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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Spatial signal error and precise point positioning evaluation of Galileo high accuracy service
DING Yao, FANG Rongxin, CHEN Guo, HU Bingyan, CHENG Yifan
 doi: 10.12265/j.gnss.2024052
[Abstract](21) [FullText HTML](7) [PDF 5630KB](2)
The high accuracy service (HAS) of the Galileo system uses E6B signals to broadcast free precision satellite orbit, clock deviation and code deviation correction information to users around the world, which is of great significance in the field of high-precision real-time satellite applications. Evaluating the spatial signal error and precise point positioning performance is an important prerequisite for using HAS well. Based on the HAS orbital clock products from December 1 to 31, 2023, the root mean square errors (RMSE) of the Galileo satellite orbit products were 4.16 cm, 8.42 cm and 7.62 cm in the radial (R), tangential (A) and normal (C) directions, and 4.52 cm, 9.99 cm and 7.07 cm in GPS, respectively, while the standard deviation (STD) of the Galileo clock products was 0.16 ns and 0.26 ns for GPS. Precise point positioning (PPP) was carried out based on the observation data of 10 stations in Europe. The results show that the positioning accuracy of Galileo in the east (E), north (N) and zenith (U) directions is 6.44 cm, 4.65 cm and 11.36 cm, GPS is 7.42 cm, 5.78 cm and 12.04 cm, and the joint positioning is 4.11 cm, 3.10 cm and 7.56 cm, respectively. The results indicate that HAS can meet the high-precision positioning requirements.
GNSS vertical time series denoising method for mining area subsidence monitoring
ZHENG Canguang, ZHENG Hui, XIE Shicheng, ZHU Mingfei, HAN Yuchen, YANG Xu
 doi: 10.12265/j.gnss.2024002
[Abstract](24) [FullText HTML](6) [PDF 2837KB](0)
The GNSS technology, as an important tool for mining subsidence monitoring, is significantly affected by the noise present in its time series. This paper proposes a denoising method that combines an Improved hybrid grey wolf particle swarm optimization (IPSOGWO) and an improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN), coupled with wavelet thresholding (WT). The IPSOGWO optimizes the hyperparameters of the ICEEMDAN algorithm to decompose the GNSS time series and extract the intrinsic mode functions (IMF). The multi-scale permutation entropy is used to select the IMF components containing noise. These components are then secondarily processed using wavelet thresholding and reconstructed with the remaining IMF components to obtain the denoised results. Experiments with simulated signals and actual data from an automated monitoring station in a mining area demonstrate that the proposed method outperforms the wavelet threshold, complete ensemble empirical mode decomposition (CEEMD), and GWO-ICEEMDAN in terms of denoising performance, providing reliable data for subsequent analysis of working face subsidence.
Improved vision/inertial guidance fusion localization algorithm for vision front-end
LI Zhizheng, NIE Zhixi, WANG Zhenjie, ZHANG Yuanfan
 doi: 10.12265/j.gnss.2024024
[Abstract](28) [FullText HTML](12) [PDF 3951KB](0)
Aiming at the problem of high-precision positioning of mobile robot in Global Navigation Satellite System GNSS denied environment, An adaptive thresholding adaptive and generic accelerated segment test AGAST feature detection algorithm is proposed to improve the visual front-end of a vision/inertial guidance fusion localization system for mobile robots. The algorithm improves the visual odometry computation method by local histogram equalization and adaptive threshold detection, improves the quality of feature point extraction, and enhances the positioning accuracy and stability of visual odometry in complex environments. Visual odometry and inertial navigation system are fused based on factor graph optimization algorithm to realize high-precision positioning of mobile robot. The results show that, compared with the mainstream VINS-Mono algorithm, the proposed algorithm improves the positioning accuracy by 22.8% in the experiment of indoor data set and 59.7% in the experiment of outdoor data set, the proposed algorithm perform better than VINS-Mono algorithm in both two experiments and it can provide better positioning services for mobile robots.
Improved MixNet for indoor localization using CSI image fingerprints
LONG Liang, WANG Xiaopeng, LI Gang, WANG Jiang
 doi: 10.12265/j.gnss.2023198
[Abstract](35) [FullText HTML](12) [PDF 2682KB](1)
To enhance the performance of indoor localization using channel state information (CSI) fingerprints, an CSI image-based indoor localization method based on the improved MixNet model is proposed. In the offline phase, the method involves selecting the three access points (APs) with the highest received signal strength indication (RSSI) at the reference point (RP), extracting their CSI data, and converting it into image. Subsequently, the improved MixNet model is employed to train on these images and save the model. The improved MixNet model introduces coordinate attention (CA) and residual connections. Specifically, it replaces the squeeze-and-excitation (SE) attention in MixNet-s with CA to enhance the network’s information representation capability and extract CSI image fingerprint features more accurately. Moreover, it incorporates residual connections, tailored to the characteristics of the MixNet-s model, to enhance the network’s representation capacity and prevent overfitting. Finally, the network depth is reduced to ensure that all network layers are adequately trained. During the online phase, CSI data from the target device is collected and converted into image, and then input into the pre-trained improved MixNet model (named MixNet-CA). The final device position is estimated using a weighted centroid algorithm based on the model's output probabilities. The proposed method is validated in an indoor environment and achieve an average positioning error of 0.362 0 m.
