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2023 Vol. 48, No. 1

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Contents
Special Column on “Satellite Navigation and Augmentation Technology”
Theory and Discussion
Technical report and application
Technical Report and Application
Review

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2023, 48(1): 1-2.

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2023, 48(1): 1-1.

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2023, 48(1): 2-2.

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Special Column on “Satellite Navigation and Augmentation Technology”

A study on impacts of ionospheric disturbances for GNSS augmentation-From the perspective of system reliability engineering

LIU Dun, LI Rui

2023, 48(1): 3-13. doi: 10.12265/j.gnss.2022209

[Abstract](517) [FullText HTML] (121) [PDF 2916KB](75)

Abstract:
A variety of ionospheric disturbance phenomena could pose grave impacts on Global Navigation Satellite System (GNSS) augmentation. The existed works, mainly for mid-latitudes ionosphere condition, are insufficient in low-latitude area where various disturbances exist. A method is proposed for GNSS augmentation study from the perspective of reliability engineering system. Attempt is made to analyze different ionospheric perturbations with failure model and effect analysis (FMEA) method to show the serious impacts. Disturbance detection procedures are also assessed for its effectiveness in augmentation system. The results show the existing designs could not cope with complex ionospheric conditions in low-latitude area for irregularity detection and identification. More efforts had to be made for augmentation systems covering China areas.

Estimation and characteristics analysis of BDS-3 uncalibrated phase delay based on different PPP models

WU Feiyang, LI Xin

2023, 48(1): 14-23. doi: 10.12265/j.gnss.2022053

[Abstract](362) [FullText HTML] (308) [PDF 6272KB](91)

Abstract:
Accurate estimation of uncalibrated phase delay (UPD) is an important precondition for ambiguity resolution of precise point positioning (PPP). The commonly used PPP models are mainly divided into the ionosphere-free (IF) combination model and the undifferenced and uncombined model, and the UPD estimation methods used for the two models are different. In this paper, the consistency of UPD estimation based on IF combination model and uncombined model is proved theoretically under the premise of using the same processing strategy. Furthermore, the UPD products of BDS-3 were estimated by using the observation data of 45 International GNSS Service (IGS) stations uniformly distributed around the world, and the time stability and consistency of UPD products obtained by the two estimation models were analyzed. The results show that the UPD of wide-lane and narrow-lane in BDS-3 maintain high stability. The average standard deviation of UPD of wide-lane in ten days is 0.0607, and that of narrow-lane in one day is 0.059 9. For BDS-2 satellites, the UPD results estimated by the two models are highly consistent. However, the UPD results of BDS-3 satellites are related to the characteristics of satellite orbit types and manufacturers. There is a significant difference in UPD between different orbit types and manufacturers of about 0.5 weeks, but there is consistency among BDS satellites of the same orbit type and manufacturer. It can be concluded that the hardware delay of the receiver corresponding to satellites produced by different orbital types and different manufacturers of BDS-3 has a systematic deviation. The estimation of inter-satellite-type bias in PPP further demonstrates this conclusion. Finally, the impact of these biased on PPP and PPP AR was carefully discussed.

Refinement of GNSS stochastic model combining elevation angle and SNR and its effect on RTK positioning performance

CAI Qinqing, ZHU Feng, CHEN Xi, MA Liye

2023, 48(1): 24-31. doi: 10.12265/j.gnss.2022070

[Abstract](778) [FullText HTML] (188) [PDF 3738KB](148)

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The accuracy of Global Satellite System Navigation (GNSS) observations will be affected by atmospheric delay, NLOS signal, multipath and other factors. However, the sensitivity of elevation angle or SNR model to different error sources is different. As a result, the traditional single random model based on elevation angle or signal noise ratio (SNR) cannot meet the high-precision positioning and navigation of the whole scene, coupled with the emergence of multi frequency and multi system, the accuracy of observations in different frequency bands of different GNSS systems and even the same system will also be different, which also brings a great challenge to the traditional model weighting. Based on the analysis of the advantages and disadvantages of elevation random model and SNR random model, a combined random model of elevation angle and SNR is proposed in this paper; The pseudo-range and phase noise of GPS, BDS, Galileo are extracted respectively through single difference between stations and cubic difference between epochs, and the combined random model of extracted and SNR is refined. Experiments show that the correct fixing rates of ambiguity of SNR model, elevation angle model and combined model are 92.42%, 95.85% and 97.69% respectively; Compared with the elevation angle model, the positioning accuracy of the combined model is improved by 50.0% in the horizontal direction and 37.1% in the elevation direction.

