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2019 Vol. 44, No. 1

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A novel engineering implementation technique for acquiring B1C signal in the BeiDou-3 receiver

YAN Shulin, DING Chao

2019, 44(1): 1-9. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.001

[Abstract](1559) [PDF 1077KB](962)

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.

Development status and trend of land-based radio navigation system

ZHEN Weiming, DING Changchun

2019, 44(1): 10-15. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.002

[Abstract](912) [PDF 824KB](282)

Abstract:
Positioning, navigation and timing (PNT) system is an essential infrastructure for the normal operation of modern society. The achievements made in military, economic and other fields of national economy and people's livelihood in recent years are obvious to all.However, with the increasingly complex highfrequency electromagnetic environment, in order to improve the reliability of PNT system, it is necessary to develop land-based radio navigation system that does not rely on satellite navigation. Land-based radio navigation system has the characteristics of low working frequency and large transmitting power, so it has high reliability and is not easy to be interfered with, and can be used as a backup of satellite navigation system.The development and construction of landbased radio navigation system is of great significance to the establishment of a robust and reliable national positioning, navigation and timing (PNT) system and the guarantee of national security and the development of national economy. This paper analyzes and introduces the development status and trend of landbased radio navigation system at home and abroad.

Quality contrast and analysis of carrier phase observations in GPS／GLONASS／BDS／Galileo system

LIU Lin, XI Ruijie

2019, 44(1): 16-22. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.003

[Abstract](779) [PDF 857KB](206)

Abstract:
Besides GPS and GLONASS, Galileo and BDS are developing fast, a multi-Global Navigation Satellite System(multi-GNSS) age is emerging, which brings a great opportunity to improve the quality of Positioning, Navigation and timing(PNT) by combining multi-GNSS and multi-frequency data. The data quality of GNSS itself is one of the preconditions for achieving high-precision results, and it is also the key to construction of stochastic model in multi-GNSS precise positioning. In order to avoid the negative effects of Code Division Multiple Access(CDMA) and Frequency Division Multiple Access(FDMA) mechanism for different GNSS systems, this paper used Geometry-free and M-W combination method to compare and analyze carrier phase single-difference(SD) residual time series for four systems where data of a zero baseline measured in Curtin University are adopted. Meanwhile, elevation-dependent stochastic models are obtained for each GNSS system based on the sinusoidal model and the exponential model. The experimental results show that the SD residual series perform different characteristics in different frequencies and systems. The precision of L1 and L2 observations in Galileo system is quite similar and about 0.9mm; however, precision of L2 observations in other systems is even worse than that of L1. The fitting results of elevation-dependent model show that the sinusoidal model and exponential model have a good consistency with precision of L1 and L2 observations of GPS and Galileo, while the sinusoidal model has a slightly worse fitness in BDS system, and using sinusoidal model to evaluate the accuracy of L2 observations in GLONASS system is inappropriate.

Analysis of ionospheric VTEC at Wuhan station during 24th Solar Cycle

LIU Lei, YANG Mei, YAO Yibin, Wang Youkun

2019, 44(1): 23-31. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.004

[Abstract](438) [PDF 1018KB](117)

Abstract:
By using the GPS-VTEC data observed at Wuhan station (30.5N, 114.4E) of Crustal Movement Observation Network of China (CMONOC) from 2008 to 2015, the variations of ionospheric Vertical Total Electron Content (VTEC) are analyzed, and the VTEC correlation with solar activities are discussed. Results show that the diurnal variations of GPS-VTEC show a peak value at about 14:00-16:00LT; meanwhile, VTEC shows day-to-day variability of ionospheric characteristics, a large difference exists especially in the VTEC peak. During high solar activity years (2011-2015), VTEC presents double-peak structure, that is, the so-called Semiannual anomaly, the Spring peak value is greater than the Autumn peak, and Winter anomaly is also more obvious during this period. Among all seasons (except for the Spring), the variation of GPS-VTEC correlated best with the F_10.7p, followed by the F_10.7, and then the SSN. The correlation between the daytime VTEC and the solar activity is superior to the correlation between the night-time VTEC and the solar activity. The correlation between VTEC and the solar activity is the best in Autumn(Max_F10.7p=0.92232, Max_SSN=0.85575), while the worst in Winter(Min_F10.7p=0.79028, Min._SSN=0.72703).

