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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As the main carrier for the development and utilization of marine resources, autonomous underwater vehicles (AUV) need accurate positioning information when performing tasks. The main navigation mode of AUV is based on strap-down inertial navigation system (SINS), assisted by acoustic navigation and geophysical field matching. This paper introduces the basic principles, advantages and disadvantages and application scenarios of various underwater navigation modes. The key technologies of various navigation modes are researched to improve the precision and stability of integrated navigation. By analyzing the existing problems at present, the future development trend of underwater navigation is forecasted.
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With the launching of the BeiDou-3 Navigation Satellite System (BDS-3), the BeiDou satellite ground-based augmentation system of Hubei province needs to be upgraded. It means the software and hardware of the entire network to achieve functional support for the BDS-3 satellite. This article introduces the content of this upgrade in detail: the upgrade of board hardware and firmware package of 72 true CORS R1 receivers, and providing support for the BDS-3 satellites; the software upgrade of the true NET platform. After the upgrade, the receiver regression test and system accuracy tests were carried out: the data quality analysis and double-difference quality analysis of the newly added frequency signal were carried out, and the number of satellites, altitude angle were analyzed for the original RINEX file; the performance of the receivers after upgrade are also evaluated. It shows that all indicators meet the requirements; the network real-time kinematic (RTK) positioning accuracy is better than 3 cm in horizontal and better than 5 cm in vertical; Differentinal Global Navigation Satellite System (DGNSS) positioning accuracy is better than 1m in horizontal and 2 m in vertical.
[Abstract](13) [FullText HTML](3) [PDF 6671KB](1)
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The stability analysis of time offset between different satellite navigation systems is of great value in modeling prediction and application of time offset. Therefore, based on the data and products provided by the International GNSS Service Center (IGS), the stability analysis of system time offset between the GPS and BeiDou-3 Navigation Satellite System (BDS-3) from three aspects: different stations, different observations, and different time lengths. The results show: due to the different models of receivers, antennas and clocks, the time offset values extracted from different stations are different, but the stability is similar; The stability of the time offset result calculated based on the carrier phase observation is better than that of the pseudo range observation, the time offset result obtained by pseudo range has a frequency stability of the order of 10−12 to 10−13 in 10 000 seconds, and the time difference obtained by phase has a frequency stability of 10−14 seconds. By comparing the time offset calculation results of single-day and multi-day data, it is obtained that the time difference stability of different durations is consistent.
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The International GNSS Service (IGS) precise ephemeris provides satellite coordinates every 15 minutes. In order to improve the positioning accuracy, it is often necessary to obtain the satellite position at any time. Interpolation and fitting of IGS precise ephemeris is a common method to obtain satellite coordinates of continuous epochs. The improved Legendre polynomial algorithm is used to fit the satellite orbit coordinates, and compared with the conventional algorithm. The results show that the conventional algorithm can maintain high accuracy only when the fitting order is low. When the fitting period is 6 h, LU decomposition method and singular value decomposition (SVD) method can maintain high accuracy in solving singular matrix, while when the fitting period is 12 h, SVD decomposition method decomposes the matrix ${\boldsymbol{B}}$ with low condition number to obtain polynomial coefficient ${\boldsymbol{C}}$, so as to avoid the error caused by ill conditioned matrix, so it can still maintain high accuracy. In high-order fitting, SVD decomposition method is superior to LU decomposition method and conventional algorithm in both accuracy and stability.
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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.
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Considering the problem that the initial phase value is difficult to estimate which may consequently cause the low precision of direction-finding result with spatial spectrum estimation, in this paper a direction-finding method with spatial spectrum estimation using less channel quasi calibration is studied based on classic multiple signal classification (MUSIC) algorithm. In this method a calibration source is added in each channel, so that initial phase difference of each two channel can be achieved, and its effects to the calculation of covariance matrix be decreased. This method is applied in the direction-finding antenna with five elements and three channels. Test results show that with this method the direction finding of single signal and multi signals can be realized under complicated scenario, which results is in accordance with that from all-channel antenna.
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In view of the large localization error in the traditional DV-Hop algorithm in wireless sensor network, node localization based on lion swarm optimization (NLLSO) algorithm is proposed in this paper. In NLLSO algorithm, the minimum-hop estimation, average hop error correction and position process are optimized to reduce the localization error. Beacon packet is transmitted in multiple communication radii way, and accuracy of estimating minimum-hop count is improved. In addition, the weight is introduced to correct the average hop. Finally, lion swarm optimization algorithm is used to solve the position of the node. The simulation results show that positioning accuracy of NLLSO algorithm is significantly improved compared with traditional DV-Hop algorithm.
