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Study on GNSS satellite signal simulator 被引量:2
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作者 李栋 李永红 +3 位作者 岳凤英 孙笠森 赵圣飞 王恩怀 《Journal of Measurement Science and Instrumentation》 CAS 2013年第4期349-352,共4页
Satellite signal simulator for global navigation satellite system(GNSS)can evaluate the accuracy of capturing,tracing and positioning of GNSS receiver.It has significant use-value in the military and civil fields.The ... Satellite signal simulator for global navigation satellite system(GNSS)can evaluate the accuracy of capturing,tracing and positioning of GNSS receiver.It has significant use-value in the military and civil fields.The system adopts the overall design scheme of digital signal processor(DSP)and field-programmable gate array(FPGA).It consists of four modules:industrial control computer simulation software,mid-frequency signal generator,digital-to-analog(D/A)module and radio frequency(RF)module.In this paper,we test the dynamic performance of simulator using the dynamic scenes testing method,and the signal generated by the designed simulator is primarily validated. 展开更多
关键词 global navigation satellite system(gnss) digital signal processor(DSP) field-programmable gate array(FPGA) SIMULATOR
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REVISITING THE DOPPLER FILTER OF LEO SATELLITE GNSS RECEIVERS FOR PRECISE VELOCITY ESTIMATION 被引量:1
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作者 Chen Xi Gao Wenyun Wan Yunheng 《Journal of Electronics(China)》 2013年第2期138-144,共7页
The theoretical aspects of the precise velocity determination of Low Earth Orbit (LEO) satellites'on board Global Navigation Satellite Systems (GNSS) receivers are derived. It shows that the receiver's Phase L... The theoretical aspects of the precise velocity determination of Low Earth Orbit (LEO) satellites'on board Global Navigation Satellite Systems (GNSS) receivers are derived. It shows that the receiver's Phase Lock Loop (PLL) is required to feature extremely small group delay within its low frequency band, which is in contrast to existing work that proposed wide band linear phase filters. Following this theory, a Finite Impulse Response (FIR) filter is proposed. To corroborate, the proposed FIR filter and an Infinite Impulse Response (IIR) filter lately proposed in literals are implemented in a LEO satellite onboard GNSS receiver. Tests are conducted using a third party commercial GPS signal generator. The results show that the GNSS receiver with the proposed FIR achieves 11 mm/s R.M.S precision, while the GNSS receiver with the IIR filter has a filter-caused velocity error that can not be ignored for space borne GNSS receivers. 展开更多
关键词 Global Navigation satellite Systems (gnss) VELOCITY Doppler filter Centimetre level
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A fine acquisition algorithm based on fast three-time FRFT for dynamic and weak GNSS signals 被引量:1
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作者 PAN YI ZHANG Sheng +2 位作者 WANG Xiao LIU Manhao LUO Yiran 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2023年第2期259-269,共11页
As high-dynamics and weak-signal are of two primary concerns of navigation using Global Navigation Satellite System(GNSS)signals,an acquisition algorithm based on threetime fractional Fourier transform(FRFT)is present... As high-dynamics and weak-signal are of two primary concerns of navigation using Global Navigation Satellite System(GNSS)signals,an acquisition algorithm based on threetime fractional Fourier transform(FRFT)is presented to simplify the calculation effectively.Firstly,the correlation results similar to linear frequency modulated(LFM)signals are derived on the basis of the high dynamic GNSS signal model.Then,the principle of obtaining the optimum rotation angle is analyzed,which is measured by FRFT projection lengths with two selected rotation angles.Finally,Doppler shift,Doppler rate,and code phase are accurately estimated in a real-time and low signal to noise ratio(SNR)wireless communication system.The theoretical analysis and simulation results show that the fast FRFT algorithm can accurately estimate the high dynamic parameters by converting the traditional two-dimensional search process to only three times FRFT.While the acquisition performance is basically the same,the computational complexity and running time are greatly reduced,which is more conductive to practical application. 展开更多
关键词 Global Navigation satellite System(gnss)signal fractional Fourier transform(FRFT) ACQUISITION high-dynamics weak-signal
