Research on GPS precise point positioning algorithm with a Sea Surface Height Constraint

Marine surveying does not receive full benefits from RTK because there are lack of near reference stations along the coastal lines. Compared with RTK, PPP can realize positioning with just a single station, which can allow a wider operation range in marine applications, but its elevation positioning accuracy is significantly lower than the horizontal direction. For some ships with relatively static offshore operations, the vertical movement of ships is mainly affected by the tide, and the fluctuation of tide can be obtained by global tide models, etc. Therefore, we propose a GPS PPP method with a sea surface geodetic height constraint to make full use of sea tide motion information to improve PPP effect. In this paper, we establish the Sea Surface Height constraint PPP (SHC-PPP) model. It is noted that the GPS height is relative to WGS-84 reference ellipsoid, thus we convert the tide fluctuation information to the sea surface height relative to WGS-84 reference ellipsoid by adding a fixed value, which is the geodetic height of GPS receiver at the first epoch obtained in advance by using the post-positioning PPP minus the corresponding epoch's water level data predicted by FES2014. Validated by kinematic experiments, our SHC-PPP method can improve the vertical positioning accuracy over conventional PPP (PPPC) by 79%.