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Currently, aliasing error of temporal signal model becomes the main factor constraining the accuracy of temporal gravity field. In provision of three types of satellite formations, i.e., GRACE-type, Pendulum-type and n-s-Cartwheel-type, which are suitable for gravity mission and composed of observation in different directions, here we design two cases and conduct a simulation experiment on the feasibility to apply satellite formations for eliminating the influence from the aliasing error of ocean tide models. The result of our experiment shows that, when the aliasing error is disregarded, n-s-Cartwheel formation can provide the best conditions for gravity field determination, which, compared with GRACE-type, can improve the accuracy by 43%. When aliasing error of the ocean tide model acts as the main source of error, the satellite formation applied in dynamic method for gravity field inversion cannot eliminate aliasing or improve the accuracy of gravity field. And due to its higher sensitivity to the high-degree variation of gravity field, the Cartwheel-type formation, which includes the radial observation, can result in the gravity field containing more high-frequency signals for the ocean tide model error, and lead to a dramatically larger error. [ABSTRACT FROM AUTHOR]

Based on pressure tide-gauge observations, sea-level records are derived for ten sites along the coast of West Greenland. The ocean tidal signal is extracted by a harmonic tidal analysis. The accuracy of the determined tidal constants is discussed in detail. The tides account for 85% of the observed sea-level standard deviation. The tide gauge records reveal significant shallow-water tidal effects, in particular compound and overtide amplitudes reaching 5 cm. The propagation of the tidal waves into the fjords depends strongly on local conditions and is in some cases accompanied by an amplification of the tidal amplitudes. The observed tidal signals are compared to the predictions of the global ocean tide model FES2004. At the outer coast, a good agreement is found. Inside the fjords, however, the model performs worse and tide gauge observations may still be indispensable when accurate tidal signals are required. [ABSTRACT FROM AUTHOR]

Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning (PPP) technique. The results were compared with predictions from seven latest global ocean tide models. Gravity measurements of OTL in Hong Kong were also used to validate the GPS results. The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models, when the K and K constituents are excluded. The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions, except for S, K and K constituents that have relatively larger errors. After removing the systematic biases between the GPS and the model estimates, the misfits of M, S, N, O, P and Q at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions, respectively, whereas K and K show relatively larger misfits of up to 2.3 mm. Both the GPS and the gravity S estimates have large biases with unknown reasons when compared with the modeled values, which needs to be further investigated. The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions, especially for coastal areas. [ABSTRACT FROM AUTHOR]