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This paper expounds the origin, concept, construction and development of digital twin earth, especially the integration of BeiDou Satellite Naviation System (BDS) and GF, digital twin and digital earth. Based on common information infrastructure such as communication and computer, the construction of digital twin earth is divided into six steps: full-chain credible space-time, holographic precision mapping, real-time ubiquitous perception, multi-module data fusion, single spatio-temporal intelligence, and all-domain shared intelligence and governance. In view of the distributed characteristics of spatio-temporal big data from collection to application, the “BDS + block chain” technology is proposed to solve the trust problem in business collaboration. It is pointed out that GF realizes the holographic image between the virtual and real earth, and BDS delivers the space-time datum for products of GF, realizing the accurate mapping between the virtual and real earth. In addition, BDS and GF are also the main technologies to realize space-time situation awareness. In view of the challenges brought by massive spatio-temporal big data to data operation and fusion, it is pointed out that grid location code of BDS is a more effective data organization mode. This paper introduces artificial intelligence and simulation driven by spatio-temporal big data, which can provide optimal scheme for planning, design and decision making. This paper analyzes the problems of duplication construction and resource waste of single intelligence, and points out that digital twin earth is the temporal and spatial base for the cross-border integration of various heterogeneous single intelligence and the realization of all-domain shared intelligence and governance.
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A new type of multifunctional Emergency position indicating radio beacon (EPIRB) based on BeiDou positioning and short message communication technology was designed to overcome the shortcomings of poor positioning accuracy and single function of traditional EPIRB and meet the needs of informatization and intelligence of fishing boats. Firstly, the hardware of EPIRB were carried out. Secondly, the yaw angle simulation experiment of EPIRB in the extreme sea conditions and the message transmission and reception test were performed, and a short message sending mechanism based on the EPIRB attitude under different attitudes are proposed. Finally, experiments are conducted to verify the mechanism, and the experimental results show that the short message sending mechanism based on the EPIRB attitude can improve effectively the short message delivery rate, and the multifunctional BeiDou EPIRB designed in this paper has a good promotion prospect in the application of smart fishing boats.
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Due to the frequent occurrence of natural disasters, complex changes in water vapor characteristics, and sparse sounding stations in Japan, it restricts the acquisition of high-precision water vapor, and lacks a high-precision Tm model in this area. In view of this article adopts the 2009 to 2016 Global Geodetic Observing System (GGOS) weighted average temperature (Tm) with the ERA-Interim 2 m Ts grid data, a new Tm model (JQTm model) suitable for the Japanese region that takes into account the seasonal variation of the Tm residual and the daily cycle variation is established. In addition, using the data of 13 sounding stations and 110 GGOS Atmosphere Tm grids in Japan in 2017, the accuracy of the newly established JQTm model in this paper is evaluated in Japan. The study found that compared with the GGOS Atmosphere Tm grid data, the bias and root mean square error (RMSE) of the JQTm model are 0.15 K and 1.92 K, respectively. The RMSE is 41.16% (1.33 K) and 44.41% (1.53 K) higher than the GPT2w-1 and GPT2w-5 models, respectively. Compared with the sounding data, the bias and RMSE of the JQTm model are –0.66 K and 2.14 K, respectively. The RMSE is 28.43% (0.85 K) and 29.61% (0.90 K) higher than the Bevis model, GPT2w-1 model, and GPT2w-5 model, respectively. The JQTm model can provide high-precision Tm values for the Japanese region and provide an important basis for studying atmospheric water vapor and extreme weather in this region.
[Abstract](16) [FullText HTML](7) [PDF 2107KB](4)
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In the process of satellite navigation and positioning, when the signal quality is poor, the auxiliary positioning algorithm can use more observed satellite data for redundant calculation, supplement the missing signal time and obtain the positioning results. The Beidou Satellite Navigation System (BDS) independently developed by China adopts a hybrid satellite constellation, including a class of Geostationary Earth Orbit (GEO) satellites, which has the advantages of 24 h visibility, high orbit, large coverage and strong signal power. This paper analyzes the auxiliary positioning algorithm and the performance difference of the algorithm when only GEO satellites can be received in special cases. The conclusion shows that without the assistance of prior information such as elevation, the direct use of five GEO satellites can also obtain a certain positioning accuracy guarantee.
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Aiming at the determination of the attitude of the moving carrier by the vehicle-mounted mobile measurement system, the attitude determination method of the vehicle-mounted Global Navigation Satellite System (GNSS) antenna array is studied, the attitude calculation formula of the direct method and the least square method is analyzed, and the GNSS is carried out. Antenna array vehicle experiment. In order to obtain the accuracy of the two attitude determination methods, the direct method and the least square method are used to calculate the attitude on the basis of different software positioning modes. The experimental and analysis results show that the accuracy of the four-antenna array least squares attitude determination is better than the three-antenna array direct method, and the reliability is higher; among all the combinations, the four-antenna array least squares attitude determination accuracy based on the moving-base positioning mode is the highest, its heading angle, pitch angle and roll angle accuracy can reach 0.066 0°, 0.168 4° and 0.267 8° respectively.