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Reference satellite selection method for GNSS high-precision relative positioning
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作者 Xiao Gao Wujiao Dai +1 位作者 Zhiyong Song Changsheng Cai 《Geodesy and Geodynamics》 2017年第2期125-129,共5页
Selecting the optimal reference satellite is an important component of high-precision relat/ve positioning because the reference satellite directly influences the strength of the normal equation. The reference satelli... Selecting the optimal reference satellite is an important component of high-precision relat/ve positioning because the reference satellite directly influences the strength of the normal equation. The reference satellite selection methods based on elevation and positional dilution of precision (PDOP) value were compared. Results show that all the above methods cannot select the optimal reference satellite. We introduce condition number of the design matrix in the reference satellite selection method to improve structure of the normal equation, because condition number can indicate the ill condition of the normal equation. The experimental results show that the new method can improve positioning accuracy and reliability in precise relative positioning. 展开更多
关键词 Global Navigation satellite System gnss)Relative positioning Reference satellite Positional dilution of precision (PDOP)Condition number
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A spawning particle filter for defocused moving target detection in GNSS-based passive radar
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作者 ZENG Hongcheng DENG Jiadong +3 位作者 WANG Pengbo ZHOU Xinkai YANG Wei CHEN Jie 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2023年第5期1085-1100,共16页
Global Navigation Satellite System(GNSS)-based passive radar(GBPR)has been widely used in remote sensing applications.However,for moving target detection(MTD),the quadratic phase error(QPE)introduced by the non-cooper... Global Navigation Satellite System(GNSS)-based passive radar(GBPR)has been widely used in remote sensing applications.However,for moving target detection(MTD),the quadratic phase error(QPE)introduced by the non-cooperative target motion is usually difficult to be compensated,as the low power level of the GBPR echo signal renders the estimation of the Doppler rate less effective.Consequently,the moving target in GBPR image is usually defocused,which aggravates the difficulty of target detection even further.In this paper,a spawning particle filter(SPF)is proposed for defocused MTD.Firstly,the measurement model and the likelihood ratio function(LRF)of the defocused point-like target image are deduced.Then,a spawning particle set is generated for subsequent target detection,with reference to traditional particles in particle filter(PF)as their parent.After that,based on the PF estimator,the SPF algorithm and its sequential Monte Carlo(SMC)implementation are proposed with a novel amplitude estimation method to decrease the target state dimension.Finally,the effectiveness of the proposed SPF is demonstrated by numerical simulations and pre-liminary experimental results,showing that the target range and Doppler can be estimated accurately. 展开更多
关键词 Global Navigation satellite System(gnss)-based passive radar(GBPR) defocused target moving target detec-tion(MTD) likelihood ratio function(LRF) spawning particle fil-ter(SPF)
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Status of UnDifferenced and Uncombined GNSS Data Processing Activities in China
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作者 Pengyu HOU Delu CHE +3 位作者 Teng LIU Jiuping ZHA Yunbin YUAN Baocheng ZHANG 《Journal of Geodesy and Geoinformation Science》 CSCD 2023年第3期135-144,共10页
With the continued development of multiple Global Navigation Satellite Systems(GNSS)and the emergence of various frequencies,UnDifferenced and UnCombined(UDUC)data processing has become an increasingly attractive opti... With the continued development of multiple Global Navigation Satellite Systems(GNSS)and the emergence of various frequencies,UnDifferenced and UnCombined(UDUC)data processing has become an increasingly attractive option.In this contribution,we provide an overview of the current status of UDUC GNSS data processing activities in China.These activities encompass the formulation of Precise Point Positioning(PPP)models and PPP-Real-Time Kinematic(PPP-RTK)models for processing single-station and multi-station GNSS data,respectively.Regarding