随着中国BeiDou系统与欧盟Galileo系统的出现以及俄罗斯GLONASS系统的恢复完善,过去单一的GPS导航卫星系统时代已经逐步过渡为多系统并存且相互兼容的全球性卫星导航系统（multi-constellation global navigation satellite systems,mul...随着中国BeiDou系统与欧盟Galileo系统的出现以及俄罗斯GLONASS系统的恢复完善,过去单一的GPS导航卫星系统时代已经逐步过渡为多系统并存且相互兼容的全球性卫星导航系统（multi-constellation global navigation satellite systems,multi-GNSS）时代,多系统GNSS融合精密定位将成为未来GNSS精密定位技术的发展趋势。本文采用GPS、GLONASS、BeiDou、Galileo 4大卫星导航定位系统融合的精密单点定位（precise point positioning,PPP）实测数据,初步研究并分析了4系统融合PPP的定位性能。试验结果表明：在单系统观测几何构型不理想的区域,多系统融合能显著提高PPP的定位精度和收敛速度。4大系统融合的PPP收敛速度相对于单GNSS可提高30%~50%,定位精度可提高10%~30%,特别是对高程方向的贡献更为明显。此外,在卫星截止高度角大于30°的观测环境下,单系统由于可见卫星数不足导致无法连续定位,而多系统融合仍然可以获得PPP定位结果,尤其是水平方向具有较高的定位精度。这对于山区、城市以及遮挡严重的区域具有非常重要的应用价值。展开更多
Inter-satellite link(ISL)scheduling is required by the BeiDou Navigation Satellite System(BDS)to guarantee the system ranging and communication performance.In the BDS,a great number of ISL scheduling instances must be...Inter-satellite link(ISL)scheduling is required by the BeiDou Navigation Satellite System(BDS)to guarantee the system ranging and communication performance.In the BDS,a great number of ISL scheduling instances must be addressed every day,which will certainly spend a lot of time via normal metaheuristics and hardly meet the quick-response requirements that often occur in real-world applications.To address the dual requirements of normal and quick-response ISL schedulings,a data-driven heuristic assisted memetic algorithm(DHMA)is proposed in this paper,which includes a high-performance memetic algorithm(MA)and a data-driven heuristic.In normal situations,the high-performance MA that hybridizes parallelism,competition,and evolution strategies is performed for high-quality ISL scheduling solutions over time.When in quick-response situations,the data-driven heuristic is performed to quickly schedule high-probability ISLs according to a prediction model,which is trained from the high-quality MA solutions.The main idea of the DHMA is to address normal and quick-response schedulings separately,while high-quality normal scheduling data are trained for quick-response use.In addition,this paper also presents an easy-to-understand ISL scheduling model and its NP-completeness.A seven-day experimental study with 10080 one-minute ISL scheduling instances shows the efficient performance of the DHMA in addressing the ISL scheduling in normal(in 84 hours)and quick-response(in 0.62 hour)situations,which can well meet the dual scheduling requirements in real-world BDS applications.展开更多
In Global Navigation Satellite Systems(GNSS) positioning,one often tries to establish a mathematic model to capture the systematic behaviors of observations as much as possible.However,the observation residuals still ...In Global Navigation Satellite Systems(GNSS) positioning,one often tries to establish a mathematic model to capture the systematic behaviors of observations as much as possible.However,the observation residuals still exhibit,to a great extent,as(somewhat systematic) signals.Nevertheless,those systematic variations are referred to as the unmodelled errors,which are difficult to be further modelled by setting up additional parameters.Different from the random errors,the unmodelled errors are colored and time correlated.In general,the larger the time correlations are,the more significant the unmodelled errors.Hence,understanding the time correlations of unmodelled errors is important to develop the theory for processing the unmodelled errors.In this study,we compare and analyze the time correlations caused by unmodelled errors of Global Positioning System(GPS) and BeiDou signals.The time correlations are estimated based on the residuals of double differenced observations on 11 baselines with different lengths.The results show that the time correlation patterns are different significantly between GPS and BeiDou observations.Besides,the code and phase data from the same satellite system are also not the same.Furthermore,the unmodelled errors are affected by not only the baseline length,but also some other factors.In addition,to make use of the time correlations with more efficiency,we propose to fit the time correlations by using exponent and quadratic models and the fitting coefficients are given.Finally,the sequential adjustment method considering the time correlations is implemented to compute the baseline solutions.The results show that the solutions considering the time correlations can objectively reflect the actual precisions of parameter estimates.展开更多