Accuracy evaluation on satellite orbit determination of BDS-3 PPP-B2b service

JIANG Wei, CHEN Xiangdong, XING Yunjian, DONG Jie, CONG Ruihao

2023, 48(1): 32-36. doi: 10.12265/j.gnss.2022154

[Abstract](390) [FullText HTML] (179) [PDF 3253KB](64)

Abstract:
With the successful networking of the BeiDou-3 Navigation Satellite System, the B2b, a new signal, can provide precise point positioning (PPP) service, which has attracted more and more attention. However, its application was not yet widespread. To explore the performance of the PPP-B2b service signal, we calculated the results of satellite orbit determination based on the B1C and PPP-B2b navigation message data received by our original-designed board. The simulation results compared with that based on the precision ephemeris products and their interpolation results provided by the German Geoscience Research Center. Two error indices (the cross-difference sequence and the root mean square error) were calculated to evaluate the orbit accuracy after broadcast ephemeris and PPP-B2b precise orbit correction. The results show that the broadcast orbit accuracy is generally 0.19 m, 0.65 m and 0.89 m in the radial (R), tangential (T) and normal (N) directions. The average accuracy of precise orbit correction is generally 0.13 m, 0.32 m and 0.29 m in the R、 T 、N directions, respectively. The PPP-B2b service signal received by our original-designed board can satisfy the application requirements of precise point positioning. This would provide data reference for the next development of related products based on PPP-B2b signal.

Evaluation of PPP-RTK under ionospheric scintillation

WANG Bo

2023, 48(1): 37-45. doi: 10.12265/j.gnss.2022142

[Abstract](397) [FullText HTML] (129) [PDF 15423KB](55)

Abstract:
Precise point positioning real time kinematic (PPP-RTK) enables fast and precise positioning with the precise atmospheric corrections from the regional network, and it is regarded as the technology of choice for autonomous driving. However, PPP-RTK is hardly maintaining stable and reliable positioning result under ionospheric scintillation which has become one of the major challenges for PPP-RTK. In this contribution, the PPP-RTK model and ionospheric scintillation characteristics are introduced. The impact of ionospheric scintillation on PPP-RTK is analyzed in four aspects: observation quality, circumferential hop detection, atmospheric products and positioning performance based on the GNSS observations from the Hong Kong Satellite Positioning Reference Station Network. The results show that ionospheric scintillation reduces observation quality and increases the probability of wrong cycle slip detection. The accuracy of the corrections of GPS, Galileo, and BDS decreased by 64.7%, 64.0%, 247.5%, respectively, and the number of which decreased by 4.5. Finally, the positioning accuracy of PPP-RTK is increases by 11.8 times compared with the normal period, and the fixing percentage is reduced by 55.76%. The GEC mixed solution can significantly improve the positioning performance, of which the positioning accuracy in improved by 93.06% and the fixing percentage is increased by 51.88% compared with the GPS-only solution.

Monitoring and analysis of GNSS landslide geological hazard based on virtual reference station

CAI Hua, LIU Xingwei, PU Dexiang, WANG Bin

2023, 48(1): 46-50, 76. doi: 10.12265/j.gnss.2022156

[Abstract](479) [FullText HTML] (282) [PDF 3300KB](30)

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The application of Global Navigation Satellite System (GNSS) technology to landslide monitoring has the problems of difficult location selection of reference stations, high construction cost and unstable datum. The method of monitoring landslide geological disasters based on virtual reference station (VRS) is used. The continuous operation reference station (CORS) is used to generate virtual reference station data in the monitoring area to replace the physical reference station for landslide monitoring. Through experiments and analysis, the monitoring accuracy of virtual reference station under different solution strategies is obtained, and the results after gross error elimination are compared with the traditional GNSS monitoring. The results show that the 2 h monitoring accuracy of the virtual reference station can reach 5 mm in plane and 25 mm in elevation. The displacement trend reflected by the virtual reference station is consistent with the traditional GNSS monitoring.

GNSS height conversion method based on ultra-high order earth gravitational model

ZHAO Baocheng, XU Jian

2023, 48(1): 51-56. doi: 10.12265/j.gnss.2022141

[Abstract](207) [FullText HTML] (117) [PDF 2349KB](25)

Abstract:
To make the ellipsoidal height obtained by Global Navigation Satellite System (GNSS) directly applied to engineering construction, it was necessary to convert the ellipsoidal height to normal height. This paper researched the GNSS height conversion method based on 5 ultra-high-order earth gravity field models combined with the improved “removal fitting recovery method”. The comparative analysis of the experimental results showed that in the experimental survey area, the height anomaly directly calculated by SGG-UGM-2 earth gravity field model was more consistent with the real height anomaly, and the mean square error was ± 0.009 3 m. When the “removal fitting recovery method” was adopted, the fitting effect of the height anomaly using XGM2019e_2159 earth gravity field model was better, and the mean square error, range, skewness value, and kurtosis value were the smallest, which were ±4.786 6 mm, 18.8757 mm, −0.648 8 and 0.887 8.

