the performance of the PPP model for each GNSS system. The results show that the performance of PPP model using the OSB product is consistent with that of the conventional DCB product, and the OSB product is more convenient to use and has more applications in future multi-frequency PPP.
Positioning performance analysis of single epoch RTK with Beidou-3 new frequency point (B1C/B2a)
TAO Zhenqiang, CHEN Jian, ZHAO Xingwang, LIU Chao, LIU Chunyang
2023, 48(2): 43-52.   doi: 10.12265/j.gnss.2022195
[Abstract](35) [FullText HTML](21) [PDF 6566KB](6)
The design of new frequency points (B1C/B2a) for BDS-3 effectively increases the diversity of multi-frequency combination positioning as well as improves the positioning performance of the BDS system. To systematically evaluate the RTK positioning performance of the new frequency point for BDS-3, 6 MGEX tracking stations were selected to form three baselines. Five single-frequency schemes of BDS-3 B1I/B3I/B1C/B2a/B2b, five dual-frequency uncombined schemes of BDS-2 B1I+B2I, BDS-2 B1I+B3I, BDS-3 B1C+B2a, BDS-3 B1I+B3I, BDS-2/BDS-3 B1I+B3I and a five-frequency uncombined scheme of BDS-3 B1I+B3I+B1C+B2a+B2b were designed for real-title kinematic(RTK) solving tests. When the baseline length does not exceed 25 km, the test results show that, in static mode, in east (E), north (N) and up (U) directions, the single-frequency positioning accuracy of BDS-3 new frequency point B1C/B2a is better than 2.85 cm, 1.67 cm and 4.02 cm respectively, and the dual-frequency positioning accuracy is better than 1.63 cm, 1.33 cm and 3.26 cm respectively, and the five-frequency positioning accuracy is better than 2.04 cm, 1.12 cm and 3.17 cm respectively; in kinematic mode, in E, N and U directions, the single-frequency positioning accuracy is better than 3.03 cm, 1.45 cm and 6.49 cm respectively, and the dual-frequency positioning accuracy is better than 1.92 cm, 0.95 cm and 6.71 cm respectively, and the five-frequency positioning accuracy is better than 2.32 cm, 0.91 cm and 4.89 cm respectively. The dual frequency positioning accuracy of BDS-3 new frequency point B1C+B2a and old frequency point B1I+B3I are compared in both modes, and are both better than that of the the BDS-2 B1I+B2I and B1I+B3I dual frequency. In addition, the positioning accuracy and stability of BDS-3 five-frequency uncombined scheme are better than single-frequency and dual-frequency uncombined schemes.
Satellite navigation signal acquisition method based on joint optimization of complexity and performance
ZHANG Pengcheng, HUANG Xinming, HOU Linyuan, LI Jingyuan, OU Gang
2023, 48(2): 53-58.   doi: 10.12265/j.gnss.2022169
[Abstract](30) [FullText HTML](4) [PDF 2254KB](3)
Aiming at the high computational complexity of short burst signal acquisition, an acquisition method based on the joint optimization of computational complexity and acquisition performance is proposed. The acquisition performance and computational complexity of the segmented correlation-video accumulation acquisition algorithm using parallel frequency search is derivatively analyzed. The joint acquisition optimization factor is constructed, and the optimal design is carried out for different frequency search intervals, different receiver sensitivities, and different numbers of correlators, and the optimal number of segments for computational complexity and acquisition performance is obtained. The simulation results show that this method can effectively control the computational complexity of the acquisition algorithm. When the input carrier-to-noise ratio is 45 dB-Hz, the number of correlators is 8, and the Doppler search interval is 2 000 Hz, meanwhile, the computational complexity can be reduced by 21.2% compared with the traditional acquisition optimization method.