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BeiDou Navigation Satellite System with global coverage (BDS-3) has been in operation for more than one year. By studying the BeiDou Navigation Satellite System (BDS) broadcast ephemeris data from August 2019 to August 2021, the orbit, clock error and signal-inspace ranging error (SISRE) of BeiDou Navigation Satellite (regional) System(BDS-2) and BDS-3 satellites are analyzed by using the post precision ephemeris. The results show that after the BDS-3 system is opened, the satellite orbit accuracy is significantly higher than that of BDS-2. The radial error root mean square (RMS) value is improved from about 0.87 m to better than 0.23 m, the accuracy is improved by about 74%, and the 3D error RMS value is improved from less than 1.5 m to better than 0.7 m, the accuracy is improved by about 53%; The accuracy of hydrogen atomic clock and rubidium atomic clock is the same. The accuracy improvement of RMS value of BDS-3 clock error is basically the same as that of BDS-2, with an accuracy improvement of about 1 ns; In SISRE accuracy comparison, the RMS value of BDS-2 SISRE is increased from 0.9 m to 0.7 m, and BDS-3 SISRE is increased from 0.8 m to 0.5 m. through comprehensive comparison, the performance of BDS-3 system is greatly improved
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According to the characteristic changes of precipitable water vapor and meteorological parameters (temperature (T), humidity (U), dew point temperature (Td), surface pressure (P)) during the rainfall process, it is possible to establish a short-term rainfall forecast model based on machine learning algorithms. This paper uses the 3-hour zenith tropospheric delay and meteorological data of the bjfs station and wuh2 station in 2020 as examples to construct the prediction model of the four algorithms: random forest (RF), support vector machine (SVM), K-nearest neighbor (KNN), and naive bayes classifier (NBC), and introduces the rainfall events at each time as the new feature vector, adopts the segmentation method of 70% and 80% training sets respectively, takes the rainfall events as the model output, and the applicability of the model is evaluated by the accuracy, precision rate and false negative rate. After obtaining the accuracy is about 0.92, the precision rate is about 80%, and the false negative rate is about 20%, the data of 150—200 days in the time series are further used as samples to predict the rainfall of 200~250 days. The results indicate that The short-term rainfall forecast model based on machine learning can predict more than 80% of the rainfall events in the next 3 hours, and the false negative rate is below 20%, among which the SVM model has better comprehensive performance. Compared with the traditional threshold model, the accuracy rate is equivalent, and the false negative rate is decreased by about 50%.
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The mathematical model of carrier phase time transfer is given, and the performance of BeiDou-2/BeiDou-3 Navigation Satellite System (BDS-2/BDS-3) combined carrier phase time transfer is analyzed based on the measured data of the multi-GNSS experiment (MGEX). The results show that the addition of BDS-3 can increase the number of visible satellites and improve the spatial configuration of satellite distribution. Compared with only using the BDS-2 system, the time transfer accuracy of MRO1-CUSV and NNOR-CUSV can be improved from 0.11 ns and 0.10 ns to 0.07 ns and 0.08 ns, and the A-class uncertainty can be improved from 0.007 ns and 0.006 ns to 0.004 ns and 0.005 ns, respectively, in the BDS-2/BDS-3 combination scenario.
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In view of the business features and off-site multi-centre development layout of the high-precision location service platform, this paper designs a distributed architecture solution for a high-precision location service platform to solve the problems of resource waste and business redundancy caused by the relative independence of the main centre and the sub-center, which cannot work together. The functional modules and platform architecture of the high-precision location service platform are designed in detail in the paper. The platform architecture is designed in a hierarchical way using a divide-and-conquer design philosophy, and the services are split and deployed according to the business design and business characteristics of the platform, solving the key problems in the process of system implementation, such as user acquisition service for distributed platform, real-time precise point positioning (RT-PPP) distributed processing and network Real-time Rinenatic (RTK) distributed processing. The design of a high performance and highly available distributed architecture solution compatible with the high-precision location service platform is finally achieved, providing an effective theoretical basis for the subsequent construction of the platform.
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The current transformation and upgrading of intelligent products, unmanned vehicles have been widely used in production and life practice and play a huge role. BeiDou Navigation Satellite System (BDS), as an independent localized advanced positioning and navigation system, will play an increasingly important role in the transformation and upgrading process of localized intelligent products. The intelligent inspection trolley needs to have autonomous navigation and positioning and environment awareness functions, and the positioning and navigation module and communication module play an important role. This paper designs a kind of intelligent inspection unmanned vehicle which is suitable for terrain scenes on land, adopts BDS satellite positioning system for positioning, senses the external environment based on multi-sensor information fusion, can realize the functions related to autonomous navigation and automatic obstacle avoidance, applies the unique short message system of BDS module to build the upper computer platform for information interaction transmission, and achieves good human-computer interaction effect. The reliability of the system is proved through the test, and it can carry out the autonomous cruise of the unmanned vehicle and the inspection path is basically consistent with the expected path. The BDS module as the core of the unmanned inspection vehicle equipped with various functional modules can create a series of related products for social production practice, which provides new ideas for the subsequent expansion of related technologies.