single-station data processing,we discuss the advancements in PPP models,particularly the extension from a single system to multiple systems,and from dual frequencies to single and multiple frequencies.Additionally,we introduce the modified PPP model,which accounts for the time variation of receiver code biases,a departure from the conventional PPP model that typically assumes these biases to be time-constant.In the realm of multi-station PPP-RTK data processing,we introduce the ionosphere-weighted PPP-RTK model,which enhances the model strength by considering the spatial correlation of ionospheric delays.We also review the phase-only PPP-RTK model,designed to mitigate the impact of unmodelled code-related errors.Furthermore,we explore GLONASS PPP-RTK,achieved through the application of the integer-estimable model.For large-scale network data processing,we introduce the all-in-view PPP-RTK model,which alleviates the strict common-view requirement at all receivers.Moreover,we present the decentralized PPP-RTK data processing strategy,designed to improve computational efficiency.Overall,this work highlights the various advancements in UDUC GNSS data processing,providing insights into the state-of-the-art techniques employed in China to achieve precise GNSS applications. 展开更多
关键词 Global Navigation satellite Systems(gnss) UnDifferenced and UnCombined(UDUC) Precise Point Positioning(PPP) PPP-Real-Time Kinematic(PPP-RTK) single-station data processing multi-station data processing
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Improved adaptively robust estimation algorithm for GNSS spoofer considering continuous observation error 被引量:2
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作者 GAO Yangjun LI Guangyun +2 位作者 LYU Zhiwei ZHANG Lundong LI Zhongpan 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2022年第5期1237-1248,共12页
Once the spoofer has controlled the navigation sys-tem of unmanned aerial vehicle(UAV),it is hard to effectively control the error convergence to meet the threshold condition only by adjusting parameters of estimation... Once the spoofer has controlled the navigation sys-tem of unmanned aerial vehicle(UAV),it is hard to effectively control the error convergence to meet the threshold condition only by adjusting parameters of estimation if estimation of the spoofer on UAV has continuous observation error.Aiming at this problem,the influence of the spoofer’s state estimation error on spoofing effect and error convergence conditions is theoretically analyzed,and an improved adaptively robust estimation algo-rithm suitable for steady-state linear quadratic estimator is pro-posed.It enables the spoofer’s estimator to reliably estimate UAV status in real time,improves the robustness of the estima-tor in responding to observation errors,and accelerates the con-vergence time of error control.Simulation experiments show that the mean value of normalized innovation squared(NIS)is reduced by 88.5%,and the convergence time of NIS value is reduced by 76.3%,the convergence time of true trajectory error of UAV is reduced by 42.3%,the convergence time of estimated trajectory error of UAV is reduced by 67.4%,the convergence time of estimated trajectory error of the spoofer is reduced by 33.7%,and the convergence time of broadcast trajectory error of the spoofer is reduced by 54.8%when the improved algorithm is used.The improved algorithm can make UAV deviate from pre-set trajectory to spoofing trajectory more effectively and more subtly. 展开更多
关键词 SPOOFING unmanned aerial vehicle(UAV) spoofer adaptively robust estimation global navigation satellite system(gnss) normalized innovation squared(NIS)
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Meteorological applications of precipitable water vapor measurements retrieved by the national GNSS network of China 被引量:7
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作者 Liang Hong Cao Yunchang +3 位作者 Wan Xiaomin Xu Zhifang Wang Haishen Hu Heng 《Geodesy and Geodynamics》 2015年第2期135-142,共8页