Influence of differential code bias on QZSS single point positioning
LI Jiahao, JIA Xiaolin, DU Yanjun, XU Yu
2023, 48(2): 59-64.   doi: 10.12265/j.gnss.2022220
[Abstract](20) [FullText HTML](9) [PDF 2516KB](2)
To investigate the effect of differential code bias on Quasi-Zenith Satellite System(QZSS) pseudorange single-point positioning, this paper derives a differential code bias(DCB) and timing group delay(TGD) correction model for QZSS pseudorange single-point positioning, and selects 6 Multi-GNSS Experiment(MGEX) stations for 7 day of continuous observation data to conduct experiments according to two different schemes. The results show that the monthly stability of DCB products is good without obvious fluctuations, and the monthly stability of each satellite is better than 0.2 ns, and the mutual difference value with TGD is better than 2.5 ns. The impact of TGD/DCB correction on SPP accuracy is of meter level, and the horizontal positioning accuracy can be improved from 4–9 m to 3–6 m after TGD/DCB correction, and the elevation direction can be improved from 7–9 m to 5–7 m, and the improvement rate is about 10%–46%, which shows that DCB has a large impact on the single-point positioning accuracy and cannot be ignored in the positioning solution.
Time-differenced Carrier Phase velocity measurement method and accuracy evaluation based on GNSS real-time data stream
HU Bingyan, LYU Huanghui, ZHENG Jiawei, FANG Rongxin
2023, 48(2): 65-70.   doi: 10.12265/j.gnss.2023009
[Abstract](23) [FullText HTML](4) [PDF 2553KB](6)
In order to meet the real-time and accurate monitoring and early warning of geological disasters, and in view of the fact that the traditional GNSS carrier phase difference speed measurement mainly adopts the post-event simulation real-time processing mode, the post-event GNSS carrier phase difference speed measurement program is improved. Added the function of real-time data stream reception and real-time decoding of the RTCM to meet the needs of real-time speed measurement. Use the static station experiment and the shaking table to simulate the sine wave vibration experiment to evaluate the accuracy of the improved GNSS real-time speed measurement program. The root mean square (RMS) of the error in NEU directions in the static experiment is better than 5 mm/s; the RMS difference between the calculated speed in NEU directions and the true value in the dynamic experiment is 10.4 mm/s. It shows that the speed measurement accuracy of the real-time GNSS speed measurement program in this experiment can reach millimeter level under static real-time speed measurement conditions, and the speed measurement accuracy can still reach centimeter level under real-time dynamic conditions.
Adaptive step detection method combining CNN-BiLSTM-SA motion pattern recognition
YANG Yuncheng, WU Fei, ZHU Hai, ZHU Runzhe, YANG Mingze
2023, 48(2): 71-80.   doi: 10.12265/j.gnss.2022167
[Abstract](12) [FullText HTML](2) [PDF 5341KB](0)
With the popularity of location based services (LBS), smartphone-based pedestrian step detection methods have important impacts on pedestrian dead reckoning (PDR). We propose an adaptive step detection method combining CNN-BiLSTM-SA motion pattern recognition to address the problem that traditional methods have large step counting errors under multiple pedestrian motion patterns. Firstly, the motion patterns are classified according to the walking characteristics of pedestrians, and the local features of different motion patterns of pedestrians are extracted by using convolutional neural network (CNN), and the weights of the extracted motion features are assigned by using self-attention (SA) mechanism, and then the bidirectional long short term memory (BiLSTM) network is combined to mine the pre-post temporal relationship of pedestrian motion features for classification and recognition. Then the peak detection algorithm with two feature constraints, adaptive minimum peak distance and adaptive dynamic threshold, is proposed to detect the step frequency according to the classification results, and the threshold size is dynamically adjusted in walking. The experimental results show that the average error rate of the proposed method for step frequency detection under eight combined motion patterns is 1.31%, which is 5.97% lower than that of the traditional peak detection, and also better than the fixed threshold method.
Evaluation and analysis of satellite data of the BDS-3 system based on provincial regional ground-based augmentation system
WEI Yikuan, LI Fangting, TANG Xiaofei, ZHAO Peng
2023, 48(2): 81-87.   doi: 10.12265/j.gnss.2022203
[Abstract](61) [FullText HTML](14) [PDF 2429KB](2)
The quality of navigation satellite observation data is a direct factor that affects the positioning accuracy of ground augmentation system. The number of satellite observations obtained by BeiDou ground-based augmentation system after the adaptive transformation of Beidou-3 Navigation Satellite System (BDS-3) has increased by 30%−50% compared with the original Beidou-2 Navigation Satellite System (BDS-2). It is very important to evaluate and analyze the quality of these observations. In this paper, we propose a method to evaluate the quality of observation values of reference stations, such as analytical data integrity and multipath error, and use two methods such as zero-base line test and precise single point positioning test, to integrate the BDS-3 data analysis method of regional ground augmentation system. Based on this method, an empirical test was conducted in the study area. The results show that the data quality of BDS-3 satellites in the Asia-Pacific region has reached the same level as that of GPS. Due to the better spatial distribution structure of BDS-3 satellites, the available observation value of high elevation angle (altitude angle >50°) obtained by the ground stations has increased more than 200% compared with that of single GPS system.
