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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With the development of Global Navigation Satellite System (GNSS) and the progress of mobile communication technology, users put forward higher requirements for location services. In this paper, GNSS data are collected by using two Android smart phones that are common in the market, and the algorithms of standard point positioning (SPP) and single frequency precise point positioning (PPP) of Android smartphone are studied. The positioning performance of SPP and PPP of smart phones under different conditions is analyzed. The results show that based on the random model of Doppler smoothing pseudo range and signal-to-noise ratio, The SPP positioning accuracy of Android smart phone GPS single system can reach within 3 m, and the positioning accuracy of GPS、Galileo、GLONASS、BDS four system can reach sub meter level. In single frequency PPP static positioning, under the single GPS system, the positioning accuracy can only reach meter level, and the convergence time is long; Under GPS、Galileo、GLONASS、BDS four system, the positioning accuracy can reach sub meter level, and the plane direction can converge within 40 min. In single frequency PPP dynamic positioning, the positioning accuracy of mobile single frequency PPP can only reach meter level.
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The common mode errors (CMEs) existing in the Global Positioning System (GPS) coordinate time series are removed using the stack filter (SF), network inverse filter (NIF) and principal component analysis (PCA) methods, to improve the accuracy of GPS monitoring regional surface displacements. By building GPS coordinate time series model, remove the obvious tectonic movements, and extract the noise residuals. Then, the CMEs in the residuals are extracted with the SF, NIF, PCA methods. Using 2019-2021 GPS coordinate time series in Japan’s Boso peninsular, the SF, NIF, and PCA methods of extracting the CMEs are compared, the effects of different GPS site spatial resolutions on the CMEs are analyzed, and the surface displacements before and after removing the CMEs are analyzed. The results show that the performances of the SF, NIF and PCA methods to extract the CMEs are consistent. The spatial resolution of GPS sites decreases, and the dispersion of the extracted CMEs increases. The CMEs affect the size and direction of the slow slip surface displacements, so they need to be removed.
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At present, the navigation of high-orbit spacecraft mainly relies on ground-based measurement and control systems. In order to study the feasibility of Global Navigation Satellite System (GNSS) technology in high-orbit spacecraft navigation, the navigation accuracy and adaptability of GNSS technology in geostationary earth orbit (GEO) and inclined geosynchronous orbit (IGSO) high-orbit spacecraft were analyzed and studied. The GNSS navigation satellite constellation was simulated using two-line orbital element (TLE) on November 9, 2021. GEO satellites at different sub-satellite points and IGSO satellites at different inclination angles were used as target satellites to carry out navigation experiments. The experimental results show that: In order to meet the number of satellites required for GNSS calculation, the number of visible satellites must be increased by receiving sidelobe signals; For GEO target satellites, when the receiver sensitivity is higher than −169 dB, the navigation accuracy can reach 30 m; The GPS system is used to conduct navigation and orbit determination experiments on 7 different GEO or IGSO orbits; The average accuracy of BeiDou-3 Navigation Satellite System (BDS-3), GPS, GLONASS, and Galileo in high-orbit spacecraft navigation is 28.03 m, 21.16 m, 37.15 m, and 25.09 m, respectively. GPS has the highest accuracy and GLONASS has the lowest accuracy, but it is also 45 m in most periods within.
[Abstract](15) [FullText HTML](1) [PDF 3539KB](1)
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GPS coordinate time series show significant seasonal variations. We here study the vertical coordinate time series of 233 GPS stations in Crustal Movement Observation Network of China (CMONOC). Based on the root mean square (RMS) reduction ratio of coordinate time series with and without the environmental loading corrections, we quantify the improvements of CMONOC coordinate time series with the corrections of different environmental loading products provided by Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ) and EOST. The statistical results show that the RMS of 90.2% and 75.54% of the stations are reduced after the correction of the environmental loading product provided by GFZ and EOST respectively. It shows that the loading products of GFZ have better performance to explain the non-linear variations of the verticals than those of EOST. It is also found that the environmental loading corrections not only have a significant improvement effect on the seasonal part of GPS verticals, but also on the non-seasonal part. After the loading correction of GFZ, the annual amplitude of 87.8% of GPS stations is decreased, and the RMS of the non-seasonal part of 82.4% of the stations is reduced.
