INTERGEO Agenda - english

Physical height reference systems are essential for monitoring climate-relevant processes such as sea-level change, mass transport, and surface deformation. Existing physical height systems are based on regional realizations tied to local datums and tide gauges, leading to systematic inconsistencies and limited temporal stability; the International Height Reference System (IHRS) was defined to provide a globally consistent, potential-based height reference. Optical atomic clocks provide a novel solution by enabling direct access to gravity potential differences through chronometric levelling, but a systematic framework for their integration into geodetic reference systems is still missing. This work develops and tests a clock-ready realization framework for physical height reference systems that integrates clock networks, gravity field information, and classical height data. A realistic European testbed is considered, exploiting the European Vertical Reference Frame (EVRF2019) and existing and planned fibre-optic links connecting current and prospective clock sites. Gravity potential differences and their temporal variations are modelled between selected clock sites, accounting for surface deformation and mass-loading effects, and these modelled differences are converted into simulated clock observables at performance levels consistent with current and near-future optical clocks. This approach allows the framework to be tested and validated in the absence of dense operational clock networks, while remaining fully compatible with future integration of real clock and quantum gravimetric observations. As a complementary methodological component, the clock-based unification of regional height systems is investigated through closed-loop simulations for Europe and Brazil, incorporating realistic network configurations, link technologies, and noise characteristics. The results demonstrate that, with clock uncertainties at the 10−18 level and optimized clock distributions, regional height systems can be unified with accuracies of 1–2 cm to a pre-defined datum and consistently related to the global geoid. Overall, this work demonstrates that a clock-ready, dynamically controlled height reference system can be realized in a pre-operational sense using existing geodetic infrastructure, providing a clear pathway toward future integration of real clock data and quantum gravimetric observation.