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2022 Vol. 47, No. 6

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2022, 47(6): 1-2.

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2022, (6)

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Navigation accuracy and applicability analysis of GNSS technology in GEO and IGSO spacecraft

MA Xiangtai, HU Yanfeng, DONG Xurong

2022, 47(6): 1-8. doi: 10.12265/j.gnss.2022089

[Abstract](257) [FullText HTML] (52) [PDF 3711KB](43)

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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.

Influence analysis of different tropospheric models on airborne precise point positioning

DONG Jianquan, GUO Jiang, LI Guangcai, LUO Feng

2022, 47(6): 9-17, 37. doi: 10.12265/j.gnss.2022095

[Abstract](190) [FullText HTML] (50) [PDF 5922KB](37)

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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.

The quality control algorithm of comprehensive corrections in augmented PPP algorithm of observation domain

HONG Ju, TU Rui, ZHANG Shixuan, ZHANG Pengfei, WANG Siyao, LI Fangxin, LIU Mingyue

2022, 47(6): 18-24. doi: 10.12265/j.gnss.2022102

[Abstract](245) [FullText HTML] (57) [PDF 2889KB](29)

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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 n the value of the differential combination, and effectively control the influence of some outliers on the positioning results.

GNSS real-time cycle slip repair algorithm and PPP test analysis

YIN Xiangfei, LIU Genyou, WANG Binbin, LYU Dong

2022, 47(6): 25-30. doi: 10.12265/j.gnss.2022150

[Abstract](270) [FullText HTML] (60) [PDF 2442KB](30)

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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.

Effects of stochastic models on BDS DCB estimation and ionospheric modeling

LIU Bingyu, WANG Zhongyuan, WANG Yangyang, GE Yuxiang, WANG Ruiguang

2022, 47(6): 31-37. doi: 10.12265/j.gnss.2022117

[Abstract](166) [FullText HTML] (52) [PDF 3034KB](17)

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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.

Research on BPSK-CSK message modulation and demodulation algorithm

WANG Huanyu, YUAN Muzi, MA Chunjiang, TANG Xiaomei, OU Gang, LIN Honglei

2022, 47(6): 38-45. doi: 10.12265/j.gnss.2022170

[Abstract](230) [FullText HTML] (158) [PDF 2804KB](53)

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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.

GNSS positioning performance analysis of Android smartphones

ZHANG Yin, TU Rui, HONG Ju, LI Fangxin, MIAO Yage, LIU Mingyue

2022, 47(6): 46-53. doi: 10.12265/j.gnss.2022126

[Abstract](297) [FullText HTML] (100) [PDF 7847KB](57)

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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.

GPS coordinate time series common mode error extraction methods

YAN Li, LUO Zhengdong, LI Meng, ZOU Xiaoping

2022, 47(6): 54-59. doi: 10.12265/j.gnss.2022135

[Abstract](250) [FullText HTML] (90) [PDF 3245KB](17)

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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.

Analysis of environmental loading corrections on CMONOC vertical coordinate time series

SUN Zhiyuan, LI Yanlin, WEI Na

2022, 47(6): 60-66. doi: 10.12265/j.gnss.2022185

[Abstract](176) [FullText HTML] (47) [PDF 4600KB](26)

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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.

Neural network optimization for the 5G positioning of the result domain

CHEN Sitong, ZHU Feng, QIN Yiduo, YANG Xiaoteng

2022, 47(6): 67-72. doi: 10.12265/j.gnss.2022077

[Abstract](152) [FullText HTML] (54) [PDF 2434KB](27)

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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 network, 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.