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The Hector software is used to calculate the time series observation data of 16 continuous stations of Crustal Movement Observation Network of China (CMONOC) in Northeast China in the past 10 years, obtain the time series data of the coordinate residuals of the continuous stations, and then determine the optimal noise model, and finally get the results based on colored noise and environmental load the corrected velocity field. The results show that white noise (WN), flicker noise (FN) and power-law noise (PL) are mainly present in CMONOC coordinate time series data in Northeast China; the optimal noise model in the north (N) and up (U) directions is WN+FN; the optimal noise model in the east (E) direction is WN+PL. Taking into account the influence of colored noise and environmental load, the average velocity of movement in the N direction of the northeast region’s CMONOC based on the ITRF14 framework is −13.003 mm/a, the average velocity of movement in the E direction is 27.020 mm/a, and the average speed of upward movement in the U direction is 0.528 mm/a, and the overall uplift trend.
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The satellite clock error data interpolation is an important link in process of high accuracy positioning data, which has directly impact on positioning accuracy. However, the common interpolation and fitting methods have different disadvantages. The generalized extension approximation method is tried to apply to the process of Quasi-Zenith Satellite System (QZSS) satellite clock error data in this paper. The principles of Lagrange interpolation, Chebyshev fitting and Generalized extension approximation method are firstly introduced, and the differences between sliding and non-sliding. Afterwards, QZSS clock error data is used to discuss the relationship between the parameters (groups) value of the above three methods and the interpolation results accuracy. Finally, when the three methods take their respectively optimal parameters (groups), the accuracy of QZSS satellite clock error is compared. The simulation results show, as long as reasonable parameter combination is selected, that the generalized extension interpolation is completely suitable to QZSS satellite clock error, and the interpolation accuracy of the generalized extension approximation method is significantly higher than other two methods.
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The construction of China’s BeiDou-3 Navigation Satellite System (BDS-3) has been basically completed. Therefore, full use of the current BDS-3 satellite for precise point positioning (PPP) time transfer requires urgent research. This article analyzes BDS-3 PPP time transfer in two aspects. 1) BeiDou-2 Navigation Satellite System (BDS-2), BDS-3 and BDS-2+BDS-3 PPP time transfer. 2) Clock model constrained BDS-3 PPP time transfer. The results show that the root mean squares (RMS) values of smoothed residual value obtained by BDS-3 and BDS-2+BDS-3 PPP can be reduced by 34.5% and 38.23%, the frequency stability of 960 s is increased by 35.81% and 37.75% respectively, compared with BDS-2 PPP; compared with the traditional white noise model, the RMS values of the smoothed residual obtained by BDS-3 and BDS-2+BDS-3 PPP time transfer with the clock model is reduced by 65.17% and 74.42%; in addition, frequency stability can be increased up to 80%.
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2022, 47(3): 1-2.
[Abstract](31) [FullText HTML](19) [PDF 1543KB](13)
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2022, 47(3): 1-8.   doi: 10.12265/j.gnss.2021111201
[Abstract](49) [FullText HTML](6) [PDF 7442KB](19)
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The common mode error (CME) is one of the major error sources in the regional Global Navigation Satellite System (GNSS) network. Aiming at the problem that GNSS time series is subject to no-Gaussian distribution, and the principal component analysis (PCA) with second-order is inaccurately employed to separate the CME. In this paper, the independent component analysis (ICA) introduces high-order statistics to extract the CME. The effectiveness of the method is validated by processing the data of GNSS stations from 2011 to 2018 in Xinjiang, China, and then compared and verified the filtering effect of PCA. We analysis the influence of the CME for GNSS coordinate time series and the yearly signal of the CME. The results show that the CME mainly consists of the 6th independent components and can be attributed to satellite orbit, surface mass loading, and clock errors. After the ICA filtering, the reduction of mean RMS is 31.83%, 32.29%, 35.49% for the north (N), east (E), and up (U) components, respectively. The reduction of velocity uncertainty can achieve 44.14%, 38.49% and 35.49% in three components. In addition, the yearly amplitude of each GNSS station is more consistent that before spatiotemporal filtering, indicating that the ICA can effectively extract the CME and further improve the accuracy of coordinate time series.
2022, 47(3): 9-15.   doi: 10.12265/j.gnss.2021111701
[Abstract](48) [FullText HTML](5) [PDF 3850KB](8)
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Receivers in ground-based pseudolite systems are often affected by the near-far effect, causing failure acquisition of far-field pseudolite signals. An optimization method based on orthogonal subspace projection is introduced in this paper, which is applied to code division multiple access (CDMA) pseudolite signals. Firstly, strong-signal code phases and Doppler frequencies are obtained through conventional sliding correlation to calculate the orthogonal projection operator. Then the weak-signal space is obtained by the received signal subtracting its projection in the strong-signal space. Finally, the re-acquisition is done in the weak-signal space to eliminate of the interference of strong signals. The experimental result indicates that the orthogonal subspace projection can effectively improve weak-signal acquisition performance in the power ratio range of lower than 30 dB, which is of great importance to widen the effective working range of ground-based pseudolite systems and the limitation of pseudolite receivers’ signal power ratio tolerance.