Research on indoor location algorithm based on 5G+UWB
ZHANG Kaili, TU Rui, LI Fangxin, XU Xiayun, WANG Bing
 doi: 10.12265/j.gnss.2024038
[Abstract](66) [FullText HTML](14) [PDF 2741KB](7)
The 5th-Generation (5G) communication technology has brought new possibilities to the field of indoor positioning. Ultra-broadband (UWB) location technology, like 5G location, has the characteristics of large bandwidth and high frequency, but there are slight differences in positioning performance. To address the issues of poor accuracy and stability in single sensor positioning, a fusion positioning algorithm of 5G+UWB was studied in this paper. It establishes an indoor positioning system based on time difference of arrival (TDOA) for 5G, a UWB indoor positioning system based on trilateral positioning algorithm, and a 5G+UWB indoor positioning model based on the fusion positioning algorithm. The initial positioning results of each single system obtained through weighted least squares (WLS) algorithm are validated, followed by verification of improved positioning results obtained through Taylor series expansion method. Furthermore, experimental verification is conducted on the combined positioning results obtained by fusing the positioning results of the two single systems. It has been indicated by the experimental results that UWB single-system positioning shows lower accuracy but higher stability, while 5G single-system positioning exhibits higher accuracy but lower stability. After the combination of the two methods, the accuracy and stability of the combined system can be relatively high. The positioning accuracy of the combined system can be as high as 0.22 m and as low as 0.73 m, enabling sub-meter level positioning.
Smartphone RTK positioning based on integrated weighting of GNSS base station signal-to-noise ratio and joint satellite system
WANG Ershen, WANG Heng, ZHANG Yize, CHENG Quanrun, TANG Wenjie, LEI Hong
 doi: 10.12265/j.gnss.2024045
[Abstract](29) [FullText HTML](8) [PDF 3056KB](0)
With the continuous improvement of smartphone chip and antenna performance, high-precision positioning based on mobile phones has gradually attracted widespread attention from academia and industry. Compared with single-point positioning, real-time kinematic (RTK) positioning usually shows higher positioning performance. However, there are still relatively few studies on the stochastic model of mobile phone RTK positioning. Therefore, this study takes Xiaomi 8 as an example to focus on the stochastic model of smartphones in a multi-system RTK positioning scenario. The research results show that different systems There are significant differences in satellite pseudorange noise, while the difference in phase noise is smaller. Based on this, this paper proposes a stochastic model of base station signal-to-noise ratio combined with comprehensive weighting between satellite systems, which is more efficient than the traditional signal-to-noise ratio model. The weight distribution between different systems was accurately considered. Static and kinematic experiments were conducted under open and occluded conditions. The results show that compared with the traditional signal-to-noise ratio model, the new model is RTK positioning accuracy in the three-dimensional direction under static openness, static occlusion, kinematic openness and kinematic occlusion has increased by 18.7%, 18.3%, 3.3% and 4.6% respectively.
Fractional cycle bias estimation and ambiguity resolution for Galileo triple-frequency uncombined PPP
XIONG Bowen, PAN Lin, PEI Gen, LIU Ning, ZHANG Xiangyue, DENG Min
 doi: 10.12265/j.gnss.2023157
[Abstract](32) [FullText HTML](14) [PDF 2642KB](3)
Galileo already has 28 in-orbit satellites, with precise positioning capabilities on a global scale. All Galileo satellites are capable of broadcasting multi-frequency signals, and multi-frequency integration is expected to further improve the performance of precise point positioning (PPP) ambiguity-fixed solutions. In this paper, the fractional cycle bias (FCB) estimation method and ambiguity resolution (AR) method for Galileo triple-frequency uncombined (UC) PPP are developed, and the derived results are compared with those of dual-frequency UC PPP ambiguity-fixed and ambiguity-float solutions. The results indicate that the standard deviation (STD) of UC FCB series on a single frequency is better than 0.04 cycles using datasets from 155 globally distributed ground tracking stations. The convergence time of Galileo dual-frequency PPP float solutions in the east, north and up directions is 32.0 min, 10.0 min and 43.5 min, respectively, and the corresponding statistic of dual-frequency PPP fixed solutions is reduced to 30.5 min, 8.5 min and 32.0 min in the three directions, respectively. The convergence time of triple-frequency PPP fixed solutions is further shortened to 16.5 min, 8.0 min and 32.0 min in the three directions, respectively.
Dynamic feature point removal method with joint target detection and depth information
YE Ruixin, ZHANG Lingwen, CHEN Jia, QIAO Shangbing, ZHU Ying
 doi: 10.12265/j.gnss.2024015
[Abstract](28) [FullText HTML](15) [PDF 3545KB](0)
Aiming at the problem that the localization accuracy and robustness of visual localization systems are easily affected by dynamic feature points in dynamic environments, a dynamic feature point removal method combining target detection and depth information is proposed. The YOLOv7 target detection network is introduced to quickly obtain the target category and position information of the current image frame, and the coordinate attention (CA) mechanism is added to optimize the deep learning model and improve the target detection accuracy of the network. In addition, a dynamic feature point optimization strategy using depth information and pairwise geometric constraints is proposed. Dynamic feature points are effectively eliminated while as many static points as possible are retained, thus reducing the impact of dynamic points on the localization accuracy and robustness of the system. Experimental validation is performed on the publicly available dataset TUM. The results show that the proposed scheme has obvious advantages in terms of localization accuracy and robustness compared with ORB-SLAM2. At the same time, compared with DynaSLAM, the localization accuracy is basically the same, but the operation speed is significantly improved.