In this study, the Global Navigation Satellite System (GNSS) network of China is discussed, which can be used to monitor atmospheric precipitable water vapor (PWV). By the end of 2013, the network had 952 GNSS sit... In this study, the Global Navigation Satellite System (GNSS) network of China is discussed, which can be used to monitor atmospheric precipitable water vapor (PWV). By the end of 2013, the network had 952 GNSS sites, including 260 belonging to the Crustal Movement Observation Network of China (CMONOC) and 692 belonging to the China Meteorological Administration GNSS network (CMAGN). Additionally, GNSS observation collecting and data processing procedures are presented and PWV data quality control methods are investigated. PWV levels as determined by GNSS and radiosonde are compared. The results show that GNSS estimates are generally in good agreement with measurements of radio- sondes and water vapor radiometers (WVR). The PWV retrieved by the national GNSS network is used in weather forecasting, assimilation of data into numerical weather prediction models, the validation of PWV estimates by radiosonde, and plum rain monitoring. The network is also used to monitor the total ionospheric electron content. 展开更多
关键词 Precipitable water vapor (PWV) Global navigation satellite system(gnss Crustal Movement ObservationNetwork of China (CMONOC)China meteorological administra-tion gnss network (CMAGN) Water vapor radiometers (WVR) Quality control Meteorological application Assimilation
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Multi-channel signal parameters joint optimization for GNSS terminals 被引量:1
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作者 WANG Qian ZHANG Chuanding XIAN Deyong 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2018年第1期39-47,共9页
Traditional global navigation satellite system(GNSS)terminals for satellite navigation adopt independent channels to track the signals from different satellites, which results in a lack of information interaction betw... Traditional global navigation satellite system(GNSS)terminals for satellite navigation adopt independent channels to track the signals from different satellites, which results in a lack of information interaction between the channels. Inspired by the vector tracking idea, and drawing lessons from the principle that in the position domain the Taylor expanded pseudorange observations can be used for positioning via the least squares method, this paper proposes a novel least squares-based multi-channel parameter joint estimation(MPJE) method in the signal domain, which not only retains the advantages of channel fusion, but also maintains the flexibility and diversity of the localization algorithm. With achieving optimal carrier to noise ratio as the goal, the proposed method obtains the required code loop and carrier loop parameters for signal tracking in the domain of whole channels. Experimental results indicate that this method fully achieves the assistant fusion advantages of frequency lock loop(FLL), phase lock loop(PLL)and delay lock loop(DLL), making good use of the robustness and dynamic properties of the FLL and the measurement accuracy of the DLL, and is helpful for achieving stable and accurate signal tracking under weak signals and high dynamic stress environments. 展开更多
关键词 least squares method signal parameter optimization vector tracking global navigation satellite system(gnss) weight matrix
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Re-scaling and adaptive stochastic resonance as a tool for weak GNSS signal acquisition 被引量:2
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作者 Rongling Lang Xinyue Li +1 位作者 Fei Gao Liang Yang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2016年第2期290-296,共7页
Weak global navigation satellite system(GNSS) signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS sign... Weak global navigation satellite system(GNSS) signal acquisition has been a limitation for high sensitivity GPS receivers. This paper modifies the traditional acquisition algorithms and proposes a new weak GNSS signal acquisition method using re-scaling and adaptive stochastic resonance(SR). The adoption of classical SR is limited to low-frequency and periodic signals. Given that GNSS signal frequency is high and that the periodic feature of the GNSS signal is affected by the Doppler frequency shift, classical SR methods cannot be directly used to acquire GNSS signals. Therefore, the re-scaling technique is used in our study to expand its usage to high-frequency signals and adaptive control technique is used to gradually determine the Doppler shift effect in GNSS signal buried in strong noises. The effectiveness of our proposed method was verified by the simulations on GPS L1 signals. The simulation results indicate that the new algorithm based on SR can reach-181 d BW sensitivity with a very short data length of 1 ms. 展开更多
关键词 weak signal detection global navigation satellite system(gnss signal acquisition stochastic resonance