Design and implementation of GPS navigation signal simulator based on PXIe bus architecture

LIU Dezhi, CHEN Chen, LI Jianwen, PAN Lin, ZHANG Lundong

2019, 44(1): 32-38. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.005

[Abstract](447) [PDF 853KB](150)

Abstract:
The satellite navigation signal simulator is an important tool for the research and development of user terminal equipment and verification of satellite navigation signal system, which provides input signal source for the design, verification and testing of user terminal equipment. The accuracy and channel consistency of the signals generated by the early RF synthesis technology are poor. The subsequent analog IF synthesis techniques have the problem of channel-to-channel skew. While the commonly used digital IF synthesis techniques will introduce phase jitter problems. Therefore, based on the software defined radio(SDR) architecture of PXI Express (PXIe) bus, this paper designs and implements a software and hardware combination simulator using digital baseband synthesis technology. LABVIEW graphical programming language, simple and high efficiency, is adopted to develop mathematics simulation software in the host computer, and the software finally generates synthesized digital baseband signals. The modular virtual instruments of national instruments(NI) are utilized to receive and deal with the synthesized digital baseband signal generated by the host computer, and then generate global positioning system(GPS) RF signals that can be received by user terminal equipment. The simulated GPS signal is verified to be correct by utilizing spectrum analyzer to analyze the frequency and bandwidth of simulator output signal. And also it verified to be accurate and effective by utilizing commercial receiver to figure out the position and to analyze the signal quality, positioning results and positioning error in static and dynamic scenes.

Research on robust algorithm of coordinate system transformation based on RANSAC

LIU Mengkui, ZHAO Mingjin, SHI Bo, WANG Yunpeng, ZHANG Qian

2019, 44(1): 39-47. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.006

[Abstract](562) [PDF 927KB](101)

Abstract:
Space coordinate transformation is widely used in geodetic surveying and engineering surveying field. When using the common point to solve the coordinate transformation parameter, the coordinate system transformation model based on Rodriguez matrix was given and a coordinate transformation robust algorithm based on Random Sample consensus (RANSAC) was proposed for the problem of multiple rough points in the common point. At the same time, the algorithm was compared with the least squares robust algorithm based on IGG3 scheme. The results of the example show that when the rough points ratio exceeds 3／10 in the simulation of 20 common points(multiple sets of data), the least squares robust algorithm based on IGG3 scheme begins to fail, while the coordinates transformation robust algorithm based on RANSAC can also ensure the accuracy of coordinate transformation, even if the rough points ratio reached 1／2. The robust algorithm applies the idea of the RANSAC algorithm to the coordinate system transformation and effectively eliminates a large number of rough points that are mixed in common points.

GNSS security, a new frontier of cyber security

LIU Chang, DING Fan, TIAN Miaoqing

2019, 44(1): 48-53. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.007

[Abstract](555) [PDF 790KB](131)

Abstract:
Modern society are facing mounting cybersecurity risk. As one of the main means to maintain the spatial and temporal reference, GNSS is the essential component to cyberspace applications. Also the spatial and temporal data provided by GNSS is one of the most important information applied in the network. Vulnerability of GNSS contributes mostly to its security risk. When interfered, the GNSS devices lose its positioning capability or even output misleading information, threatening the security of GNSS applications or even that of the whole cyber-space. All-round countermeasures should be developed to safeguard the security of cyberspace, including the deepening of understanding, system development, technology advancing, and law enforcement.