A quality evaluation method of 3D water vapor tomography based on multi-GNSS observations
GAO Fenglin, DING Nan, ZHANG Kefei, ZHANG Shubi, ZHANG Wenyuan, YAN Xiangrong
 doi: 10.12265/j.gnss.2024004
[Abstract](33) [FullText HTML](14) [PDF 2760KB](1)
In this paper, we present an evaluation of the water vapor tomography results from four systems-GPS, BDS, GLONASS, and Galileo in terms of accuracy, using the proposed water vapor tomography profile evaluation index TPFS. The results show that the differences in the water vapor tomography solving results of each GNSS are negligible, with the maximum RMSE difference being within 11%. Among these, BDS performs the best in water vapor tomography, while GLONASS performs the worst. Compared with GPS, GLONASS, and Galileo, BDS has a significant advantage in the lower layer (below 2406m). In particular, in the bottom layer, BDS shows a respective improvement of 3.2%, 16.2%, and 5.2% in RMSE compared to GPS, GLONASS, and Galileo. Furthermore, in the comparison of TPFS of tomography water vapor profiles, BDS has the smallest average TPFS and the lowest TPFS of water vapor profiles under heavy rainfall, which is improved by 25.2%, 31.5%, and 32.8% compared to GPS, GLONASS, and Galileo.
Research on evaluation of GNSS system broadcast ERP parameters
ZHANG Fen, RUAN Rengui, JIA Xiaolin, ZHU Yongxing, WANG Long
 doi: 10.12265/j.gnss.2023191
[Abstract](22) [FullText HTML](9) [PDF 2594KB](1)
Modernized navigation messages of global navigation satellite systems like BDS, GPS, QZSS and IRNSS include earth rotation parameters (ERPs), namely the pole coordinates and UT1-UTC (ΔUT1). Broadcast ERPs are primarily needed for space-borne GNSS applications that require transformations between earth-fixed and inertial reference frames like satellite precise orbit determination as well as earth to the moon navigation. Based on the International GNSS Service (IGS), we obtained broadcast ERP data for BDS, GPS, QZSS, and IRNSS from January 1, 2022 to June 5, 2023. Evaluate the discontinuity of broadcast ERP, the results show that for GPS and IRNSS, the discontinuity of polar motion is 0.9 to 1.4 mas, and the ∆UT1 discontinuity is about 0.2 ms. The discontinuity of polar motion is about 0.1 mas, and the ∆UT1 discontinuity is about 0.02 ms for QZSS. The discontinuity of BDS polar motion is about 4.5 mas, and the ∆UT1 discontinuity is about 1.3 ms. Compared with the external reference 14C04 sequence of the International Earth Rotation and Reference System Service (IERS), the QZSS polar motion error is about 0.6 mas, and the ∆UT1 error is about 0.27 ms. The polar motion of GPS and IRNSS is about 2.4 mas. For ∆UT1, the GPS error is about 0.36 ms, the IRNSS is about 10.47 ms, which is a significant difference. BDS polar motion error is about 6 mas, and ∆UT1 error is about 1.2 ms. Due to less frequent update intervals, compared with GPS, BDS performs worse by a factor of 1.5 and 2.5 for polar motion and ∆UT1 error, respectively.
Design and implementation of multi-frequency and multi-GNSS data preprocessing software
HU Weijian, LU Liguo, WU Tangting, LIANG Qiao
 doi: 10.12265/j.gnss.2024011
[Abstract](47) [FullText HTML](14) [PDF 3873KB](7)
GNSS data preprocessing plays a crucial role in achieving high-precision navigation, positioning, and attitude applications. However, existing GNSS preprocessing tools and modules face challenges in handling multi-frequency and multi-GNSS observation data. To address this issue, we have developed a GNSS data preprocessing software called (GDPS). GDPS includes modules for data download, format conversion, data editing, quality check and auxiliary tools. The software has been implemented using the PYQT5 tool, which enables a graphical user interface. Experimental tests have demonstrated that the software offers a clear interface, strong interactivity, stable module operation, and comprehensive software functions. Consequently, it effectively caters to the diverse needs of users for preprocessing multi-frequency and multi-GNSS observation data.
Application research of RINGO software in multi-system GNSS data preprocessing
FAN Jiuguo, LI Jianyong
 doi: 10.12265/j.gnss.2023202
[Abstract](90) [FullText HTML](17) [PDF 4282KB](9)
Data preprocessing is a prerequisite for achieving high-precision positioning with the Global Navigation Satellite System (GNSS) and is also a vital step in data processing. As the number of satellite systems, numbers, and versions of Receiver Independent EXchange format (RINEX) increase, the GNSS data types and formats become progressively complex. Thought there are various data preprocessing software options available, multiple programs are required to complete the preprocessing stage, resulting in inefficiency and complexity. Therefore, to achieve efficient data preprocessing, developers have created the “RINGO” data preprocessing software, which supports all RINEX versions of multi-system data preprocessing. To achieve effective data preprocessing, developers created the “RINGO” software which supports all RINEX versions of multi-system data preprocessing. The study demonstrates the main functions, usage and principles of RINGO, with a focus on investigating and explaining confusing functions such as receiver clock jump correction. The test results demonstrate that RINGO can effectively and independently preprocess vast amounts of multi-system GNSS data, which can significantly ease the complex task of GNSS data management and foster the adoption of the latest version of RINEX observation records.