[Abstract](13) [FullText HTML](2) [PDF 2455KB](1)
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Global Navigation Satellite System (GNSS) can provide users with positioning, navigation and timing services, and is widely used in national defense security and national economic construction. Real time precise point positioning (PPP) is a high precise satellite navigation positioning method, this paper discusses the current problems of the algorithm that long reinitialization time caused by signal interruption , and proposes a cycle slip repair algorithm based on the differential pseudorange and carrier phase observations. It designs a real-time precise point positioning algorithm and introduces its implementation process. The success rate of the cycle slip repair experiment using the data of the IGS observatory is more than 99%, and shorten the reconvergence time. The cart experiment was carrier out on the roof of the building, and the real-time precise point positioning accuracy was better than 1 cm in the horizontal direction, and the accuracy was 2~3 cm in the vertical direction.
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For signals that have higher requirements on the information transmission rate, such as precision positioning signals, a combined binary phase shift keying-code shift keying (BPSK-CSK) modulation method is proposed to solve the problem of the high demodulation computational complexity of the traditional code shift keying (CSK). This method subdivides the modulated message into polar bits and code phase bits, so that the receiver converts demodulating message by correlating and summation into two steps to complete the message demodulation through less times of correlating summation and subcode matching. It reduces the number of correlators required for the receiver to demodulate the message and reduces the data magnitude involved in the operation. When the number of polar bits is 1 or 2, compared with the CSK, the performance of bit error rate is negligible, and the computational complexity is reduced to 50% or 25% of the computational complexity of the original method. When the number of polar bits is greater than 2, the computational complexity will be reduced at the expense of the bit error rate, but at this time, combined with the error-correcting coding, BPSK-CSK can still reduce the bit error rate under the same computational complexity.
[Abstract](10) [FullText HTML](2) [PDF 3555KB](0)
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In order to maintain the geosynchronous characteristics of geostationary earth orbit (GEO) satellites, frequent orbital maneuvers are required. Timely and accurate dynamic monitoring of the state of satellite orbit maneuvers is helpful for repairing the true satellite orbit, so that it can still provide basic orbital parameters during maneuvering. In this paper, 12 historical maneuvers of each of the two GEO satellites of BeiDou-3 Navigation Satellite System (BDS-3) are analyzed using a satellite orbit monitoring model based on the principle of time differential velocity measurement. The results show that the station network of different spatial scales selected in this paper can monitor the maneuver period and orbital dynamic variation of the C59 satellite in real time, and the monitoring results are basically consistent. In addition, the station networks of different spatial scales selected in this paper can accurately detect the maneuver period of the C60 satellite, but when monitoring its orbital state in real time, the monitoring results of the station network with a larger spatial scale are better.
[Abstract](11) [FullText HTML](2) [PDF 2993KB](0)
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As an important error source in ionospheric modeling and navigation, so it is very important to estimate and solve it. In order to improve the accuracy of differential code bias (DCB) estimation and ionospheric modeling, this paper proposes a multi-factor stochastic model based on altitude angle, the distance between the station and the satellite and station latitude, and analyzes the influence of different stochastic models on the accuracy of DCB estimation and ionospheric vertical total electron content (VTEC) modeling. The results indicated that different stochastic models may produce about 0.2 ns difference in satellite DCB. Compared with altitude angle weighting method, the estimation accuracy of station DCB was improved by 0.13 ns on average, and the ionospheric modeling accuracy was improved by about 0.2 TECU when the combine model of the elevation angel and the distance from the satellite to the ground station was used. Under the new stochastic model, the DCB solution of low latitude stations was worse than the first two methods, but the DCB solution of high latitude stations was better, and the modeling accuracy of ionospheric VTEC was improved significantly, which was 0.88 TECU and 0.68 TECU respectively, compared with the first two stochastic models.
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To meet the demand of the 5G positioning requirements in indoor environment, we proposed a method to optimize the rough positioning results by using neural network algorithms, which reduced the positioning error caused by multipath and non-line-of-sight propagation, and improved the positioning accuracy of the result domain. The optimization algorithm used the time of arrival (TOA) method and the time difference of arrival (TDOA) method in ranging positioning to obtain rough positioning results, and combined separately with BP neural network, Elman neural networks, as well as genetic algorithm (GA)-BP network and GA-Elman network to obtain a better positioning results, then the four neural network algorithms were analyzed and evaluated. Compared with the BP algorithm, Elman algorithm has the characteristics of fast iteration convergence, few iterations and good error correction, which is more suitable for the optimization of the 5G localization result domain. The accuracy of the results is improved after incorporating the GA, among which the GA-Elman algorithm can be trained to obtain the best localization results.
