Feasibility of real-time high-resolution geoid height monitoring combining optical lattice clocks, inertial measurement unit, GNSS, and star trackers

Optical lattice clocks with 18-digit precision can resolve gravitational potential differences corresponding to a 1 cm difference in physical height, enabling centimeter-level comparisons of geoid heights between remote locations when combined with GNSS-derived ellipsoidal heights [1]. Building on this capability, we propose a method for real-time, high-resolution geoid mapping that employs a vehicle traveling between clock stations. The deflection of the vertical—representing the horizontal gradient of the geoid height— along the vehicle’s trajectory is estimated using an inertial measurement unit (IMU) and a single GNSS receiver, both mounted onboard, and star trackers co-located with the clocks at both ends.

We experimentally validated this approach by measuring the deflection of the vertical along a 35 km highway using the IMU and GNSS. We assumed that the geoid height difference between the start and end points could be measured by optical lattice clocks and that the deflection of the verticals could be measured by a star tracker without errors. Under these assumptions, the geoid height estimated in this experiment agreed with the Japanese geoid model within a root-mean-square difference of 7 mm. These results demonstrate the feasibility of real-time, high-resolution geoid determination and expand the potential applications of optical lattice clocks.

 

[1] J. Grotti et al., Physical Review Applied 21, L061001 (2024).