Finnish Regional Chrono-Geoid Determination Using Least-Squares Collocation

by Lecomte, H., Bilker-Koivula, M. and Lion, G.
Gravity, Geoid and Height Systems 2026 Symposium
October, 2026

Chronometric geodesy exploits the gravitational redshift of optical atomic clocks to measure gravity potential differences at fractional frequency levels approaching 10⁻¹⁸, corresponding to a geopotential height measurement of approximately one centimetre. Combined with terrestrial gravimetry, clock-based observations offer a constraint on the long-wavelength components of the gravity field for geoid determination. It complements classical geodetic techniques for vertical reference frame determination. We investigate the integration of synthetic clock-based measurements of potential differences into regional geoid estimation over Finland using Least-Squares Collocation (LSC). We assess the performance of LSC under two contrasting landforms: a flat region representative of southern Finland, and a region with stronger relief in the north. This two-domain design is motivated by the known limitations of classical LSC implementations, which rely on a single stationary and isotropic covariance structure. We follow a simulation-based approach in which a high-resolution synthetic reference gravity field is constructed from a global geopotential model complemented by local data. Synthetic observations of gravity disturbances and clock potential differences are sampled at realistic locations with instrument-consistent noise, and the disturbing potential is recovered via LSC within a remove-compute-restore framework. Results are compared against the existing simulations in literature

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