基于GPS双频原始观测值的精密单点定位算法及应用

Precise Point Positioning Algorithm Based on Original Dual-frequency GPS Code and Carrier-phase Observations and Its Application

提出一种基于GPS双频原始观测值的PPP算法。与基于消电离层组合观测值的传统PPP算法不同,鉴于电离层的弥散特性,本文算法参数化L1频率上的站星视线方向电离层延迟,可有效避免传统PPP方法中观测值组合过程所引起的观测噪声以及多路径效应被放大的不利影响。同时在利用扩展卡尔曼滤波模型进行未知参数的递归估计过程中,通过对大气延迟参数引入符合实际的约束,可以加快滤波收敛,提高参数估值的可靠性,视线方向电离层延迟可与其余未知参数同时估计得到,进而便于利用PPP技术进行单站电离层的提取和精密建模,此外,对于可能的模型误差(如码观测值粗差、相位观测值周跳等),基于DIA的质量控制策略以消除或削弱其对参数估值的不利影响。利用实测数据对算法在静态、低动态以及高动态定位应用方面的精度进行检验,结果表明,静、动态定位结果的外符合精度可分别达到1～2cm和7～8cm。通过比较两种PPP算法在低动态试验中的定位结果,表明本文算法能显著地减少滤波收敛时间,提高滤波收敛解的稳定性,进而验证了算法的可行性和有效性。

A precise point positioning（PPP）algorithm based on original dual-frequency GPS code and phase observations is presented.Instead of forming the ionosphere-free code and phase observations as usually done for standard PPP algorithm,by taking the dispersive property of ionosphere into account,the first-order ionospheric delay effects of L1 frequency along satellite-receiver line-of-sight（LOS）are incorporated into the state vector which is estimated by extended Kalman filter（EKF）technique.This alternative algorithm could avoid the adverse effect of amplified multipath and measurement errors existing in the ionosphere-free observations,In the meantime,several constraints can be introduced to the LOS ionospheric delay parameters during the filtering process,to improve the convergence of the filter to more reliable and precise solutions.The LOS ionospheric delays could be obtained simultaneously with other unknown parameters,which would facilitate the research on ionosphere at a single site.Besides,the recursive DIA-procedure is adopted as quality control strategy to guarantee the reliability of the estimators from the proposed PPP implementations.The performance of proposed algorithm is evaluated for different positioning applications：static,low-dynamic and high-dynamic test,and a positioning accuracy of about 1~2 cm and 7~8 cm can be achieved respectively for static and kinematic positioning.The convergence behavior and repeatability of filtered solutions can be well improved by comparing the positioning performance of proposed and standard PPP implementations for low-dynamic test.