The combination of Precision Point Positioning(PPP)with Multi-Global Navigation Satellite System(MultiGNSS),called MGPPP,can improve the positioning precision and shorten the convergence time more effectively than the...The combination of Precision Point Positioning(PPP)with Multi-Global Navigation Satellite System(MultiGNSS),called MGPPP,can improve the positioning precision and shorten the convergence time more effectively than the combination of PPP with only the BeiDou Navigation Satellite System(BDS).However,the Inter-System Bias(ISB)measurement of Multi-GNSS,including the time system offset,the coordinate system difference,and the inter-system hardware delay bias,must be considered for Multi-GNSS data fusion processing.The detected ISB can be well modeled and predicted by using a quadratic model(QM),an autoregressive integrated moving average model(ARIMA),as well as the sliding window strategy(SW).In this study,the experimental results indicate that there is no apparent difference in the ISB between BDS-2 and BDS-3 observations if B1I/B3I signals are used.However,an obvious difference in ISB can be found between BDS-2 and BDS-3 observations if B1I/B3I and B1C/B2a signals are used.Meanwhile,the precision of the Predicted ISB(PISB)on the next day of all stations is about 0.1−0.6 ns.Besides,to effectively utilize the PISB,a new strategy for predicting the PISB for MGPPP is proposed.In the proposed strategy,the PISB is used by adding two virtual observation equations,and an adaptive factor is adopted to balance the contribution of the Observed ISB(OISB)and the PISB to the final estimations of ISB.To validate the effectiveness of the proposed method,some experimental schemes are designed and tested under different satellite availability conditions.The results indicate that in open sky environment,the selective utilization of the PISB achieves almost the same positioning precision of MGPPP as the direct utilization of the PISB,but the convergence time of MGPPP is reduced by 7.1%at most in the north(N),east(E),and up(U)components.In the blocked sky environment,the selective utilization of the PISB contributes to more significant improvement of the positioning precision and convergence time than that in the open sky environment.Compared with the direct utilization of the PISB,the selective utilization of the PISB improves the positioning precision and convergence time by 6.7%and 12.7%at most in the N,E,and U components,respectively.展开更多
为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性...为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性、可达性、通畅性及舒适度等5个维度15个指标,建立地铁站点与常规公交的衔接换乘评价指标体系;选取CRITIC(criteria importance through inter-criteria correlation)方法对指标进行客观赋权,采用云模型生成基于基本算法的评价标准云和结果云,评价结果通过云的数字特征和云图直观展现,进而对识别出的问题和不足采取相应改进措施.以中国青岛市主城区45个地铁站点与常规公交衔接换乘为案例进行评价,结果表明,衔接换乘综合评价等级为“中等”,准则层(便利性、可靠性、可达性、通畅性和舒适度)的衔接换乘评价等级均为“中等”以上,基本符合青岛市主城区地铁站点与常规公交衔接换乘的特点,验证了评价模型的有效性和合理性.评价结果有助于优化公共交通资源配置,提高城市交通系统的整体运行效率,缓解城市交通拥堵.展开更多
With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form d...With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form double-difference observation equations within their respective systems,and the positioning effect is improved.However,the interchangeability and compatible interoperability between global navigation satellite systems(GNSS)cannot be truly realized.At the same time,when the number of visible satellites decreases abruptly,the positioning performance deteriorates sharply.This paper focuses on the GNsS multi-system tight combination relative positioning technique,gives a mathe-matical model of multi-system tight combination relative positioning considering differential inter-system bias(DISB),and analyzes the time-varying characteristics of DISB at overlapping and non-overlapping frequencies among GPS/Galileo,GPS/BDS,and GPS/QZSS in terms of receiver brand,tem-perature,and receiver restart.The GNsS tight combination relative positioning performance is verified by static data from Curtin University and dynamic data measured at Taiyuan University of Technology.The results show that compared with loose combination,the ambiguity-fixed rate increases from 62.18%to 97.60%for static data and from 74.97%to 99.53%for dynamic data when the elevation mask angle is 50°,resulting in a significant improvement in positioning performance.展开更多
为解决数据混合存储导致精准查找速度慢、数据未分类分级管理造成安全治理难等问题,构建基于主从多链的数据分类分级访问控制模型,实现数据的分类分级保障与动态安全访问。首先,构建链上链下混合式可信存储模型,以平衡区块链面临的存储...为解决数据混合存储导致精准查找速度慢、数据未分类分级管理造成安全治理难等问题,构建基于主从多链的数据分类分级访问控制模型,实现数据的分类分级保障与动态安全访问。首先,构建链上链下混合式可信存储模型,以平衡区块链面临的存储瓶颈问题;其次,提出主从多链架构,并设计智能合约,将不同隐私程度的数据自动存储于从链;最后,以基于角色的访问控制为基础,构建基于主从多链与策略分级的访问控制(MCLP-RBAC)机制并给出具体访问控制流程设计。在分级访问控制策略下,所提模型的吞吐量稳定在360 TPS(Transactions Per Second)左右。与BC-BLPM方案相比,发送速率与吞吐量之比达到1∶1,具有一定优越性;与无访问策略相比,内存消耗降低35.29%;与传统单链结构相比,内存消耗平均降低52.03%;与数据全部上链的方案相比,平均存储空间缩小36.32%。实验结果表明,所提模型能有效降低存储负担,实现分级安全访问,具有高扩展性,适用于多分类数据的管理。展开更多
基金supported by“The National Key Research and Development Program of China(No.2020YFA0713502)”“The National Natural Science Foundation of China(No.41874039)”+1 种基金“Jiangsu National Science Foundation(No.BK20191342)”“Fundamental Research Funds for the Central Universities(No.2019ZDPY-RH03)”。