Extraction of common mode error based on SSA method and its impact analysis on GNSS vertical coordinate time series
 doi: 10.12265/j.gnss.2023223
[Abstract](26) [FullText HTML](13) [PDF 2160KB](0)
This study, based on eight years of data from 24 Global Navigation Satellite Systems (GNSS) stations in northern Germany, introduces the singular spectrum analysis method. It proposes a common mode error identification method that considers the inter-correlation of different residual subcomponents and their contribution rates. The impact of common mode errors on GNSS coordinate time series noise and parameter estimation is explored. Compared with the principal component analysis (PCA) method, it is found that the method proposed in this paper closely aligns with the common mode errors extracted by PCA, confirming the feasibility of the new method. The GNSS common mode error sequence mainly contains white noise, flicker noise, and power-law noise with non-integer spectral indices. After removing common mode errors, the magnitude of white noise and colored noise at each station decreased by an average of 30.32% and 52.61% respectively, indicating that colored noise dominates in common mode errors. Furthermore, after correcting common mode errors, the annual and semi-annual cycle amplitudes of coordinates are reduced, and the root mean square error of parameter fitting is decreased by 16.7%. In summary, the method described in this paper is of significant practical importance in improving the quality of GNSS coordinate time series.
Ship trajectory analysis system based on satellite navigation and spatio-temporal entity
LU Wei
 doi: 10.12265/j.gnss.2024009
[Abstract](28) [FullText HTML](12) [PDF 2956KB](0)
Based on satellite navigation, spatio-temporal entities, web geographic information system (WebGIS), spatial databases, etc., key information on ship attributes, real-time positions, historical paths, associated relationships, and operating statuses has been extracted, leading to the construction of ship entity resources and the establishment of a ship trajectory analysis system. The system provides functions such as map services, trajectory data management, trajectory visual query display, trajectory spatio-temporal analysis display and analysis model parameter configuration. It enables management and analysis of multi-source, multi-temporal and diversified ship trajectory data, presenting ship element characteristics and analysis results, increasing information value density, and enhancing query and analytic abilities. Thus, it enhances the efficiency and accuracy of ship trajectory analysis, serving as a more effective support for ship trajectory analysis business and related applications.
GNSS/IMU/LiDAR fusion positioning research
LIU Ao, GUO Hang, XIONG Jian, WANG Mengli
 doi: 10.12265/j.gnss.2024013
[Abstract](93) [FullText HTML](16) [PDF 2345KB](5)
To improve the anti-interference and positioning accuracy of conventional integrated navigation and positioning under the conditions of low-cost satellite receivers and IMU, this paper proposes to fuse GNSS, inertial measurement unit (IMU), and laser radar (LiDAR) to enhance the robustness and accuracy of positioning. In complex environments such as high-rise buildings, where satellite signals are lost, the robustness and accuracy of navigation and positioning can be improved by fusing IMU and GNSS. However, if the satellite signal loss time is too long, the IMU/GNSS integrated positioning accuracy under low-cost conditions is still not ideal. This paper proposes to use the position information output by the LiDAR odometer and the conventional integrated navigation to perform fusion positioning through extended Kalman filter (EKF). The experiments show that in the unobstructed environment, the fusion positioning standard deviation (STD) accuracy is 53.7% higher than the satellite positioning, the root mean square error (RMSE) accuracy is 56% higher, the fusion positioning STD accuracy is 37.9% higher than the GNSS/IMU integrated positioning, and the RMSE accuracy is 38.6% higher. In the obstructed environment, the fusion positioning STD accuracy is 59.4% higher than the satellite positioning, the RMSE accuracy is 71.3% higher, the fusion positioning STD accuracy is 26.3% higher than the GNSS/IMU integrated positioning, and the RMSE accuracy is 33.7% higher.
Improved algorithm for tree height extraction based on sparse and dense image matching with epipolar constraints
CAI Xiangyuan, CHEN Xiaotong, LI Ronghao, WEI Jiangnan, LI Shuai, ZHAO Hongying
 doi: 10.12265/j.gnss.2023221
[Abstract](34) [FullText HTML](11) [PDF 3018KB](3)
Tree height is a crucial parameter for monitoring forest conditions,and photogrammetry stands out as an essential method for tree height acquisition due to its low cost and flexibility. As a passive remote sensing approach, the traditional photogrammetric method often requires a substantial quantity of images with high overlap, which is associated with the sparsity of traditional image features. To enhance tree height extraction accuracy under limited image availability, a proposed approach combines sparse feature matching with dense pixel matching, by employing the epipolar constraint to filter outliers, dense and highly accurate matching results are obtained. The three-dimensional reconstruction algorithm is then applied to generate a point cloud representing the forest scene. This method demonstrates the capability to reconstruct the forest scene comprehensively and extract tree heights even with a small number of images. Comparison with results from LiDAR point clouds yields a correlation coefficient of 0.91 and a maximum error of 1.64 meters. Notably, the algorithm requires only a small number of overlapping images, indicating its potential in handling high-resolution satellite imagery.
Architecture design of radiation source positioning system based on TDOA
HU Anyi, WANG Dengliang, QIN Bingkun, ZHANG Faxiang
 doi: 10.12265/j.gnss.2023174
[Abstract](81) [FullText HTML](49) [PDF 2726KB](7)
To ensure the normal application of the Global Navigation Satellite System (GNSS), monitoring and localization of GNSS interference radiation sources are required. This paper presents the design of a radiation source positioning system architecture. By designing the system functions, architecture, grid monitoring equipment and workflows, high-precision time synchronization and reliable time difference measurements are achieved using BeiDou/GPS timing + high-stability crystal oscillators and a generalized weighted time delay estimation algorithm, which ensures the accuracy of time difference of arrival (TDOA) localization. The effective location of radiation source is realized through system application test.
2024, 49(2): 1-2.  