Wavelet denoising and cycle slip detection and repair of BDS triple-frequency signal
CAI Wei, CHEN Mingjian, ZHOU Shuhan
2023, 48(2): 88-94.   doi: 10.12265/j.gnss.2022175
[Abstract](18) [FullText HTML](1) [PDF 3497KB](0)
The traditional triple-frequency code-phase combination method is easily affected by the pseudorange observation noise, and it is difficult to detect the insensitive small cycle slip. The triple-frequency geometry-free (GF) phasemethod has the ability to detect sensitive small cycle slip, but it has the problem of ill-conditioned equations. In view of this, this paper proposes a method of combining code-phase combination and GF model using wavelet denoising. Firstly, the pseudorange observations were denoised by wavelet transform. Then, the optimal combination model is constructed by selecting the optimal combination coefficient. Therefore, the quality of source data is ensured by wavelet denoising, and the accuracy of cycle-slip detection and repair is improved by code-phase combination and GF combination. At the same time, the problem of ill-conditioned equations is solved. Finally, the least square method combined with QR decomposition algorithm is used to fix the optimal integer of the cycle slip and repair the cycle slip by using spatial search and 1-norm minimum principle, and the triple-frequency measurement data of the BeiDou Navigation Satellite System (BDS) is collected for experimental verification. The experimental results show that the optimal combination model of wavelet transform denoising can detect and repair all kinds of cycle slips, especially for insensitive small cycle slips.
Automatic acquisition method of BeiDou Satellite Navigation weak signal based on density clustering
LIU Lunyan, ZHOU Yan, TANG Liyi
2023, 48(2): 95-100.   doi: 10.12265/j.gnss.2022198
[Abstract](26) [FullText HTML](5) [PDF 2697KB](3)
In order to effectively capture BeiDou Satellite Navigation (BDS) weak signal information under the influence of external RF signals and mixed frequency processing noise of navigation receiver, the automatic acquisition method of BDS weak signal based on density clustering is studied. The density clustering is used to design the satellite beam direction from the cluster center of BDS signal source in combination with the cluster center, and constrain the receiving range of satellite navigation signals, and resist the airspace interference of jamming signals. The noise information of navigation signal under the effect of beam anti-jamming is removed by wavelet threshold method. The correlation between the de-noised navigation signal and the known weak signal is calculated using the correlation function modulus calculation method. If the correlation is greater than the threshold value, the de-noised navigation signal is a weak signal. The experiment verifies that under the interference of external RF signals and mixers, this method has the ability to automatically capture the weak signals of BDS.
Precision analysis of BDS-3 multi-frequency undifferenced and uncombined precision orbit determination
JING Xin, LI Jianwen, ZHOU Shuhan, CAI Wei, KE Neng
2023, 48(2): 101-110.   doi: 10.12265/j.gnss.2022219
[Abstract](5) [FullText HTML](2) [PDF 4007KB](0)
In view of the observation data of BDS-3 at 5 frequencies and the theory of un-differenced and un-combined (UDUC) precise orbit determination, this paper introduces the UDUC model and parameter estimation method, proposes the strategy of station selection using the K-means algorithm, and analyzes the advantages of UDUC method. Through two kinds of station selection schemes, manual experience selection and K-means, 3 frequency selection methods of BDS-3 5-frequency, B1C+B2a, B1I+B3I are used respectively, and 30 IGS observation stations are used to carry out precise orbit determination for BDS-3 MEO and IGSO satellites. The experimental results show that when the stations which can receive B1C+B2a frequency observation data are insufficient, the UDUC method can increase the number of observation data and optimize the station layout by using the 5-frequency observation data so that the orbit determination accuracy can be improved. Compared with B1C+B2a, the monthly average RMS of 5-frequency in A, C and R directions increase by 0.003 m, 0.004 m, 0.003 m respectively, and that of 3D RMS increases by about 0.007 m. The stations selected through the K-means algorithm are more reasonably distributed and have higher orbit determination accuracy than manual experience selection scheme. With the 3 frequency selection methods, the monthly average RMS of MEO satellites in A, C and R directions are improved by 0.009 m, 0.017 m, 0.009 m respectively.
