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
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.
