Accuracy assessment of ocean tide models in China using GPS

Surface displacement due to ocean tide loading (OTL) is an important signal and correction in many geophysical applications, such as Global Positioning System (GPS) data analyses and removing unwanted signals from altimeter (e.g., T/P) or time-variable gravity measurements (e.g., GRACE). In this paper, we access the accuracy of seven OTL models CSR4.0,NAO99b,FES2004,TPXO7.2,HAMTIDE11a,DTU10,EOT11a,GOT4.7, using 260 daily continuous GPS stations of crustal movement observation network in China spanning 2011-2015. After removal of a prior body tide model, OTL displacements are estimated using the precise point positioning (PPP) technique and then combined through a kalman filter. Then the OTL displacements obtained by GPS were compared with the predicted results from OTL models above. As expected, most OTL models fit the GPS estimates well in the inland area while different significantly in the coastal area where the amplitude of OTL signals are much larger. The large discrepancies between them may indicate there is a need for an improved local model in the coastal area.