对使用序贯最小二乘估计非差宽巷FCB的方法进行论述,指出其不足在于事先假定了单天内的(接收机端和卫星端)宽巷FCB稳定不变,而对其时变性质缺少讨论与分析。处理了全球350个IGS测站共10d的GPS观测数据,从站星非差FCB、站间单差FCB序列两方面对接收机端宽巷FCB的时变特性进行详细的分析和讨论。数据处理结果表明:①在没有周跳的连续弧段内非差宽巷FCB的历元平滑结果具有较好的稳定性,使用不少于90个历元(45min)的数据即可收敛到0.1周以内保持精度稳定,因此,建议计算非差宽巷FCB的最短弧段不应少于45min;②接收机端宽巷FCB在每一天内随时间变化速率不一样,一天内最大变化量可以达到0.3周,并且接收机重启会使其重新赋值,破坏FCB值的连续性。关于接收机端宽巷FCB时变特性的分析表明文献[4—5]等的序贯最小二乘法所依据的假设前提并不可靠。为获得更高精度的非差卫星宽巷FCB估值,对于接收机重新启动的观测数据,需要新增一个接收机FCB参数;而对于接收机FCB的时变特性,可以在估计时将其作为随机游走过程进行估计。
The approach of estimating undifferencedwide-laneFCBbysequential least squares is discussed. Then, it is pointed out that the daily wide-lane FCBs in satellites and receivers are assumed unchanged in advance, while lack of discussion and analysis of its time-varying property. Global GPS observations of ten days on 350 stations are processed and the time-varying property of wide-lane FCB in satellites and receivers is analyzed and discussed in detail from two aspects, undifferenced FCB between receiver and satellite and single-difference FCB between receivers. Results show that, O After smoothing, undifferencedwide-laneFCBisstablein a continuous arc without cycle slip, and can converge to 0. ] cycles by using more than 90 epochs(45 minutes) data, so it is suggested the shortest arc to estimate wide-lane FCB should be longer than 45 minutes; Q The rate of change disagrees over time in different days for wide-lane FCB in receivers, the maximum change in one day can reach up to 0. 3 cycles. Besides, receiver reboot will make FCB reinitialize and destroy its continuity. Thus, the analysis of wide-lane FCB time-varying property in receivers indicates that the assumption of sequential least squares proposed by reference [4-5] is not reliable. In order to obtain more precise undifferenced wide-lane FCB in satellites, the instability of daily wide-lane FCB in receivers needs to be considered. A new receiver FCB parameter should be added in the case of receiver reboot and the receiver FCB parameter can be estimated as a random walk process.