Analysis of precision characteristics of HNGG2017

ZENG Xiangqiang, AO Minsi, CHENG Chunhua, LI Chenxi

2019, 44(1): 54-61. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.008

[Abstract](514) [PDF 968KB](113)

Abstract:
Precision evaluation and verification is the precondition for the construction and application of GNSS quasi-geoid model. In view of the HNGG2017 model in Hunan Province, a large number of GNSS/leveling observations and historical models are introduced, and a comprehensive checking method for internal and external accuracy and characteristic areas is proposed. The checking results show that the internal and external coincidence accuracy of the model is better than 2.2 cm. Compared with the historical model, the accuracy of the new model has been significantly improved in the northern Changde Hanshou and the southwestern Yongzhou Jiangyong areas. At the same time, the raw level data of Hupingshan area in northern Hunan may have systematic errors, which needs to be verified by more data.

The application of Kalman filter with colored noise in mitigation of multi-path error

LI Chuan, WEI Shiyu, LIU Xing, LIU Lian, HU Zhumin

2019, 44(1): 62-67. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.009

[Abstract](407) [PDF 805KB](132)

Abstract:
Multi-path error is a space-time environment effect, it is difficult to eliminate it through building accurate mathematical model, and the error also has no spatial correlation at both ends of the baseline, it can't eliminate it through using the differential technology, it is one of the main errors in GNSS high accuracy measurement of short baseline. To further mitigate the multi-path error, this paper take the multi-path error in GNSS carrier phase observation value as the research object, establish the multi-path error state space model, estimate the multipath error correction sequence from coordinate residual sequence adopt the standard Kalman filter and the Kalman filter with colored noise, and based on the daily repetition characteristics of multi-path error, correct the coordinate sequences of the subsequent days using the multi-path error correction sequence obtained on the first day. Finally, through the experimental analysis, it is concluded that the Kalman filter with colored noise estimation method is better than the standard Kalman filter. The research results are of great practical value to improve GNSS positioning accuracy.

A comprehensive CORS performance test method

WANG Fangchao, LYU Zhiping, LIU Chunhe, LI Linyang, KUANG Yingcai

2019, 44(1): 68-75. doi: DOI:10.13442/j.gnss.10089268.2019.01.010

[Abstract](484) [PDF 959KB](145)

Abstract:
The performance test of the continuous operation reference station(CORS) system is critical and its metrics directly determine the accuracy, availability and reliability of the services provided. A comprehensive CORS network data quality inspection and performance testing method is established based on the CORS data processing practice. This method uses GAMIT, TEQC and other software to introduce data integrity, cycle-to-hop ratio, multipath, static and dynamic positioning accuracy. Performance metrics such as system reliability, time availability, and space availability are tested for performance on the server and the client. The CORS data of Zhengzhou (ZZCORS) spanning one year and the static and dynamic measured data of several days are selected in the experiment. The results show that at the service end, the data quality of the base station is better and the position accuracy is higher, but the vertical settlement of individual base stations is larger; on the user side, the space availability in most areas of Zhengzhou City is good, which can meet the user's different precision positioning requirements.

Jam analysis and coping strategies of 4G on BeiDou RDSS system

WANG Fujun, WANG Qian, BAI Yingguang, XIE Weihua

2019, 44(1): 76-81. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.011

[Abstract](438) [PDF 700KB](180)

Abstract:
Aimed at the problem of adjacent frequency jam caused by 4G system on Radio Determination Satellite Service (RDSS) of Beidou system, the analysis way based on the decomposition of wholemachine module is proposed. The main technical measures of restraining from outofband jam are summarized theoretically. Effective bandwidth and processing gain are two key indexes, and the main module is Radio Frequency (RF) module. According to the results of theory analysis, the different RF channels of different apparatus parameters are designed, and the outofband rejection ability of each RF channel is verified on the united test platform. The law and otherness of the test results are described. The research results can provide technical foundation for the compatible coexistence of Beidou system and 4G system.