The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the t...The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the tracking loop.Since the frequency step is usually 500 Hz or larger,the Doppler shift estimation accuracy cannot guarantee that satellite signals are brought into a stable tracking state.The straightforward solutions consist in increasing the sampling time and using zero-padding to improve the frequency resolution of the FFT.However,these solutions intensify the complexity and amount of computation.The contradiction between the acquisition accuracy and the computational load leads us to research for a more simple and effective algorithm,which achieves fine acquisition by a look-up table.After coarse acquisition using the parallel frequency acquisition(PFA)algorithm,the proposed algorithm optimizes the Doppler shift estimation through the look-up table method based on the FFT results to improve the acquisition accuracy of the Doppler shift with a minimal additional computing load.When the Doppler shift is within the queryable range of the table,the proposed algorithm can improve the Doppler shift estimation accuracy to 50 Hz for the BeiDou B1I signal.展开更多
This paper introduces the Chinese BeiDou satellite system and its comparison with the actual completed American GPS and the Russian GLONASS systems. The actual BeiDou system consists of 14 satellites covering totally ...This paper introduces the Chinese BeiDou satellite system and its comparison with the actual completed American GPS and the Russian GLONASS systems. The actual BeiDou system consists of 14 satellites covering totally the Asia-Pacific area. A Single Point Positioning (SPP) test has been realised in Changsha, Hunan province, China, to show the advantage of using combined pseudorange solutions from these 3 satellite navigation systems especially in obstructed sites. The test shows that, with an elevation mask angle of 10°, the accuracy is improved by about 20% in horizontal coordinates and nearly 50% in the vertical component using the simultaneous observations of the 3 systems compared to the GPS/GLONASS solution. For the processing with an elevation mask angle of 30°, most of the time less than 4 GPS satellites were available for the GPS-only case and no solution was possible. However, in this difficult situation, the combined GPS/GLONASS/ BeiDou solutions provided an accuracy (rms values) of about 5 m.展开更多
Due to the civil BeiDou navigation system is open,unauthenticated,and non-encrypted,civilian BeiDou navigation signals may have great security loopholes during transmission or reception.The main security loophole here...Due to the civil BeiDou navigation system is open,unauthenticated,and non-encrypted,civilian BeiDou navigation signals may have great security loopholes during transmission or reception.The main security loophole here is spoofing attacks.Spoofing attacks make the positioning or timing results of BeiDou civilian receivers wrong.Such errors may cause a series of security problems,which lays a serious hidden danger for Bei-Dou satellite information security.This article proposes an anti-spoofing method for BeiDou navigation system based on the combination of SM commercial cryptographic algorithm and Timed Efficient Stream Loss-tolerant Authentication(TESLA)for spoofing attacks.In this solution,we use the SM3 algorithm to generate a TESLA key chain with time information,and then use the key in the key chain to generate the message authentication code for the BeiDou D2 navigation message.The message authentication code is inserted into a reserved bit of the D2 navigation message.In addition,this solution uses the SM2 algorithm to protect and encrypt time information in the TESLA key chain to prevent key replay attacks in TESLA.The experimental results tested on the experimental platform built in this paper show that this scheme reduces the possibility of the BeiDou navigation system being deceived and enhances the safety of the BeiDou navigation system.展开更多
Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese...Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese BeiDou are developing rapidly. With the new IGS project known as IGS MGEX which produces highly accurate GNSS orbital and clock products, multi-constellations PPP becomes feasible. On the other hand, the un-differenced ionosphere-free is commonly used as standard precise point positioning technique. However, the existence of receiver and satellite biases, which are absorbed by the ambiguities, significantly affected the convergence time. Between-satellite-single-difference (BSSD) ionosphere free PPP technique is traditionally used to cancel out the receiver related biases from both code and phase measurements. This paper introduces multiple ambiguity datum (MAD) PPP technique which can be applied to separate the code and phase measurements removing the receiver and satellite code biases affecting the GNSS receiver phase clock and ambiguities parameters. The mathematical model for the three GNSS PPP techniques is developed by considering the current full GNSS constellations. In addition, the current limitations of the GNSS PPP techniques are discussed. Static post-processing results for a number of IGS MGEX GNSS stations are presented to investigate the contribution of the newly GNSS system observations and the newly developed GNSS PPP techniques and its limitations. The results indicate that the additional Galileo and BeiDou observations have a marginal effect on the positioning accuracy and convergence time compared with the existence combined GPS/GLONASS PPP. However, reference to GPS PPP, the contribution of BeiDou observations can be considered geographically dependent. In addition, the results show that the BSSD PPP models slightly enhance the convergence time compared with other PPP techniques. However, both the standard un-differenced and the developed multiple ambiguity datum techniques present comparable positioning accuracy and convergence time due to the lack of code and phase-based satellite clock products and the mathematical correlation between the positioning and ambiguity parameters.展开更多
This paper introduces a new dual-frequency precise point positioning (PPP) model, which combines the observations of three different GNSS constellations, namely GPS, Galileo, and BeiDou. Our model is based on between-...This paper introduces a new dual-frequency precise point positioning (PPP) model, which combines the observations of three different GNSS constellations, namely GPS, Galileo, and BeiDou. Our model is based on between-satellite single-difference (BSSD) linear combination, which cancels out some receiver-related biases, including receiver clock error and non-zero initial phase bias of the receiver oscillator. The reference satellite can be selected from any satellite system GPS, Galileo, and BeiDou when forming BSSD linear combinations. Natural Resources Canada’s GPS Pace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data sets at four IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the IGS-MGEX network are used to correct both of the GPS and Galileo measurements. It is shown that using the BSSD linear combinations improves the precision of the estimated parameters by about 25% compared with the GPS-only PPP solution. Additionally, the solution convergence time is reduced to 10 minutes for both BSSD scenarios, which represent about 50% improvement in comparison with the GPS-only PPP solution.展开更多
China launched the 33rd and 34th satellites of the BeiDou navigation system into their preset orbits using a LM-3B/ Yuanzheng I carrier rocket from the Xichang Satellite Launch Center at 09:48 Beijing time on July 29,...China launched the 33rd and 34th satellites of the BeiDou navigation system into their preset orbits using a LM-3B/ Yuanzheng I carrier rocket from the Xichang Satellite Launch Center at 09:48 Beijing time on July 29,2018.展开更多