文摘The combination of Precision Point Positioning(PPP)with Multi-Global Navigation Satellite System(MultiGNSS),called MGPPP,can improve the positioning precision and shorten the convergence time more effectively than the combination of PPP with only the BeiDou Navigation Satellite System(BDS).However,the Inter-System Bias(ISB)measurement of Multi-GNSS,including the time system offset,the coordinate system difference,and the inter-system hardware delay bias,must be considered for Multi-GNSS data fusion processing.The detected ISB can be well modeled and predicted by using a quadratic model(QM),an autoregressive integrated moving average model(ARIMA),as well as the sliding window strategy(SW).In this study,the experimental results indicate that there is no apparent difference in the ISB between BDS-2 and BDS-3 observations if B1I/B3I signals are used.However,an obvious difference in ISB can be found between BDS-2 and BDS-3 observations if B1I/B3I and B1C/B2a signals are used.Meanwhile,the precision of the Predicted ISB(PISB)on the next day of all stations is about 0.1−0.6 ns.Besides,to effectively utilize the PISB,a new strategy for predicting the PISB for MGPPP is proposed.In the proposed strategy,the PISB is used by adding two virtual observation equations,and an adaptive factor is adopted to balance the contribution of the Observed ISB(OISB)and the PISB to the final estimations of ISB.To validate the effectiveness of the proposed method,some experimental schemes are designed and tested under different satellite availability conditions.The results indicate that in open sky environment,the selective utilization of the PISB achieves almost the same positioning precision of MGPPP as the direct utilization of the PISB,but the convergence time of MGPPP is reduced by 7.1%at most in the north(N),east(E),and up(U)components.In the blocked sky environment,the selective utilization of the PISB contributes to more significant improvement of the positioning precision and convergence time than that in the open sky environment.Compared with the direct utilization of the PISB,the selective utilization of the PISB improves the positioning precision and convergence time by 6.7%and 12.7%at most in the N,E,and U components,respectively.
文摘为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性、可达性、通畅性及舒适度等5个维度15个指标,建立地铁站点与常规公交的衔接换乘评价指标体系;选取CRITIC(criteria importance through inter-criteria correlation)方法对指标进行客观赋权,采用云模型生成基于基本算法的评价标准云和结果云,评价结果通过云的数字特征和云图直观展现,进而对识别出的问题和不足采取相应改进措施.以中国青岛市主城区45个地铁站点与常规公交衔接换乘为案例进行评价,结果表明,衔接换乘综合评价等级为“中等”,准则层(便利性、可靠性、可达性、通畅性和舒适度)的衔接换乘评价等级均为“中等”以上,基本符合青岛市主城区地铁站点与常规公交衔接换乘的特点,验证了评价模型的有效性和合理性.评价结果有助于优化公共交通资源配置,提高城市交通系统的整体运行效率,缓解城市交通拥堵.
基金supported by the Natural Science Foundation of Shanxi Provincial(Grant No.202203021211153)the Basic Research Program of Shanxi Province(Grant No.202203021212284)+2 种基金Open Foundation of the State Key Laboratory of Satellite Navigation System and Equipment Technology(Grant No.CEPNT2022B07)the Open Foundation of the State Key Laboratory of Geodesy and Earth's Dynamics(Grant No.SKLGED2022-3-4)the research on application technology of Beidou in the field of energy and power(Grant No.CEEC2022-ZDYF-01).
文摘With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form double-difference observation equations within their respective systems,and the positioning effect is improved.However,the interchangeability and compatible interoperability between global navigation satellite systems(GNSS)cannot be truly realized.At the same time,when the number of visible satellites decreases abruptly,the positioning performance deteriorates sharply.This paper focuses on the GNsS multi-system tight combination relative positioning technique,gives a mathe-matical model of multi-system tight combination relative positioning considering differential inter-system bias(DISB),and analyzes the time-varying characteristics of DISB at overlapping and non-overlapping frequencies among GPS/Galileo,GPS/BDS,and GPS/QZSS in terms of receiver brand,tem-perature,and receiver restart.The GNsS tight combination relative positioning performance is verified by static data from Curtin University and dynamic data measured at Taiyuan University of Technology.The results show that compared with loose combination,the ambiguity-fixed rate increases from 62.18%to 97.60%for static data and from 74.97%to 99.53%for dynamic data when the elevation mask angle is 50°,resulting in a significant improvement in positioning performance.
文摘为解决数据混合存储导致精准查找速度慢、数据未分类分级管理造成安全治理难等问题,构建基于主从多链的数据分类分级访问控制模型,实现数据的分类分级保障与动态安全访问。首先,构建链上链下混合式可信存储模型,以平衡区块链面临的存储瓶颈问题;其次,提出主从多链架构,并设计智能合约,将不同隐私程度的数据自动存储于从链;最后,以基于角色的访问控制为基础,构建基于主从多链与策略分级的访问控制(MCLP-RBAC)机制并给出具体访问控制流程设计。在分级访问控制策略下,所提模型的吞吐量稳定在360 TPS(Transactions Per Second)左右。与BC-BLPM方案相比,发送速率与吞吐量之比达到1∶1,具有一定优越性;与无访问策略相比,内存消耗降低35.29%;与传统单链结构相比,内存消耗平均降低52.03%;与数据全部上链的方案相比,平均存储空间缩小36.32%。实验结果表明,所提模型能有效降低存储负担,实现分级安全访问,具有高扩展性,适用于多分类数据的管理。