[Abstract](73) [FullText HTML](57) [PDF 2043KB](9)
Theory and Discussion
The performance of SF-PPP corrected by different ionospheric models
WU Pituan, QIN Xian, WEI Jia, XIAO Minghong, HUANG Ming, YANG Zhao
2024, 49(2): 1-8.   doi: 10.12265/j.gnss.2023225
[Abstract](109) [FullText HTML](25) [PDF 2653KB](19)
Ionospheric delay can seriously affect the positioning accuracy of single-frequency global navigation satellite system (GNSS) receiver. Thus, this paper assessed the positioning error of single-frequency GNSS receiver corrected by four commonly used ionospheric delay correction methods, i.e., broadcast ionospheric correction models (strategy 1), time-rotation interpolation of Global Ionosphere Map (GIM) considering the variation of the position for the sun (strategy 2), GIM corrected by ionospheric mapping function (strategy 3), and half-sum correction model (strategy 4). Meanwhile, the correction results of different methods for the single-frequency precise point positioning (SF-PPP) were evaluated by using the data collected by ground-based GNSS stations over different latitudes on solar condition days. The assessment results were listed as follows. 1) The positioning error of SF-PPP corrected by the half-sum correction model was the best, then was the ionospheric delay corrected GIM. The positioning error corrected by broadcast ionospheric model was the worst. 2) On different solar condition days of each strategy, the positioning error for low-latitude stations was the largest, the was high-latitude stations. The positioning error for mid-latitude stations was the smallest. 3) The horizontal positioning error of strategy 2 and strategy 3 was about 0.150 m over different latitudes on different solar activity periods, while the 3D positioning error is about 0.700 m. The corresponding errors were about 0.100 m and 0.500 m for strategy 4.
GNSS coordinate time series denoising analysis combined with weighted wavelet and EEMD
WEI Guanjun, ZHANG Pei, WANG Liyang
2024, 49(2): 9-15.   doi: 10.12265/j.gnss.2023096
[Abstract](87) [FullText HTML](32) [PDF 2986KB](7)
Aiming at the problem that it is difficult to accurately separate the useful signal and noise in the GNSS coordinate time series, this paper proposes a noise reduction method based on combined weighted wavelet Z-transform (WWZ) and set empirical mode decomposition (EEMD). Through the noise reduction processing of the vertical coordinate time series of 70 continuous stations in the northwest region, the root mean square error (RMSE), signal-to-noise ratio (SNR), flicker noise (FN) amplitude and velocity uncertainty are used as the evaluation indicators respectively, which verifies that the noise reduction effect of the method in this paper is superior to wavelet noise reduction and EEMD noise reduction to a certain extent. The results show that compared with wavelet denoising and EEMD denoising, the RMSE of signal sequence after denoising is reduced by 0.331 mm and 0.757 mm respectively, and the SNR is increased by 1.911 dB and 3.635 dB respectively; The uncertainty of FN amplitude and velocity has been significantly improved, which verifies the effectiveness of the noise reduction method in this paper.
5G channel state information signal quality and positioning performance analysis
CHENG Zhenhao, LI Linyang, GUO Wenzhuo, LAI Luguang, ZHAO Dongqing
2024, 49(2): 16-22.   doi: 10.12265/j.gnss.2023119
[Abstract](100) [FullText HTML](22) [PDF 2505KB](10)
5G channel state information (CSI) has rich feature information, but it is greatly affected by environmental information , which directly affects the fingerprint positioning performance. In order to analyze the degree of influence of different factors on 5G signal quality and positioning performance, this paper first expounds the 5G signal characteristics and positioning algorithm based on support vector regression (SVR), analyzes the influence of terminal height, direction, human body occlusion and other factors on signal quality during data acquisition, and tests the positioning performance in three scenarios: hallway, small office and medium-sized conference room. The results show that the 5G signal is greatly affected by the surrounding environment, and the positioning accuracy of the location fingerprint localization algorithm based on 5G channel state information has positioning accuracy of 0.93 m, 1.46 m and 1.94 m respectively in three scenarios, which can meet the needs of most indoor positioning applications.
Application of robust Vondrak filtering method in time-frequency transmission
ZHANG Zhichao, JIA Xiaolin, JIAO Wenhai, YAN Xianggao, LI Jiahao
2024, 49(2): 23-29.   doi: 10.12265/j.gnss.2023192
[Abstract](69) [FullText HTML](14) [PDF 2999KB](6)
The results of time-frequency transfer will be affected by the non-modeling error and observation noise, which is often high-frequency signals, and the construction of low-pass filter can eliminate the high-frequency noise signals in the observation sequence to a certain extent. In this paper, we analyze the nature of the Vondrak filter function, weight the clock difference sequence by the IGG3 algorithm and select the suitable filtering factor by the frequency response method; we conduct the satellite two-way time and frequency transfer experiment (TWSTFT), the satellite two-way time and frequency transfer experiment based on the software receiver (SDR-TWSTFT), and the short-baseline common-view time and frequency transfer experiment on the different links, and use the short-baseline common-sight time and frequency transfer method on the results. experiments, and the clock difference results are smoothed and denoised by anti-differential Vondrak filtering. The results show that: the filtered clock sequence can well reflect the trend of the original clock sequence; the daily fluctuation effect is effectively suppressed and the accuracy of the smoothed TWSTFT clock result is significantly improved; the accuracy of the common-view clock result is significantly improved, and the difference between the result and the precise point positiening (PPP) timing result is kept in the range of −1.0 to 1.0 ns.