Dual-frequency satellite positioning receivers are widely used because they can eliminate ionospheric delay and solve the full-circumference ambiguity quickly.However,in traditional dual-frequency receivers,the releva...Dual-frequency satellite positioning receivers are widely used because they can eliminate ionospheric delay and solve the full-circumference ambiguity quickly.However,in traditional dual-frequency receivers,the relevance of dual-frequency signals are not considered,and,with no improvement imposed to the tracking loop,two independent tracking loops are used to achieve the tracking of dual-frequency signals.In this paper,the Bei Dou dual-frequency signals joint tracking algorithm based on Kalman filter is proposed for the tracking of Bei Dou B1I and B3I dual-frequency signals.Taking the relevance of B1I and B3I signals into consideration,the algorithm adds a Kalman filter between the phase detector and carrier loop filter of the traditional dual-frequency independent tracking loop.The output results of the phase detectors of the B1I and B3I branches are then combined and filtered by the Kalman filter,and the results are input to the carrier loop filters of the corresponding branches.Proved by experiments,the algorithm not only enables the loop to enter a stable tracking state quickly,but also reduces the noise bandwidth of the two loop filters by about 10 Hz with the same tracking performance obtained.展开更多
Water vapor monitoring system by Beidou satellite is a new detection system in meteorological department,which makes receiving amount of detected data and data storage and transmission pressure increase. Here,we try t...Water vapor monitoring system by Beidou satellite is a new detection system in meteorological department,which makes receiving amount of detected data and data storage and transmission pressure increase. Here,we try to use data compression to relieve pressure. Compression software of water vapor monitoring system by Beidou satellite can be designed into three components: real-time compression software,check compression software and manual compression software,which respectively completes the compression tasks under real-time receiving,in-time check and separate compression,thereby forming a perfect compression system. Taking the design of manual compression software as guide,and using c language to develop,compression test of original receiving data is conducted. Test result proves that the system can carry out batch automatic compression,and compression rate can reach 30%,which can reach the target of saving space in a degree.展开更多
CHINA launched the last satellite of the BeiDou Navigation Satellite System(BDS),the 55th in the BeiDou family,on June 23 in Xichang Satellite Launch Center in Sichuan Province.It marks the completion of the deploymen...CHINA launched the last satellite of the BeiDou Navigation Satellite System(BDS),the 55th in the BeiDou family,on June 23 in Xichang Satellite Launch Center in Sichuan Province.It marks the completion of the deployment of China’s own global navigation system.On its journey to explore a path of developing a navigation satellite system suitable for its national conditions since the late 20th century,China formulated a three-step strategy of development for BDS:to complete the construction of BDS-1 and provide services to the whole country by the end of 2000;to complete the construction of BDS-2 and provide services to the Asia-Pacific region by the end of 2012;and to complete the construction of BDS and provide services worldwide around 2020.展开更多
Aiming at the issue of influence of blanket jamming on performances of Beidou navigation signals, through studying Beidou signals based on the BOC modulation technology, establishing a blanket jamming mathematical mod...Aiming at the issue of influence of blanket jamming on performances of Beidou navigation signals, through studying Beidou signals based on the BOC modulation technology, establishing a blanket jamming mathematical model, and performing modeling and simulation on multiple jamming technologies, to attain the jamming curves of time domains and frequency domains of Beidou signals, and the correlation curve of the signal-to-jamming rate and the bit error rate under blanket jamming, and thus realizing evaluation on the jamming performance.展开更多
BeiDou navigation satellite system(the BeiDou system) is the only PNT(Positioning, Navigation and Tim-ing) resource in China that has coverage of the globe and near-Earth space and provides continuous high-precision,l...BeiDou navigation satellite system(the BeiDou system) is the only PNT(Positioning, Navigation and Tim-ing) resource in China that has coverage of the globe and near-Earth space and provides continuous high-precision,low-cost positioning, navigation and timing solutions for users in a unified spatio-temporal benchmark. As an importantspatio-temporal benchmark transmission system, the BeiDou system is the most important resource for the nationalPNT system to provide a PNT capability under a unified spatial-temporal benchmark. This paper proposes the con-cept, composition and development model of the space-based PNT system design based on the BeiDou system withall its space characteristics, as well as the advantages of the system. It opens up a new direction for the construction ofChina's PNT system and expands a new horizon in the research of a PNT system in China.展开更多