[Abstract](12) [FullText HTML](1) [PDF 3412KB](0)
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BeiDou-3 Navigation Satellite System (BDS-3) has provided positioning navigation and timing (PNT) services for users worldwide. This paper analyzed the single-frequency single-point positioning (SPP) performance of BDS-3 and its combination with other Global Navigation Satellite System (GNSS) in terms of the mean number of visible satellites, geomettic dilution of precision (GDOP), positioning accuracy, positioning success ratio and pseudo-range residuals using 7 day observations collected at MGEX WHU2 station. The results show that, in the Asia-Pacific region, the RMS of BDS-3 SPP results is 1.19 m, 2.34 m, and 2.38 m in horizontal, vertical and three-dimensional (3D), respectively, the performance of BDS-3 SPP is better that the GPS, GLONASS and Galileo. The 3D accuracy of BDS-3 SPP is improved by 54.8%, 27.2%, 86.4% and 1.2%, respectively, compared with the BDS-2, GPS, GLONASS and Galileo SPP. The accuracy of the combined BDS/GPS/Galileo SPP is 0.96 m, 1.66 m and 1.77 m in horizontal, vertical and 3D, respectively, which is the best among the multi-GNSS SPP. Compared with the BDS SPP results, the accuracy of the combined BDS/GPS/Galileo SPP is improved by 18.6%, 19.4%, and 17.3% in horizontal, vertical and 3D, respectively.
[Abstract](11) [FullText HTML](2) [PDF 5923KB](1)
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Tropospheric delay is one of the main factors that affect the performance of precise point positioning (PPP), especially the accuracy of elevation direction solution. Generally, model correction and parameter estimation are used to deal with it. The accuracy of elevation direction solution is very important for gravity field recovery in airborne gravimetry. Therefore, GMF, NMF, VMF1 and VMF3 are respectively used as mapping functions, and 4 $\rm{m}\rm{m}/\sqrt{\rm{h}}$, 10 $\rm{m}\rm{m}/\sqrt{\rm{h}}$, 50 $\rm{m}\rm{m}/\sqrt{\rm{h}}$ and 100 $\rm{m}\rm{m}/\sqrt{\rm{h}}$ are respectively selected as random walk noise parameters to compare and analyze the influence of different tropospheric models on precise point positioning of airborne large dynamic data. The experimental results show that different tropospheric models have great influence on the positioning results in north (N) and up (U) directions, and the model difference can reach 3 mm to 4 mm; VMF1 and VMF3 models are superior to GMF and NMF models in positioning accuracy; selecting $4\;\rm{m}\rm{m}/\sqrt{\rm{h}}$ as random walk noise has higher positioning accuracy than the other three models.
[Abstract](11) [FullText HTML](1) [PDF 2503KB](1)
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Spoofing interference is a major threat to the development of Global Navigation Satellite System (GNSS) applications. In order to solve the large computation resource consumption problem of estimation methods, this paper proposed a spoofing signal parameters estimation method based on Newton’s method. This method constructed a nonlinear estimation model of signal parameters in the spoofing scenario, taking the estimation of code phases as the core. The code phases were iterated by Newton’s method, and the signal amplitudes and carrier phases were estimated by the least square method. The simulation results showed that the average number of iterations was about 10, greatly improving the effectiveness of signal parameters estimation compared with the traditional estimation method. Moreover, this method could also improve the estimation accuracy in the small delay scenarios.
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In order to optimize the signal reception performance under the saturation condition of the satellite transponder channel, the generation of the intermodulation signal in the saturated state of the transparent transponder is analyzed, and the influence of the intermodulation signal on the deterioration of the channel carrier-to-noise ratio (CNR) is weakened. This paper studies the problem by establishing the channel model, calculating the channel parameters, optimizing the analysis and simulation. The direct influence of the transponder gain adjustment on the CNR of the receiver and the indirect influence of the intermodulation signal on the CNR of the receiver are respectively studied, and did the theoretical calculation and simulation analysis. The results show that under saturation conditions, the transponder gain back off can improve the CNR loss. When the transmit power of the interfering signal is 45 dBW, the minimum CNR loss of −1.55 dB can be achieved by the back-off of the transponder −1 dB. As the interference increases, the optimal gain back off value will gradually increase, and the minimum CNR loss will also increase. The research results in this paper can be applied to satellite transponder channels to provide guidance for the optimization of transponder gain adjustment under saturation conditions.
