北斗广域差分分米级定位的分区切换算法

从2017年1月开始,北斗系统在播发基本导航电文的同时,提供了包含实时轨道改正数、钟差改正数、电离层格网改正数和分区综合改正数四重广域差分参数,使得系统具备了基于系统广播的电文参数实现广域单站实时动态分米级定位的能力。实际应用表明,北斗系统播发的分区综合改正数存在中断的情况,使得实时定位存在因重新收敛而造成跳变的情况。本文分析了分区中断期间定位跳变产生的原因,提出一种适用于分区切换的广域差分分米级定位算法。采用中国境内7个北斗测站10d的静态数据和车载动态数据对新算法进行评估验证。结果表明,在分区改正数中断的情况下,分区切换算法得到的坐标误差与使用连续分区综合改正数结果一致,双频动态定位水平和高程方向分别小于0.3m和0.5m,平均三维定位精度优于0.5m;车载实时动态定位测试中,分区切换前后的单双频定位精度不受切换影响,与切换前保持一致。分区切换算法有效保证了分区改正数中断后北斗广域分米级实时动态定位的连续性。

PPP algorithm using BDS new SBAS differential corrections

Since January 2017, BDS provides users with decimeter-level SBAS point positioning capability through the broadcasting of upgraded differential corrections, including satellite orbit error corrections, satellite clock error corrections, ionosphere grid corrections and zone corrections. In practice, however, the real-time zone corrections experience discontinuities causing the re-initialization of carrier-phase based positioning. We develop a new BDS SBAS precise point positioning (PPP) algorithm based on the switching of zone corrections among neighboring zones. Applying the new algorithm, users switch to use the zone corrections of the neighboring zones in case of no corrections received of the current zone, and thus avoid positioning re-initialization. Data of 7 BDS tracking stations and real-time kinematic on-road tracks are used to evaluate the new algorithm. Results show that with the implementation of the new algorithm, the positioning accuracy of BDS kinematic dual-frequency PPP is better than 0.3 m and 0.5 m in horizontal and vertical during the period of zone switching. On-road real-time single and dual frequency kinematic PPP shows no positioning re-initialization and the positioning accuracy remains at the level of better than 0.5 m during the discontinuity of zone corrections.