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Performance evaluation of neural network TEC forecasting models over equatorial low-latitude Indian GNSS station 被引量:1
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作者 G.Sivavaraprasad V.S.Deepika +2 位作者 D.Sreenivasa Rao M.Ravi Kumar M.Sridhar 《Geodesy and Geodynamics》 2020年第3期192-201,共10页
Global Positioning System(GPS)services could be improved through prediction of ionospheric delays for satellite-based radio signals.With respect to latitude,longitude,local time,season,solar cycle and geomagnetic acti... Global Positioning System(GPS)services could be improved through prediction of ionospheric delays for satellite-based radio signals.With respect to latitude,longitude,local time,season,solar cycle and geomagnetic activity the Total Electron Content(TEC)have significant variations in both time and space.These temporal and spatial TEC variations driven by interplanetary space weather conditions such as solar and geomagnetic activities can degrade the communication and navigation links of GPS.Hence,in this paper,performance of TEC forecasting models based on Neural Networks(NN)have been evaluated to forecast(1-h ahead)ionospheric TEC over equatorial low latitude Bengaluru e12:97+N;77:59+ET,Global Navigation Satellite System(GNSS)station,India.The VTEC data is collected for 2009 e2016(8 years)during current 24 th solar cycle.The input space for the NN models comprise the solar Extreme UV flux,F10.7 proxy,a geomagnetic planetary A index(AP)index,sunspot number(SSN),disturbance storm time(DST)index,solar wind speed(Vsw),solar wind proton density(Np),Interplanetary Magnetic Field(IMF Bz).The performance of NN based TEC forecast models and International Reference Ionosphere,IRI-2016 global TEC model has evaluated during testing period,2016.The NN based model driven by all the inputs,which is a NN unified model(NNunq)has shown better accuracy with Mean Absolute Error(MAE)of 3.15 TECU,Mean Square Deviation(MSD)of 16.8 and Mean Absolute Percentage Error(MAPE)of 19.8%and is 1 e25%more accurate than the other NN based TEC forecast models(NN1,NN2 and NN3)and IRI-2016 model.NNunq model has less Root Mean Square Error(RMSE)value 3.8 TECU and highest goodness-of-fit(R2)with 0.85.The experimental results imply that NNunq/NN1 model forecasts ionospheric TEC accurately across equatorial low-latitude GNSS station and IRI-2016 model performance is necessarily improved as its forecast accuracy is limited to 69 e70%. 展开更多
关键词 Global Positioning System(GPS) Global navigation satellite systems(gnss) Total electron content(TEC) International reference ionosphere(IRI) Neural networks
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Evaluation of global navigation satellite system spoofing efficacy 被引量:1
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作者 WANG Yue SUN Fuping +2 位作者 HAO Jinming ZHANG Lundong WANG Xian 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2022年第6期1238-1257,共20页
The spoofing capability of Global Navigation Satellite System(GNSS)represents an important confrontational capability for navigation security,and the success of planned missions may depend on the effective evaluation ... The spoofing capability of Global Navigation Satellite System(GNSS)represents an important confrontational capability for navigation security,and the success of planned missions may depend on the effective evaluation of spoofing capability.However,current evaluation systems face challenges arising from the irrationality of previous weighting methods,inapplicability of the conventional multi-attribute decision-making method and uncertainty existing in evaluation.To solve these difficulties,considering the validity of the obtained results,an evaluation method based on the game aggregated weight model and a joint approach involving the grey relational analysis and technique for order preference by similarity to an ideal solution(GRA-TOPSIS)are firstly proposed to determine the optimal scheme.Static and dynamic evaluation results under different schemes are then obtained via a fuzzy comprehensive assessment and an improved dynamic game method,to prioritize the deceptive efficacy of the equipment accurately and make pointed improvement for its core performance.The use of judging indicators,including Spearman rank correlation coefficient and so on,combined with obtained evaluation results,demonstrates the superiority of the proposed method and the optimal scheme by the horizontal comparison of different methods and vertical comparison of evaluation results.Finally,the results of field measurements and simulation tests show that the proposed method can better overcome the difficulties of existing methods and realize the effective evaluation. 展开更多