For scale cotton-picker operation, combination of production resources including field, machine, and drivers, should be organized reasonably both in temporal and spatial dimensions. Xinjian Agri. is such a scale cotto...For scale cotton-picker operation, combination of production resources including field, machine, and drivers, should be organized reasonably both in temporal and spatial dimensions. Xinjian Agri. is such a scale cotton picking service company, which owns more than 400 cotton-pickers, hires nearly 1000 personnel, and works for more than ten big farms each season. The total operation area is about 90,000 ha. In this paper, a Cotton-picker Operation Scheduling & Monitoring System (CPOSMS) was developed for Xinjian Agri. CPOSMS is a WebGIS and BeiDou based management software, which includes four main function modules. Overall scheduling module aims to help the company to create machine fleets for the farms based on operation demands and operation capacity. A real-time evaluation model was studied to adjust the rationality. Local scheduling module is to dispatch machines and personnel to form machine unit. Central navigating module is to guide staff to specific field. Operation monitoring module is to monitor and analyze operation process. Experiments in 2015 showed that the CPOSMS is the necessary tool for the company, and the evaluation model and BeiDou based system can improve management efficiency.展开更多
文摘随着中国BeiDou系统与欧盟Galileo系统的出现以及俄罗斯GLONASS系统的恢复完善,过去单一的GPS导航卫星系统时代已经逐步过渡为多系统并存且相互兼容的全球性卫星导航系统（multi-constellation global navigation satellite systems,multi-GNSS）时代,多系统GNSS融合精密定位将成为未来GNSS精密定位技术的发展趋势。本文采用GPS、GLONASS、BeiDou、Galileo 4大卫星导航定位系统融合的精密单点定位（precise point positioning,PPP）实测数据,初步研究并分析了4系统融合PPP的定位性能。试验结果表明：在单系统观测几何构型不理想的区域,多系统融合能显著提高PPP的定位精度和收敛速度。4大系统融合的PPP收敛速度相对于单GNSS可提高30%~50%,定位精度可提高10%~30%,特别是对高程方向的贡献更为明显。此外,在卫星截止高度角大于30°的观测环境下,单系统由于可见卫星数不足导致无法连续定位,而多系统融合仍然可以获得PPP定位结果,尤其是水平方向具有较高的定位精度。这对于山区、城市以及遮挡严重的区域具有非常重要的应用价值。
基金supported by the National Natural Science Foundation of China(61773120)the National Natural Science Fund for Distinguished Young Scholars of China(61525304)+2 种基金the Foundation for the Author of National Excellent Doctoral Dissertation of China(2014-92)the Hunan Postgraduate Research Innovation Project(CX2018B022)the China Scholarship Council-Leiden University Scholarship。
文摘Inter-satellite link(ISL)scheduling is required by the BeiDou Navigation Satellite System(BDS)to guarantee the system ranging and communication performance.In the BDS,a great number of ISL scheduling instances must be addressed every day,which will certainly spend a lot of time via normal metaheuristics and hardly meet the quick-response requirements that often occur in real-world applications.To address the dual requirements of normal and quick-response ISL schedulings,a data-driven heuristic assisted memetic algorithm(DHMA)is proposed in this paper,which includes a high-performance memetic algorithm(MA)and a data-driven heuristic.In normal situations,the high-performance MA that hybridizes parallelism,competition,and evolution strategies is performed for high-quality ISL scheduling solutions over time.When in quick-response situations,the data-driven heuristic is performed to quickly schedule high-probability ISLs according to a prediction model,which is trained from the high-quality MA solutions.The main idea of the DHMA is to address normal and quick-response schedulings separately,while high-quality normal scheduling data are trained for quick-response use.In addition,this paper also presents an easy-to-understand ISL scheduling model and its NP-completeness.A seven-day experimental study with 10080 one-minute ISL scheduling instances shows the efficient performance of the DHMA in addressing the ISL scheduling in normal(in 84 hours)and quick-response(in 0.62 hour)situations,which can well meet the dual scheduling requirements in real-world BDS applications.
