Journal of the Geodetic Society of Japan
Online ISSN : 2185-517X
Print ISSN : 0038-0830
ISSN-L : 0038-0830
ORIGINAL PAPER
Perturbations on the Geopotential at the Earth's Surface due to Earth Tides and Ocean Tidal Loading:
Evaluation for Geodetic Application of Precision Clock Comparison to Differential Geopotential Measurements
Yuki Kuroishi
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2017 Volume 63 Issue 1 Pages 33-43

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Abstract

Emerging engineering advancement of precise comparison of synchronously linked optical lattice 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 such “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 on some realistic baselines taken from the Japanese leveling routes, with 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 200 km OTL can produce DP with a maximum difference exceeding 1 cm EHD, and over a distance of 1000 km even root-mean-square amplitudes of OTL-induced DP can reach about 2 cm EHD. Therefore, future geodetic application of clock comparison to constraining a nationwide height datum over a long baseline must unavoidably take into consideration the removal of perturbation due not only to ET, but also to OTL.

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© 2017 The Geodetic Society of Japan
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