2022, 47(3): 16-24.   doi: 10.12265/j.gnss.2022047
[Abstract](39) [FullText HTML](7) [PDF 3403KB](9)
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Multi-constellation combined positioning can improve the performance of navigation and positioning, but a suitable stochastic model needs to be considered when combining observations from different constellations. The traditional method is to directly set the equivalent weight of each system based on experience, which will lead to inaccurate determination of the stochastic model, and thus affect the performance improvement of the combined system. In this paper, Helmert variance component estimation method is applied to GPS/GLONASS/BDS/Galileo combined precise point positioning to adaptively determine the weight ratio between systems. The static and pseudo-dynamic tests were carried out using the daily observation dataset collected at 10 stations in the global International GNSS Service (IGS) Multi-GNSS experiment (MGEX) observation network over one week of February 8 to February 14, 2021. The results show that the Helmert variance component estimation weighting method can significantly improve the convergence speed of GPS/GLONASS/BDS/Galileo combined precise point positioning (PPP), with an average increase of 52% in static mode and 64% in pseudo-dynamic mode. Because the positioning accuracy is mainly determined by the carrier phase observation accuracy and error correction level, the Helmert variance component estimation method has no obvious improvement on positioning accuracy in static and pseudo-dynamic tests.
2022, 47(3): 25-33.   doi: 10.12265/j.gnss.2022021
[Abstract](47) [FullText HTML](15) [PDF 4507KB](12)
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Precision positioning quality control and integrity assessment is an integral part of real-time Global Navigation Satellite System (GNSS) navigation applications, especially in GNSS vulnerable urban canyon scenarios. Wide-area precise point positioning (PPP) instantaneous decimeter level positioning can be realized by using the observation values of two wide lanes formed by GNSS three-frequency signal. However, in the complex urban environment, the impact of reflected signals, serious multipath and other signal interference on positioning cannot be accurately evaluated and identified, which limits the application of PPP instantaneous decimeter-level point positioning. advanced receiver autonomous integrity monitoring (ARAIM) in the concept of integrity can calculate the upper limit protection level (PL) of the minimum confidence interval of user positioning error to evaluate the positioning effectiveness, which can be used for quality control of PPP instantaneous positioning after some improvement. Aiming at the problem that the error model used to calculate the PL in ARAIM is difficult to meet the requirements of high-precision positioning, an improved ARAIM PL algorithm which is called B-ARAIM is proposed in this paper. The residual of PPP three-frequency combination observation value is used to modify the ARAIM weight and error model to calculate the PL. This paper verifies the algorithm based on on-board data collected in environments with different complexity levels, and evaluates the improvement of PL and the improvement of navigation availability. The results show that the PL obtained by the improved B-ARAIM algorithm is more in line with the needs of city positioning than that obtained by the traditional method, and the PL is reduced by 30% to 70% in different environments. This method is helpful to the application of ARAIM algorithm in GNSS positioning.
2022, 47(3): 34-39.   doi: 10.12265/j.gnss.2021112601
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Low Earth Orbit Satellite (LEO) has the advantages of rapid change of geometric configuration relative to the ground and low loss of broadcast signal link. With the gradual reduction of low orbit satellite load development and launch cost, low orbit satellite navigation enhancement technology has become a research hotspot in the field of satellite navigation. At present, the research on LEO navigation enhancement technology at home and abroad is in its infancy. There is no mature LEO navigation satellite constellation, and there is no effective means to verify the service performance of LEO navigation enhancement system. In this paper, the orbit extrapolation method of LEO navigation satellite and the signal acquisition and tracking technology of LEO satellite are studied, and the semi-physical simulation platform of LEO navigation enhancement system is designed and constructed. On the basis of the simulation platform, the high-precision fast precision positioning method of the combined application of BeiDou / LEO enhancement system is verified, which realizes the rapid convergence of precision single point positioning (PPP) and has high internal coincidence accuracy. It has certain scientific and engineering value for the construction and application of LEO satellite navigation enhancement system.
2022, 47(3): 40-45.   doi: 10.12265/j.gnss.2021122101
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Aiming at the problem of large number of field control points and heavy workload in the spatial triangular processing of unmanned aerial vehicle , the BeiDou Navigation Satellite System (BDS) assisted unmanned aerial vehicle large-scale image control free accuracy verification method is proposed in this paper. The unmanned aerial vehicle photogrammetry platform equipped with dual frequency Global Navigation Satellite System (GNSS) receiver is used to receive BDS data. The key technologies of high-precision BDS camera station coordinate solution and joint adjustment of BDS data and unmanned aerial vehicle image data are discussed and analyzed. Finally, an engineering example is given to verify the effectiveness of the method. The experimental results show that the method can meet the accuracy requirements of 1∶500 large scale mapping without the participation of image control points.