[Abstract](16) [FullText HTML](3) [PDF 3642KB](1)
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Based on the IGS-MGEX observation data, the BeiDou-3 Navigation Satellite System (BDS-3) satellite uncalibrated phase delay (UPD) is estimated. In order to analyze the performance current BDS-3 constellation, both the float and fixed precise point positioning (PPP) are tested. The results show that the accuracy of BDS-3 PPP is roughly equivalent to that of GPS. The average root mean square (RMS) of BDS-3 float PPP solutions are 1.4 cm, 1.0 cm, and 1.6 cm for east (E), north (N), and up (U) direction, while the accuracy can be improved to 0.9 cm, 0.7 cm, and 1.4 cm respectively with ambiguity resolution.
[Abstract](50) [FullText HTML](6) [PDF 2898KB](5)
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If there are gross errors or cycle slips in the Global Navigation Satellite System (GNSS) comprehensive corrections in observation space representation, it will inevitably affect precise point positioning (PPP) augmented performance. Aiming at the possible anomalies in the comprehensive corrections, a quality control algorithm for the comprehensive corrections was studied and an algorithm for identifying and controlling outliers was proposed. According to the characteristics of the comprehensive corrections, the median absolute deviation was used to identify and locate the outliers for the combined value of comprehensive corrections after inter-frequency difference and second-order inter-epoch. The satellites with outliers used were control by the means of ambiguity reinitialization, weight reduction or elimination to reduce the impact of outliers on the results. The method was validated with a reference network composed of some Hong Kong continuously operating reference stations (CORS) with an average side length of 26 km and zero baseline data from Curtin University. The results showed that the method can effectively detect most of the large anomalies more than 1 cycle and some anomalies within 1 cycle, and effectively control the influence of some outliers on the positioning results.
[Abstract](39) [FullText HTML](23) [PDF 3018KB](10)
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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.
[Abstract](50) [FullText HTML](27) [PDF 3229KB](9)
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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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2022, 47(5): 1-8.   doi: 10.12265/j.gnss.2022112
[Abstract](54) [FullText HTML](12) [PDF 2098KB](16)
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As the modern society is changing from the information age to the intelligent age, the number and performance requirements of navigation, communication and detection signals have increased dramatically, and the demand for multi-functional integrated signals is becoming more and more urgent. In this field, it is a crucial issue to achieve efficient utilization of resources and dynamic adjustment of functions through flexible signal design. This paper first proposes a signal design framework based on the idea of “building blocks”. The designed signals are represented in the form of signal vectors and waveform basis functions. The corresponding signal design can be equivalently represented by reconstructing the signal vector with the coefficient combinations of the basis functions, thereby converting the signal optimization in the waveform space into the vector optimization in the signal space. Further, this paper analyzes the traditional signal evaluation methods, and derives the navigation, communication, and detection signal evaluation criteria under the integrated signal design framework. Finally, this paper proposes quantifiable optimization objectives for integrated signal design, and makes some discussion on design constraints, including energy constraints, spectrum constraints, peak-to-average ratio, etc.
2022, 47(5): 9-15.   doi: 10.12265/j.gnss.2022092
[Abstract](74) [FullText HTML](11) [PDF 5063KB](26)
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The first step is to design a low earth orbit satellite (LEO) for navigation augmentation using low earth orbit satellites. When designing the constellation configuration, the stability and comprehensive cost of the constellation are two important factors to be considered. This paper presents an optimal design method for low earth orbit navigation constellation considering constellation stability and comprehensive cost. First, the Iridium constellation is optimized by genetic algorithm. Compared with Iridium constellation, the mean number of visible satellites increases from 2.3 to 2.9, the standard deviation of visible satellites decreases from 2.3 to 0.7, and the comprehensive cost factor decreases from 5.3 to 4.5, which proves the effectiveness of this method. Then, taking Walker constellation as the basic configuration, the low earth orbit hybrid constellation is optimized by genetic algorithm, considering the navigation performance and comprehensive cost on the basis of ensuring the stability of the hybrid constellation. The optimized low earth orbit hybrid constellation is combined with the BDS constellation. Compared with the BDS, the mean number of visible satellites increases from 6.9 to 9.3, and the standard deviation of visible satellites decreases from 1.1 to 0.4.
