Test of Determining Geopotential Difference between Two Sites at Wuhan Based on Optical Clocks’ Frequency Comparisons

Hoang, Anh The; Shen, Zhongjie; Wu, Kuangchao; An, Ning; Shen, Wenbin

doi:10.3390/rs14194850

Cited by 7 publications

(3 citation statements)

References 35 publications

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“…Many researchers have studied their application in geodetic work, recognizing the considerable benefits of optical clock networks [28]- [31]. International proposals for potential optical clock networks have emerged, including in Europe [32], the United States [33], and Japan [34].…”

Section: Introductionmentioning

confidence: 99%

Unifying the Regional Height System Using Optic-Fiber Clock Network: A Simulation Test for Southeast Asia

Hoang,

Shen,

Shen

2023

IEEE Access

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Orthometric height datum systems are critical in the geodetic community. Nonetheless, individual nations or local regions maintain their distinct height systems. These systems, primarily determined by conventional spirit leveling, exhibit inhomogeneity, as the mean sea level does not represent an equi-geopotential surface. As such, accurately unifying global height systems is a persistent challenge. The gravity frequency shift equation provides a promising approach to this issue, offering a means to unify global height systems by comparing the frequencies of two distant clocks via optical fibers. In this study, we develop a model based on the Optical Fiber Frequency Transfer (OFFT) method, recognized for its unparalleled precision. We simulated a network of optical clocks interconnected by optical fibers to unify the height system across Southeast Asia. Our study suggests that the optical fiber clock network can realize height propagation between any two height datums at the centimeter level, providing a favorable opportunity for achieving regional height system unification. INDEX TERMS Regional height system; optical clocks network; OFFT; gravity frequency shift; frequency transfer; geopotential.

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Section: Introductionmentioning

confidence: 99%

Unifying the Regional Height System Using Optic-Fiber Clock Network: A Simulation Test for Southeast Asia

Hoang,

Shen,

Shen

2023

IEEE Access

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“…The most precise method for comparing clocks in different places is to connect them via optical fiber links (OFLs) [25]. Therefore, an increasing number of discussions and experiments on clocks connected by OFLs have been carried out and discussed [26][27][28][29]. Recently, the most precise measurement in OFL chronometric leveling was conducted by [30].…”

Section: Introductionmentioning

confidence: 99%

Unification of a Global Height System at the Centimeter-Level Using Precise Clock Frequency Signal Links

Shen

Zhang

et al. 2023

Remote Sensing

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The International Association of Geodesy (IAG) aims to establish the International Height Reference System (IHRS) as one of its primary scientific objectives. Central to the realization of the IHRS is global vertical datum unification, which requires the connection of existing local vertical height reference systems (VHS) robustly and consistently. However, conventional methods are not suitable for estimating the offsets between two distant local height systems. In this paper, we propose a framework for connecting two local VHSs using ultraprecise clock frequency signal links between satellites and ground stations, referred to as the satellite frequency signal transmission (SFST) approach. The SFST approach allows for the direct determination of the geopotential and height differences between two ground datum stations without any location restrictions between the two VHSs. The simulation results show that the VHSs of China and the US can be unified with an accuracy of several centimeters, provided that the stability of atomic clocks used on-board the satellite and at on-ground datum locations reaches 4.8×10−17τ−1/2 for an averaging time τ (in seconds). We conclude that the SFST approach shows promise for achieving centimeter-level accuracy in unifying the global vertical height datum and represents a new paradigm for the realization of the IHRS.

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“…In order to determine the geopotential difference with a precision of 0.1 m 2 /s 2 , corresponding to an orthometric height difference of 1 cm, it is necessary to measure the frequency shift between the clocks to a precision of around 1×10 −18 [8]. Modern optical atomic clocks have reached instabilities as low as 2×10 −18 after 10 minutes of integration [9], and have been demonstrated to be sensitive to height differences as small as 7 mm [10].…”

Section: Introductionmentioning

confidence: 99%

Optical Frequency Transfer for Geopotential Difference Measurements via a Flying Drone

Dix-Matthews¹,

Gozzard²,

Walsh³

et al. 2022

Preprint

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<p>Geopotential and orthometric height differences between distant points can be measured via timescale comparisons between atomic clocks. Modern optical atomic clocks have residual instabilities on the order of 10^-18}, allowing height differences of around 1 cm to be measured. Frequency transfer via free-space optical links will be needed for measurements where linking the clocks via optical fiber is not possible, but requires line of sight between the clock locations, which is not always practical due to local terrain or over long distances. We present an active optical terminal, phase stabilization system, and phase compensation processing method robust enough to enable optical frequency transfer via a flying drone, greatly increasing the flexibility of free-space optical clock comparisons. We demonstrate a residual instability of 2.5x10^-18 after 3 s of integration, corresponding to a height difference of 2.3 cm, suitable for applications in geodesy, geology, and fundamental physics experiments.</p>

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Test of Determining Geopotential Difference between Two Sites at Wuhan Based on Optical Clocks’ Frequency Comparisons

Cited by 7 publications

References 35 publications

Unifying the Regional Height System Using Optic-Fiber Clock Network: A Simulation Test for Southeast Asia

Unifying the Regional Height System Using Optic-Fiber Clock Network: A Simulation Test for Southeast Asia

Unification of a Global Height System at the Centimeter-Level Using Precise Clock Frequency Signal Links

Optical Frequency Transfer for Geopotential Difference Measurements via a Flying Drone

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