2022, 47(3): 46-50.   doi: 10.12265/j.gnss.2021123101
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Aiming at the strict confidentiality of coordinate transformation parameters and quasi geoid model results in urban satellite navigation and positioning continuous operation reference station (CORS) system, a general real-time encryption transformation method of urban CORS system is proposed based on bursa seven parameters and bilinear interpolation method, which realizes the real-time acquisition of plane and normal height results of urban local coordinate system This method has been verified in the application of CORS in Hefei city (HFCORS), and can provide reference for the application service of urban CORS surveying and mapping benchmark.
2022, 47(3): 51-55, 72.   doi: 10.12265/j.gnss.2021051401
[Abstract](31) [FullText HTML](13) [PDF 11883KB](8)
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In the relative positioning baseline calculation process, selection of the coordinate position of the control network constraint point has a certain impact on the data calculation accuracy. This paper discusses the site selection method of the control network configuration considering the minimumgeometric factor of precision (GDOP), the selection of 6 constraint point reference stations for the global MGEX (Multi-GNSS Experiment) stations, and the use of BeiDou-2/BeiDou-3 (BDS-2/BDS-3) actual measurement data to compare the results of 18 Interactive Generator of Multimedia Application System (iGMAS) stations around the world. The station coordinates are calculated and compared with the accuracy of the results of the global grid-based random station selection method. The experimental results show that compared with the grid-based random station selection method, when the GDOP value selection method is used to calculate the relative positioning baseline, the standard deviation of the baseline length above 6 000 km can be increased by about 7 mm. For the long baseline, the standard deviation accuracy in east (E), north (N), up (U) can be increased by about 5 mm; the position accuracy of the pending point can be increased by about 40%. It can be seen that GDOP method can improve the relative positioning accuracy of BDS-2/BDS-3.
2022, 47(3): 56-64.   doi: 10.12265/j.gnss.2021120205
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With the development of precision positioning technology, high-frequency GPS has been able to accurately record surface displacement data. Research on high frequency GPS can make a certain supplement to earthquake early warning. In view of the high false alarm rate of single station in earthquake early warning, we introduce deep learning technology and use the long short-term memory (LSTM) neural network to combine with surrounding stations to give early warning to single station. First, the seismic-free time series of multiple stations are obtained by solving the 1 Hz high-frequency GPS data in the southern region of New Zealand Then the data is used to train the network to obtain a high-precision model that integrates regional features. The model can predict the seismic-free time series and dynamically formulate a threshold interval. When the actual observation value exceeds the confidence interval, an abnormality is determined. By comparing with the traditional short-time window averaging/long-time window averaging algorithm (STA/LTA) and the single station model without regional features, the results show that the single station model fusing regional features can effectively reduce false alarms. It performs better than traditional methods on seismic-free long sequences of multiple stations and has certain application values.
2022, 47(3): 65-72.   doi: 10.12265/j.gnss.2021120202
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Abstract:
High precision time-frequency reference requires high precision time-frequency transfer technology. The satellite-ground two-way time difference of carrier phase measurement can achieve higher time-frequency transfer accuracy. However, in the complex satellite-ground environments, due to the high flight dynamics of the spacecraft and the high transmission frequency of the time-frequency link, and the carrier doppler effect is large, gross errors and cycle slips are more likely to occur. This paper focuses on a carrier phase cycle slip detection and reparation algorithm for satellite-ground two-way time difference measurement system in high dynamic environment, and proposes a two-way cycle slip detection and reparation method for three-frequency mode. This method combined with Melbaurne wubbena (MW) combination method can realize the detection and repair of different types of cycle slips. For the three links, the existence of cycle slips can be detected and the mm-level cycle slip repair accuracy can be realized. The satellite-ground time synchronization performance of the satellite-ground two-way time difference measurement system based on carrier phase measurement is further analyzed. After cycle slip detection and repair, and link delay data processing, the time synchronization accuracy is better than 0.3×10–12 s.
2022, 47(3): 73-78.   doi: 10.12265/j.gnss.2022019
[Abstract](25) [FullText HTML](8) [PDF 2421KB](6)
Abstract:
In order to broadcast precise ephemeris data with high speed, code shift keying (CSK) modulation is likely to be adopted in next generation satellite navigation system. The correlation values of various code phase offsets are needed during demodulation, so the frequency domain demodulation algorithm based on fast Fourier transform (FFT) is usually used. According to the characteristic that only partial output are needed in CSK frequency domain demodulation, an efficient demodulation algorithm for CSK signal based on partial output FFT is proposed in this paper. The algorithm optimizes the butterfly-shaped structure of traditional FFT, and reduces the computational complexity of demodulation by defining computing nodes to eliminate invalid computations irrelevant to the output results. Taking the CSK(4,1023) modulated signal with a code rate of 1.023 Mcps as an example, the algorithm proposed in this paper can reduce about 45.6% of the calculation, which is of great significance to the design of the next generation satellite navigation receiver.