LEO enhanced Beidou PPP-RTK positioning method and experimental analysis

DENG Zhixu, FU Yuanchen, LI Xin

2023, 48(1): 57-63. doi: 10.12265/j.gnss.2023008

[Abstract](656) [FullText HTML] (249) [PDF 3617KB](107)

Abstract:
Low earth orbit (LEO) constellation has the advantages of large number of satellites and rapid change of geometric configuration, which is conducive to the rapid convergence of ambiguity parameters in precise single point positioning (PPP). However, it is difficult to achieve rapid convergence of ambiguity in several seconds or even instantaneous because of the influence of atmospheric delay. In this contribution, a LEO constellation enhanced PPP-RTK method is proposed, which makes full use of the high-precision atmospheric information and ambiguity resolution (AR) method to further improve the positioning performance of Beidou. A polar orbit constellation containing 192 LEO satellites was designed, and the observations of 22 ground stations were simulated. After estimating the UPD and precision atmospheric delay correction, the positioning performance of LEO enhanced PPP, PPP-AR and PPP-RTK are evaluated respectively. The results show that under the enhancement of LEO constellation, the number of visible satellites increases by 4~6, and the average PPP initialization time of 22 stations is shortened from 552.1 s to 102 s, with the improvement of 81.52%. After the ambiguity resolution, the initialization time is further shortened to less than 1 minute. With the regional network augmentation, the LEO enhanced PPP-RTK can achieve a positioning accuracy of centimeter degree, and the positioning accuracy can be improved by 98.5% compared with PPP. Even when the ground reference network is expanded to 500 km, the LEO enhanced PPP-RTK can still achieve rapid convergence of about 10 seconds.

Theory and Discussion

Accuracy evaluation of BeiDou-3 PPP-B2b signal

CAI Zirui, FANG Rongxin, HU Bingyan, XIONG Heng

2023, 48(1): 64-70. doi: 10.12265/j.gnss.2022217

[Abstract](474) [FullText HTML] (576) [PDF 3609KB](106)

Abstract:
The BeiDou-3 Navigation Satellite System (BDS-3) B2b signal is a signal broadcast by three geosynchronous orbit satellites of BDS-3, which can provide users with open and free high-precision services, and is of great significance on high-precision applications in several fields such as land surveying, marine surveying and health monitoring of bridges and buildings. The accuracy evaluation of precision single point positioning (PPP)-B2b signals is a key link to realize its high-precision applications. To evaluate the accuracy of PPP-B2b products, by correcting the broadcast ephemeris with PPP-B2b signals using self-compiled program, the precise orbit and clock products corrected by the PPP-B2b products were obtained. Taking the after-event precision products (WUM) provided by the IGS Data Center of Wuhan University as a reference, the precision of the precision products corrected by PPP-B2b is evaluated. The results show that the root-mean-square (RMS) value of the radial direction (R), tangential direction (A) and normal direction (C) of the BeiDou satellite orbit after correction is 6.26 cm, 24.21 cm, and 21.79 cm respectively, and the average value of the standard deviation (STD) of the clock difference is 0.33 ns. Finally, the results of the PPP using the corrected precise orbit and clock products show that the accuracy of PPP positioning in the east (E), north (N) and zenith (U) directions is 0.07 m, 0.07 m and 0.15 m respectively. The precise orbit and clock error products of broadcast ephemeris corrected by BDS-3 B2b are as accurate as IGS post-event precision products, which can meet the application requirements of single-station real-time high-precision positioning and navigation.

NLOS error elimination 3D positioning model based on improved Gauss-Newton method

LIU Chen

2023, 48(1): 71-76. doi: 10.12265/j.gnss.2022153

[Abstract](235) [FullText HTML] (80) [PDF 2527KB](26)

Abstract:
To address the problem of low accuracy caused by the non line of sight (NLOS) propagation of signals in the indoor positioning process of wireless sensor networks, a three-dimensional indoor positioning model with NLOS error elimination based on the improved Gauss Newton method was proposed. Firstly, the initial solution of the target position is obtained by using the least square algorithm based on the Euclidean distance. In order to further reduce the influence of NLOS error, the nonlinear least square estimation value is iterated according to the improved Gauss-Newton method, and the final accurate position is obtained by convergence. The experimental results show that the positioning error of the model in three-dimensional space is about 0.64 m, the maximum positioning error is not more than 1.29 m, and the probability of error less than 1.2 m is 96.5%, which is better than other positioning methods.