Analysis on the influence of geomagnetic storm of BDS pseudorange positioning

WANG Wei, LIU Chen, WANG Yupu, JIANG Yi, XU Fen

2019, 44(1): 82-88. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.012

[Abstract](403) [PDF 810KB](118)

Abstract:
Geomagnetic storms are a natural phenomenon that often occurs in the near-earth space. When a magnetic storm happens, the ionosphere fluctuates significantly,which leads to the reduction of the accuracy of ionosphere correction model and then affects the positioning result of single-frequency user. By using three stations’ observations of Harbin, Beijing and Sanya, we calculate the changes of ionosphere before and after a geomagnetic storm which occurs in April 2017, and then calculate the SPP results of dual-frequency mode, single-frequency basic navigation mode and single-frequency enhancement mode respectively. Comparing the results between different modes, and the results show that, during geomagnetic storms, the results of dual-frequency positioning are the best, and the results of single-frequency enhancement mode are slightly better than that of dual-frequency mode, and the two modes are generally superior to the basic single-frequency navigation mode.

Analysis of positioning accuracy of mobile stations under the framework of BDS ground-based augmentation system

WANG Tao, CAI Dongjian, ZHOU Wanghui, XIE Wen

2019, 44(1): 89-93. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.013

[Abstract](370) [PDF 649KB](142)

Abstract:
Suzhou Branch of Jiangsu CORS has built a whole city covering BeiDou ground-based augmentation system framework network.It provides services to regional users based on this framework network. A series of tests were conducted on the stability and limitations of the connection of various source nodes under different environments. The results show that its positioning accuracy can meet the requirements. The plane accuracy is better than 5 cm and the elevation accuracy is better than 10 cm, whether the receiver adopts single star mode, double star mode or three star mode when the satellite is not occluded. In the satellite occlusion case, three star mode advantage is particularly obvious,its initialization time, stability and positioning accuracy are better than the other two modes.

Quality analysis of GPS observation data of global IGS stations

ZONG Gan, GUO Jinyun

2019, 44(1): 94-100. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.014

[Abstract](649) [PDF 803KB](169)

Abstract:
The continuous construction of global navigation satellite system and its extensive application have expanded the service areas of IGS GNSS continuous observation stations, thus improving the requirements of their data quality, so it is necessary to understand its data quality in a wide area of the world. Considering system global coverage and development maturity, this paper aims at GPS, makes a statistical analysis about multipath impacts, data observation integrity and o／slps, and obtains preliminary conclusions on IGS GPS data quality.

Study on GNSS zenith tropospheric delay spatial interpolation in -Beijing-Tianjin-Hebei region

WANG Yong, HAO Zhenhang, LOU Zesheng, SHI Qiang, LI Jiangbo

2019, 44(1): 101-107. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.015

[Abstract](338) [PDF 750KB](130)

Abstract:
The difference of zenith tropospheric delay (ZTD) during different periods affects the accuracy of InSAR deformation; changes in precipitable water vapor (PWV) affect weather changes. The ZTD has a good correlation with PWV, so it is necessary to carry out an interpolation study of GNSS ZTD. Taking Beijing-Tianjin-Hebei region as an example, the spatial interpolation of ZTD is studied for GNSS ZTD. Firstly, the comparative analysis of ZTD and PWV in GNSS is carried out. The two have significant positive correlation characteristics, and the correlation is larger than 91.7％. The feasibility of ZTD to replace PWV is demonstrated. Then, using the inverse distance weighting method, that of 12 groups of GNSS stations in Beijing-Tianjin-Hebei region from September 2016 to August 2017 are spatially interpolated. The spatial interpolation accuracy is verified by extracting the ZTD of the interpolation points and that of the GNSS station. The average deviation of the annual data is 1.12 cm, the root mean square error is 0.89 cm; the average deviation of non-precipitation is 1.25 cm, the root mean square error is 0.82 cm, and the average deviation of precipitation is 1.08 cm, the root mean square error is 1.38 cm. The GNSS ZTD spatial interpolation results in as a Beijing-Tianjin-Hebei plain area meet the meteorological requirements, which can provide as a reference for meteorological forecasting and InSAR atmospheric correction.