关键词 Global Navigation satellite System(gnss)spoofing index system for spoofing strategy game aggregated weight model grey relational analysis and technique for order preference by similarity to an ideal solution(GRA-TOPSIS)method dynamic game method
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Mathematical model for computing precise local tie vectors for CMONOC co-located GNSS/VLBI/SLR stations 被引量:1
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作者 Shen Yunzhong You Xinzhao +4 位作者 Wang Jiexian Wu Bin Chen Junping Ma Xiaping Gong Xiuqiang 《Geodesy and Geodynamics》 2015年第1期1-6,共6页
The seven co-located sites of the Crustal Movement Observation Network of China(CMONOC) in Shanghai, Wuhan, Kunming, Beijing, Xi'an, Changchun, and Urumqi are equipped with Global Navigation Satellite System(GNSS... The seven co-located sites of the Crustal Movement Observation Network of China(CMONOC) in Shanghai, Wuhan, Kunming, Beijing, Xi'an, Changchun, and Urumqi are equipped with Global Navigation Satellite System(GNSS), very long baseline interferometry(VLBI), and satellite laser ranging(SLR) equipment. Co-location surveying of these sites was performed in 2012 and the accuracies of the solved tie vectors are approximately 5 mm.This paper proposes a mathematical model that handles the least squares adjustment of the 3D control network and calculates the tie vectors in one step, using all the available constraints in the adjustment. Using the new mathematical model, local tie vectors can be more precisely determined and their covariance more reasonably estimated. 展开更多
关键词 Co-located site Tie vector(TV) Reference point Global Navigation satellite system(gnss Very long baseline interferometry(VLBI)
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Airborne GNSS-Receiver Threat Detection in No-Fading Environments
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作者 Omid Sharifi-Tehrani 《Journal of Beijing Institute of Technology》 EI CAS 2022年第6期613-620,共8页
Jamming and spoofing detection of global navigation satellite systems(GNSS)is of great importance.Civil and military aerial platforms use GNSS as main navigation systems and these systems are main target of threat att... Jamming and spoofing detection of global navigation satellite systems(GNSS)is of great importance.Civil and military aerial platforms use GNSS as main navigation systems and these systems are main target of threat attacks.In this paper a simple method based on different empirical probability density functions of successive received signal powers and goodness of fit tech-nique is proposed for airborne platforms such as unmanned aerial vehicle(UAV),in no fading envi-ronment.The two different paths between UAV-satellite and UAV-threat,experience different empirical probability density functions which can be used to distinguish between authentic and threat signals.Simulation results including detection and false alarm probabilities show good perfor-mance of proposed method as well as low computational burden. 展开更多
关键词 detection global navigation satellite systems(gnss) jamming SPOOFING unmanned aerial vehicle
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Adaptive beamforming and phase bias compensation for GNSS receiver
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作者 Hongwei Zhao Baowang Lian Juan Feng 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2015年第1期10-18,共9页
Adaptive antenna arrays have been used to mitigate the interference on global navigation satellite system(GNSS) receivers. The performance of interference mitigation depends on the beamforming algorithms adopted by ... Adaptive antenna arrays have been used to mitigate the interference on global navigation satellite system(GNSS) receivers. The performance of interference mitigation depends on the beamforming algorithms adopted by the antenna array. However,the adaptive beamforming will change the array pattern in realtime, which has the potential to introduce phase center biases into the antenna array. For precise applications, these phase biases must be mitigated or compensated because they will bring errors in code phase and carrier phase measurements. A novel adaptive beamforming algorithm is proposed firstly, then the phase bias induced by the proposed algorithm is estimated, and finally a compensation strategy is addressed. Simulations demonstrate that the proposed beamforming algorithm suppresses effectively the strong interference and improves significantly the capturing performance of GNSS signals. Simultaneously, the bias compensation method avoids the loss of the carrier phase lock and reduces the phase measurement errors for GNSS receivers. 展开更多