Application research of gray model in unmanned motion target localization
ZHANG Fengwei, CUI Jianyong, ZHANG Zhengyu, ZHANG Xianzhi, DOU Sai
2024, 49(2): 30-35.   doi: 10.12265/j.gnss.2023190
[Abstract](81) [FullText HTML](19) [PDF 2392KB](7)
A method based on grey theory is proposed to solve the problem of unmanned moving target positioning caused by weak signals or strong interference in the BeiDou Navigation System (BDS). The method uses the grey model GM(1,1) to establish a coordinate prediction model based on the historical discrete data of unmanned moving targets, and verifies the validity of the model using measured data. The accuracy of the grey model in positioning prediction is quantitatively analyzed through simulation experiments, and its error probability is calculated. Compared with traditional positioning methods, this model requires less data and is computationally convenient, with lower complexity.
Signal quantization loss analysis based on automatic gain control
WANG Yan, CHEN Xiaofei, JING Wenfang
2024, 49(2): 36-42.   doi: 10.12265/j.gnss.2023084
[Abstract](67) [FullText HTML](18) [PDF 2958KB](8)
Quantization is an important part of analog-to-digital conversion in satellite signal reception. Signal quantization brings energy loss, which affects the subsequent signal processing. It can effectively improve this loss on choosing appropriate quantization bits and system reference power according to signal characteristics. The quantization loss is visually expressed in the form of signal-to-noise ratio comparison, and a general analysis formula is introduced. The function of automatic gain control (AGC) module in signal quantization is explained. Combined with quantization loss formula, a selection method of reference power is explained by determining the best gain coefficient, which makes the quantization loss of signals with different signal-to-noise ratios obviously reduced. Simulation results show that this method can improve the quantization loss of satellite navigation signals by about 1.5 dB when quantizing low bits. It has certain reference significance for the design and engineering implementation of the receiver.
Building extraction based on advanced attention gate U-Net
REN Yuanrui, CHEN Pengdi, GAO Xiaolong
2024, 49(2): 43-53.   doi: 10.12265/j.gnss.2023175
[Abstract](61) [FullText HTML](17) [PDF 5840KB](3)
To facilitate the problems of low accuracy, fuzzy boundary, and difficulty in identifying small targets in building extraction using deep learning semantic segmentation networks, we propose an advanced attention gate U-Net (AA_U-Net) to improve the effect of building extraction. This network improves the structure of classic U-Net, using VGG16 as the backbone feature extraction network, attention-gated module participating in skip connection, and bilinear interpolation instead of deconvolution for upsampling. In the experiment, we use the Wuhan University building dataset (WHD) to compare the extraction effect of the proposed network and some classical semantic segmentation networks and explore the influence of each module of the network improvement on the extraction. The results show that the total accuracy, intersection of union, precision, recall rate, and F1 score of the network are 98.78%, 89.71%, 93.30%, 95.89%, and 94.58%, respectively. All evaluation indexes are better than the classical semantic segmentation network, and the improved modules can effectively improve the extraction accuracy. The problem of unclear outlines of buildings and fragmentation of small target buildings was improved, too. It can be used to accurately extract building information from high-resolution remote sensing images, which has guiding significance for urban planning, land use, production, life, and military reconnaissance.
Effect of phase center correction models of different receivers on GPS/BDS precision positioning
TIAN Xiaojing, QIN Shimin, WANG Jianwen, LI Xiuming
2024, 49(2): 54-60.   doi: 10.12265/j.gnss.2022223
[Abstract](114) [FullText HTML](22) [PDF 2299KB](10)
In view of the difference of antenna phase center (APC) model and instrument manufacturer model of domestic ground receiver of different brands and models, relative positioning and precise single point positioning (PPP) methods are adopted respectively in this paper, based on the analysis of the difference of the estimated position caused by different APC correction models in GPS/BDS high precision positioning, the average difference value of the influence of different APC correction models of each antenna on the estimated position of the station is obtained. The experimental results show that different APC correction models have the same effect on the positioning accuracy of the station, but have little effect on the estimated position in the plane direction and the elevation direction. The influence of the same type of antenna on the different experimental area is consistent, and the influence of the same brand antenna on the estimated position of the station is similar, especially with the brand with the series of products its phase center closer to the impact.
Technical Report and Application
A rapid PWV tomography technique based on water vapor vertical index distribution characteristics
YAN Xiangrong, YANG Weifang, LI Deyan, DING Nan, GAO Fenglin
2024, 49(2): 61-68.   doi: 10.12265/j.gnss.2023164
[Abstract](165) [FullText HTML](43) [PDF 3112KB](17)
Global navigation satellite system (GNSS) water vapor tomography technique can be used to retrieve the three-dimensional spatiotemporal variation of the atmospheric water vapor, but this technique is complicated, which requires a large number of computation and a certain amount of time. Therefore, this paper proposes a rapid tomography technique that uses the precipitable water vapor (PWV) from ground-based GNSS inversion and combines with the exponential distribution characteristics of water vapor in the vertical direction to calculate the three-dimensional distribution of atmospheric water vapor. In this paper, the GNSS data over Hong Kong area, China in August 2022 are used to carry out the experiment in which the rapid tomography technique are compared with the traditional GNSS tomography technique. The experimental results show that the two methods have good agreement with the radiosonde data. Due to lacking of some details of water vapor change in the bottom region, the accuracy of the rapid tomography technique in such region is slightly lower than that of the traditional tomography technique. However, the accuracy of the rapid tomography technique is improved in the middle and high levels, and the results of the tomography technique solution are good. In addition, the rapid tomography technique proposed in this paper does not need to construct and solve complex tomography equations, and can reduce the computational complexity and improve the computing power when a large number of GNSS stations participate in water vapor tomography technique. At the same time, the water vapor density at any level can be obtained rapidly, which is a simple and efficient tomography technique.
