A computationally efficient approach for estimating high-rate satellite clock corrections in realtime
A computationally efficient approach for estimating high-rate satellite clock corrections in realtime
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DOI：
10.1007/s10291-011-0206-z
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发表时间：
2012-01-01
期刊：
影响因子：
4.9
通讯作者：
Wickert, Jens
中科院分区：
文献类型：
--
作者：
Ge, Maorong;Chen, Junping;Wickert, Jens
实时卫星钟差通常利用全球网络的非差相位和距离观测值来估计。由于必须估计大量的模糊度参数，计算很耗时。因此，大多数国际GNSS服务组织（IGS）实时分析中心仅处理数量有限的稀疏全球站网，更新率为5秒。此外，非常需要具备同时估计多个全球导航卫星系统（GNSS）星座钟差的能力。尽管通过消除模糊度的历元差分观测可以加快估计速度，但由此得出的钟差可能包含特定于卫星的偏差，这会降低距离观测值的贡献。我们引入一种计算高效的实时钟差估计方法。将历元差分相位和非差距离观测值一起用于估计历元差分卫星钟差以及每个卫星和接收机的初始钟差。然后将从估计的历元差分钟差累积的有偏钟差与估计的钟差偏差进行校准，并作为最终钟差提供给用户。该算法被纳入德国地学研究中心（GFZ）开发的EPOS - RT软件中，并通过IGS全球网络进行了实验验证。与德国地学研究中心快速产品的比较表明，新方法的钟差估计精度与非差方法相当，而计算时间减少到十分之一。因此，从大型参考网络估计高速率卫星钟差以及跟踪多个全球导航卫星系统星座的卫星成为可能。
Realtime satellite clock corrections are usually estimated using undifferenced phase and range observations from a global network. Because a large number of ambiguity parameters must be estimated, the computation is time-consuming. Consequently, only a sparse global network of limited number of stations is processed by most IGS Realtime Analysis Centers with an update rate of 5 s. In addition, it is very desirable to build the capability to simultaneously estimate clock corrections for multi-GNSS constellations. Although the estimation can be sped up by epoch-differenced observations that eliminate ambiguities, the derived clocks can contain a satellite-specific bias that diminishes the contribution of range observations. We introduce a computationally efficient approach for realtime clock estimation. Both the epoch-differenced phase and undifferenced range observations are used together to estimate the epoch-differenced satellite clocks and the initial clock bias for each satellite and receiver. The biased clock corrections accumulated from the estimated epoch-differenced clocks are then aligned with the estimated clock biases and provided as the final clock corrections to users. The algorithm is incorporated into the EPOS-RT software developed at GFZ (GeoForschungsZentrum) and experimentally validated with the IGS global network. The comparison with the GFZ rapid products shows that the accuracy of the clock estimation with the new approach is comparable with that of the undifferenced approach, whereas the computation time is reduced to one-tenth. As a result, estimation of high-rate satellite clocks from a large reference network and tracking satellites of multi-GNSS constellations becomes achievable.