2022, 47(5): 16-21.   doi: 10.12265/j.gnss.2022083
[Abstract](38) [FullText HTML](5) [PDF 1962KB](7)
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The combined adjustment solutions of the linear observation model in the observation domain and in the adjustment range are completely equivalent. However, in practice, the observation models of the combined adjustment are mostly nonlinear, which always need to be linearized in parameter estimation, resulting in linearized model error. The influence of this error on the equivalence of the two-domain adjustment solutions remains to be discussed. Thus, taking pseudo-range single point positioning (SPP) as an example, the solution formulas of the combined adjustment in the adjustment range of the observation model are deduced in this paper, on which the reason why the two-domain combined adjustment cannot be completely equivalent under the SPP model is presented and a numerical analysis is carried out with the example data. Research shows, the two-domain adjustment solution of SPP cannot be equivalent because it is assumed that the initial value of each iteration solution of a single system is the same as that of the combined adjustment of the observation range. And under the same configuration, the two-domain adjustment position solutions of different Global Navigation Satellites System (GNSS) combined SPP are the same value on the order of millimeter, that is, for the application of SPP, the two-domain adjustment solutions can be considered the same. The content of this paper also has certain reference significance for some other GNSS applications.
2022, 47(5): 22-27.   doi: 10.12265/j.gnss.2022064
[Abstract](76) [FullText HTML](13) [PDF 2752KB](37)
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The vehicle dynamic data characteristics for BDS-3 new signals of B1C/B2a are analyzed using four indices, i.e. carrier noise ratio (CNR), data integrity rate, observation noise and multipath. The kinematic precise point positioning (PPP) performance for BDS-3 new signals is also tested and compared with the other GNSS. The test results show that the average CNR of BDS-3 B2a new frequency is better than those of the other BDS frequencies, but slightly worse than that of GPS L5. The data integrity rate of BDS is relatively higher compared with the other GNSS. Further, the data integrity rate of the BDS-3 B2a new frequency is the highest. The noise of BDS-3 pseudorange observation at B2b frequency is the lowest, and the pseudorange observation noise at B1C and B2a frequencies is about three times of that of the B2b signal. However, the noise of phase observations at different frequencies is in the same level. For pseudorange multipath, the BDS-3 B1C/B2a signal is slightly smaller than the B2b signal, and overall, the GPS L5 signal has the strongest ability to suppress the multipath. In terms of kinematic PPP performance, the BDS-3 B1C/B2a dual-frequency combined kinematic PPP achieves the best positioning accuracy with a three-dimensional root mean square error of 0.439 m. Compared with the BDS B1I/B3I, GPS L1/L2, GLONASS G1/G2, and Galileo E1/E5a dual-frequency combined PPP, the accuracy improvement rates are 49%、56%、81% and 42% respectively.
2022, 47(5): 28-34.   doi: 10.12265/j.gnss.2022087
[Abstract](51) [FullText HTML](10) [PDF 4031KB](11)
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To address the problems that Global Navigation Satellite System (GNSS) and ultra-wideband (UWB) positioning systems have limited range in complex indoor and outdoor environments, and that no single source can obtain continuous and reliable positioning results from outdoor to indoor. In this paper, we investigate the BeiDou Navigation Satellite System (BDS)+GPS/UWB loose combination positioning method, design dynamic indoor and outdoor positioning experiments and static positioning experiments in the transition area, use the extended Kalman filter to optimally estimate the positioning error state, and analyze and evaluate three positioning modes: BDS+GPS combination, UWB and loose combination. The experimental results show that the combination of BDS+GPS/UWB improves the positioning accuracy and extends the range of GNSS-real-time kinematic (GNSS-RTK) in the indoor-outdoor transition area, and the combination of BDS+GPS/UWB improves the continuity and usability of the system from outdoor to indoor positioning compared with each single source.
2022, 47(5): 35-44.   doi: 10.12265/j.gnss.2022059
[Abstract](59) [FullText HTML](11) [PDF 3057KB](16)
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Since the BeiDou Navigation Satellite System (BDS) has been formally networked, it is necessary to evaluate and analyze the positioning performance of the BDS. This article mainly through 5 days observation data from 8 stations in MGEX (Multi-GNSS Experiment), give priority to with BeiDou-2/ BeiDou-3 (BDS-2/BDS-3) to analysis BDS-2/BDS-3, BDS-2/BDS-3/Galileo, BDS-2/BDS-3/GPS, BDS-2/BDS-3/GPS/Galileo four different combination of satellite system static precise point positioning (PPP) performance, the experimental results show that the positioning accuracy and convergence speed of BDS-2/BDS-3 static PPP in east (E), north (N) and up (U) directions are better than 2.49 cm, 2.27 cm, 4.04 cm and 34.6 min, 19.3 min and 28.1 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GALIEO static PPP in E, N and U directions are better than 1.81 cm, 1.65 cm, 2.94 cm and 20.4 min, 13.0 min, 18.6 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GPS static PPP in E, N and U directions are better than 1.67 cm, 1.62 cm, 2.82 cm and 18.3 min, 10.2 min, 16.1 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GPS/Galileo static PPP in E, N and U directions are better than 1.46 cm, 1.40 cm, 2.45 cm and 14.5 min, 9.3 min, 14.5 min, respectively.