Study on PM2.5 concentration prediction by integrating GNSS, ERA5 PWV, and atmospheric pollutants
LIU Yanping, SI Tian, BI Huili, ZHANG Manqi, WANG Yong, XU Zuhao
2024, 49(2): 69-75.   doi: 10.12265/j.gnss.2023151
[Abstract](121) [FullText HTML](35) [PDF 2646KB](17)
The prediction of air quality during the winter and spring seasons can be used for the public to make reasonable arrangements for travel and traffic management by relevant government departments. The main influencing factors of PM2.5 concentration include atmospheric pollutants, precipitable water vapor (PWV), etc. To improve the accuracy of PM2.5 concentration prediction, taking Beijing-Tianjin-Hebei region as an example, it was combined fast Fourier transform (FFT) and LSTM neural network methods, considered observation elements such as GNSS, ERA5 PWV, and atmospheric pollutants, and constructed the PM2.5 concentration prediction model to predict the concentration of PM2.5 in the next 24 hours. It was used GNSS PWV to correct the ERA5 PWV in the region and evaluated the accuracy. The public change period of air pollutants, ERA5 PWV and other observation elements are extracted by FFT, and the optimal public period is 78 hours; Select various factors with the best common cycle length as the model input, and the PM2.5 concentration of the 24 hour sequence as the model output. Evaluate model accuracy through RMSE evaluation indicators. The research results are indicated that the accuracy of ERA5 PWV correction model based on GNSS is better than 2 mm in autumn and winter seasons. The prediction accuracy of the FFT-LSTM model is 10.22 μg/m3 in plain, 8.56 μg/m3 in mountainous, and 9.02 μg/m3 in plateau regions, while the predicted time limit of 24 hours. It can effectively predict the PM2.5 concentration in the next 24 hours. This model can provide reference for relevant departments in air pollution control.
Analysis of anomalous environmental responses to the 5.5 earthquake in Pingyuan County, Dezhou in august 2023 based on GNSS
WANG Xuke, CHEN Liangzhou, YAO Wei
2024, 49(2): 76-81.   doi: 10.12265/j.gnss.2023219
[Abstract](76) [FullText HTML](25) [PDF 3672KB](10)
To investigate the abnormal environmental response caused by the magnitude 5.5 earthquake in Pingyuan County, Shandong Province, on August 6th, 2023, this study based on the Global Navigation Satellite System (GNSS) observation data located about 26 km northeast of the epicenter, proposes a moving time-varying frequency method and incorporates the interquartile range (IQR) method to analyze the abnormal environmental responses triggered by the earthquake. The results indicate significant anomalies in the N and E directional coordinate velocity time series at 9 to 10 seconds after the earthquake, with a minor anomaly in the U direction at 16 seconds. Moreover, the sliding time-varying frequency method detects noticeable changes 5 to 10 seconds before the abnormal jump in the velocity time series, demonstrating higher sensitivity. The study also discovered abnormal disturbances in the ionosphere above the epicenter the day before the earthquake, with the anomaly reaching 4 TECU. This research demonstrates the effectiveness of GNSS technology in detecting abnormal environmental responses during earthquakes, offering a new perspective and tools for earthquake monitoring and early warning.
Tidal signal extraction under high noise conditions
JIANG Yingming, GAO Yi, HUANG Lingyong, HOU Xiaowei, LIU Jizhou, YANG Lei
2024, 49(2): 82-87.   doi: 10.12265/j.gnss.2023201
[Abstract](72) [FullText HTML](19) [PDF 2502KB](7)
In response to the accuracy issue in tidal signal calculation during Global Navigation Satellite System (GNSS) buoy ocean measurements, particularly in high-noise conditions affecting wave parameter calculations, this paper proposes a novel step detection and restoration method based on the sliding window cumulative sum (CUSUM) algorithm, which has been extensively utilized in non-intrusive load monitoring. The algorithm is applied to detect and correct step discontinuities in the sea surface height (SSH) obtained from precise point positioning (PPP) computations and the significant wave height (SWH) extracted from the SSH time series. The performance of the method is evaluated by comparing it with reference data from tide gauge stations and dedicated wave buoys. The results demonstrate that the proposed method significantly improves the accuracy and reliability of GNSS technology in inverting wave parameters. The root mean square error (RMSE) of SSH is enhanced by 75.5%, and the correlation is increased by 7.46%. Moreover, the RMSE of SWH is improved by 65.22%, and the correlation is boosted by 208.28%. These findings underscore the effectiveness of the proposed method in enhancing the accuracy of wave parameter extraction using GNSS technology. The method's implications for enhancing marine engineering safety and economic benefits are also highlighted, making it a valuable contribution to GNSS step detection and providing valuable insights into the extraction and application of tidal signals using GNSS technology.