基金supported by the National Natural Science Foundations of China(41574023,41622401,41374031)supported by the Fund of Youth 1000-Plan Talent Program
文摘In Global Navigation Satellite Systems(GNSS) positioning,one often tries to establish a mathematic model to capture the systematic behaviors of observations as much as possible.However,the observation residuals still exhibit,to a great extent,as(somewhat systematic) signals.Nevertheless,those systematic variations are referred to as the unmodelled errors,which are difficult to be further modelled by setting up additional parameters.Different from the random errors,the unmodelled errors are colored and time correlated.In general,the larger the time correlations are,the more significant the unmodelled errors.Hence,understanding the time correlations of unmodelled errors is important to develop the theory for processing the unmodelled errors.In this study,we compare and analyze the time correlations caused by unmodelled errors of Global Positioning System(GPS) and BeiDou signals.The time correlations are estimated based on the residuals of double differenced observations on 11 baselines with different lengths.The results show that the time correlation patterns are different significantly between GPS and BeiDou observations.Besides,the code and phase data from the same satellite system are also not the same.Furthermore,the unmodelled errors are affected by not only the baseline length,but also some other factors.In addition,to make use of the time correlations with more efficiency,we propose to fit the time correlations by using exponent and quadratic models and the fitting coefficients are given.Finally,the sequential adjustment method considering the time correlations is implemented to compute the baseline solutions.The results show that the solutions considering the time correlations can objectively reflect the actual precisions of parameter estimates.
基金the Open Project of State Key Laboratory of Automotive Simulation and Control,Jilin University(20161108)the National Natural Science Foundation of China(51505221)the Fundamental Research Funds for the Central Universities(NS2019022).
文摘The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the tracking loop.Since the frequency step is usually 500 Hz or larger,the Doppler shift estimation accuracy cannot guarantee that satellite signals are brought into a stable tracking state.The straightforward solutions consist in increasing the sampling time and using zero-padding to improve the frequency resolution of the FFT.However,these solutions intensify the complexity and amount of computation.The contradiction between the acquisition accuracy and the computational load leads us to research for a more simple and effective algorithm,which achieves fine acquisition by a look-up table.After coarse acquisition using the parallel frequency acquisition(PFA)algorithm,the proposed algorithm optimizes the Doppler shift estimation through the look-up table method based on the FFT results to improve the acquisition accuracy of the Doppler shift with a minimal additional computing load.When the Doppler shift is within the queryable range of the table,the proposed algorithm can improve the Doppler shift estimation accuracy to 50 Hz for the BeiDou B1I signal.
文摘This paper introduces the Chinese BeiDou satellite system and its comparison with the actual completed American GPS and the Russian GLONASS systems. The actual BeiDou system consists of 14 satellites covering totally the Asia-Pacific area. A Single Point Positioning (SPP) test has been realised in Changsha, Hunan province, China, to show the advantage of using combined pseudorange solutions from these 3 satellite navigation systems especially in obstructed sites. The test shows that, with an elevation mask angle of 10°, the accuracy is improved by about 20% in horizontal coordinates and nearly 50% in the vertical component using the simultaneous observations of the 3 systems compared to the GPS/GLONASS solution. For the processing with an elevation mask angle of 30°, most of the time less than 4 GPS satellites were available for the GPS-only case and no solution was possible. However, in this difficult situation, the combined GPS/GLONASS/ BeiDou solutions provided an accuracy (rms values) of about 5 m.
基金supported in part by the Joint Foundation of National Natural Science Committee of China and Civil Aviation Administration of China under Grant U1933108in part by the Scientific Research Project of Tianjin Municipal Education Commission under Grant 2019KJ117.
文摘Due to the civil BeiDou navigation system is open,unauthenticated,and non-encrypted,civilian BeiDou navigation signals may have great security loopholes during transmission or reception.The main security loophole here is spoofing attacks.Spoofing attacks make the positioning or timing results of BeiDou civilian receivers wrong.Such errors may cause a series of security problems,which lays a serious hidden danger for Bei-Dou satellite information security.This article proposes an anti-spoofing method for BeiDou navigation system based on the combination of SM commercial cryptographic algorithm and Timed Efficient Stream Loss-tolerant Authentication(TESLA)for spoofing attacks.In this solution,we use the SM3 algorithm to generate a TESLA key chain with time information,and then use the key in the key chain to generate the message authentication code for the BeiDou D2 navigation message.The message authentication code is inserted into a reserved bit of the D2 navigation message.In addition,this solution uses the SM2 algorithm to protect and encrypt time information in the TESLA key chain to prevent key replay attacks in TESLA.The experimental results tested on the experimental platform built in this paper show that this scheme reduces the possibility of the BeiDou navigation system being deceived and enhances the safety of the BeiDou navigation system.
