Research On GNSS Precise Point Positioning Algorithm With A Sea Surface Height Constraint

Marine positioning is the basis of marine survey.At present,the positioning of offshore operations is mainly carried out through the Global Navigation Satellite System(GNSS).The commonly used methods are Real Time Kinematic(RTK)carrier phase difference and Precise Point Positioning(PPP).RTK needs to set up a reference station near the operation area to help determine and correct the positioning error.In the ocean environment where there is no condition to set up a reference station,especially in the medium and far sea areas,RTK is not suitable for positioning.Compared with RTK,PPP can realize positioning by single station,and the operation distance is independent of the reference station,so long as the observation conditions permit.In the marine environment,the current PPP method provides acceptable horizontal positioning accuracy,but the vertical positioning accuracy is still poor.For the ships with relatively static operation at sea,the change of vertical position is mainly affected by the tide.At present,tide information can be obtained from tide stations on the shore,or from global tide models such as Finite Element Solution(FES).Therefore,in this paper,the sea tide fluctuation information is added to the conventional PPP solution model,and a PPP method with sea surface height constraint(SHC-PPP)is studied to improve the vertical positioning accuracy of PPP.The main works of this paper are as follows:1.A simple method to obtain the local mean sea surface geodetic height is proposed,and based on this,the method of obtaining height constraint data from tide level information is proposed.The tide level information is obtained from the observation of traditional tide gauge or the prediction of global tide model.2.The SHC-PPP algorithm is proposed,and the effectiveness of this method is verified by experiments.The results show that SHC-PPP can improve the vertical positioning accuracy significantly.