Estimates of ocean tide loading displacements and its impact on position time series in Hong Kong using a dense continuous GPS network |
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| Authors: | L G Yuan X L Ding P Zhong W Chen D F Huang |
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| Institution: | (1) School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE2 1JU, UK |
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| Abstract: | Three-dimensional ocean tide loading (OTL) displacements of eight diurnal and semidiurnal constituents at 12 sites in Hong
Kong were estimated using 3–7 years of continuous global positioning system (GPS) observations. OTL displacements were estimated
using the precise point positioning (PPP) technique on a daily basis and then combined. The OTL displacements obtained by
GPS were compared with predictions using seven recent global ocean tide models. The effect of OTL displacements on GPS position
time series was also investigated. The study shows that the GPS-derived OTL displacements (excluding K1 and K2 constituents)
agree best with those predicted by the GOT4.7 and NAO99b models. The GPS/model agreement is generally at the sub-millimeter
level, except for S2, K1, and K2 constituents with relatively large errors. After systematic biases between the GPS and model
values are removed, the misfits of all sites for M2, S2, N2, O1, P1, and Q1 are less than 0.5 and 1.0 mm in the horizontal
and vertical components, respectively, while larger misfits (within 2.5 mm) are observed for K1 and K2. Integer ambiguity
fixing slightly improves the east component of OTL displacement estimates. The study also finds that GPS-derived OTL corrections,
instead of model predicts, can be used in daily data processing with the exception of K1 and K2. Including K2 corrections,
a secular vertical rate of up to 1 mm/year in position time series can be induced, which needs to be confirmed by further
studies. |
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