文摘Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese BeiDou are developing rapidly. With the new IGS project known as IGS MGEX which produces highly accurate GNSS orbital and clock products, multi-constellations PPP becomes feasible. On the other hand, the un-differenced ionosphere-free is commonly used as standard precise point positioning technique. However, the existence of receiver and satellite biases, which are absorbed by the ambiguities, significantly affected the convergence time. Between-satellite-single-difference (BSSD) ionosphere free PPP technique is traditionally used to cancel out the receiver related biases from both code and phase measurements. This paper introduces multiple ambiguity datum (MAD) PPP technique which can be applied to separate the code and phase measurements removing the receiver and satellite code biases affecting the GNSS receiver phase clock and ambiguities parameters. The mathematical model for the three GNSS PPP techniques is developed by considering the current full GNSS constellations. In addition, the current limitations of the GNSS PPP techniques are discussed. Static post-processing results for a number of IGS MGEX GNSS stations are presented to investigate the contribution of the newly GNSS system observations and the newly developed GNSS PPP techniques and its limitations. The results indicate that the additional Galileo and BeiDou observations have a marginal effect on the positioning accuracy and convergence time compared with the existence combined GPS/GLONASS PPP. However, reference to GPS PPP, the contribution of BeiDou observations can be considered geographically dependent. In addition, the results show that the BSSD PPP models slightly enhance the convergence time compared with other PPP techniques. However, both the standard un-differenced and the developed multiple ambiguity datum techniques present comparable positioning accuracy and convergence time due to the lack of code and phase-based satellite clock products and the mathematical correlation between the positioning and ambiguity parameters.
文摘This paper introduces a new dual-frequency precise point positioning (PPP) model, which combines the observations of three different GNSS constellations, namely GPS, Galileo, and BeiDou. Our model is based on between-satellite single-difference (BSSD) linear combination, which cancels out some receiver-related biases, including receiver clock error and non-zero initial phase bias of the receiver oscillator. The reference satellite can be selected from any satellite system GPS, Galileo, and BeiDou when forming BSSD linear combinations. Natural Resources Canada’s GPS Pace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data sets at four IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the IGS-MGEX network are used to correct both of the GPS and Galileo measurements. It is shown that using the BSSD linear combinations improves the precision of the estimated parameters by about 25% compared with the GPS-only PPP solution. Additionally, the solution convergence time is reduced to 10 minutes for both BSSD scenarios, which represent about 50% improvement in comparison with the GPS-only PPP solution.
文摘China launched the 33rd and 34th satellites of the BeiDou navigation system into their preset orbits using a LM-3B/ Yuanzheng I carrier rocket from the Xichang Satellite Launch Center at 09:48 Beijing time on July 29,2018.
基金supported by the National Natural Science Foundation of China (No.51505221)the Nanjing University of Aeronautics and Astronautics Graduate Innovation Base (Lab) Open Fund (No.kfjj20190312)
文摘Dual-frequency satellite positioning receivers are widely used because they can eliminate ionospheric delay and solve the full-circumference ambiguity quickly.However,in traditional dual-frequency receivers,the relevance of dual-frequency signals are not considered,and,with no improvement imposed to the tracking loop,two independent tracking loops are used to achieve the tracking of dual-frequency signals.In this paper,the Bei Dou dual-frequency signals joint tracking algorithm based on Kalman filter is proposed for the tracking of Bei Dou B1I and B3I dual-frequency signals.Taking the relevance of B1I and B3I signals into consideration,the algorithm adds a Kalman filter between the phase detector and carrier loop filter of the traditional dual-frequency independent tracking loop.The output results of the phase detectors of the B1I and B3I branches are then combined and filtered by the Kalman filter,and the results are input to the carrier loop filters of the corresponding branches.Proved by experiments,the algorithm not only enables the loop to enter a stable tracking state quickly,but also reduces the noise bandwidth of the two loop filters by about 10 Hz with the same tracking performance obtained.
