Accurately tracking changes in the Earth—such as sea level rise, ice loss, and plate motion—depends on having precise reference frames. These are systems that help scientists measure positions on Earth (the International Terrestrial Reference Frame, or ITRF) and in the sky (the International Celestial Reference Frame, or ICRF), and how Earth moves between them (Earth Orientation Parameters, or EOPs).

Right now, these systems don’t fully match up. While Earth-based measurements use modern techniques and careful combinations of data, the sky-based system (ICRF3) is based on older methods and is not yet connected to data from the Gaia space telescope. Also, different groups use different strategies to build Earth-based reference frames, leading to small—but important—differences in results. Outdated models of how Earth rotates make things even more complicated.

In this study, we look at where these mismatches happen, how trustworthy the reported errors are, and how choosing one reference system over another can affect results. We also highlight new efforts to update global standards and models. Improving the way these systems work together is essential for ensuring reliable Earth monitoring and for supporting science that depends on understanding our planet’s changing shape, rotation, and position in space.