北斗卫星伪距测量中的常数偏差特性分析及其对导航服务的影响

Nominal signal deformations of navigation satellites may result in pseudorange biases. The biases depend on receiver configuration parameters such as bandwidth, correlator spacing and other parameters. The distortions differ from satellite to satellite, and thus, the receiver’s filter response also differs for each satellite and causes satellite-dependent biases. Pseudorange biases are affected both by receiver configuration parameters and by signal distortions. As a consequence, the pseudorange biases cannot be represented by satellite-dependent or receiver-dependent differential code bias (DCB) parameters, thus resulting in positioning errors and integrity risks. This project focuses on characterization of BDS pseudorange bias and studies its effect on BDS real-time service and post-processing. Firstly, calculation algorithms for pseudorange bias will be concluded and used to character the BDS pseudorange bias using measurements from BDS monitoring network, IGS, MGEX and iGMAS. Then the effect of pseudorange biases on positioning accuracy and integrity will be derived theoretically and verified by the measured data. A new integrity monitoring approach, which considers pseudorange bias as a new error source, is proposed to reduce integrity risks. Furthermore, the effect of pseudorange biases on post-processing activities, such as precise orbit determination, satellite clock offsets determination and precise point positioning will be derived theoretically and verified by the measured data. The project regards pseudorange bias as a new error source. The research achievements will be meaningful for the further development of BDS and an important part of GNSS data processing theory.

导航信号的非理想特性导致对该信号的伪距测量存在常数偏差。对于特定的下行信号，该偏差随接收机状态参数的不同而变化。由于不同卫星下行信号的非理想特性不同，同一接收机对不同卫星测量的伪距偏差也存在差异。因此，伪距偏差无法用卫星和接收机码偏差参数表达，从而成为影响北斗系统服务精度和完好性的重要误差。本项目将伪距偏差作为新的误差源，深入分析北斗卫星伪距测量的常数偏差特性并研究其对北斗系统实时服务和精密后处理的影响。首先提出伪距偏差计算算法，利用北斗地面监测网络、IGS、MGEX和iGMAS的观测数据提取北斗卫星伪距偏差特性。然后通过理论分析和实测数据处理，研究伪距偏差对北斗系统服务精度和完好性的影响，提出一种顾及伪距偏差的完好性监测算法。最后，通过理论分析和实测数据验证研究伪距偏差对北斗卫星精密定轨、钟差解算和精密单点定位的影响。本项目研究成果可为北斗系统进一步发展与完善提高科学积累。

导航信号的非理想特性导致对该信号的伪距测量存在常数偏差。对于特定的下行信号，该偏差随接收机状态参数的不同而变化。伪距偏差无法用卫星和接收机码偏差参数表达，从而成为影响北斗系统服务精度和完好性的重要误差。本项目将伪距偏差作为新的误差源，深入分析北斗卫星伪距测量的常数偏差特性并研究其对北斗系统实时服务和精密后处理的影响。首先给出伪距偏差的定义，及与其他误差显著不同的特征，然后给出伪距偏差计算算法，利用实测数据提取了北斗卫星伪距偏差特性。结果表明，北斗卫星伪距偏差不随时间变化，与接收机的空间位置也无显著关系，与接收机的参数设置高度相关。北斗三号卫星伪距偏差较北斗二号卫星显著改善。在1.5G频段，B1I伪距偏差大于L1C/A，B1C频点伪距偏差得到显著改善。在1.2G频段，B2a伪距偏差和B3I伪距偏差显著小于L5和L2C。实测数据分析表明，伪距偏差是影响北斗系统实时服务性能和高精度数据处理精度的关键因素。伪距偏差将用户定位误差增加30%以上，并显著降低星基增强定位精度，增加系统完好性服务的漏警率和虚警率。伪距偏差对卫星精密定轨和钟差解算性能也有较大影响，会引起卫星钟差解算结果中约10ns左右的偏差误差。本项目研究成果完善了卫星导航领域相关的理论，即提出了伪距偏差的普遍存在性，及其应作为卫星导航数据处理新的误差源的观念。本项目部分研究成果已应用于北斗系统的建设，还可进一步应用于北斗系统的发展与完善，并为相关理论发现提供科学积累。