The GPS satellite transmitter antenna phase center offsets (PCOs) can be estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). Therefore, the derived PCO values rest on the terrestrial scale parameter of the frame. Consequently, the PCO values transfer this scale to any subsequent GNSS solution. A method to derive scale-independent PCOs without introducing the terrestrial scale of the frame is the prerequisite to derive an independent GNSS scale factor that can contribute to the datum definition of the next ITRF realization. By fixing the Galileo satellite transmitter antenna PCOs to the ground calibrated values from the released metadata, the GPS satellite PCOs in the z-direction (z-PCO) and a GNSS-based terrestrial scale parameter can be determined in GPS + Galileo processing. An alternative method is based on the gravitational constraint on low earth orbiters (LEOs) in the integrated processing of GPS and LEOs. We determine the GPS z-PCO and the GNSS-based scale using both methods by including the current constellation of Galileo and the three LEOs of the Swarm mission. For the first time, direct comparison and cross-check of the two methods are performed. They provide mean GPS z-PCO corrections of \(- 186 \pm 25\) mm and \(- 221 \pm 37\) mm with respect to the IGS values and \(+ 1.55 \pm 0.22\) ppb (parts per billion) and \(+ 1.72 \pm 0.31\) in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS + Galileo + Swarm in which both methods are applied, the constraint on Galileo dominates the results. We discuss and analyze how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCO in the combined GPS + Galileo + Swarm processing propagates to the respective freely estimated z-PCO of Swarm and Galileo.

通过将地面站坐标约束到当前的国际地面参考框架（ITRF），可以在全局调整中估算GPS卫星发射机天线的相位中心偏移（PCO）。因此，导出的PCO值取决于帧的地面比例参数。因此，PCO值会将此比例转换为任何后续的GNSS解决方案。在不引入帧的地面比例的情况下，获得与比例无关的PCO的方法是获得独立GNSS比例因子的先决条件，该因子可有助于下一个ITRF实现的基准定义。通过将Galileo卫星发射机天线PCO固定到已发布元数据中的地面校准值，可以在GPS + Galileo处理中确定z方向上的GPS卫星PCO（z-PCO）和基于GNSS的地面比例参数。一种替代方法是基于GPS和LEO的综合处理中对低地球轨道器（LEO）的重力约束。我们通过包括伽利略的当前星座和Swarm任务的三个LEO，使用这两种方法确定GPS z-PCO和基于GNSS的比例。首次对这两种方法进行了直接比较和交叉检查。他们提供了平均GPS z-PCO校正 我们通过包括伽利略的当前星座和Swarm任务的三个LEO，使用这两种方法确定GPS z-PCO和基于GNSS的比例。首次对这两种方法进行了直接比较和交叉检查。他们提供了平均GPS z-PCO校正 我们通过包括伽利略的当前星座和Swarm任务的三个LEO，使用这两种方法确定GPS z-PCO和基于GNSS的比例。首次对这两种方法进行了直接比较和交叉检查。他们提供了平均GPS z-PCO校正 相对于IGS值分别为\（-186 \ pm 25 \）  mm和\（-221 \ pm 37 \） mm和\（+ 1.55 \ pm 0.22 \）  ppb（十亿分之一）和\（+ 1.72 \ pm 0.31 \）相对于IGS14参考系的地面尺度。两种方法的结果彼此一致，只有很小的差异。由于伽利略观测的数量更多，因此伽利略-PCO固定方法可产生更精确和稳定的结果。在应用这两种方法的GPS + Galileo + Swarm的联合处理中，对Galileo的约束决定了结果。我们讨论并分析在GPS + Galileo + Swarm处理组合中固定Galileo发射机天线z-PCO或Swarm接收机天线z-PCO如何传播到Swarm和Galileo的各自自由估计的z-PCO。