Analysis of cycle slip processing algorithm for precipitation observation data based on GNSS polarimetric occultation signal

AN Hao, BIAN Shuangshuang, DU Xiaoyong

2023, 48(1): 77-82. doi: 10.12265/j.gnss.2022205

[Abstract](299) [FullText HTML] (58) [PDF 8281KB](23)

Abstract:
Extracting precipitation information by Global Navigation Satellite System (GNSS) polarimetric occultation signal is a new research field in the world. Based on the previous theoretical research, simulation analysis and ground-based experiments, this paper focuses on solving the problem of cycle slip in the data of ground-based experiments. Combined with the characteristics of carrier phase data of ground-based experiments, the feasibility and application scope of six commonly used cycle slip detection algorithms, such as high-order difference method and doppler observation value method, are systematically compared and analyzed, and then the high-order difference method is improved to solve the problem of manually determining the number of times of difference. Finally, the reliability and effectiveness of this method are verified through simulation analysis and measured data. The results show that this method can accurately detect all kinds of cycle slips of horizontally polarized carrier phase and vertically polarized carrier phase under rain free and rainy conditions, and can be effectively applied to the precipitation observation data processing of GNSS polarimetric occultation signal.

The effects of higher order ionosphere on GNSS tropospheric parameters estimation

WEI Tong, YAN Weidong, MA Jian

2023, 48(1): 83-97. doi: 10.12265/j.gnss.2022157

[Abstract](476) [FullText HTML] (114) [PDF 6986KB](30)

Abstract:
In order to study the influence of the high-order ionosphere on the Global Navigation Satellite System (GNSS) tropospheric parameter estimation eight MGEX (Multi GNSS Experience) tracking stations in the Asia Pacific region were selected during the quiet and active periods of solar activity The influence of high-order ionosphere delay on tropospheric parameter estimation in Beidou-2 Navigation Satellite System (BDS-2), Beidou-3 Navigation Satellite System (BDS-3), Global Positioning System (GPS), Global Navigation Satellite System (GLONASS) and Galileo is analyzed through GAMIT10.71 The experimental results show that during the quiet period of solar activity, the maximum influence of high-order ionosphere delay on Galileo’s zenith total delay (ZTD), precipitable water (PW) and north south gradient (${{NS}}_{\text{grad}}$) is 7.70 mm, 1.26 mm and 6.77 mm respectively; The maximum effect of high-order ionosphere delay on the tropospheric east west gradient (${{EW}}_{\text{grad}}$) of GLONASS is 9.30 mm during the active solar period, high-order ionosphere has greater influence on the tropospheric parameter estimation of GNSS among them, the maximum impact of high-order ionosphere delay on the tropospheric ZTD and PW of BDS-2 is 21.30 mm and 3.49 mm respectively; The maximum influence of high-order ionosphere delay on the tropospheric ${{NS}}_{\text{grad}}$ of Galileo is 19.87 mm; The maximum effect of high-order ionosphere delay on tropospheric ${{EW}}_{\text{grad}}$ of GLONASS is 21.21 mm The experimental results further show that high-order ionosphere has little influence on the tropospheric PW estimation of GNSS; ZTD, ${{NS}}_{\text{grad}}$ and ${{EW}}_{\text{grad}}$ have greater influence high-order ionosphere delay has little effect on BDS-3 and GPS tropospheric parameter estimation; Galileo, BDS-2 and GLONASS have greater influence

Technical report and application

Research on short-term clock bias prediction of BeiDou satellite based on optimized residual difference combination

ZHOU Shiqi, CAI Chenglin

2023, 48(1): 98-104. doi: 10.12265/j.gnss.2022136

[Abstract](240) [FullText HTML] (86) [PDF 4002KB](25)

Abstract:
In order to solve the problem of poor prediction accuracy caused by the traditional model using the satellite clock bias primary difference sequence and further improve the prediction accuracy, an optimized residual combination is proposed to forecast the satellite clock bias primary difference sequence. This method firstly according to the characteristics of the beidou satellite clock bias sequence, using quarterback method instead of the median method of time difference sequence preprocessing, and then using autoregressive moving average (ARMA) model after preprocessing the satellite clock bias of a differential sequence is divided into trend item and random item residual, then using the extreme learning machine (ELM) model to simulate the residual part modeling prediction, Finally, the prediction results of ARMA model and residual prediction results of ELM neural network are summed and then differentially restored. The results show that when the satellite clock bias is nonlinear, the prediction accuracy of the combined model is 38.2% higher than that of the traditional model, which has certain feasibility in the short-term prediction of the BeiDou satellite clock bias.

