The International GNSS Service (IGS) provides combined satellite and station clock products, which are generated from the individual clock solutions produced by the analysis centers (ACs). Combinations for GPS and GLONASS are currently available, but there is still a lack of combined products for the new constellations such as Galileo, BeiDou, and QZSS. This study presents a combination framework based on least squares variance component estimation using the ACs’ aligned clock solutions. We present the various alignments required to harmonize the solutions from the ACs, namely the radial correction derived from the differences of the associated orbits, the alignment of the AC clocks to compensate for different reference clocks within each AC solution, and the inter-system bias (ISB) alignment to correct for different AC ISB definitions when multiple constellations are used. The combination scheme is tested with IGS MGEX and repro3 products. The RMS computed between the combined product and the aligned ACs’ solutions differ for each constellation, where the lowest values are obtained for Galileo and GPS with on average below 45 psec (13 mm) and reaching more than 150 psec (45 mm) for QZSS. The same behavior is repeated when the process is performed with the repro3 products. A clock and orbit combination validation is done using precise point positioning (PPP) that shows ionosphere-free phase residuals below 10 mm for all constellations, comparable with the AC solutions that are in the same level.

国际 GNSS 服务 (IGS) 提供组合的卫星和站时钟产品，这些产品是由分析中心 (AC) 生成的单独时钟解决方案生成的。目前已有GPS和GLONASS的组合产品，但仍缺乏针对伽利略、北斗、QZSS等新星座的组合产品。本研究提出了一种基于使用 AC 对齐时钟解决方案的最小二乘方差分量估计的组合框架。我们提出了协调 AC 解决方案所需的各种对齐方式，即从相关轨道差异导出的径向校正、AC 时钟对齐以补偿每个 AC 解决方案内的不同参考时钟，以及系统间偏差(ISB) 对齐，以在使用多个星座时纠正不同的 AC ISB 定义。该组合方案使用 IGS MGEX 和 repro3 产品进行了测试。每个星座的组合产品和对齐的 AC 解决方案之间计算的 RMS 有所不同，其中伽利略和 GPS 获得最低值，平均低于 45 皮秒（13 毫米），QZSS 达到超过 150 皮秒（45 毫米） 。当使用 repro3 产品执行该过程时，会重复相同的行为。使用精确点定位 (PPP) 完成时钟和轨道组合验证，显示所有星座的无电离层相位残差均低于 10 毫米，与同一水平的 AC 解决方案相当。