2022, 47(5): 45-50.   doi: 10.12265/j.gnss.2022097
[Abstract](38) [FullText HTML](9) [PDF 2467KB](8)
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Ionospheric delay is an important error source in GNSS high-precision navigation and positioning applications. Through the measurement and short-term prediction of total ionospheric electron content (TEC), the positioning accuracy of GNSS single frequency users can be effectively improved, and the ionospheric effect of other radio systems can also be effectively alleviated. In the past two decades, many effective short-term prediction methods have been proposed, but none of them is absolutely leading, and the prediction accuracy of all these methods needs to be improved. In this paper, using the TEC observation data of five grid points arbitrarily selected from the Madrigal database, the autocorrelation and autoregressive moving average (ARIMA) methods are compared, and then the influence of two parameters on the prediction error in the autocorrelation prediction method is studied. Finally, an optimized parameter setting scheme is put forward for the autocorrelation prediction method. The experimental results show that: 1) The prediction error of the autocorrelation method is slightly smaller than that of the ARIMA method, and the time taken by the autocorrelation method is obviously less than that of the ARIMA method. Therefore, the comprehensive performance of the autocorrelation method is better than ARIMA method; 2) For the autocorrelation method, compared with the traditional “4+12”scheme, “3+9” scheme has better prediction performance on the whole, indicating that the ionosphere current state may be mainly related to the state of the previous three days. The relevant results can be used as a useful reference scheme for the implementation of ionospheric short-term prediction engineering.“3+9” scheme has better prediction performance on the whole, indicating that the ionosphere current state may be mainly related to the state of the previous three days. The relevant results can be used as a useful reference scheme for the implementation of ionospheric short-term prediction engineering.
2022, 47(5): 51-56.   doi: 10.12265/j.gnss.2022099
[Abstract](20) [FullText HTML](3) [PDF 3401KB](6)
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Aiming at the problem of low localization accuracy and poor map effect of visual simultaneous localization and mapping (SLAM) in indoor dynamic environment, a indoor dynamic SLAM method is proposed based on geometric constraints and target detection. The target detection network is used to obtain semantic information and a method for missing detection of moving objects is proposed. Based on prior knowledge, an information determination method is proposed to accurately identify dynamic regions. Dynamic points are eliminated based on geometric constraints and deep learning. Static points are used to estimate camera pose. A closed-loop static map is builded based on the stored information. The experiment on TUM dataset shows that the localization accuracy is 97.5% higher than that of ORB-SLAM2 and the performance is better than other dynamic SLAM. The experiment in the indoor real environment shows that the static map is more accurate. The localization accuracy and the map effect of indoor dynamic SLAM are improved effectively.
2022, 47(5): 57-64.   doi: 10.12265/j.gnss.2022096
[Abstract](74) [FullText HTML](11) [PDF 3481KB](19)
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Based on the measured data in the airborne kinematic scene, this paper uses the open-source PRIDE PPP-AR software to construct a dual-frequency ionosphere-free combination (IF) using the pseudorange and carrier phase observations for kinematic precise point positioning (PPP) experiment, and it also compares the performance of a single BDS system and BDS/GNSS in airborne large kinematic positioning. The results show that the number of satellites, satellite geometry and position dilution of precision (PDOP) of the multi-system combination are superior. In a single system, the positioning accuracy in the plane (east (E), north (N) and up (U) )directions are improved by 10% and 12% respectively. In addition, this paper compares the solution results of the open-source software PRIDE PPP-AR with the commercial software WayPoint, the results show that the positioning accuracy of the former is improved by 46% and 36% in the E and U directions respectively, and the N direction is the most improved, nearly doubled. Therefore, PRIDE PPP-AR has higher solution accuracy and better solution performance.
2022, 47(5): 65-71, 80.   doi: 10.12265/j.gnss.2021112202
[Abstract](54) [FullText HTML](17) [PDF 3347KB](18)
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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.