2022, 47(3): 79-84.   doi: 10.12265/j.gnss.2021120901
[Abstract](31) [FullText HTML](4) [PDF 4368KB](6)
Abstract:
At present, for the Global Navigation Satellite System /Inertial Navigation System (GNSS/INS) performance test and evaluation the evaluation method is single and automatic data processing is still at a low level. Aiming at the attitude performance evaluation of the system, this paper studies a new dynamic test and evaluation method of GNSS/INS performance, and develops corresponding automatic control test and evaluation software. Based on the high-precision three-axis dynamic benchmark simulation turntable, this method first tests through the task of multi rotation and multi attitude motion scene, collects the three-axis motion attitude data of turntable and the output data of integrated navigation system, then processes the measured data by Thompson singular value elimination method, and finally analyzes the uncertainty combined with the measured data of turntable so as to complete the test and evaluation work. In this paper two groups of tests are carried out on a Micro Electro Mechanical System (MEMS) integrated navigation product. Results show that this method can better suppress the singular value points in the integrated navigation system, and the uncertainty values of the turntable are within 0.2", which verifies the high feasibility and reliability of the test and evaluation method.
2022, 47(3): 85-90.   doi: 10.12265/j.gnss.2021092603
[Abstract](43) [FullText HTML](4) [PDF 3344KB](65)
Abstract:
Chinese area positioning system (CAPS) is a new satellite navigation system with independent intellectual property rights in China. Based on the working mode of the satellite forwarding the navigation signal generated on the ground, the satellite navigation function is realized. Navigation integrated baseband is an important terminal equipment of the main control station of CAPS. The architecture of navigation integrated baseband is designed by software radio design. Standard PCI extensions for instrumentation (PXI) chassis structure and bus-based design with strong scalability is selected. The key technologies of baseband are described including frequency compensation technology of transmitting signals, high precision receiving technology, high stability delay keeping technology of equipment. The actual test results show the good performance of the integrated baseband equipment. The measurement accuracy of pseudorange is better than 0.20 ns. The stability of channel delay is better than 0.25 ns, and the accuracy of frequency compensation is better than 0.8 Hz, which can meet the needs of CAPS.
2022, 47(3): 91-98.   doi: 10.12265/j.gnss.2022050
[Abstract](34) [FullText HTML](17) [PDF 2746KB](7)
Abstract:
For the needs and characteristics of remote sensing observing. We proposes an unmanned aerial vehicle (UAV) track planning algorithm based on remote sensing tasks in concave polygonal areas. The algorithm aims to ensure UAV’s non-collision and full area coverage with shorter total time consumption. According to remote sensing image acquisition characteristics, the UAV track planning is carried out by unified main flight direction and fixed-point shooting. The UAV track optimization under the selected main flight direction is obtained through five steps: route segmentation point calculation, polygon division, UAVs assignment, fragment polygon merging and UAVs reassignment, and waypoint information calculation. The global optimal solution is obtained by selecting the main direction of the edges of the concave polygon and its convex hull, respectively. The experimental results show that the algorithm can reasonably assign UAVs and carry out track planning, which is more efficient and more applicable than traditional methods.
2022, 47(3): 99-103.   doi: 10.12265/j.gnss.2021120602
[Abstract](48) [FullText HTML](22) [PDF 3954KB](23)
Abstract:
2022, 47(3): 104-108, 113.   doi: 10.12265/j.gnss.2021121401
[Abstract](431) [FullText HTML](3) [PDF 3008KB](8)
Abstract:
In this paper, a method of continuously operating reference station (CORS) normal height service based on grid is proposed. By modifying the data generation and broadcast mode of the traditional virtual reference station technology, the grid virtual observation data is generated through the way of grid division, and the elevation anomaly correction is added to the grid virtual observation data, so as to realize real-time normal height measurement. The method provides users with real-time normal height measurement results without reducing their accuracy, which can enhance the service capability of the CORS system and can provide reference for the construction of CORS systems in other provinces and municipalities.
2022, 47(3): 109-113.   doi: 10.12265/j.gnss.2021121601
[Abstract](35) [FullText HTML](13) [PDF 2002KB](9)
Abstract:
When using the traditional real-time dynamic positioning (RTK) technology, one must keep the antenna phase center of the Global Navigation Satellite System (GNSS) receiver relatively perpendicular to the measurement point during the measurement to ensure the accuracy of the measurement results. Generally a tripod should be erected. When using the centering rod for measurement, the surveyor must ensure that the leveling bubble of the centering rod call is relatively centered in order to ensure the accuracy of the measurement results. The measurement process is time-consuming and laborious. The emergence of Inertial Navigation System (INS) technology has changed the traditional habit of RTK Surveying and mapping technology. In the measurement process, there is generally no need to erect a tripod, and the measuring centering rod maintain an arbitrary tilt state within a certain range. The measurement process is relatively easy and free, which greatly reduces the labor intensity of measurement and improves the efficiency of surveying and mapping. This paper mainly analyzes the positioning principle and technical advantages of INS technology, and emphasizes that only by mastering the precautions of INS RTK technology in practical application, can it give full play to its maximum benefit and efficiency.