Reseacher on eLoran noise error model and generation method

XIAO Zaihui, YAN Wenhe, LIU Kaiqi, LI Shifeng, ZOU Yun

2022, 47(6): 73-78, 122. doi: 10.12265/j.gnss.2022100

[Abstract](152) [FullText HTML] (57) [PDF 3075KB](21)

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The enhanced Loran (eLoran) system is complementary to the Global Navigation Satellite System (GNSS), making it the best backup system. The receiver performs timing and positioning by measuring time of arrival (TOA). Noise is an important factor affecting the TOA accuracy of eLoran signal, and white Gaussian noise (WGN) is ubiquitous in noise. This paper based on the maximum likelihood estimation method was deduced under WGN of TOA error model, then using the method of linear congruence and Box - Muller transform method to generate WGN, the simulation analysis of the time and frequency domain properties of a gaussian white noise, the use of noise simulating TOA measurement error, and comparing with theoretical TOA model, The results show that the theoretical error model is consistent with the simulation TOA value error, which verifies the correctness of the TOA measurement error model and noise generation studied in this paper. The research results of this paper can provide reference for the TOA error model of eLoran signal and noise generation in the simulator, and promote the application development of eLoran system.

BDS-3 precise point positioning ambiguity resolution and performance assessment

TAN Han

2022, 47(6): 79-85. doi: 10.12265/j.gnss.2022107

[Abstract](232) [FullText HTML] (61) [PDF 3642KB](30)

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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.

GNSS spoofing signal parameters estimation based on Newton’s method

WANG Jiaqi, TANG Xiaomei, SUN Guangfu

2022, 47(6): 86-90. doi: 10.12265/j.gnss.2022171

[Abstract](246) [FullText HTML] (85) [PDF 2475KB](25)

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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.

The technology of GNSS interference detection and identification based on navigation receiver

JIN Ruimin, GUO Yi, YANG Huiyun, CHE Lei, XU Wenpu, ZHEN Weimin

2022, 47(6): 91-95. doi: 10.12265/j.gnss.2022218

[Abstract](365) [FullText HTML] (79) [PDF 2437KB](59)

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Global Navigation Satellite System (GNSS) has been widely used in various military and civil systems. But the GNSS signal is weak, and the format of civil signal is open, so it is extremely vulnerable to various electromagnetic interference. For GPS L1 C/A code, the noise higher than −160 dBm/Hz will affect the acquisition of the receiver. But generally, the sensitivity of spectrum interference monitoring equipment is −150 dBm/Hz and cannot detect the weak interference. This paper proposed methods that utilize the information of automatic gain control (AGC), carrier to noise ratio (${\rm{C/{N_0}}}$) and position of the general receiver to realize jamming and spoofing detection and identification. The methods were tested by setting up a real environment and the results showed that the methods in this paper can detect and identify GNSS jamming and spoofing. The detection accuracy can reach 96%, and the identification accuracy of jamming and spoofing can reach 94%.

Design and analysis of optimal power gain for satellite transponder channel saturation condition

HOU Linyuan, HUANG Xinming, ZHANG Pengcheng, XIAO Wei, LI Jingyuan, LI Zhengrong

2022, 47(6): 96-101. doi: 10.12265/j.gnss.2022093

[Abstract](135) [FullText HTML] (43) [PDF 2508KB](15)

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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.

Single-frequency single-point positioning performance analysis of combined BDS-3/GNSS systems in Asia-Pacific

GUAN Qinglin, FAN Chunming, WANG Junjie

2022, 47(6): 102-108. doi: 10.12265/j.gnss.2022042

[Abstract](154) [FullText HTML] (45) [PDF 3018KB](19)

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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.

Direction finding method based on spatial spectrum estimation with less channel quasi calibration

MA Baotian, GUO Shuli, LIU Shaolin

2022, 47(6): 109-113. doi: 10.12265/j.gnss.2022091

[Abstract](166) [FullText HTML] (109) [PDF 3126KB](21)

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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 can realize the direction finding of single signal and double signals in complex scenes. Under the condition of low signal to noise ratio (SNR), the direction finding error can still be kept at about 3.5°, and the direction finding accuracy is high. The direction finding results are basically consistent with the direction finding results of the whole channel.

Real-time monitoring of orbital maneuvers of BDS-3 GEO satellites based on station networks of different spatial scales

MIAO Yage, TU Rui, HONG Ju, LIU Mingyue

2022, 47(6): 114-122. doi: 10.12265/j.gnss.2022133

[Abstract](183) [FullText HTML] (66) [PDF 3808KB](18)

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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.