Technical Report and Application
Analysis of atmospheric error correction in satellite-ground time comparison and its influencing factors
WANG Rong, BAI Yan, ZHAO Jiaqi, GUO Yanming, CHEN Xiaofeng
2023, 48(2): 111-119.   doi: 10.12265/j.gnss.2022187
[Abstract](36) [FullText HTML](9) [PDF 2654KB](2)
Due to the complex space environment, the influence of the atmosphere on the radio and microwave signals is one of the main error sources for the high-precision satellite-to-earth two-way time matching. In order to meet the requirements of the satellite-ground time comparison, the ionospheric error correction method and dispersive troposphere delays correction method in the triple-frequency system are studied, the main factors affecting the atmospheric error correction are discussed, and the atmospheric error correction and the satellite-ground time comparison results under different scenarios are simulated and analyzed. The simulation results show that when the satellite attitude error is controlled within 100 as, the phase center calibration error is controlled within 5 mm, and the orbit position error is controlled within 30 cm.The root mean square (RMS) of ionospheric and tropospheric error residual are less than 0.006 ps and 0.06 ps respectively after correction, and the accuracy of star-ground time comparison is better than ps level.
BDS navigation satellite clock difference prediction based on PSO-Elman neural network
WANG Jingli, TONG Xiaoyu, ZHANG Mei
2023, 48(2): 120-126.   doi: 10.12265/j.gnss.2022183
[Abstract](24) [FullText HTML](6) [PDF 2402KB](0)
Satellite clock error is one of the important factors affecting the positioning accuracy of navigation and positioning system. Aiming at the problem of optimizing the precision clock error prediction performance of the BeiDou Navigation Satellite System (BDS), a method of optimizing the Elman neural network clock error prediction model based on particle swarm optimization (PSO) is proposed to solve the influence of the local optimal problem of Elman neural network on the clock error prediction results. Firstly, the clock error product is preprocessed. The initial weights and thresholds of Elman neural network are determined by iterative optimization of PSO algorithm, and the preprocessed sequence data are used for training modeling. The BDS precision clock error product data provided by IGS Data Analysis Center (WHU) of Wuhan University are used to predict the clock error, and then the prediction results are restored to predict the clock error. The results show that compared with the quadratic polynomial (QP) model, the polynomial (SA) model with additional period term, and the grey (GM) model, the accuracy is improved by 90.7%, 84.2%, 81.6%, and the stability is improved by 85.3%, 76.3%, 36.1%, respectively. The experimental results show that the prediction accuracy and stability of PSO-Elman model are significantly improved in 1−12 h short term forecast simulation, which verifies the feasibility of the proposed method.