2022, 47(3): 114-118, 126.   doi: 10.12265/j.gnss.2021120604
[Abstract](37) [FullText HTML](9) [PDF 2397KB](14)
Abstract:
With the persistent research and rapid commercialization of 5th generation mobile communication technology (5G), China has built one of the largest commercial 5G network. Suppliers of 5G equipment start to provide new positioning features based on 5G new radio (NR). It is highly probable that the high-precision positioning technology will be gradually commercialized in the next few years. Compared with 4G long term evolution (LTE), denser network deployments and wider transmission bandwidth of 5G can bring about a significant improvement in positioning accuracy. Hopefully, 5G positioning can mitigate coverage and accuracy problems of Global Navigation Satellite Systems (GNSS) in difficult environments such as indoor and urban canyons. This article describes the differences between 5G and 4G in the measurement domain. Then the precision of Sub-6G (FR1) and high frequency mm wave (FR2) ranging measurements with Cramér-Rao bound is assessed. Followed by the description of positioning algorithms, eleven scenarios are listed with typical simulation parameters based on 3GPP specifications and commercial network configurations. The simulation results show that the precision of network synchronization is the main factor affecting the positioning quality. If the time synchronization error is 50 ns, 5G positioning precision is over 10 m. A larger bandwidth can significantly improve the ranging precision of 5G signals if the time synchronization problem can be solved by ideal synchronization or double-differencing with positioning nodes near a user end. Under ideal conditions, 5G FR1 can achieve an accuracy of about 1 m, and FR2 can achieve an accuracy of 0.16 m.
2022, 47(3): 119-126.   doi: 10.12265/j.gnss.2021092604
[Abstract](21) [FullText HTML](6) [PDF 2467KB](6)
Abstract:
Integrating Global Navigation Satellite System (GNSS) and Fengyun meteorological satellite FY-4A can obtain high-precision and high-spatial resolution water vapor distribution information. This paper used the GNSS observation data from crustal movement observation network of China (CMONOC) to carry out the FY-4A water vapor correction study in the Beijing-Tianjin-Hebei region. Firstly, the Beijing-Tianjin-Hebei region was divided into four regions, and the correlation analysis between GNSS precipitable water vapor (PWV) and FY-4A PWV was carried out by regions and seasons. Secondly, different function models were selected by region and season and combined with GNSS PWV data to construct the FY-4A PWV correction models. Then, the GNSS PWV was compared with the results of the regional model and the single-site model respectively to carry out the reliability test of the model. Finally, the corrected FY-4A PWV distribution in the Beijing-Tianjin-Hebei region was obtained through regional FY-4A PWV correction and mosaiced. Research shows that the FY-4A PWV has a good correlation with GNSS PWV, and the accuracy of the regional FY-4A PWV correction model is equivalent to that of the single-site model, which can replace the single-site model for the FY-4A PWV correction. The regional model based on CMONOC GNSS PWV can improve the accuracy of FY-4A PWV to a certain extent, and provide references for the short-term weather forecast and InSAR atmospheric correction.
2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1264) [PDF 1536KB](1116)

2020, 45(1): 19-25.   doi: DOI:10.13442/j.gnss.1008-9268.2020.01.003
[Abstract](533) [PDF 750KB](132)

2018, 43(1): 43-48.   doi: 0.13442/j.gnss.1008-9268.2018.01.008
[Abstract](1149) [PDF 1895KB](252)

2018, 43(6): 1-7.   doi: doi:10.13442/j.gnss.1008-9268.2018.06.001
[Abstract](918) [PDF 93258KB](213)

2017, 42(1): 70-73.   doi: 10.13442/j.gnss.1008-9268.2017.01.014
[Abstract](521) [PDF 476KB](109)

2018, 43(5): 77-83.   doi: 10.13442/j.gnss.1008-9268.2018.05.015
[Abstract](681) [PDF 648KB](182)

2017, 42(6): 16-23.   doi: 10.13442/j.gnss.1008-9268.2017.06.003
[Abstract](805) [PDF 2113KB](122)

2017, 42(3): 32-37.   doi: 10.13442/j.gnss.1008-9268.2017.03.007
[Abstract](687) [PDF 618KB](79)

2017, 42(2): 15-20.   doi: 10.13442/j.gnss.1008-9268.2017.02.004
[Abstract](368) [PDF 668KB](68)

2017, 42(1): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.01.011
[Abstract](352) [PDF 678KB](117)

2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1264) [PDF 1536KB](71)
Abstract:
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.
2018, 43(6): 8-13.   doi: doi:10.13442/j.gnss.1008-9268.2018.06.002
[Abstract](1046) [PDF 62945KB](108)
Abstract:
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.

2019, 44(5): 1-9.   doi: DOI:10.13442/j.gnss.1008-9268.2019.05.001
[Abstract](1074) [PDF 1146KB](76)
Abstract:
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.
2017, 42(5): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.05.011
[Abstract](1001) [PDF 778KB](60)
Abstract:
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.
2019, 44(1): 1-9.   doi: DOI:10.13442/j.gnss.1008-9268.2019.01.001
[Abstract](977) [PDF 1077KB](72)
Abstract:
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.

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