CORS coordinate time series preprocessing and software implementation in Sichuan-Tibet area
LU Fuxin, GONG Xiaoying, SUN Mingwei, YU Zhangying, HUANG Dingfa
2024, 49(2): 88-97.   doi: 10.12265/j.gnss.2023177
[Abstract](86) [FullText HTML](32) [PDF 3635KB](7)
In this paper ,aiming at the characteristics of the site coordinates of the continuously operating reference stations (CORS) in Sichuan-Tibet region containing complex influence factors and abundant and weak beneficial signals ,in order to solve the problem that the regional large-scale time series data analysis and processing process is cumbersome and cannot be processed in large quantities, this paper designs and develops a GNSS coordinate time series preprocessing system, which supports the multi-site batch solving mode of large area, realizes data product preprocessing, download and visualization, and realizes least squares fitting, coarse rejection, and integration of integrated functional modules such as modeling interpolation and common-mode error correction. The long-term coordinate time series data of the crustal movement observation network of China (CMONOC) is used to evaluate the performance of the software from the aspects of solution accuracy and efficiency. The results show that the goodness of fit R2 of the least squares fitting in the N direction and E direction of each station in the CMONOC is about 99%, and the fitting effect is good. The WRMS values of the time series after coarse rejection are lower than those in all directions before rejection. The RMSE values of the results after horizontal interpolation are better than 8 mm. After the common-mode error is removed, the RMS values in both the horizontal and vertical directions decrease.
Space station orbital accuracy analysis based on the SGP4 model
XU Lingling, ZHAO Hang, SONG Jing, CHEN Shupeng, PAN Zhibing
2024, 49(2): 98-105.   doi: 10.12265/j.gnss.2023194
[Abstract](128) [FullText HTML](29) [PDF 4371KB](24)
In the ground antenna observation mission of low-orbit space station, the azimuth and elevation angle of the antenna to the space station are usually planned based on the satellite tool kit (STK) software, and then the antenna automatically tracks the space station. In order to ensure the accuracy and reliability of antenna tracking, it is necessary to calculate the accurate space station orbit and antenna’s azimuth and elevation angle regularly and update the planning task. Therefore, scientific analysis and evaluation of the long-term forecast accuracy of space station orbit provided by the two-line orbit root number two line elements (TLE) of LEO satellites is of great significance for ground stations to achieve accurate tracking of satellites. In this paper, taking the Mengtian space lab module of China Space Station (CSS) as an example, based on the TLE data, the simplified general perturbations (SGP4) model provided by STK software is used to calculate the satellite’s orbit as well as the space station’s azimuth and elevation angle relative to the Xi’an Ground Station, and to analyse the effect of the accuracy under different strategies. The experimental results show that updating the space station’s two rows of orbital roots on the second day can obtain better orbital results to ensure the tracking accuracy of the antenna.
Dichotomy method for inversion of rainfall intensity by polarimetric phase shift of GNSS signal
CHEN Zheng, TANG Feifei, HU Chuan
2024, 49(2): 106-110.   doi: 10.12265/j.gnss.2023160
[Abstract](53) [FullText HTML](19) [PDF 2081KB](5)
The function expression of the rain intensity- polarimetric phase shift model is complex, making it difficult to derive an analytical expression for inverting the rainfall intensity. Simulated annealing is an effective method for inverting rain intensity, but it is computationally time-consuming. In response to this problem, a rain intensity inversion algorithm based on the bisection method is proposed. Firstly, the rain intensity inversion problem is transformed into a function zero-point solving problem. Then, the bisection method is employed for model calculation, and a rain intensity inversion algorithm based on the bisection method is presented. Finally, the efficiency of the new algorithm is verified through simulation experiments. The results show that compared with the simulated annealing algorithm, the bisection method can significantly improve the inversion efficiency while ensuring the inversion accuracy, reducing the average required time for each inversion by about 75%.
Status and development of the ionospheric error correction techniques in satellite navigation
HAN Xihao, ZHENG Shuaiyong, YANG Jianlei, JIN Xiaowei, GAO Mengzhi, HUANG Zhigang, LI Kun, YANG Peng
2024, 49(2): 111-126.   doi: 10.12265/j.gnss.2023105
[Abstract](143) [FullText HTML](17) [PDF 3807KB](22)
Ionospheric error seriously affects the positioning accuracy of the global navigation satellite system. GPS, BDS, Galileo and GLONASS all adopt different ionospheric error correction methods. The ionospheric error correction methods in satellite navigation are introduced, and the principle and development of single frequency ionospheric error correction, dual-frequency ionospheric error correction and multi-frequency ionospheric error correction are summarized in this paper. In the single frequency correction, the ionospheric error correction techniques in enhanced systems, BDGIM model, Klobuchar model, optimization of single frequency ionospheric error correction technology-IRI constraint model and NeQuick-G model are summarized; In the dual-frequency correction, the ionosphere-free model and the ionospheric error correction methods in the PPP-RTK technology are summarized; In the multi-frequency correction, the optimization and improvement of ionospheric error correction technique with the high order correction and geomagnetic field model are summarized. Finally, the ionospheric error correction techniques and their derivative are analyzed and encapsulated, the development trend and future hotspots of ionospheric error correction technology in satellite navigation are listed and analyzed.
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](2164) [PDF 1536KB](1276)
  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](1684) [PDF 1895KB](342)
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](942) [PDF 750KB](193)
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](1463) [PDF 93258KB](304)
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](723) [PDF 678KB](151)
A Survey of Fusion Algorithms for Multi-source Navigation Fusion System
TANG Luyang, TANG Xiaomei, LI Baiyu, LIU Xiaohui
2018, 43(3): 39-44.   doi: 10.13442/j.gnss.1008-9268.2018.03.007
[Abstract](663) [PDF 668KB](163)
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](780) [PDF 476KB](141)
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](1029) [PDF 1830KB](173)
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](261) [PDF 2013KB](78)
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](911) [PDF 648KB](215)
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](2164) [PDF 1536KB](305)
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](1764) [PDF 62945KB](189)
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](1513) [PDF 1146KB](150)
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](1410) [PDF 1077KB](137)
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](1621) [PDF 778KB](178)
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