Construction and development of satellite navigation augmentation systems
GUO Shuren, LIU Cheng, GAO Weiguang, LU Jun
2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1572) [PDF 1536KB](1197)
  Dynamic Positioning Accuracy Test and Analysis of BeiDou Satellite Navigation System
ZHANG Fengzhao, LIU Ruihua, NI Yude, WANG Ying
2018, 43(1): 43-48.   doi: 0.13442/j.gnss.1008-9268.2018.01.008
[Abstract](1375) [PDF 1895KB](301)
Accuracy analysis of BDS-2/BDS-3 standard point positioning
FANG Xinqi, FAN Lei
2020, 45(1): 19-25.   doi: DOI:10.13442/j.gnss.1008-9268.2020.01.003
[Abstract](656) [PDF 750KB](167)
Overview of Satellite Navigation Spoofing Signal Detection Technology
2018, 43(6): 1-7.   doi: doi:10.13442/j.gnss.1008-9268.2018.06.001
[Abstract](1114) [PDF 93258KB](257)
Positioning Performance Comparison and Analysis on BDS Dual and Triple Frequency Static Precise Point Positioning
2017, 42(1): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.01.011
[Abstract](493) [PDF 678KB](131)
A New Method of NMEA0813 Protocol Parsing
LIU Fushan, GUO Chengjun, JIA Zhendong
2017, 42(1): 70-73.   doi: 10.13442/j.gnss.1008-9268.2017.01.014
[Abstract](636) [PDF 476KB](128)
Analysis of Galileo Signal Quality and Positioning Performance
ZHOU Xingyu, CHEN Hua, AN Xiangdong
2018, 43(1): 19-24.   doi: doi:10.13442/j.gnss.1008-9268.2018.01.004
[Abstract](720) [PDF 1830KB](151)
Effect of image control point layout on the accuracy of real-world modeling of small-scale irregular areas of UAVs
ZHANG Guangzu, WANG Chun, XU Yan, TAO Yu, WU Liang, SHENG Shuai
2020, 45(2): 60-67.   doi: DOI:10.13442/j.gnss.1008-9268.2020.02.010
[Abstract](172) [PDF 2013KB](74)
The Method of Comparative Analysis Sliding and Non Sliding GPS Precise Ephemeris Interpolation
XU Wei, JIA Xue, YAN Chao, LIU Yang, DU Wenxuan, WANG Tao
2017, 42(2): 15-20.   doi: 10.13442/j.gnss.1008-9268.2017.02.004
[Abstract](420) [PDF 668KB](87)
High Precision GPS/BDS Data Processing and Precision Contrast Analysis Based on GAMIT10.61
LIU Xingwei, PU Dexiang, GAO Xiang, ZHANG Shiyong, XIA Dinghui
2018, 43(5): 77-83.   doi: 10.13442/j.gnss.1008-9268.2018.05.015
[Abstract](769) [PDF 648KB](210)
Construction and development of satellite navigation augmentation systems
GUO Shuren, LIU Cheng, GAO Weiguang, LU Jun
2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1572) [PDF 1536KB](134)
Since the birth of satellite navigation system, a variety of enhancement technologies and means are developed, and a large number of enhancement systems are established to meet the needs of users with higher accuracy and integrity. However, as a matter of fact, they are generated  later than the basic system and built independently on the respective demands, there are problems of “fragmentation” and “patch”  development, functional overlap with each other, lack of unified planning and standards, and unsystematic construction. This paper reviews and summarizes the generation and development process of satellite navigation augmentation technology, combings the relevant technical connotation and definition, and focuses on the related construction and development of China BeiDou Satellite navigation system augmentation system. On this basis, combined with emerging technologies such as 5G communication and loworbit satellites, the future development of satellite navigation augmentation system is prospected and analyzed.  Finally, suggestions are made for the augmentation system construction of the future BeiDou positioning, navigation and timing (PNT) comprehensive service.
Performance Analysis Joint of GPS/GLONASS/Galileo Precise Point Positioning Under Occlusion Condition
TIAN Xiancai, ZHAO Xingwang, XU Miaoqiang
2018, 43(6): 8-13.   doi: doi:10.13442/j.gnss.1008-9268.2018.06.002
[Abstract](1252) [PDF 62945KB](120)
For poor precision single point positioning performance of single GPS system under Occlusion Condition,to improve performance of precision single point positioning cross multisystem in this paper, By setting different Elevation mask angle, the environment around the city is divided into normal environment, general occlusion and heavy occlusion. Using GPS, GPS/GLONASS, GPS/Galileo, GPS/GLONASS/Galileo different modes respectively, the static PPP simulation experiments were carried out on four continuously operating reference stations in hong kong under the environment. the results show that multisystem combination can effectively remedy the shortage of satellites in the occlusion environment around the city, and the PPP performance of GPS/GLONASS, GPS/Galileo, GPS/GLONASS/Galileo combination is improved to varying degrees compared with that of a single GPS system.