关键词 global navigation satellite system(gnss space-time adaptive processing(STAP) adaptive beamforming bias compensation
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Geodynamics of the Calabrian Arc area (Italy) inferred from a dense GNSS network observations
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作者 Oiuseppe Casula 《Geodesy and Geodynamics》 2016年第1期76-86,共11页
The tectonics and geodynamics of the Calabria region are presented in this study. These are inferred by precise computation of Global Navigation Satellite Systems (GNSS) per~ manent station velocities in a stable Eu... The tectonics and geodynamics of the Calabria region are presented in this study. These are inferred by precise computation of Global Navigation Satellite Systems (GNSS) per~ manent station velocities in a stable Eurasian reference framework. This allowed computation of the coordinates, variance and covariance matrixes, and horizontal and vertical velocities of the 36 permanent sites analyzed, together with the strain rates, and using different techniques. Interesting geodynamic phenomena are presented, including compressional, and deformational fields in the Tyrrhenian coastal sites of Calabria, extensional trends of the Ionian coastal sites, and sliding movement of the Crotone Basin. Conversely, on the northern Tyrrhenian side of the network near the Cilento Park area, the usual extensional tectonic perpendicular to the Apennine chain is observed. The large- scale pattern of the GNSS height velocities is shown, which is characterized by general interesting geodynamic vertical effects that appear to be due to geophysical movement and anthropic activity. Finally, the strain-rate fields computed through three different tech- niques are compared. 展开更多
关键词 Global Navigation satellite Systems(gnss)GeodesyGeodynamicsCalabrian ArcStrain rateTectonicsReference frameNetwork adjustment
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GPS观测得的2023年2月土耳其双震前后的地壳形变 被引量:2
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作者 顾国华 《地球科学前沿(汉斯)》 2023年第6期636-644,共9页
2023年2月6日土耳其发生7.8级双震,相隔仅9小时、相距近,都是近直立断层走滑型地震,是利用GPS观测研究地震前后地壳形变稀有震例。利用美国网站得到131个GPS站欧亚(板块)参考框架位移数据,分析了2次地震前后的地壳形变。同震水平位移是... 2023年2月6日土耳其发生7.8级双震,相隔仅9小时、相距近,都是近直立断层走滑型地震,是利用GPS观测研究地震前后地壳形变稀有震例。利用美国网站得到131个GPS站欧亚(板块)参考框架位移数据,分析了2次地震前后的地壳形变。同震水平位移是分析大地震前兆地壳运动的关键现象。GPS分别观测得的2次地震同震位移,特征显著:水平位移最大达4.4 m;向西、向东和向南水平位移3个分区明显,与区域内3个板块构造运动密切相关;而垂直位移较小,无明显分区。2次地震前震中附近的水平位移分别出现(第一次地震)峰值和(第二次地震)闭锁2种类型,但无明显的垂直位移积累。与其他震例一样,在震前两种类型的水平位移区域,同震水平位移是震前位移在时间或空间上的(弹性)回跳,表明大地震有前兆形变。2次地震重合的孕震区内,有对2次地震同震水平位移影响相近的区域。GPS观测明确显示,地壳水平运动是2次大地震的成因。尽管观测不足和未能预报2次地震,但仍突显GNSS可在地震监测、预警和地震预测中发挥作用的优势。 展开更多
关键词 gnss (Global Navigation satellite System) GPS (Global Positioning System) 同震水平位移 地壳形变 土耳其大地震 地震预测
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A regional GNSS-VTEC model over Nigeria using neural networks: A novel approach
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作者 Daniel Okoh Oluwafisavo Owolabi +5 位作者 Christovher Ekechukwu Olanike Folarin Gila Arhiwo Joseph Agbo Segun Bolaji Babatunde Rabiu 《Geodesy and Geodynamics》 2016年第1期19-31,共13页
A neural network model of the Global Navigation Satellite System - vertical total electron content (GNSS-VTEC) over Nigeria is developed. A new approach that has been utilized in this work is the consideration of th... A neural network model of the Global Navigation Satellite System - vertical total electron content (GNSS-VTEC) over Nigeria is developed. A new approach that has been utilized in this work is the consideration of the International Reference Ionosphere's (IRI's) critical plasma frequency (foF2) parameter as an additional neuron for the network's input layer. The work also explores the effects of using various other input layer neurons like distur- bance storm time (DST) and sunspot number. All available GNSS data from the Nigerian Permanent GNSS Network (NIGNET) were used, and these cover the period from 2011 to 2015, for 14 stations. Asides increasing the learning accuracy of the networks, the inclusion of the IRI's foF2 parameter as an input neuron is ideal for making the networks to learn long-term solar cycle variations. This is important especially for regions, like in this work, where the GNSS data is available for less than the period of a solar cycle. The neural network model developed in this work has been tested for time-varying and spatial per- formances. The latest 10% of the GNSS observations from each of the stations were used to test the forecasting ability of the networks, while data from 2 of the stations were entirely used for spatial performance testing. The results show that root-mean-squared-errors were generally less than 8.5 TEC units for all modes of testing performed using the optimal network. When compared to other models, the model developed in this work was observed to reduce the prediction errors to about half those of the NeQuick and the IRI model. 展开更多