Technical Report and Application

Design of mixed functional ephemeris characterization for GEO ring target orbit based on static ground properties

LIU Longdi, DU Lan, LIU Zejun, ZHANG Zhongkai, ZHOU Peiyuan, HUANG Junjia

2023, 48(1): 105-110. doi: 10.12265/j.gnss.2022188

[Abstract](177) [FullText HTML] (49) [PDF 3151KB](18)

Abstract:
The geostationary earth orbit (GEO) ring is a unique class of orbital resources with a strategic high altitude location. For a long time, the GEO ring cataloging target adopts two-line element and simplified general Perturbations-4 model TLE-SDP4 for generic orbit calculation, but this analytic algorithm has disadvantages such as limited extrapolation accuracy, complicated use process and difficult to understand by users. In this paper, we design a mixed functional parametric ephemeris model combining the classical Keplerian elements and polynomial-Fourier series for the GEO’s static ground characteristics, which can be used for 12~24 h orbit fitting and simultaneous release of parametric groups of high-precision numerical integration orbits, with a concise user calculation model. The 1-year ephemeris fitting experiments for three representative GEO targets show that the mean value of 1 day fitting root mean square (RMS) is better than 20 m. When the fitting length is shortened to 12 h, the fitting accuracy is better than 0.15 m. This can provide a reference for the hierarchical management of China’s space target cataloguing database.

Multi-interference source direction finding and positioning technology for satellite navigation and its application

YIN Zan, ZHEN Weimin, JIN Ruimin, LIN Ziyang, WANG Runzi, CHE Lei

2023, 48(1): 111-116. doi: 10.12265/j.gnss.2023006

[Abstract](493) [FullText HTML] (149) [PDF 3053KB](80)

Abstract:
Aiming at the problems that are difficult to detect and find in the navigation countermeasures environment, this paper presents the design scheme and interference source search process of the satellite navigation interference source air-ground cooperative direction finding and positioning system, and conducts simulation analysis on the interference detection technology used in the system, improved spatial spectrum estimation and multi-interference source direction finding technology combined with correlation interferometer. The system is tested and verified in practice. The actual test results show that the system can simultaneously detect the number of multiple interference sources of the same frequency is 4, the direction finding accuracy is 1.4 degrees (root mean square error), the system positioning accuracy is less than 5%R (R is the distance between the interference source and the monitoring point), can meet the actual use requirements.

CSI indoor positioning algorithm based on GMM-DBC

LI Xinchun, LI Ying

2023, 48(1): 117-124. doi: 10.12265/j.gnss.2022184

[Abstract](228) [FullText HTML] (168) [PDF 2974KB](33)

Abstract:
A channel state information (CSI) location algorithm based on the Gaussian mixture model and density based clustering (GMM-DBC) is proposed to deal with the low positioning accuracy and high time complexity of Bayesian indoor positioning technology. The GMM probability distribution model is constructed through the initial estimation of the parameters of the sub-model, and the errors were calculated. Then, introduce a strategy to determine the number of sub-models (DSM) to update the parameters of the GMM and reduce the localization error caused by the model accuracy. The tightness between reference points is judged on the basis of the distribution characteristics of different reference points, and the closely connected reference points are classified into one class to reduce the search scope and time complexity. The weights are calculated via the improved Bayesian probability algorithm according to the clustering results, so as to obtain the final positioning results. The experimental results show that the proposed algorithm can well improve the positioning accuracy and reduce the time complexity.

Review

Technical progress of satellite-borne GNSS-R monitoring sea surface targets

HU Yuan, GU Shisen, LIU Wei, JIANG Zhihao, YUAN Xintai

2023, 48(1): 125-132. doi: 10.12265/j.gnss.2021030902

[Abstract](488) [FullText HTML] (93) [PDF 2307KB](79)

Abstract:
Global Navigation Satellite System (GNSS) has opened up a GNSS-reflection (GNSS-R) technology with great potential in many other remote sensing applications because its direct signal is reflected by the sea surface. Progress has been made at home and abroad in the field of on-board GNSS-R monitoring of the sea surface. This paper summarizes the progress of monitoring sea surface targets using satellite-borne GNSS-R data. The technology of monitoring sea surface targets with satellite-borne GNSS-R is summarized and summarized from four aspects: initial experiment, monitoring based on delay Doppler map (DDM) observation value, monitoring based on inverse scattering coefficient and monitoring using neural network.