Improving carrier-phase ambiguity resolution in global GPS network solutions
Improving carrier-phase ambiguity resolution in global GPS network solutions
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DOI：
10.1007/s00190-005-0447-0
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发表时间：
2005-06-01
影响因子：
4.4
通讯作者：
Zhang, FP
中科院分区：
文献类型：
--
作者：
Ge, M;Gendt, G;Zhang, FP
整周载波相位模糊度解算是大地测量学和地球动力学中精确GPS应用的关键问题之一。为了解算出尽可能多的整周模糊度，必须定义“最易确定”的双差模糊度。为此，现有的GPS软件包中实施了几种策略，比如根据基线长度或估计的实值模糊度的方差来选择模糊度。尽管它们的有效性在实践中得到了证明，但本文证明它们没有反映出变化的数据质量的所有影响，因为它们是基于GPS数据处理的理论考虑。因此，提出了一种新方法，该方法根据双差模糊度被固定为最接近整数的概率来选择它们。该概率是根据宽巷和窄巷模糊度的估计值和方差计算出来的。结合一种优化的模糊度确定程序，这种新方法在波茨坦地学研究中心（GFZ）的国际GPS服务（IGS）的常规数据处理中得到了应用。在一个约由90个IGS站组成的子网内，结果表明，与一种常用方法的75%相比，超过97%的独立模糊度被正确确定，而且在站点分布稀疏的区域，额外确定的模糊度使站点坐标的重复性提高了10 - 26%。
Integer carrier-phase ambiguity resolution is one of the critical issues for precise GPS applications in geodesy and geodynamics. To resolve as many integer ambiguities as possible, the 'most-easy-to-fix' double-difference ambiguities have to be defined. For this purpose, several strategies are implemented in existing GPS software packages, such as choosing the ambiguities according to the baseline length or the variances of the estimated real-valued ambiguities. Although their efficiencies are demonstrated in practice, it is proven in this paper that they do not reflect all effects of varying data quality, because they are based on theoretical considerations of GPS data processing. Therefore, a new approach is presented, which selects the double-difference ambiguities according to their probability of being fixed to the nearest integer. The probability is computed from estimates and variances of wide-lane and narrow-lane ambiguities. Together with an optimized ambiguity fixing procedure, the new approach is implemented in the routine data processing for the International GPS Service (IGS) at GeoForschungsZentrum (GFZ) Potsdam. Within a sub-network of about 90 IGS stations, it is demonstrated that more than 97% of the independent ambiguities are fixed correctly compared to 75% by a commonly used method, and that the additionally fixed ambiguities improve the repeatability of the station coordinates by 10-26% in regions with sparse site distribution.