Accuracy estimation of global tide models using continuous gravity observation data in northern China

To evaluate the applicability of the global tide models for tide correction in China, this paper firstly assessed the data accuracy of ten gravity observation from 2016 to 2018, and then made the accuracy assessment for the seven global tide model by the evaluation indicators such as the root mean square （RMS）, the root sum square （RSS）, latitude dependence of the gravimetric amplitude factor, and residual gravity. The result shows that some of the evaluation indicators have achieved or even surpassed the accuracy of the early superconducting gravimeters in ten gravity observations. For example, the RMS of the M₂ gravimetric amplitude factor was less than 0.000 70, withthe highest RMS about 0.000 14, and the stability of five main tide waves was less than 0.001 5. As for the ten observed and the seven global tide models, the RSS of DDW-NHi and M2001 models with the Earth’s oblateness influence is only about 0.288×10⁻⁸ m/s², which is smaller than others. Comparison of the tide corrected accuracies by Molodensky, DDW-NHi, M2001, and the observed tide models suggests that residual gravity corrected by DDW-NHi （±0.4×10⁻⁸—±1.0×10⁻⁸ m/s²） is larger than that by observed one （±0.1×10⁻⁸—±0.5×10⁻⁸ m/s²） for Wushi gravity observatory with the highest tide accuracy, but still smaller than that by M2001 （±0.7×10⁻⁸—±1.4×10⁻⁸ m/s²）. Furthermore, the residual gravity corrected by DDW-NHi is less about 1×10⁻⁸—2×10⁻⁸ m/s² than by the traditional Molodensky model.