[G07-P] Poster

[G07-P-07] Effects of tidal perturbation on the geopotential for application of precise clock comparison to long-distance leveling: Case study of Japan as coastal areas

^○Yuki Kuroishi (The University of Tokyo, Tokyo, Japan)

Recent engineering advancement of precise comparison of optical clocks at a great distance, targeting to an accuracy equivalent to 1 cm in height difference, sheds new light on accurate geodetic leveling over long distances. Based on the theory of relativity, the rate difference between the clocks reflects the geopotential difference between the clock locations. Deriving the geopotential difference from the clock rate difference, however, requires removal of significant perturbation on the geopotential associated with time-variable tides, for example.
Supposing the application of chronometric leveling to coastal regions such as Japanese islands, we concern about the perturbation due not only to earth tides (ET) but to ocean tidal loading (OTL). Here, we evaluate the magnitudes of differential perturbation (DP) due to both ET and OTL separately over different distances ranging from a few tens to a thousand of kilometers. The results show that over a distance of 50 km the temporal changes in combined DP due to ET and OTL can reach the magnitude of 1 cm in terms of equivalent height difference (EHD). Over a distance of 600 km OTL can produce DP with a peak-to-peak amplitude of 1 cm EHD, and over a distance of 1000 km even root-mean-square amplitudes of OTL-induced DP reach about 2 cm EHD. Therefore, future geodetic application of precise clock comparison to constraining a nationwide height datum over long distances must unavoidably take into consideration the removal of perturbation due not only to ET but to OTL.