关键词 Global Navigation satellite System(gnss ionosphereTotal electron content (TEC)Nigerian permanent gnss network(NIGNET)Neural networkInternational reference ionosphere(IRI)
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Collecting volunteered geographic information from the Global Navigation Satellite System(GNSS):experiences from the CAMALIOT project
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作者 Linda See Benedikt Soja +10 位作者 Grzegorz Klopotek Tobias Sturn Rudi Weinacker Santosh Karanam Ivelina Georgieva Yuanxin Pan Laura Crocetti Markus Rothacher Vicente Navarro Steffen Fritz Ian McCallum 《International Journal of Digital Earth》 SCIE EI 2023年第1期2818-2841,共24页
Raw observations(carrier-phase and code observations)from the Global Navigation Satellite System(GNSS)can now be accessed from Android mobile phones(Version 7.0 onwards).This paves the way for GNSS data to be utilized... Raw observations(carrier-phase and code observations)from the Global Navigation Satellite System(GNSS)can now be accessed from Android mobile phones(Version 7.0 onwards).This paves the way for GNSS data to be utilized for low-cost precise positioning or in ionospheric or tropospheric applications.This paper presents results from data collection campaigns using the CAMALIOT mobile app.In the frst campaign,116.3 billion measurements from 11,828 mobile devices were collected from all continents.Although participation decreased during the second campaign,data are still being collected globally.In this contribution,we demonstrate the potential of volunteered geographic information(VGl)from mobile phones to fill data gaps in geodetic station networks that collect GNSS data,e.g.in Brazil,but also how the data can provide a denser set of observations than current networks in countries across Europe.We also show that mobile phones capable of dual-frequency reception,which is an emerging technology that can provide a richer source of GNSS data,are contributing in a substantial way.Finally,we present the results from a survey of participants to indicate that participation is diverse in terms of backgrounds and geography,where the dominant motivation for participation is to contribute to scientific research. 展开更多
关键词 Citizen science crowdsourcing volunteered geographicinformation(VGl) global navigation satellite system(gnss) mobile apps Earth observation
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Scene image recognition with knowledge transfer for drone navigation
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作者 DU Hao WANG Wei +2 位作者 WANG Xuerao ZUO Jingqiu WANG Yuanda 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2023年第5期1309-1318,共10页
In this paper,we study scene image recognition with knowledge transfer for drone navigation.We divide navigation scenes into three macro-classes,namely outdoor special scenes(OSSs),the space from indoors to outdoors o... In this paper,we study scene image recognition with knowledge transfer for drone navigation.We divide navigation scenes into three macro-classes,namely outdoor special scenes(OSSs),the space from indoors to outdoors or from outdoors to indoors transitional scenes(TSs),and others.However,there are difficulties in how to recognize the TSs,to this end,we employ deep convolutional neural network(CNN)based on knowledge transfer,techniques for image augmentation,and fine tuning to solve the issue.Moreover,there is still a novelty detection prob-lem in the classifier,and we use global navigation satellite sys-tems(GNSS)to solve it in the prediction stage.Experiment results show our method,with a pre-trained model and fine tun-ing,can achieve 91.3196%top-1 accuracy on Scenes21 dataset,paving the way for drones to learn to understand the scenes around them autonomously. 展开更多
关键词 scene recognition convolutional neural network knowledge transfer global navigation satellite systems(gnss)-aided
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