2022, 47(5): 72-80.   doi: 10.12265/j.gnss.2022054
[Abstract](42) [FullText HTML](19) [PDF 5839KB](30)
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With the development of chip technology, the smartphone has become the most widely used Global Navigation Satellite System (GNSS) device, and its ability to provide location services is gradually being demonstrated. To investigate the feasibility of using a smartphone as a professional GNSS device and to take advantage of the opportunity of opening GNSS raw measurements on an Android smart terminal, an real-time kinematic (RTK) positioning APP was designed and implemented, and a high-precision positioning application test was performed based on it. The results show that the APP's real-time positioning accuracy can achieve about 1 dm under static conditions, and can reach sub-meter levels in plane and 1 to 2 m in vertical under dynamic situations of pedestrians and automobiles. The RTK positioning accuracy is significantly higher than that of the built-in chip solution, but the stability is slightly worse. The results also show that when using a smartphone to imitate RTK point measurement, the plane accuracy can reach about 1 m, which is sufficient for sub-meter to meter-level low-precision professional applications such as geographic information collecting and survey.
2022, 47(5): 81-87.   doi: 10.12265/j.gnss.2022067
[Abstract](30) [FullText HTML](7) [PDF 5204KB](6)
Abstract:
Maritime transport is often affected by high temperature, high salt and high humidity environment, especially for valuable and precision cargoes, which are prone to damage risk during transportation. Therefore, it is important to establish a cargo communication monitoring system for improving the quality of marine transportation. In this paper, a maritime transport monitoring system based on BeiDou Navigation Satellite System (BDS) was designed, which combined the internet of things technology and BDS to achieve the real-time monitoring, navigation, positioning and communication functions of cargo. Taking the transportation of multiphase flow meter as an example, the realization method of the system function was described in detail. The system can be used as an industrialized assistant tool to reduce the cost of cargo damage and improve the efficiency of transportation management.
2022, 47(5): 88-93.   doi: 10.12265/j.gnss.2022075
[Abstract](21) [FullText HTML](2) [PDF 2519KB](5)
Abstract:
To address the problem that the Kalman filter was prone to filter divergence when using the virtual balise (VB) information fusion, an information fusion method based on the improved Sage-Husa adaptive filtering algorithm was proposed: firstly, the adaptive filtering was used to dynamically adjust the noise statistical characteristics parameters to suppress filter divergence, secondly, an attenuation factor was introduced into the prediction error variance matrix to reduce the influence of stale data and thus improve the filtering accuracy, and finally, simulation experiment was conducted to compare the proposed algorithm with the Kalman filter and Sage-Husa adaptive filter in terms of position and velocity error of the VB. The simulation outcome reveals that the algorithm has an obvious advantage in the positioning error of the VB with better stability in the same time.
2022, 47(5): 94-99.   doi: 10.12265/j.gnss.2022026
[Abstract](27) [FullText HTML](4) [PDF 2858KB](6)
Abstract:
During the outbreak of COVID-19, early quarantine from high risk areas is an effective measure to curb the spread of the epidemic. To avoid people leaving the quarantine area without authorization, a large number of supervisors are required to conduct 24 hours supervision, which not only needs much of labor and money, but also have the problems of information leakage, non real-time information collection and the safety of supervisors. It is necessary to realize automatic real-time quarantine monitoring by using the existing infrastructure. This paper realized it by collecting and analyzing the position and carrier noise ratio (CNR) information of Global Navigation Satellite System (GNSS) chip receiver in cellphone. Through analysis of the actual detection data, the result shows that the method can accurately and effectively distinguish whether the people leave of the quarantine area.
2022, 47(5): 100-110.   doi: 10.12265/j.gnss.2022119
[Abstract](42) [FullText HTML](4) [PDF 11642KB](17)
Abstract:
In June 2020, the BeiDou Navigation Satellite System (BDS) completed its global coverage deployment. In order to analyze the accuracy of BDS derived water vapor information, the observed data of 15 MGEX stations in October and November 2021 were used to invert carry out water vapor. The well-known comprehensive GNSS data processing software package GAMIT was used to calculate the observation data of BDS, GPS, Galileo and GLONASS respectively, and the tropospheric zenith total delay (ZTD) was compared with the results provided by IGS, and the PWV was compared with the PWV derived from radiosonde and ERA5 data. Results show that when cutoff angle is set to 5°, the root mean square (RMS) of the ZTD estimated by four satellite systems are all less than 13 mm. Compared with RS-PWV, GPS-PWV, BDS-PWV, Galileo-PWV and GLONASS-PWV, the mean RMSs are 2.25 mm, 2.46 mm, 2.52 mm and 2.84 mm, respectively, all RMSs are less than 3 mm. Compared with ERA5-PWV, the mean RMSs are 1.63 mm, 1.86 mm, 1.76 mm and 1.99 mm, respectively, all RMSs are less than 2 mm. GPS has the highest water vapor determination accuracy, while BDS’s accuracy of water vapor detection is lower than that of GPS and Galileo, but higher than GLONASS, which can meet the requirements of meteorological applications.