文摘Water vapor monitoring system by Beidou satellite is a new detection system in meteorological department,which makes receiving amount of detected data and data storage and transmission pressure increase. Here,we try to use data compression to relieve pressure. Compression software of water vapor monitoring system by Beidou satellite can be designed into three components: real-time compression software,check compression software and manual compression software,which respectively completes the compression tasks under real-time receiving,in-time check and separate compression,thereby forming a perfect compression system. Taking the design of manual compression software as guide,and using c language to develop,compression test of original receiving data is conducted. Test result proves that the system can carry out batch automatic compression,and compression rate can reach 30%,which can reach the target of saving space in a degree.
文摘CHINA launched the last satellite of the BeiDou Navigation Satellite System(BDS),the 55th in the BeiDou family,on June 23 in Xichang Satellite Launch Center in Sichuan Province.It marks the completion of the deployment of China’s own global navigation system.On its journey to explore a path of developing a navigation satellite system suitable for its national conditions since the late 20th century,China formulated a three-step strategy of development for BDS:to complete the construction of BDS-1 and provide services to the whole country by the end of 2000;to complete the construction of BDS-2 and provide services to the Asia-Pacific region by the end of 2012;and to complete the construction of BDS and provide services worldwide around 2020.
文摘Aiming at the issue of influence of blanket jamming on performances of Beidou navigation signals, through studying Beidou signals based on the BOC modulation technology, establishing a blanket jamming mathematical model, and performing modeling and simulation on multiple jamming technologies, to attain the jamming curves of time domains and frequency domains of Beidou signals, and the correlation curve of the signal-to-jamming rate and the bit error rate under blanket jamming, and thus realizing evaluation on the jamming performance.
文摘BeiDou navigation satellite system(the BeiDou system) is the only PNT(Positioning, Navigation and Tim-ing) resource in China that has coverage of the globe and near-Earth space and provides continuous high-precision,low-cost positioning, navigation and timing solutions for users in a unified spatio-temporal benchmark. As an importantspatio-temporal benchmark transmission system, the BeiDou system is the most important resource for the nationalPNT system to provide a PNT capability under a unified spatial-temporal benchmark. This paper proposes the con-cept, composition and development model of the space-based PNT system design based on the BeiDou system withall its space characteristics, as well as the advantages of the system. It opens up a new direction for the construction ofChina's PNT system and expands a new horizon in the research of a PNT system in China.
文摘For scale cotton-picker operation, combination of production resources including field, machine, and drivers, should be organized reasonably both in temporal and spatial dimensions. Xinjian Agri. is such a scale cotton picking service company, which owns more than 400 cotton-pickers, hires nearly 1000 personnel, and works for more than ten big farms each season. The total operation area is about 90,000 ha. In this paper, a Cotton-picker Operation Scheduling & Monitoring System (CPOSMS) was developed for Xinjian Agri. CPOSMS is a WebGIS and BeiDou based management software, which includes four main function modules. Overall scheduling module aims to help the company to create machine fleets for the farms based on operation demands and operation capacity. A real-time evaluation model was studied to adjust the rationality. Local scheduling module is to dispatch machines and personnel to form machine unit. Central navigating module is to guide staff to specific field. Operation monitoring module is to monitor and analyze operation process. Experiments in 2015 showed that the CPOSMS is the necessary tool for the company, and the evaluation model and BeiDou based system can improve management efficiency.