Establishment of IGS coordinate time series noise model and its influence on station speed based on MLE

WANG Ziyu, LI Zhongqin

2019, 44(1): 108-112. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.016

[Abstract](350) [PDF 548KB](120)

Abstract:
Based on the coordinates of 30 GPS base stations, the noise characteristics of GPS time series are determined by AIC and BIC noise model estimation criteria respectively. The characteristics of GPS time series noise model are compared and analyzed. Determine the impact of the degree. The results show that the GPS station coordinate sequence noise model mainly shows the characteristics of FN+WN, PL and FN+RW+WN noise models; the influence of different noise models on the GPS station speed estimation is relatively small, but the U component is the most obvious; In addition, the influence of RW on station speed uncertainty can not be neglected. It is of great significance to correctly obtain the actual uncertainty of model parameter estimation and correct the noise component for the reasonable application of GPS coordinate time series data.

Variation of ionospheric slab thickness analysis using GPS observations at Qingdao

ZHOU Yufeng, LI Shicheng, FENG Jian

2019, 44(1): 113-118. doi: 10.13442/j.gnss.1008-9268.2019.01.017

[Abstract](319) [PDF 574KB](120)

Abstract:
The slab thickness is an important ionospheric parameter and is defined as the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2). The variation of ionospheric slab thickness is analyzed by using GPS and ionosonde observations from August 2000 to April 2006 at Qingdao (120.3^oE, 36.0^o N). An enhanced peak of slab thickness occurs around 04-06LT in different season and solar activity. The slab thickness changes mainly between 200 and 500 kilometers. The slab thickness is greater for day-time in summer and for night-time in winter. The slab thickness of day-time reduces with the degradation of solar activity at same season, but the one of night-time changes less between high and low solar activities. Moreover, analyzes the distribution of the relative deviation of slab thickness and finds the perturbation of slab thickness happens easier in night-time than day-time.

Modeling and research on weighted average atmospheric temperature in Hongkong

WANG Hao, ZHAO Xingwang

2019, 44(1): 119-124. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.018

[Abstract](337) [PDF 571KB](123)

Abstract:
Aiming at the accuracy of calculation results of atmospheric precipitation affected by the precision of atmospheric weighted mean temperature in the groundbased GPS water vapor retrieval process, the regression analysis method is used to study the sounding data of Hong Kong from 2006 to 2016, and the singlefactor and multi-factor atmospheric weighted mean temperature calculation models for Hong Kong are constructed. The two models are used to predict the 2017 weighted mean temperature. Compared with the results of various empirical formulas and true values, the deviations between the two models and true values account for 80.72％ and 85.26％ respectively in the range of -5 K~5 K, which is obviously better than other empirical formulas. Moreover, the accuracy of the weighted mean temperature calculated by seasonal modeling has not been significantly improved, but the accuracy of the calculated results can be significantly improved by diurnal modeling. Therefore, in order to improve the accuracy of the water vapor retrieval calculation, the local meteorologic data in the air should be used to construct a local weighted mean temperature calculation model, which is of great significance for improving the accuracy of GPS total water vapor retrieval.

Realization of straw incineration fire point identification in Hebei Province by improved MODIS fire point detection algorithm

WEI Yingce, SANG Huiyong, ZHANG Tao, CONG Yang, GU Xianghui

2019, 44(1): 125-130. doi: DOI:10.13442/j.gnss.1008-9268.2019.01.019

[Abstract](247) [PDF 677KB](102)

Abstract:
Accurately understanding the spatial distribution of straw burning points in Hebei province, we can provide support for the realization of straw burning monitoring, the development of banned burning work and the improvement of environmental quality. Based on MODIS L1B data, MODIS standard fire point product MOD14, and national straw burning fire point daily report data, the improved MODIS fire detection algorithm is adopted, and the IDL language is used to obtain the space segmentation information of straw burning fire point, and space and Quantitative accuracy analysis. The research shows that the fire point is mainly concentrated in the southern part of Hebei Province, especially Xiangtan, Shijiazhuang, and the number of cockroaches; the algorithm is fast, and the obtained straw burning point data has certain detection accuracy and reliability, and the monitoring of straw burning has certain practical.