| Summary: | >The novel method of relativistic geodesy using clock networks hasreached an accuracy level that will enable interesting applications in the near future. High-performance clocks with a fractional frequency uncertainty of 10^-18 can detect a gravitational-potential change of 0.1 m^2/s^2 or a corresponding height difference of 1 cm between two clock sites. Here, we explore the advantages of terrestrial clock networks for the detection oftime-variable gravity signalsand for height system unification bysimulations where we consider realistic observation scenarios. On the deformable Earth, terrestrial clock observations containpotential variations due to mass changes andsurface displacements. Four case studies were conducted in the Himalayas, Amazon, Greenland, and Fennoscandia to studydifferent mass change processes like seasonal precipitation, present-day ice mass loss, and glacial isostatic adjustment (GIA).Height system unification involves the estimation of differenterrors (e.g. tilts and offsets) between the local/regional height reference systems. As a test case, an a priori height system was classified into local systems where various errors have been added.The reunification and estimation of error parameters werecarried out using simulated clock measurements. The considered errors include tilts along latitude, tilts along longitude, offsets, tilts that depends upon the distance from the tide gauge, tilts associated with certain levelling lines, systematic noise associated with the elevation of the levelling points, etc. Also, the tidal effects on the clock observations are investigated. Moreover, the optimal number and spatial distribution of the clocks aredetermined for each scenario.
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