As its contribution to the latest release of the International Terrestrial Reference Frame, ITRF2020, the International GNSS Service (IGS) provided a 27-year-long series of daily “repro3” terrestrial frame solutions obtained by combining reprocessed solutions from ten Analysis Centers. This contribution represents an improvement over the previous contribution to ITRF2014, not only by the inclusion of more stations with longer and more complete position time series, but also by a general reduction in random and systematic errors. The IGS contribution to ITRF2020 also provided, for the first time, an independent estimate of the terrestrial scale based on the calibration of the Galileo satellite antennas. Despite the various observed improvements, the repro3 station position time series remain affected by a variety of random and systematic errors. This includes spurious periodic variations in several frequency bands, originating mostly from orbit and tide modeling errors, on top of a combination of white and flicker noise, whose origins remain to be precisely understood. These various components should carefully be accounted for when modeling GNSS station position time series and interpreting them in terms of Earth’s surface deformation. The Galileo-based scale of the repro3 solutions is found to be significantly offset (by \(+\)4.3 mm at epoch 2015.0) and drifting (by \(+\)0.11 mm/year) from the SLR/VLBI-based scale of ITRF2020. The reasons for this offset and drift remain to be uncovered.

作为对最新发布的国际地面坐标系ITRF2020的贡献，国际全球导航卫星系统服务（IGS）提供了长达27年的一系列每日“repro3”地面坐标系解决方案，这些解决方案是通过结合十个分析中心的再处理解决方案而获得的。这一贡献代表了对 ITRF2014 的先前贡献的改进，不仅包括了更多具有更长和更完整位置时间序列的站点，而且还普遍减少了随机和系统误差。 IGS 对 ITRF2020 的贡献还首次提供了基于伽利略卫星天线校准的陆地尺度的独立估计。尽管观察到了各种改进，repro3 站位置时间序列仍然受到各种随机和系统误差的影响。这包括几个频段的寄生周期性变化，主要源于轨道和潮汐建模误差，以及白噪声和闪烁噪声的组合，其起源仍有待准确理解。在对 GNSS 站位置时间序列进行建模并根据地球表面变形对其进行解释时，应仔细考虑这些不同的组成部分。发现 repro3 解决方案的基于 Galileo 的尺度与基于 SLR/VLBI 的尺度有显着偏移（在 2015.0 纪元偏移 \(+\)4.3 毫米）并漂移（\(+\)0.11 毫米/年） ITRF2020 的。这种偏移和漂移的原因仍有待揭示。