2022, 47(5): 111-117.   doi: 10.12265/j.gnss.2022123
[Abstract](27) [FullText HTML](7) [PDF 4877KB](11)
Abstract:
Using the BeiDou observation data of 49 continuously operating reference stations in Shandong Province (SDCORS) in 2020, the atmospheric water vapor inversion was carried out using GAMIT software, and the annual hourly precipitable water vapor (PWV) series were obtained. Comparing the PWV obtained by inversion with the PWV observed by radiosonde weather station, the average deviation is 2.4 mm, the root mean square error is 3.4 mm, and the correlation coefficient reaches 0.98, indicating that the accuracy of inversion results meets the needs of meteorological research. The changes of PWV in the rainstorm process were analyzed from a single CORS station and the whole province. It was found that PWV began to rise 5 hours to 12 hours before the rainstorm. At the time of the rainstorm, the maximum value of PWV generally reached more than 60 mm, and the average change rate reached 1 to 3 mm/h. The closer the rainstorm occurred, the greater the change range of PWV. After the precipitation ended, PWV will decline rapidly. The change of PWV is highly correlated with the occurrence of rainstorm, which can be used for rainstorm warning research.
2022, 47(5): 118-126.   doi: 10.12265/j.gnss.2022147
[Abstract](24) [FullText HTML](5) [PDF 4728KB](30)
Abstract:
Aiming at the needs of Loran-C to receive radio navigation signals, a high-performance Loran-C small active receiving antenna is studied, which can greatly facilitate the use of Loran-C navigation receivers. It is of high practical significance to reduce the volume of the antenna to reduce the difficulty of installation. The main body of the antenna adopts a magnetic rod coil antenna to receive the Loran-C signal in the long-wave band. The front-end signal conditioning circuit including amplifier circuit, band-pass filter circuit, differential output circuit and power supply circuit is designed to increase signal sensitivity and signal-to-noise ratio; an integrated antenna structure is designed for engineering application. Simulations show that the antenna can efficiently receive Loran-C signals. It can amplify the weak Loran-C signal and filter out out-of-band noise, and the signal strength and signal-to-noise ratio meet the requirements. The antenna has the characteristics of small size, high sensitivity and convenient use, and can be used in Loran-C radio navigation, combined Navigation, additional secondary phase delay calculation and other scenarios.
2022, 47(5): 1-2.
[Abstract](46) [FullText HTML](13) [PDF 1911KB](19)
Abstract:
2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1395) [PDF 1536KB](1177)

2020, 45(1): 19-25.   doi: DOI:10.13442/j.gnss.1008-9268.2020.01.003
[Abstract](611) [PDF 750KB](158)

2018, 43(1): 43-48.   doi: 0.13442/j.gnss.1008-9268.2018.01.008
[Abstract](1237) [PDF 1895KB](295)

2018, 43(6): 1-7.   doi: doi:10.13442/j.gnss.1008-9268.2018.06.001
[Abstract](1017) [PDF 93258KB](244)

2017, 42(1): 70-73.   doi: 10.13442/j.gnss.1008-9268.2017.01.014
[Abstract](592) [PDF 476KB](127)

2017, 42(1): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.01.011
[Abstract](415) [PDF 678KB](130)

2018, 43(1): 19-24.   doi: doi:10.13442/j.gnss.1008-9268.2018.01.004
[Abstract](673) [PDF 1830KB](148)

2018, 43(5): 77-83.   doi: 10.13442/j.gnss.1008-9268.2018.05.015
[Abstract](745) [PDF 648KB](208)

2017, 42(2): 15-20.   doi: 10.13442/j.gnss.1008-9268.2017.02.004
[Abstract](407) [PDF 668KB](87)

2017, 42(6): 16-23.   doi: 10.13442/j.gnss.1008-9268.2017.06.003
[Abstract](872) [PDF 2113KB](143)

2019, 44(2): 1-12.   doi: DOI:10.13442/j.gnss.1008-9268.2019.02.001
[Abstract](1395) [PDF 1536KB](103)
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](1140) [PDF 62945KB](118)
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](1179) [PDF 1146KB](87)
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.
2019, 44(1): 1-9.   doi: DOI:10.13442/j.gnss.1008-9268.2019.01.001
[Abstract](1069) [PDF 1077KB](83)
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.
2017, 42(5): 53-58.   doi: 10.13442/j.gnss.1008-9268.2017.05.011
[Abstract](1095) [PDF 778KB](72)
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.

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