Fog positioning and its applications
SHI Chuang, GU Shengfeng, JING Guifei, GENG Jianghui, LOU Yidong, TANG Weiming
2019, 44(5): 1-9.   doi: DOI:10.13442/j.gnss.1008-9268.2019.05.001
[Abstract](1280) [PDF 1146KB](91)
With the development of GNSS, the LBS (Location Based Service) has been popularized rapidly. Meanwhile, people’s demand for PNT service with high reliability, high credibility and high precision is increasingly urgent. PNT is a system which integrates multi-technology and multilevel systems. Focusing on the optimization of PNT service, domestic and overseas scholars have put forward several new architectures and technical systems such as All Source Positioning and Navigation, Resilient PNT and Cloud Positioning. This study states, that with heterogeneous positioning resources which are capable in communication, calculation, storing, positioning and sensing as infrastructure construction, PNT service with high reliability, high credibility and high precision can be realized by intelligent management and scheduling of heterogeneous positioning resources distributed in different geolocations. Further, the definitions of Fog Positioning and Omnipresent Positioning and Navigation are given. It is argued that the definition of Fog Positioning is evolved from distributed computing architecture and emphasizes the architecture for PNT service. While the definition of Omnipresent Positioning and Navigation is evolved from the development of positioning technology and emphasizes the ability to realize omnipresent positioning by collaborative fusion processing of omnipresent positioning resources. On this basis, by comparing Fog Positioning with Cloud Positioning, this study points out that Fog Positioning is the extension of Cloud Positioning towards the user side and the omnipresent realization of positioning resources. Meanwhile, Fog Positioning is one kind of dynamic and elastic cloud, so Fog Positioning can be seen as a PNT architecture with the property of elasticity. Omnipresent positioning is an important target of PNT architecture, and Fog Positioning gives the potential means for this target, e.g., Omnipresent Positioning and Navigation. At last, this contribution analysis the basic service mode for Fog Positioning or Omnipresent Positioning and Navigation under the city environment and indoor environment.
A novel engineering implementation technique for acquiring B1C signal in the BeiDou-3 receiver
YAN Shulin, DING Chao
2019, 44(1): 1-9.   doi: DOI:10.13442/j.gnss.1008-9268.2019.01.001
[Abstract](1159) [PDF 1077KB](86)
The modern signals of the Chinese BeiDou-3 navigation system bring new features compared to the previous civilian signals, such as longer spreading code, involving secondary code, new modulation technique (i.e. Binary Offset Carrier BOC), data/pilot channels and so on. These innovations are able to enhance the signal acquisition robustness, but they also require specific acquisition techniques to handle the large data stream, deal with the problem of sign transition and side peaks caused by the secondary code and the BOC modulation respectively. This paper proposes a novel two-stage acquisition technique for realizing efficient acquisition of the B1C signal in the engineering implementation of the modern receiver. The first stage employs an extended parallelized Averaging Correlation (AC) search structure, which can cope with the sign transition problem, to coarsely capture the signal with high efficiency. At the second stage, a fine-search process is completed within a reduced searching range to provide high precision result. The involving of the later stage aims to avoid the side peaks effect in the tracking stage that can easily cause a false lock. In addition, both of the single and channel combining acquisition techniques are introduced, which give designers an option of implementing the acquisition with higher sensitivity but more resources. The experiment results demonstrate that the proposed method allows to use much cheaper FFT blocks and enables fast acquisition by parallel process. The proposed method can reduce the number of multiplications by at least 61% when the sampling frequency is over 50 MHz while providing quite similar acquisition precisions with the conventional method.
  Research Progress and Prospect of PPP/INS Integration System
WANG Haoyuan, SUN Fuping, XIAO Kai
2017, 42(5): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.05.011
[Abstract](1237) [PDF 778KB](78)
With the construction of GNSS multi-system, precise point positioning (PPP) technology is developing in the direction of real-time and ambiguity-fixed solution. The PPP/INS integration system has a wide application prospect in the navigation and surveying field, since the convenience of not laying base station. In this paper, the contributions of GNSS multi-system, PPP ambiguity fixing, INS-aided to the PPP/INS integration system are systematically summarized. And the progresses of filtering method, smoothing algorithm and stochastic model establishment in integration system are generalized. The development trend of the PPP/INS integration system is discussed.

Bimonthly, Established 1976

Sponsored by:China Institute of Radio Transmission

Competent Authorities:China Electronics Technology Group Corporation

ISSN 1008-9268

CN 41-1317/TN